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Streamlining precast back-frame design: automated design using Revit plugin

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Streamlining precast back-frame design: automated design using Revit plugin

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Content STREAMLINING PRECAST BACK-FRAME DESIGN:
AUTOMATED DESIGN USING REVIT PLUGIN
by
Victoria Dam
A Thesis Presented to the
FACULTY OF THE USC SCHOOL OF ARCHITECTURE
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF BUILDING SCIENCE
August 2022
Copyright 2022 Victoria Dam
i
Acknowledgments
I would like to thank my mother and my sister for their unconditional love and continued
support, especially during my time at the University of Southern California. I would like to
express my deep gratitude to the chair of my thesis committee, Professor Douglas Noble, and
committee member, Professor Karen Kensek, for their constant support and motivation.
Professor Douglas Noble, thank you for advising me to begin my building science degree sooner;
it has allowed me to gain a much broader academic experience. Professor Karen Kensek, thank
you for motivating me to do this thesis topic, which has allowed me to hone my programming
skills. Both actions have opened many opportunities and excitement for my career. Finally, I
would like to thank Steven Seal at Clark Pacific for sharing his knowledge of precast concrete
and for his time in helping me with my thesis. I also want to thank the MBS faculty and students
for their encouragement and support.
Committee Chair:
Professor Douglas E. Noble, Ph.D., FAIA
School of Architecture
Associate Dean for Academic Affairs
Associate Professor
dnoble@usc.edu
Committee Members:
Professor Karen M. Kensek, LEED AP BD+C
School of Architecture
ACSA Distinguished Professor
Professor of Practice in Architecture
kensek@usc.edu
Steven Seal
Engineering Manufacturing Manager, Facades
Clark Pacific
sseal@clarkpacific.com
ii
Table of Contents
Acknowledgments............................................................................................................................ i
List of Tables ................................................................................................................................. vi
List of Figures ............................................................................................................................... vii
Abstract .......................................................................................................................................... xi
Chapter 1 INTRODUCTION TO COMPUTER TOOL FOR GENERATING BACK FRAME .. 1
1.1 Rationale for the Use of Precast Concrete ............................................................................ 2
1.2 Precast Concrete .................................................................................................................... 2
1.2.1 Benefits of Precast Concrete .......................................................................................... 5
1.2.2 Installation process of precast concrete .......................................................................... 8
1.2.3 Types of Precast Wall Systems ...................................................................................... 8
1.3 Introduction of prefabricated facades systems .................................................................... 12
1.3.1 Current practices of the Steel Framework System ....................................................... 13
1.3.2 Typical Connection Details .......................................................................................... 15
1.3.3 Introduction of Infinite Facades/ Why Prefabricated Façade Systems ........................ 19
1.3.4 Precast Concrete Components – Composite Architectural Panels ............................... 20
1.4 Building Information Modeling (BIM) ............................................................................... 24
1.4.1 Popular BIM-related Software's ................................................................................... 25
1.4.2 Revit vs. AutoCAD ...................................................................................................... 26
1.4.3 Revit API and SDK ...................................................................................................... 28
1.4.4 Dynamo ........................................................................................................................ 33
1.5 Design Automation of Precast Concrete / Main Challenges of Widespread Precast
Concrete .................................................................................................................................... 37
1.6 Summary ............................................................................................................................. 38
Chapter 2 LITERATURE REVIEW FOR THE PRECAST FRAME DEVELOPMENT ........... 40
2.1 Rationale for the Use of Precast Concrete / Precast Concrete Automation Potential ......... 40
2.2 Precast Concrete .................................................................................................................. 41
iii

2.2.1 Fabrication methods of precast concrete ...................................................................... 41
2.3 Prefabricated façade system case study (Case Study) ......................................................... 44
2.4 Building Information Modeling / Case Studies ................................................................... 47
2.4.1. Benefits of using BIM ................................................................................................. 48
2.4.2 Using BIM in the Fabricating Process/Introducing Fabricators in the
Design Process....................................................................................................................... 49
2.4.3 From file to factory ....................................................................................................... 51
2.5 Design automation of precast concrete ............................................................................... 52
2.5.1 Automated planning of concrete joint layouts with 4D-BIM ....................................... 53
2.6 Summary: ............................................................................................................................ 54
Chapter 3 METHODOLOGY ....................................................................................................... 56
3.1 Methodology Overview ....................................................................................................... 57
3.2 Research .............................................................................................................................. 58
3.3 Planning ............................................................................................................................... 59
3.3.1 Preparing Revit Native Geometry ................................................................................ 60
3.3.2 Preparing Revit Native Geometry – Families .............................................................. 61
3.3.3 Preparing Revit Native Geometry – Family Flexing .................................................... 62
3.3.4 Preparing Revit Native Geometry – Titleblocks .......................................................... 63
3.4 Programming ....................................................................................................................... 64
3.4.1 Programming – API Setup............................................................................................ 65
3.4.2 Programming – Visual Studio API Setup ..................................................................... 67
3.4.2 Programming – User Interface ..................................................................................... 70
3.4.3 Programming – Manifesting ......................................................................................... 71
3.5 Validation ............................................................................................................................ 73
3.6 Back frame Plug-In Methodology (Current versus Proposed). ........................................... 74
3.7 Back frame Methodology (Proposed) ................................................................................. 76
3.8 Sheeting Tool Methodology ................................................................................................ 81
3.9 Summary ............................................................................................................................. 82
Chapter 4 TOOL DEVELOPMENT ............................................................................................. 84
4.1 Research Methodology ........................................................................................................ 84
4.2 Research – Current Workflow ............................................................................................. 85
iv
4.2.1 Revised Workflow ........................................................................................................ 88
4.3 Planning - Preparing Revit Native Geometry – Families .................................................... 90
4.3.1 Preparing Revit Native Geometry – Loadable Families – Wall / Floor ....................... 93
4.3.2 Preparing Revit Native Geometry – Parametric Families ............................................ 95
4.3.3 Openings ....................................................................................................................... 96
4.4.1 Programming Setup .......................................................................................................... 97
4.4.1 Programming – Setting Up Coding Environment ........................................................ 97
4.4.2 Programming – User Interface ..................................................................................... 99
4.5 Validation .......................................................................................................................... 105
4.6 Back frame Plug-In Code .................................................................................................. 107
4.6.1. IExternalCommand Method ...................................................................................... 108
4.6.1 Load Families ............................................................................................................. 109
4.6.2 Filtering Elements ...................................................................................................... 111
4.6.1 User Inputs Overrides ................................................................................................. 112
4.6.2 Loading Windows Forms Inputs ................................................................................ 114
4.6.2 Accessing Placed Instances ........................................................................................ 116
4.6.3 Methods for Placing Instances.................................................................................... 117
4.6.3 Moving Frames ........................................................................................................... 119
4.6.3 XML code ................................................................................................................... 121
4.7 Sheeting Code ................................................................................................................... 121
4.7.1 Referencing Geometry ................................................................................................ 123
4.7.1 Sheet Generation ........................................................................................................ 123
4.8 Summary ........................................................................................................................... 128
Chapter 5 INSTALLATION AND TUTORIAL ........................................................................ 129
5.1 Plug-in Package and Preparation ....................................................................................... 129
5.1.1. Revit Interface ........................................................................................................... 131
5.2 Case Study ......................................................................................................................... 132
5.2.1 Running Backframe and Sheeting Tool – Rectangle (Defaults) ................................ 132
5.2.2 Running Back frame and Sheeting Tool – Rectangle Reveal, default, 2 inches ........ 139
5.2.3 Running Back frame and Sheeting Tool – Windows ................................................. 142
5.3 Summary ........................................................................................................................... 143
v

Chapter 6 – Discussion and Future Work ................................................................................... 144
6.1. Discussion ........................................................................................................................ 144
6.2 Evaluation and Limitations ............................................................................................... 157
6.2.1 Limitations of the back frame tool – Panels with multiple reveals ............................ 158
6.2.2 Limitations of the back frame tool – Frame extends outside the panel ...................... 161
6.2.3 Limitations of the back frame tool – openings ........................................................... 162
6.2.4 Limitations of the back frame tool – Stiffener Ribs .................................................. 162
6.2.5 Limitations of the back frame tool – Uneven arrays .................................................. 164
6.3. Future Work ..................................................................................................................... 165
6.4. Conclusion ........................................................................................................................ 171
References ................................................................................................................................... 173
Appendices .................................................................................................................................. 176
Appendix A- Current workflow at Clark Pacific .................................................................... 176
Appendix B: ............................................................................................................................ 177
B.1 Method – Split with Gap ............................................................................................... 177
B.2 Method – Precast Panels Using Reveals ....................................................................... 178
B.3 Method – Precast Panels Using Parts ........................................................................... 180
B.4 Method - Revit Precast Panels Using Curtain Walls ................................................... 183
B.5 Method - Revit Precast Panels Using Voids ................................................................. 186
B.6 Method - Using Wall Openings .................................................................................... 189
Appendix C: GFRC ................................................................................................................. 191
Appendix D: Code ................................................................................................................... 194
D.1 Back frame code ........................................................................................................... 194
D.2 Sheeting code ................................................................................................................ 212

vi
List of Tables
Table 1-1 Overview of popular BIM software solutions in current market (Eastman et al. 2008;
Smith and Tardif, 2009) ................................................................................................................ 25
Table 2-1 Families (Author) ......................................................................................................... 80
Table 4-1 Families (Author) ......................................................................................................... 93
Table 6-1 Families created (Author) ........................................................................................... 149
vii
List of Figures
Figure 1-1 Prefabricated Concrete Panels (Source: (Gio Valle, n.d.) ............................................. 3
Figure 1-2 Cast in Place Concrete Walls (PCI 2014) ..................................................................... 4
Figure 1-3 Installation of precast panels on-site (Precast Bloks 2019) ......................................... 5
Figure 1-4 Inlay Materials - Brick (Manufacturing Process) (Jen Levisen, Dan Stenzel, and
Daniel Delisle 2021) ....................................................................................................................... 7
Figure 1-5 Inlay terracotta examples (Jen Levisen, Dan Stenzel, and Daniel Delisle 2021) ......... 7
Figure 1-6 Pre-glazing of Panels (Precast/Prestressed Concrete Institute 2007) ............................ 8
Figure 1-7 Comparison of three basic types of precast concrete (Precast/Prestressed Concrete
Institute 2013) ............................................................................................................................... 10
Figure 1-8 Solid concrete wall (ACCG 2021) .............................................................................. 10
Figure 1-9 Thin shell precast concrete panels attached to steel (Precast Bloks 2019) ................. 11
Figure 1-10 Precast prestressed insulated sandwich panel (Losch 2019) ..................................... 11
Figure 1-11 Typical Precast Panel Section (Precast/Prestressed Concrete Institute 2007) .......... 13
Figure 1-12 Figure Typical Arrangement of GFRC Stud Frame (PCI 2014) ............................... 16
Figure 1-13 Typical flex anchor indicating degrees of freedom (PCI 2014) ................................ 17
Figure 1-14 - Typical gravity anchor acting as a strut and tie system (PCI 2014) ....................... 18
Figure 1-15 Infinite facades exploded model (Clark Pacific 2021) .............................................. 19
Figure 1-16 Breakdown of parts, note CIP = Cast – In- Place (Author) ...................................... 21
Figure 1-17 Cast in place concrete connection (Author) .............................................................. 23
Figure 1-18 Revit Interface (Author) ............................................................................................ 26
Figure 1-19 Visual Studio setup showing C# for Grasshopper API (Author) .............................. 29
Figure 1-20 AGACAD Rebar Modeling Automation, paid service (AGACAD 2020) ............... 30
Figure 1-21 IMPACT plugin showcasing standard precast structural elements (StruSoft) .......... 31
Figure 1-22 Metal Framing (AGACAD 2020) ............................................................................. 32
Figure 1-23 Plugin for Revit families (Forge 2020) ..................................................................... 33
Figure 1-24 Dynamo Layout (AGACAD 2021) ........................................................................... 34
Figure 1-25 Adding grout tubes to precast walls using Dynamo (Autodesk Solutions 2018) ..... 35
Figure 1-26 Reinforcement opening around wall opening using Dynamo (Autodesk Solutions
2018) ............................................................................................................................................. 35
Figure 1-27 Automatic rebar generation (Kensek et al. 2017) ..................................................... 36
Figure 1-28 Dynamo script workflow for automatic rebar generation (Kensek et al. 2017) ........ 37
Figure 2-1 Diagram of the suggested evaluation method (Austern, Capeluto, and Grobman
2018b) ........................................................................................................................................... 43
Figure 2-2 Optimization results: original shape (top), and optimized results (bottom), the
numbers in red denote the relative percentage from the needed improvement (Austern,
Capeluto and Grobman 2018b) ..................................................................................................... 44
Figure 2-3 CSU LA Student Housing (Clark Pacific) .................................................................. 45
Figure 2-4 CSU LA Student Housing Six Panel Setup (Clark Pacific) ........................................ 46
Figure 2-5 FLV Curved Glazing Automation, Parametric Instantiation and Frequency
Analysis (Inocente 2018) .............................................................................................................. 50
Figure 2-6 Design Logic of Concrete (Sheikhkhoshkar, Rahimian, and Kaveh 2019) ................ 54
Figure 3-1 Methodology diagram for main tool (back frame tool) (Author) .............................. 58
Figure 3-2 Methodology diagram for sheeting tool (Author) ....................................................... 58
viii

Figure 3-3 Door family showing multiple options (Author) ........................................................ 62
Figure 3-4 Family type designer (Author) .................................................................................... 63
Figure 3-5 Visual studio script showing how to place a group in Revit (Author) ........................ 65
Figure 3-6 Revit API (Author) ...................................................................................................... 66
Figure 3-7 Visual Studio API Setup (Graham 2020) .................................................................... 68
Figure 3-8 Class Library (Graham 2020)...................................................................................... 69
Figure 3-9 Windows Form (Microsoft 2015) ............................................................................... 71
Figure 3-10 Adding a manifest file (Graham 2020) ..................................................................... 72
Figure 3-11 Adding a manifest file (Graham 2020) ..................................................................... 73
Figure 3-12 Current workflow at Clark Pacific, Larger Image in Appendix A (Author) ............. 75
Figure 3-13 3D model workflow (Author) ................................................................................... 76
Figure 3-14 Relationship between programming and Revit geometry (Author) .......................... 81
Figure 3-15 Sheeting tool methodology diagram (Author) .......................................................... 82
Figure 4-1 Current workflow at Clark Pacific, Larger Image in Appendix A (Author) ............... 86
Figure 4-2 Revised workflow (Author) ........................................................................................ 87
Figure 4-3 Wall Type Editor (Author) .......................................................................................... 94
Figure 4-4- Wall Systems (Author) .............................................................................................. 94
Figure 4-5 - Loadable Families (Author) ...................................................................................... 95
Figure 4-6 Default Windows and Openings in Revit (Author)..................................................... 96
Figure 4-7 - Revit titleblock (Author) ........................................................................................... 97
Figure 4-8 API Reference API (Author) ....................................................................................... 98
Figure 4-9 Revit API in Visual Studio (Author) ........................................................................... 99
Figure 4-10 Visualization of the steps (Author) ......................................................................... 102
Figure 4-11 Visual Studio Interface using Windows Form (Author) ......................................... 103
Figure 4-12 Properties Window (Author) ................................................................................... 103
Figure 4-13 Windows Form for Back frame plugin (Author) .................................................... 104
Figure 4-14 Event Handler Button (Author) ............................................................................... 105
Figure 4-15 Clark Pacific Double Panel (Clark Pacific) ............................................................ 106
Figure 4-16 Revit Plugin Panel (Author) .................................................................................... 106
Figure 4-17 Remodeling it using double panel (Author) ............................................................ 107
Figure 4-18 External Method (Author) ....................................................................................... 108
Figure 4-19 User Interface , Load Families (Author) ................................................................. 110
Figure 4-20 Load Families Code (Author) ................................................................................. 111
Figure 4-21 Load FilterElementCollector (Fast) Author ............................................................ 112
Figure 4-22 Loading by Database Element (Author) ................................................................. 112
Figure 4-23 User Overrides (Author) ......................................................................................... 113
Figure 4-24 User Input Validation Box (Author) ....................................................................... 114
Figure 4-25 External Command, take data from UI form for Builder (Author) ......................... 115
Figure 4-26 User input data to Frame Builder (Author) ............................................................. 115
Figure 4-27 Placed Instances (Author) ....................................................................................... 117
Figure 4-28 Creating initial boundary HSS (Author) ................................................................. 118
Figure 4-29 HSS interior array (Author) .................................................................................... 119
Figure 4-30 Family Instance Placement (Author) ...................................................................... 119
Figure 4-31 Moving entire backframe as a group (Author) ........................................................ 120
Figure 4-32 Translation Method (Author) .................................................................................. 120
ix
Figure 4-33 Translation Method (Author) .................................................................................. 120
Figure 4-34 Addin information (Author) .................................................................................... 121
Figure 4-35 Windows Form for Sheeting Tool (Author) ............................................................ 122
Figure 4-36 Windows Forms generated code (Author) .............................................................. 122
Figure 4-37 User Interface External Command (Author) ........................................................... 123
Figure 4-38 Box orientation (Author) ......................................................................................... 124
Figure 4-39 Label lengths (Author) ............................................................................................ 125
Figure 4-40 Get name of drawings (Author) .............................................................................. 126
Figure 4-41 Get title blocks for placement (Author) .................................................................. 127
Figure 5-1 Contents of package (Author) ................................................................................... 129
Figure 5-2 Addin (Author) .......................................................................................................... 130
Figure 5-3 Hidden folder (Author) ............................................................................................. 131
Figure 5-4 Default drawings (Author) ........................................................................................ 133
Figure 5-5 Clark Pacific Drawing (Clark Pacific) ...................................................................... 134
Figure 5-6 Wall panel (Author) .................................................................................................. 135
Figure 5-7 Revit Plugin - Rectangular (Author) ......................................................................... 136
Figure 5-8 External Tools (Author) ............................................................................................ 136
Figure 5-9 Sheet Tool in Revit (Author)..................................................................................... 137
Figure 5-10 Sheet Tool in Revit (Author)................................................................................... 138
Figure 5-11 Pick a panel (Author) .............................................................................................. 139
Figure 5-12 Clark Pacific Panel (Clark Pacific) ......................................................................... 140
Figure 5-13 Double panel sweep method (Author) .................................................................... 141
Figure 5-14 Double panel in Revit, without using two systems (Author) .................................. 142
Figure 5-15 Windows option, rendered (Author) ....................................................................... 143
Figure 6-1 Methodology diagram for back frame tool (Author) ................................................ 145
Figure 6-2 Current workflow (Author) ....................................................................................... 146
Figure 6-3 Proposed workflow (Author) .................................................................................... 146
Figure 6-4 Split with gap (Author) ............................................................................................. 151
Figure 6-5 Interface of back frame tool (Author) ....................................................................... 152
Figure 6-6 Back frame tool output (Author) ............................................................................... 153
Figure 6-7 Methodology diagram for sheeting tool (Author) ..................................................... 154
Figure 6-8 Final sheeting tool interface (Author) ....................................................................... 154
Figure 6-9 Sheeting tool output (Author) ................................................................................... 155
Figure 6-10 Standard panel with windows completely inside panel. A- input, B- geometry
Revits reads , C- output with back frame (Author) ................................................................... 158
Figure 6-11 Panel with reveal (input geometry), Revit API cannot read reveals and sees it as
panel (Author) ............................................................................................................................. 159
Figure 6-12 Panel with center points (Author) ........................................................................... 160
Figure 6-13 Panel with a sweep (Author) ................................................................................... 160
Figure 6-14 HSS Panel that over the frame (Author) ................................................................. 161
Figure 6-15 Nonstandard vs standard windows (Author) ........................................................... 162
Figure 6-16 Window stiffener ribs (Clark Pacific/Author)......................................................... 163
Figure 6-17 Window stiffener ribs (Clark Pacific/Author)......................................................... 164
Figure 6-18 Window stiffener ribs (Clark Pacific/Author)......................................................... 165
Figure 6-19 Future work, openings (Author) .............................................................................. 166
x
Figure 6-20 Openings (Author) .................................................................................................. 167
Figure 6-21 Sheeting errors, lack of dimensions and sizing errors (Author) .............................. 168
Figure 6-22 Scope box (Author) ................................................................................................. 169
Figure 6-23 Paneling tool (Skindesigner 2020) .......................................................................... 170
Figure 6-24 Panel schedule (Author) .......................................................................................... 171
Figure B-1 Split Method with Gaps (Author) ............................................................................. 177
Figure B-2 Reveals (Author).......................................................................................................
Figure B-3 Reveals (Author).......................................................................................................
Figure B-4 Type properties (Author)...........................................................................................
Figure B-5 Reveal profile (Author).............................................................................................
Figure B-6 Parts interface in Revit (Author)...............................................................................
Figure B-7 Edit sketch (Author)..................................................................................................
Figure B-8 Division Geometry (Author).................................................................................... .
Figure B-9 Division profile (Author)..........................................................................................
Figure B-10 Parts Visibility in Revit interface (Author) ............................................................
Figure B-11 Precast panels curtain walls (Author).....................................................................
Figure B-12 Precast panels curtain walls (Author) .....................................................................
Figure B-13 Curtain walls dialog box (Author) .........................................................................
Figure B-14 Model in-place component (Author)......................................................................
Figure B-15 Voids modeled (Author) ........................................................................................
Figure B-16 Voids Result (Author) ............................................................................................
Figure B-17 Wall openings (Author) …………………………………………………….........
Figure B-18 Wall openings (Author) .........................................................................................
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Abstract
Precast design can take advantage of building information modeling and custom tools to help in
the design process of panels. Currently, the traditional 2D design techniques used to create
precast panels do not meet the needs of the customer in both quality and speed. As a result, many
industries have already made the transition of moving from 2D to using building information
modeling software programs. Revit is a common program used by many professionals in the
architecture, engineering, and construction industry. The software can be further approved by
developing plug-ins in C# for simple or complex tasks by working with the interface of the
software (Revit API).

Most thin-shell precast panels are rectangular in design. The precast's weight is supported by a
steel back frame made of HSS tubes and anchors that connect to the building. Several design
rules that the façade engineers use can be programmed into an app for repetitive tasks. The
facade engineers can receive different deliverables from an architect, such as 2D plans or a 3D
Revit model. The plugin comes with modeled families to assist with creating a basic architectural
model in Revit. After having a base architectural model, the façade skin is panelized. The plugin
is then used to reference the geometry of a panel. After getting the boundary shape of the panel,
it will create the initial frame offset. If the wall is generic, the plugin can also override the
materials settings for a type of precast panel. The next step will create the max spacing and array
of the frame. After that, it will find the connection points of the frame to the floor. It will also
load the anchor families and find the points. It will also load the pins, and it is parametrically
increase into the wall. When a window is added, the panel will recalculate the back frame and
xii
move the related connections, anchors, and pins. This plugin automates less complex panels and
allows the façade engineers to alleviate some of their work.
A second Revit plug-in helps with documentation by quickly and easily making shop drawings
and enabling the configurations of shop drawing templates. After the panels are framed, the shop
drawings are set up.
KEYWORDS: Revit API, Precast Concrete, Building Information Modeling (BIM), Envelopes,
Facades
HYPOTHESIS:
A digital tool using Revit API and C# can be created to facilitate the structural frame
modeling of precast panels.
RESEARCH OBJECTIVES:
• Develop a tool that can be used to layout the structural frame and connection locations
thin shell precast concrete panels.
• Study and understand the process to create a precast framework.
• Explore the process between engineer and fabricator for precast frames.
1

Chapter 1 INTRODUCTION TO COMPUTER TOOL FOR GENERATING BACK
FRAME

Facades are becoming increasingly complex as research shows how the skin of the building
affects different systems of the building (Herzog, Krippner, and Lang 2018). Façade fabrication
has evolved from "exposed glass windows" to a "partially exposed glass frame" or "hidden frame
with a full glass" (Herzog, Krippner, and Lang 2018). As the industry goes further into
sustainability and high-performance design, building elements such as energy-efficient facades
and photoelectric facades are gaining popularity. As a result of industry pressures, the use and
need of BIM software for façade modeling has become increasingly important. Building
Information Modeling (BIM) uses digital 3D building models to facilitate collaboration in the
design process. Architecture, engineers, and construction firms use BIM software due to its
advantages of visualization, coordination, simulation, and drawing creation. BIM software is
used not only by architects but also by contractors and fabricators.

Construction trends show that businesses are changing their methods for building residential and
complex commercial projects and integrating newer technologies. The traditional approach to
construction management is no longer viable for construction firms trying to stay competitive in
the market. A common technique to shorten construction schedules while maintaining quality is
to use prefabrication, modular, or offsite construction (Bertram et al., 2019). One type of
prefabrication is using precast concrete panels. Precast concrete structural components are the
most often used elements of offsite construction (PCI, n.d.).

2

A challenge with prefabrication is the rapid development speed of new materials, construction
techniques, and software. Precast concrete is a popular building material but has far fewer
software design options than glass materials. This chapter is about the rationale for the use of
precast concrete for the building envelope, precast concrete, prefabricated facades systems (and
its components), building information modeling (BIM), and the design automation of precast
concrete

1.1 Rationale for the Use of Precast Concrete
The building envelope can be considered one of the most challenging building elements to
design, increasing in difficulty as design teams are expected to meet aesthetic objectives while
still meeting performance standards and building regulations (Herzog, Krippner, and Lang 2018).
As more design aspects become complicated, the architecture, engineering, and construction
industries put more resources into design automation (or partial design automation) (Bertram et
al., 2019). Prefabricated façade systems, or single-source building envelopes, are gaining
popularity for quality control, workplace safety, and accelerated delivery. The single-source
building envelope is expected to reduce some risks for design teams and owners, including labor
and supply-chain issues (Bertram et al., 2019).

1.2 Precast Concrete
Precast concrete, sometimes known as "prefabricated" or "premade" concrete, refers to concrete
cast somewhere other than where it will be installed (Figure 1-1). In contrast, “cast-in-place” or
“site-cast” concrete is poured into site-specific forms and cured on site (Figure 1-2). There are
specific applications where this type of casting is ideal. For example, it would be more feasible
3

to use cast-in-place concrete for very large concrete components or foundations that can be
difficult to transport between a concrete plant or job site. It is also more typical to use cast-in-
place with small projects, as precast concrete pricing scales with the project, so smaller projects
can cost more (Precast/Prestressed Concrete Institute 2007). Cast in place can also be more
effective for one-of-a-kind castings or projects without repeating elements(Precast/Prestressed
Concrete Institute 2007).

Figure 1-1 Prefabricated Concrete Panels (Source: (Gio Valle, n.d.)
4

Figure 1-2 Cast in Place Concrete Walls (PCI 2014)

Precast Concrete is typically poured in a steel or wooden mold, often with wire mesh, rebar, or
prestressed cable (Precast/Prestressed Concrete Institute 2007). The filled mold is cured in a
controlled casting environment, making it easier to control and monitor the quality of the
material. Afterward, it is transported to a construction site and put into place (Figure 1-3). Since
the curing process happens offsite, the delivered product can be used right away, shortening
schedules on construction projects.

5

Figure 1-3 Installation of precast panels on-site (Precast Bloks 2019)

1.2.1 Benefits of Precast Concrete
There are many reasons that precast concrete outperforms cast-in-place concrete in many
situations. Precast concrete is more durable, higher quality, and more efficient than cast-in-place
concrete for most applications. One characteristic of precast concrete is its durability, which has
lent its use to create entire buildings and bridges (Precast/Prestressed Concrete Institute 2007). It
is a versatile material due to its ability to change color, texture, and size. The unique
characteristic of precast concrete also allows for buildings designs that are attractive and
functional. Efficiently is also important since one does not need to worry about scheduling
pouring concrete for a small window of opportunity on-site (a common issue is that weather
could postpone a project) (Precast/Prestressed Concrete Institute 2007). This process allows the
precast materials to be made in advance and stored until they are needed on site. This process
6

reduces the need for labor and the stress of coordinating on-site skilled labor and logistics
(Precast/Prestressed Concrete Institute 2007).

Another benefit to offsite fabrication of precast panels is installing insulation on the back of the
panel, installing windows in the face of the panel, and completing all caulking within the panel
before shipping the walls to the job site for erection. This process greatly decreases the amount
of time required on-site for facades installation by all trades.

Precast is not limited to one color or material. Some finished panels can often be nearly
completed within 24 hours. Some panels will need a finishing step, such as sandblasting, but
these types of steps do not take very much time in the days after casting. Panels are often
completed many days or weeks before they are needed to be onsite for installation. A precast
panel is typically stripped from the form the next day; 1 – 2 days are required for patching before
sandblast. Typically, a finished aesthetically acceptable panel is ready within five days of
casting.

This process allows the panels to be fully checked and prepared for transportation. Materials
such as brick and stone can also be inlayed. A manufacturing example is using brick as an in-lay
material (Figure 1-4)., allowing for a large variety of bricks that can be sourced. This method can
also be applied to the terracotta (Figure 1-5). Using this method also removes the need for
additional subcontractors on-site (PCI 2014).

7

Figure 1-4 Inlay Materials - Brick (Manufacturing Process) (Jen Levisen, Dan Stenzel, and Daniel Delisle 2021)

Figure 1-5 Inlay terracotta examples (Jen Levisen, Dan Stenzel, and Daniel Delisle 2021)
8

1.2.2 Installation process of precast concrete
Precast concrete facades, floors, walls, cores, stairs, and landings are manufactured in concrete
plants to precise standards. These pieces are cured offsite (offsite referring to not being on the
building site but at the precast plant), and logistics people coordinate deliveries to the site. Once
on-site, precasters use their cranes and crews to install the shell and core of the building. A small
crew installs the panels (Figure 1-6). In one 8-hour shift, 12–20 precast panels can be installed,
allowing the entire façade to be built on the building's structure (Clark Pacific 2022).

Figure 1-6 Pre-glazing of Panels (Precast/Prestressed Concrete Institute 2007)

1.2.3 Types of Precast Wall Systems
There are several types of precast wall systems available in North America, but most of them fall
into three categories: solid walls, thin walls, or sandwich panels (Figure 1-7). The panels can be
9

a structural wall, have a structural veneer, or a combination of both. Panels can be conventionally
reinforced or prestressed and come in a variety of colors, textures, and finishes (PCI 2014).

Solid walls are wall sections made out of solid concrete and reinforcing (Figure 1-8). Thin walls
panels are made of thinner sections with a framing system attached (Figure 1-9). They are often
used for architectural veneers and most commonly attached to a concrete or steel structural
system. Some of these wall panels systems will have insulation installed at the manufacturing
facilities so utilities can start work on-site immediately (PCI 2014). Sandwich panels, also
known as insulated precast concrete wall panels, have two layers of concrete separated by a layer
of rigid insulation (Figure 1-10). Concrete wythes that vary in thickness (depending on structural
and architectural requirements of the project) are installed to connect both layers of concrete
through the rigid insulation. This allows all the layers to act as a monolithic system when
exposed to loads (Losch 2019).

10
Figure 1-7 Comparison of three basic types of precast concrete (Precast/Prestressed Concrete Institute 2013)
Figure 1-8 Solid concrete wall (ACCG 2021)
11

Figure 1-9 Thin shell precast concrete panels attached to steel (Precast Bloks 2019)

Figure 1-10 Precast prestressed insulated sandwich panel (Losch 2019)
12

1.3 Introduction of prefabricated facades systems
Prefabricated facade systems are fabricated offsite and assembled on-site as an alternative to
traditional site-based construction. This process typically allows for shorter building times,
higher quality due to better supply chain coordination, and manufacturing in regulated factory
environments (Precast/Prestressed Concrete Institute 2007; PCI, n.d.).

Precast concrete components reduce installation time since they are ready for immediate use
upon delivery, while cast-in-place concrete is not. Using precast concrete instead of cast-in-place
concrete eliminates the unnecessary time needed to set up formwork, bend and position rebar,
pour and vibrate concrete, and then wait for the concrete to cure. Removing these steps saves
valuable time in terms of project duration and decreases labor costs (Precast/Prestressed
Concrete Institute 2007).

Prefabricated facades systems solve another common construction problem: lack of space on
site. It is a future-proof method for the increasingly busy city. Some people envision precast
concrete as dull grey concrete blocks, but it is a material that can offer unlimited design options.
There are many options, from brickwork to decorative concrete to natural stone and multiple
finishes. It is possible to make single skin precast cladding and insulated precast sandwich
panels. A precast sandwich element normally comprises three layers: inner surface (reinforced
concrete structure), insulation layer, and outer layer (façade layer) (Losch 2019). This sandwich
element is fitted with a steel frame and glazing for one integrated solution. Once this is installed,
the exterior caulking is installed around the perimeter of the panels, i.e., panel joints, and the
13

caulking has cured the façade can be considered watertight. Also, this design is coordinated with
multiple trades ahead of time, thus eliminating the need for multiple trades on site.

1.3.1 Current practices of the Steel Framework System
There are several types of options for precast concrete wall panels. The most common approach
for the thin shell concrete is to use a steel framework to provide structural support. The steel stud
support frame is normally constructed of a steel support frame, angle connections, and anchors
(Figure 1-11).

Figure 1-11 Typical Precast Panel Section (Precast/Prestressed Concrete Institute 2007)
14
The steel stud frame is made of a heavy-duty G90 galvanized steel stud frame
(Precast/Prestressed Concrete Institute 2007). The stud framing members are 16 Gauge formed
from steel corresponding to ASTM A 570-50, with a minimum yield of 50,000 psi. This allows
for fewer on-site trades and faster construction schedules. The material also allows for drywall to
be installed. The prefabricated panels consist of a 2 ¼" thick concrete skin attached to the steel
stud frame system. The overall thickness of the system is typically 7 ½", with studs typically
placed at 2’-0" on center and have 3/8" diameter galvanized steel pins welded to the frame.
These pins are embedded in the 2 ¼ in concrete skin which is reinforced by steel mesh. The
maximum size of the panel is determined by material properties, project requirements, and
delivery/shipping limits(Precast/Prestressed Concrete Institute 2013; Loesch 2019;
Precast/Prestressed Concrete Institute 2007). In the Infinite Facades system, the framing is
neither galvanized or stainless steel. Since the Infinite Facades system is a full system when it is
installed and includes the exterior caulking, insulation, drywall, and firesafing of the framing, the
framing is no longer exposed to the elements. Due to this reason, corrosion is not an issue (Clark
Pacific 2021).
The main consideration is what material can be used to avoid the risk of corrosion. Stainless steel
or suitably treated and protected mild steel is used for the frame. This selection also depends on
local building regulations. The wall construction can vary but is typically an inner skin of
gypsum plasterboard. The inner and outer skin space is filled with an insulating material such as
Rockwool to give thermal insulation and good fire resistance (PCI, n.d.).
15

The use of the stud frame construction is often the most economical and preferred method to
construct medium to large panels (Precast/Prestressed Concrete Institute 2007). A single stud
frame can be designed to support several panels with physical joints between them. Larger stud
frame panels can also benefit from the use of diagonal members to control the resulting
deflection. Serviceability conditions, especially allowable deflections, govern the maximum size
of the stud frame and how many individual panels it can support. Other limitations also include
issues of deliverability and the size of the precast bed (Precast/Prestressed Concrete Institute
2007). The frame is supporting multiple skins within the same panels.

At the other end of the scale, the use of stud frame construction can also simplify production and
the fixing of small panels, such as doing a mock corbel (Precast/Prestressed Concrete Institute
2007).

1.3.2 Typical Connection Details
The anchoring connections that connect the precast wall panels to the building frame are
important to the successful installation of precast concrete panels. The arrangement of the
connections depends on the spacing of the stud frame. An individual panel will require at a
minimum of six connections, with the process involving, at minimum, the precast fabricator,
engineer, and erector. The smaller panels will typically have 4 connection points, two at the
bottom and two at the top. The largest panels have no more than 8 connection points back to the
building.The stud frame layout of a single skin of GFRC can vary (Figure 1-12). The anchor
system for any precast concrete is quite similar. Note that all the gravity and the flex anchors
point toward the center of the panel to allow free shrinkage (PCI 2014).
16

Figure 1-12 Figure Typical Arrangement of GFRC Stud Frame (PCI 2014)

On each panel, there are flex anchors (L Shaped flexible anchors), gravity anchors (support
anchors), and lateral anchors(Precast/Prestressed Concrete Institute 2007). The flex anchors act
as lateral anchors while giving some degree of rotation and allows for possible
shrinkage/moisture movement of GFRC or Precast Concrete (Figure 1-13).

17

Figure 1-13 Typical flex anchor indicating degrees of freedom (PCI 2014)

The regular spacing of the flex anchors and the lateral anchors ensures that the effects of the
wind loading are evenly distributed over large areas of the panel. There are normally two gravity
connections (eccentric or direct bearing) located at the same elevation near the columns in multi-
level building frames and a minimum of four lateral load tiebacks (Figure 1-14). It is possible
that the gravity connections can accommodate lateral loads and gravity loads and thus reduce the
need for separate connections. This form of construction is popular when the panels are generally
flat and very large. This system allows the stud frame panels from 30 feet to 60 feet to be
manufactured, transported, and erected (Precast/Prestressed Concrete Institute 2007; Gio Valle,
n.d.).

18

Figure 1-14 - Typical gravity anchor acting as a strut and tie system (PCI 2014)

The precast manufacturer's engineers determine the need for more connections, who consider the
panels loads, articulation, and connection capacities. Additional connections are also added to
maintain alignment and reduce bowing. The connections between architectural precast concrete
wall panels and the structure must be strong enough to withstand gravity, wind, and seismic
stresses. At the same time, it must also account for the construction tolerances and the final
alignment of the panels during erection and sliding capabilities, where they are designed to allow
for seismic, thermal, and shrinkage movements. These wall panel anchoring systems often fall
into two types of connection types: direct bearing (gravity), shims (for panel edges), eccentric
bearing (gravity), and lateral tie-back (PCI 2014).

19

Additional connectors can also be added for panel alignment with respect to adjacent building
assemblies. They also can be used or not to transfer design loads. There are also lifting,
transportation, and installation hardware that can be added. These hardware's are often on the
Precast wall panels to assist with transferring the panels from the precast plant to the storage
yards, then the movement of the panels on the transportation trailer, and lastly, to lift the panels
from the transportation trailers onto the buildings.

Steel stud frames often have three leveling bolts that can help facilitate full adjustability of the
construction from the underside of the slab (PCI 2014).

1.3.3 Introduction of Infinite Facades/ Why Prefabricated Façade Systems
One special type of prefabricated façade system is the Infinite Façade System by Clark Pacific
(Figure 1-15). It is a thin shell concrete panel system connected to a steel stud back frame.

Figure 1-15 Infinite facades exploded model (Clark Pacific 2021)
20
The Infinite Façade (owned by Clark Pacific) system is a prefabricated precast building envelope
of four parts: a standard steel frame, continuous insulation, precast with integrated finishes
(terracotta, tile, stone, etc.) windows. It is currently being marketed as a "single-source solution
for the complete building envelope that meets or exceeds energy and code requirements, utilizes
a standard frame and connections while giving design flexibility” (Clark Pacific 2021). The
Infinite Facades system allows the design team to use prefabricated systems for reduced costs,
increased efficiency, and less risk while not compromising design. It is an aesthetically flexible
system; the exterior finish options are broad. There can be a variety of textures and colors with
traditional precast. Also, other materials can be used or inlayed. As of July 2020, there are over
150 standard color finishes (Clark Pacific 2021).
The Infinite Facades allow for a higher install speed while maintaining a face-sealed weather
barrier and design flexibility.
1.3.4 Precast Concrete Components – Composite Architectural Panels
The Infinite Facades system is a standardized composite architectural panel system (Clark
Pacific 2021; PCI 2014). It consists of several parts (Figure 1-16).
21
Figure 1-16 Breakdown of parts, note CIP = Cast – In- Place (Author)
It consists of
1. Architectural precast concrete is normally 30lbs per sq. ft and 2" thick precast concrete.
This concrete is 1/3 the thickness (and thus 1/3 of the weight) of traditional concrete,
which allows for lighter structural and foundation costs (Precast/Prestressed Concrete
Institute 2007).
2. Steel back frame/steel stud frame – integrated heavy-duty G90 steel frames. It is
prepared for drywall. The stud framing also means fewer on-site trades and faster
construction schedules (PCI 2014; Precast/Prestressed Concrete Institute 2007). For the
Infinite Facades, it is typically not galvanized unelss it is explosed in the final condition
of the building (Clark Pacific 2021).
3. Factory installed insulation
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4. Factory installed windows
5. Panel joints – Joints to connect to the steel frame or other standard connections
6. Anchors (flex, gravity, lateral pins)
a. Flex anchors – Conventional type of flex anchor consists of a bent bar welded to a
steel plate. The flex anchor is then bolted to a vertical member of the stud frame.
Conventional methods include using a captive nut that is hand tightened or a
specially bent bar that is threaded through a vertical slotted hole and rotated 90
degrees (Clark Pacific 2021).
b. Gravity anchors – Conventional type of gravity anchor is made of two betn bars
welded to a vertical steel memebr of the stud frame. It acts as a 'strut and tie
system. Precast concrete panels are very rigid and will not allow a reliable
distrubution of gravity loads that is more than two bearing points. These bearing
connections are located at the same elevation so deflections of supporting frame
members do not cause distribution of gravity load different than planned (Clark
Pacific 2021).
c. Lateral pins- Deal with lateral loads (Clark Pacific 2021)
7. Concrete connections

a. Connections include any elements used to make the attachment of the unit to the
structure and will consist of parts that are embedded in the concrete and parts that
are field installed(pieces known as a connector) (PCI 2014). Connections include
items such as the cast-in-place (CIP) floor slab connection (Figure 1-17).
23

For the Infinite Panel system, in the base model, the concrete is flat 2 1/4" thick with a ½" deep
max reveal (Clark Pacific 2021). There are also special designs that allow articulation up to 4"
total skin thickness except at returns. This is different from the typical weight of typical 6"
Precast concrete panel fabrication at 70-75 PSF (Precast/Prestressed Concrete Institute 2007). As
the profile thickness of the panel increases, the weight will increase, and the effective square
footage of the panel because of the increased same frame size. Medium weight aggregate face
mix will also increase with the panel weight at about 20 PSF.

There are many advantages of using lightweight panels. For example, on multi-story steel
structures, there are dramatic reductions in the amount of steel required in a building structure on
Figure 1-18 Cast in place concrete connection (Author)

24
multi-story steel structures. This reduces the size, weight, and cost of the building foundation,
beams, and columns (Precast/Prestressed Concrete Institute 2007; PCI 2014).
It is also important to note that on steel frame structures, the support brackets for the precast
concrete connections (such as the gravity and lateral support brackets) should be shop welded to
the structural steel columns using the precaster's drawings rather than being field welded
(Bertram et al. 2019).
1.4 Building Information Modeling (BIM)
The US National Building Information Model Standard Project Committee has the following
definition for Building Information Modeling:
“Building Information Modeling (BIM) is a digital representation of the physical and
functional characteristics of a facility. A BIM is a shared knowledge resource for
information about a facility forming a reliable basis for decisions during its life cycle,
defined as existing from earliest conception to demolition” (States 2014).
A benefit to using BIM is greatly improved with better information management and business
process re-engineering to create standard information exchanges between the stakeholders. It can
be used for various purposes such as energy simulation, clash detection, cost evaluation, facility
management, and structural analysis.
25

1.4.1 Popular BIM-related Software's
Many BIM-related software programs exist in the market, including Revit, Bentley, Vico, and
ArchiCAD (Table 1). The choice of software comes down to most common markets,
interoperability, and supported functions. Revit is the most common one used in the United
States (NBS 2019).

Table 1-1 Overview of popular BIM software solutions in current market (Eastman et al. 2008; Smith and Tardif, 2009)
26

1.4.2 Revit vs. AutoCAD
Revit is a design and documentation BIM-based platform supporting the design, drawing, and
schedules (Autodesk.com) (Figure 1-18). Revit has been widely used in the AEC industry to
support all phases and disciplines involved in a building project (Autodesk.com). It also allows
users to create new features for existing functions and customize their workflow by building
plugins via the Revit API and SDK or by coding visually in Dynamo.

Figure 1-19 Revit Interface (Author)

Revit is a building information program, while AutoCAD is a CAD system. They are
fundamentally different in that BIM software is based on components (like windows, doors, etc.)
in one building database, whereas CAD is a drawing tool based on lines, circles, etc.
27

Autodesk Revit is a BIM solution used by architecture and construction firms to design floor
plans. It is popular for collaboration with professionals across different disciplines and can also
be used for construction management for the entire life cycle of a construction project (NBS
2019). Tekla Structures is another BIM software that is used for modeling structures. Other
software exists but not used as much.

The building information model is object-oriented. BIM is based on the objects of components
such as walls, doors, and windows, unlike other 3D modeling software focused on geometry
(Kensek 2014b). Each component has its own set of parameters and information, resulting in a
comprehensive and well-organized database for the buildings that can be utilized to execute
various simulations throughout the early stages of design. Using an object-oriented method to
build the project model often saves time and effort for the architects and engineers because they
do not need to spend as much time on 2D documentation since it is relatively straightforward to
produce this from the 3D models. Another benefit is that this object-oriented method allows
clash detection in tools like Navisworks to check and correct the clash between components.
This also reduces the chance of rework for the construction team.

A main characteristic of BIM is the high interoperability, or ability to do data exchange, between
different BIM software tools. Avoiding remodeling in other applications saves time and assures
correctness (Eastman 2008). Although the transmission of information is theoretically
conceivable, there are still several issues with the interchange of BIM data across software
systems in practice. One feature of all software is that they must support some method of moving
28

data between software programs for collaboration. For BIM, the Industry Foundation Class (IFC)
formats were created to make it easier to transfer data from a BIM model to programs such as
energy modeling software, sequencing software, and operations and maintenance (O&M)
software.

For example, a typical IFC workflow could be the following:

An architect creates their design in software such as Revit and exports an IFC version to share
with the consulting engineers. The HVAC engineer can reference the IFC file in their software
and use this for coordination. An energy simulator can also use this model as a basis for energy
analysis. The IFC provides enough information for the software to read and analyze the spaces in
the referenced model.

Integrating BIM into precast panel design can help shorten the time to fabricate precast panels
and create higher accuracy (Austern, Capeluto, and Grobman 2018b; Dritsas 2012).

Another feature of most BIM software is the ability to create customized tools or plug-ins within
the software.

1.4.3 Revit API and SDK
The Revit Application Programming Interface (API) is a set of tools that allows users to
customize command functions, add new features to the software, and create custom plugins
(Kensek 2014). Revit API integrates the parametric modeling and programming function
29

allowing users to manipulate and customize Revit elements using the algorithm and
computational logic (Yang, Koehl, and Grussenmeyer, 2017). Revit API allows users to program
with compliant languages like C#, C++, Python. The most popular language used in API is C#
and most of the code samples are written in Visual Studio (Figure 1-19).

Figure 1-20 Visual Studio setup showing C# for Grasshopper API (Author)

The advantage of the Revit API is that it saves time by automating repetitive manual tasks or
merging all related parts into a single interface. There are potentially hundreds of Revit API
plugins that have been built for sale and only for usage in an office. Lumion, Enscape, FBX
Review, Flux, Coins Auto-Section Box, Palladio X BIM Windows Layout, CTC Express Tools,
and BIM Track are some of the programs available (NBS 2019). Examples include rebar
30

modeling automation for Revit that was introduced by AGACAD (Figure 1-20) (BFT 2020).
Another third party tool is Edge Revit which aids the creation of single assembles for precast
concrete shop drawings (AU 2016). IMPACT, a software by StrucSoft, models solid wall precast
projects (Figure 1-21).

Figure 1-21 AGACAD Rebar Modeling Automation, paid service (AGACAD 2020)

31

Figure 1-22 IMPACT plugin showcasing standard precast structural elements (StruSoft)

There are several options that uses the Revit API that can be combined in principle in order to
make a mockup of a proper functioning precast concrete panel plugin.

Two examples of specialized plugins are the use of the ACAGAD plugin used for steel framing
and a plug-in to place families.

The first example is ACAGAD Metal Framing Suite (Figure 1-22). Metal Framing Suite makes
designing the primary structures of light-steel framed buildings. Revit® users may build multi-
layer, metal-framed walls, floors, and roofs, as well as prefabricated panels, rafters, and trusses,
32

with this powerful and adaptable BIM program. It also generates correct bills of materials and
shop drawings and views with automatic proportions for wall panels or segments.

Figure 1-23 Metal Framing (AGACAD 2020)

In the Revit API, it is possible to create a Revit window family online using Design Automation
for Revit API (Figure 1-23) (Autodesk Forge 2020).In this example, a user selects the different
window styles which prompts the different families types. This leads to the family name file and
output file. After that, the user clicks “Create” and the rest will be done with Design Automation
for Revit API.

33

Figure 1-24 Plugin for Revit families (Forge)

1.4.4 Dynamo
Dynamo is an open-sourced visual programming tool in Revit. It is a built-in visual
programming tool using Revit API in a graphical way. Users interact with the elements in
Dynamo is called "nodes." Each node has several "ports" acts as inputs and outputs (Figure 1-
16). The ports enable interaction within different nodes along "connector." In order to connect
two ports, the types of outputs ports should match with the type of input ports in the node needed
to connect (Kensek 2014). There are many built-in nodes and customized packages online. Users
can also create their own nodes by programming in Python script.

34

Figure 1-25 Dynamo Layout (AGACAD 2021)

Dynamo is more user-friendly and easier for people who have no programming skills than Revit
API. However, because Dynamo is a subset of the Revit API, it will fail more frequently while
doing complex operations. It is also less stable than working directly with the Revit API. One
example of using dynamo for a precast application including add grout tubes (Figure 1-25) and
reinforcement detailing (Figure 1-26).

35

Figure 1-26 Adding grout tubes to precast walls using Dynamo (Autodesk Solutions 2018)

Figure 1-27 Reinforcement opening around wall opening using Dynamo (Autodesk Solutions 2018)
36

Dynamo was also used by Dieter Vermeulen at Autodesk to show how it could be used for
automatic rebar creation in walls (Figure 1-27) (Kensek et al. 2017).

Figure 1-28 Automatic rebar generation (Kensek et al. 2017)

The Dynamo script allows the user to select the rebar type and assign the number or spaces
between rebars (Figure 1-28).

37

Figure 1-29 Dynamo script workflow for automatic rebar generation (Kensek et al. 2017)

1.5 Design Automation of Precast Concrete / Main Challenges of Widespread Precast
Concrete
From a designer's standpoint, one of the challenges of creating precast concrete facades is that
the designer must envision the erection process to utilize precast concrete successfully
(Sheikhkhoshkar et al., 2019; Maloča, 2016).

There is currently a lack of software to efficiently design the steel back framework and
connections for precast. The process is currently being the slower process of CAD. There is a
huge data disconnect from design to manufacturing since the current process is a 3D model
converted into 2D drawings. Compared with the traditional building industry, façade design
engineering is mostly based on custom manufacturing in plants. It is an industry that is forged
through the close combinations of both building and industrial manufacturing.
38

A possible solution is creating a BIM 3D plugin to help model the parts for a precast panel. The
technology can help automate developing panel fabrication drawings by programming the plugin
to framing rules. Hopefully, creating an accurate 3D model can be used to semi-automate the 2D
drawings that can be sent to the cutting machines in the plants. This will allow fabricators to plan
ahead and easily create more components offsite, resulting in increased productivity and lower
construction costs.

1.6 Summary
This chapter is about rationale for the use of precast concrete , precast concrete, prefabricated
facades systems, building information modeling (BIM), and the design automation of precast
concrete.

The different building components of precast concrete panel has been introduced and the basic
API interface for Revit. The use of Visual Studio is discussed to interact with the Revit API to
create a plug-in in order to increase the functionality of the software. Alternatively, the use of
Dynamo and its visual programming language is also introduced. There exists a lack of software
to design the steel framework and connection for precast concrete. There is currently a data
disconnection from design to manufacturing where a 3d model is converted to 2d drawings. A
possible workflow to help aid the design of precast panels is to leverage the use of the building
information model in order to detail the precast panels.

39

The next chapter looks into the literature review on rationale of using precast concrete, precast
concrete, prefabricated façade system case study, building information modeling (BIM) / case
studies, and design automation of precast concrete.

40

Chapter 2 LITERATURE REVIEW FOR THE PRECAST FRAME DEVELOPMENT
Designing a plugin to help with the design of the precast back frame requires an understanding of
the manufacturing of precast concrete and the application of BIM tools and Revit programming.
This chapter looks into the literature review on rationale of using precast concrete, precast
concrete, prefabricated façade system case study, building information modeling (BIM) / case
studies, and design automation of precast concrete.

2.1 Rationale for the Use of Precast Concrete / Precast Concrete Automation Potential
Concrete is well suited to produce free-form geometry due to the liquid properties. Currently,
most thin shell concrete panels are flat and rectangular. GFRC is used if there is a non-
rectangular profile. However, with the vicious materiality of precast, it is possible to create
complex geometries with normal precast. To create the full range of complex geometries of
precast panels, complex 3D molds are required. These molds are normally made using milled or
hot-wire cut EPS (Expanded Polystyrene) or CNC cut, bent plywood sheets. These methods
create a large amount of waste and machine time, which have tempted others to devise
alternative fabrication techniques such as reusable, flexible molds (Hawkins et al. 2016). While
there are many proposed benefits of this technology, Hawkins reviews also claim that there are
several reasons that prevent the industry to adopt flexible models such as geometric constraints,
modeling issues, and uncertainty. Another method that to get rid of the formwork is to use 3D
printing. The industry has been using basic 3D printing techniques to create simple 2D
extrusions but have not been developing to produce complex geometries (Hawkins et al. 2016).

41

2.2 Precast Concrete
There are several methods to design precast concrete panels. The range of precast panels can
vary greatly from different precast plants depending on the skill sets of the precasters. Other
factors include limitations on the side of the bed size where the panel can be fabricated. The
precast shop bed size affects the size of the components that can be created. The location of the
precast plant and the ease of acquiring materials is also factored in when designing precast
concrete panels. All precasters also have has their own methods of dealing with different types of
systems and building codes.

2.2.1 Fabrication methods of precast concrete
While physically it is possible to create complex geometry using precast concrete panels, it is
important to also be able to replicate this geometry in a computer to be able to use its data. It is
important to study the difference between a computer model and as-built product.
At Israeli Institute of Technology, a case study optimization project was done in looking to
improve the feasibility of different geometry with a time-frame suitable to building industry with
minimal changes to the initial design (Austern, Capeluto, and Grobman 2018a). The result was a
Grasshopper plugin tool. Grasshopper was used because it is widely adopted in the modeling
environment. The tool output provided designers with fabrication estimations. The estimations
were tested on fabrication scenarios and shows a close similarity to the actual performance of
CNC milled molds. The ten panels were compared the performance to real fabricated setups. The
test showed average errors in 5% in all the measured criteria. Deviations came from differences
in standard milling practices. Through several iterations, the author said that the "numeric nature
42

of digital fabrication techniques has made it possible to embed fabrication awareness into the
computational design process" (Austern, Capeluto, and Grobman 2018a).
The authors researched using a fabrication evaluation method. Mathematical abstractions were
used to calculate material use, flexibility, and machine time required to fabricate a geometry
(Figure 2-1). The general structure of their workflow was the following:
1. NURBS geometry input – This is done via Rhino and Grasshopper to create fabrication
paramters such as design telorence, materiality, dimensions. In the interface of GH, there
is also analysis tolerance which is done through distributing sampling points on the
surface.
2. "Dual Analysis of the input geometry as a NURBS surface and a half-edge mesh" -
The NURBS geometry is analyzed using a freeform geometric modeling environment
known as IRIT. This is used to pull out the different curvature values related to the
sampling points. These points are also used to create a surface that is a "half-edge mesh
representation" that shows the local condtions around the sampling points.
3. Translation of the geometry into molds – This is an automated process. The geometry
is translated into molds by using the material parameters and the fabrication process. This
is to replace the lengthy translation into CAM software. The molds are then used to
estimate the material use and the machine time (next step)
a. Feasibility Evaluation: The feasibility of the molds made from bent sheets is
evaluated using sampling points. The feasibility of mill molds is evaluated with
the curvature ratio and half-edge-based representation. To check the feasibility of
hot-wire cutting, concave double curved points are disqualified. This is because
43

they will not be accessible with a wire. Additionally, a line is rotated around the
sampling points until there is an accessibly points.
b. Matching Estimations: A rapid extreme point heuristic is usd to estimate the
matching time in sheet material cut. Different formulas were use to calculate path
length into machine time, accoutn materiality, and avaliablie tooling.
4. Used mathetmatical approximations to estimate feasbility and machine time –
Currently utilied in the industry, having reliable estimatations save significational
computatonal resources in simulating machine behavior.
5. Numerical and Graphic Display of the Results (Figure 2-2)

Figure 2-1 Diagram of the suggested evaluation method (Austern, Capeluto, and Grobman 2018b)
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Figure 2-2 Optimization results: original shape (top), and optimized results (bottom), the numbers in red denote the relative
percentage from the needed improvement (Austern, Capeluto, and Grobman 2018b)

2.3 Prefabricated façade system case study (Case Study)
A project that is currently being marketed as a timesaver by Clark Pacific is the new South
Village at California State University, Los Angeles, it is the campus's first traditional-style
student dormitory (Figure 2-3). A large plaza and garden surround the 380,000 square foot dorm.
The location adjacent to the Long Beach Freeway and surrounded by other school facilities
presented logistical, safety, site management, and material delivery issues. To keep on schedule
and on budget, traditional construction was substituted with a prefabricated building facade
supplied by Clark Pacific. Furthermore, because the project was built early in the pandemic, a
prefabricated method decreased the number of employees on-site, allowing the CDC and
government to meet their requirements. The Infinite Facade from Clark Pacific is made offsite in
a climate-controlled facility, which improves quality and consistency.

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Figure 2-3 CSU LA Student Housing (Clark Pacific)

The project uses a six-panel setup that is rotated to provide flexibility in the design while
decreasing multiple panels (Figure 2-4).

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Figure 2-4 CSU LA Student Housing Six Panel Setup (Clark Pacific)

For the building envelope, Clark Pacific's Infinite Facade was chosen. The Infinite Facade
employs the standard frame and connections while meeting or surpassing building and energy
code standards, allowing the architect to create their design. The architect may freely design their
concept using a variety of external treatments, colors, textures, and form liners. The architect
imagined a 'dynamic' facade that resembled a play curtain with movement created by the sun's
shadows and angles.

This project had 60 different panels on this entire project but only six different form setups. In
order to achieve high aesthetics and the appearance of randomness, they were able to move
around these vertical reveals by adding a panel on top of one window (to remove the bottom
panels) and then moving the windows boxes again. Each of the 60 different form setups was
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documented using a drafting workflow (AutoCAD) versus a modeling workflow. When any
changes to the design or structural requirements were made, the drafter had to restart the entire
documentation process for the specific form setup. When working in a (3D) modeling workflow,
changes to the Model update the entire 3D visualization and reconfigure established
relationships, dependent elements, or data points. For example, if a wall was moved in a
modeling workflow, the wall location moves in plan and section. In a drafting workflow, if a
wall is redrawn in a new location, the location of the wall in plan and section is not automatically
updated. The plan and section will need to be redrafted. This highlights one benefit of using a 3D
modeling workflow versus a 2D drafting workflow.

2.4 Building Information Modeling / Case Studies
If an architecture firm is not simply using old-fashioned hand-drafting or using a straightforward
type drafting software like AutoCAD, they are most likely using a modeling method by using a
three-dimensional design software with building information modeling (BIM) features.

BIM is an information technology-enabled approach that can reduce modeling errors and allows
for design integrity, virtual prototyping, simulations, distributed access, retrieval, and
maintenance of the building data. BIM is more an extension to Computer-Aided Design (CAD)
for design disciplines. For non-design disciplines, it is perceived more as an intelligent Data
Management System (DMS) to take off data quickly and directly from CAD. While there are
evident overlaps, BIM application vendors aim to integrate the two requirements. Most recently,
CAD packages such as ArchiCAD and AutoCAD have adopted the object-oriented approach
with certain capabilities borrowed from the contexts in which object-oriented design has a more
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established history. Major BIM applications such as Bentley MicroStation and Autodesk Revit
have also started including tools and capabilities which can be developed further to facilitate
fully parametrized object-oriented design and production. However, such attempts, although they
have provided a broad range of potentials (Poorang Piroozfar* 2019).

Usually, the use of Revit software for architectural design is achieved through the menu or
toolbar commands, while Revit also provides application programming interface API, so that the
external program through API can manipulate and access Revit. API.NET is API Revit, so as
long as the.NET Framework Microsoft 2 compatible language can be fully invoked API, such
as VB.NET, Visual C# Microsoft language. API Revit provides access to the various functions
of Revit, the integration of analysis and visualization applications and building information
model, users can expand the Revit corresponding functions according to their own needs, and as
a software developer can also be achieved at any time to access all information models, query,
change component properties and create new components" (Nan et al. 2016).

2.4.1. Benefits of using BIM
While BIM has offered some advantages, without it, the AEC (architecture, engineering,
construction) industry would not have been able to respond to the level of project complexity,
accuracy, and timelines as it does now. However, it still has its own disadvantages (Eastman
1977). This includes

• Increased building performance and quality
• Improved collaboration using integrated project delivery
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• Earlier collaboration of multiple design disciplines
• Use of design model as the basis for fabricated components
• Better implementation of lean construction techniques (Poorang Piroozfar* 2019)

A clear account of BIM advantages is provided by FMI/CMAA 2007 Eighth Annual Survey of
Owners. Those advantages which can be extrapolated to what customization (with respect to
product platform and configuration) can support include the following:
• Broader strategic perspective and innovation
• Easier to achieve process standardization
• More reliable compliance with specifications and regulations
• Improved communication and collaboration amongst project participants
• Greater productivity from
• Decreased labor costs (Poorang Piroozfar* 2019)

2.4.2 Using BIM in the Fabricating Process/ Introducing Fabricators in the Design Process
One of the issues facing today's architectural designers is the construction of the digital
workflows between design and fabrications. To navigate this successfully, designers need to
understand the production, methods, and tools. A good way to introduce constraints is to involve
fabricators early in the design process (Larsen and Schindler 2008). Though fabricators are
normally only introduced after the design is approved, making the design much more difficult to
change. Thus, researchers are constantly looking for methods to incorporate fabrication
information during the design process without limiting the designer's freedom (Pottmann 2010).

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One of the methods to rationalize a design is by using computational methods to simplify the
form. In this method of rationalization, the initial design is arrived at without looking into the
specific fabrication constraints that come with the materials. An optimization algorithm is then
used to adjust the geometry to better fit a fabrication method (Austern, Capeluto, and Grobman
2018a). An example of this includes Frank Gehry's Louis Vuitton Foundation Museum, where
the glazing was done according to the fabrication constraints of the rolling and bending
techniques (Figure 2-5). Another example of how sheet materials can be optimized to minimize
minimal waste is a CNC cut sheet material pavilion.

Figure 2-5 FLV Curved Glazing Automation, Parametric Instantiation and Frequency Analysis (Inocente 2018)

These examples look at using an initial design as the base geometry and using computer
algorithms to achieve a specific fabrication goal. This method is an established workflow of
architectural practices in firms such as Frank Gehry and Zaha Hadid. However, studies show that
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this is hard to implement and computationally expensive (Dritsas 2012). This research aims to
find easy-to-implement computational procedures that today's professionals can use.

2.4.3 From file to factory
A "file-to factory" is speculation on creating an "almost automated process from design to
construction on site" (Kaiser, Larsson, and Girhammar 2019). The project looks if there is a way
to create a “file-to-factory” type of computer technology that will streamline the building process
and increase the building performance. A series of stacked multi-story timber buildings are used
as templates that is fed to an algorithm in order to create a factory-produced timber ground-
scraper.

This paper uses data-to-site feedback loops. The idea is stripping data from a several projects and
feeding it in an algorithm that learns different details of a project. In this example, it looks at
different versions of modular timber buildings and figures out the relationship of the design of
the building to the environmental and contextual factors. The purpose is that the algorithm loop
can help the user create a large-scale version of the project and generate construction drawings.
It relies on the idea that machine learning and artificial intelligence could influence the speed of
this process.

Technology advances have influenced the tectonics of timber structures from the artisanal
"wooden age" to today's "digital aid." Having established that the "ability to control machines
with the help of a computer code eliminates the need for serial production," the authors continue
to explain that the easy machinability of wood "makes it an ideal material for digitally controlled
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processing portals," which has led to timber "taking on the status of a high-tech material" (Buri
and Weinand 2011) Kaiser also talks about adding to the digitally controlled processing of high
tech materials is possible because different systems can communicated with each other, and thus
we end up with process where computer-aided manufacturing (CAM) and computer numerically
controlled (CNC) technologies can be linked to parametric design software (and the possibility
of real-time site data). This would create full file-to-factory operation. (Kaiser, Larsson, and
Girhammar 2019). New fabrication methods allow new structures, new ways of using these new
structures, and thus new architecture.

The file to factory process is particularly appealing because it is a production strategy that allows
for mass customization. Mass customization is defined by Anderson as "the ability to design and
manufacture customized products at mass production efficiency and speed" (Anderson, 2003).
Engineered timber is used in this example, but the somewhat regime and systematic design of
prefabricated precast concrete panels lends well to this system. This could technically allow
someone to design a building constructed from precut and fabricated elements to an architect's
specification offsite. Thus, everything must be to the architect's specifications and the design
must be finished when it leaves the architect's office.

2.5 Design automation of precast concrete
As mentioned in Chapter 1, there is not one third-party software that can fully automate the
modeling of a precast panels. The closest third party softwares, such as AGACAD and
Edge^Revit focuses on solid wall concrete panels.

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2.5.1 Automated planning of concrete joint layouts with 4D-BIM
The task of the façade engineer is to manage and apply these constraints to obtain the best
possible design. Concrete pouring is considered a critical path activity in construction and
requires meticulous planning to ensure both the aesthetic and structural integrity of the
joints(Sheikhkhoshkar, Rahimian, and Kaveh 2019). This study looked at using a developed
structural Revit model, extracting spatial information in Microsoft Excel and MATLAB using
Dynamo (Figure 2-6).

This developed Revit plugin in this study shows a shift towards a 4D BIM application for
designing concrete structures. Concrete planning is a major construction milestone in a
construction schedule that is often affected by design limitations, structural considerations, and
on-site operational constraints. Due to this, it is important to have meticulous planning to ensure
the structural strength and aesthetic of the concrete. Failure to adequately plan concrete pouring
can lead to structural defects; The system is a prototype integrating real-time joint layout
planning. This process should improve the integration of a structural design process and ease
decision-making prior to the construction phase. It should also reduce structural damage caused
by operational shortfalls and supply-chain issues. The current study shows that limitations still
need to be studied. There are areas where the system can be improved by adopting machine
learning, sensors, and data science methods (Sheikhkhoshkar, Rahimian, and Kaveh 2019).

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Figure 2-6 Design Logic of Concrete (Sheikhkhoshkar, Rahimian, and Kaveh 2019)

2.6 Summary:
This chapter investigates the literature review on rationale of using precast concrete, precast
concrete, prefabricated façade system case study, building information modeling (BIM) / case
studies, and design automation of precast concrete.

There are currently several methods to create a precast panel. For example, complex geometry
can be made using specialized molds. There are developments in comparing the 3d form versus
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the built form in these geometrically complex forms. For examples, grasshopper can be used for
NURBS geometry to rationalize paneling of a façade skin.

The CSULA building by Clark Pacific is made out of rectangular panels. The project uses a six-
panel setup that is rotated to provide visual interest to the project. This is an example of a project
that uses a steel back frame. The design and engineering of this back frame was tedious as each
panel was drawn using AutoCAD. A series of paper were looking at the benefits of using BIM.
Building information modeling allows better collaboration between trades and the use of the
design model for fabricating. The benefit of using a design model is that the file can be used for
other processes. For example, a timber project was analyzed to be used as a template for other
timber projects. Another study looked at using the structural model and extracting the data to
create a schedule for scheduling the joint level.

Some common types of precast panels use a steel back frame. The design and engineering of
this back frame can be tedious and time-consuming. Creating a software tool to assist in this
process might be helpful to professionals in the precast industry. This tool could be linked to
building information modeling software. The integration of the back frame with BIM can semi-
automate specific steps of the back frame design process. This might reduce errors (when
compared to the drafting method) and create a more accurate model that can be used to create
construction drawings. This next chapter introduces the overall workflow for creating the Revit
plugin including model preparation, material requirements, structural back frame, and
construction documents.
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Chapter 3 METHODOLOGY

This chapter introduces the overall workflow for creating the back frame and sheet tool plugin.
This chapter is about the methodology, research, planning, programming, validation, back frame
plug-in methodology (current versus proposed), back frame methodology (proposed), and the
sheeting tool methodology. Both plugins use a four-process workflow: research, planning,
programming, and validation. In the back frame research process, it includes research the precast
process through interviews, publications, and visiting a precast plant. After gathering information
about the back frame process, the planning stage consists of creating of materials to make one
complete building information model. This includes items such as Revit families, templates, and
material information. Drawings that are procured during the research stage are analyzed for their
rulesets. After creating the necessary objects in planning stage, these items need to be
programmed using C#. The Revit API is setup using Visual Studio. The plugin will load the
created items from the planning stage, such as the families and template. Code will be written to
reference the geometry and create rulesets. A user interface is also designed and implemented in
order to guide the user through the use of the plugin. In the validation process, the final
construction documents produced by the plugin will be compared to those done by experts for
analysis. The code will be revised.

The sheeting tool also uses a four-process workflow: research, planning, programming, and
validation. During research, typical documentation and construction drawings will be retrieved.
During planning, items that will be needed for the sheeting tool such as titleblocks, dimensions
styles, and a 3d model will be acquired. Afterward in the programming stage, Visual Studio will
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be used again with the Revit API in order to reference the 3d geometry model. The plugin will
create multiple elevations of the model and lay out the drawings onto sheets. In the validation, a
comparison of the built drawings and the plugin drawings will be compared.

Chapter 4 will explain the C# code written to create both plugins.

3.1 Methodology Overview
Currently, Infinite Panel back frame design is a manual and cumbersome process. Since it uses a
drafting workflow, the drawings can quickly become outdated when design revisions or
structural revisions. Due to the current engineering design method, the work is slower than
possible, can have mistakes, and can lead to missed opportunities. To overcome these
disadvantages, a software plugin might work. The plugin could semi-automate certain steps with
the aid of a design engineer.

The process for the main tool is done in four main parts: research, planning, programming, and
validation (Figure 3-1). The second tool, which is a tool that helps layout the 3d model, has a
similar methodology (Figure 3-2).
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Figure 3-1 Methodology diagram for main tool (back frame tool) (Author)

Figure 3-2 Methodology diagram for sheeting tool (Author)

3.2 Research
It is important to understand the process of creating a precast panel from design to completion.
To obtain this information, interviews will be conducted, and on-site observations of both the
engineering and construction process will be documented. A detailed step-by-step back frame
design is recorded.
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Drawings are also requested in order to compare the plug-in drawings versus the traditional
method drawings. Clark Pacific, a leading manufacturer of precast and prefabricated building
systems will be contacted to seek their expertise and advice about how the process currently
works and what ideas they might have for improvements. Their Southern California fabrication
facility is within driving distance of USC and allows for on-site observations. Clark Pacific is
able to bridge the gap between construction and manufacturing by designing, manufacturing, and
constructing prefabricated building systems. Visiting an existing precasters allows one to watch
and learn the steps.

Several interviews will be conducted via video conference calls since the design, facades
engineering, and structural teams are located in different offices. This research was done during
the pandemic. While studying the current process, create a step-by-step written guide on how the
work is currently done. This written guide is to be approved by several professionals with
different roles in the company. It was useful to identify which steps are the most challenging and
valuable and make these the priority element, understand if there is any “domino-effect,” and
identify steps that are not capable of being coded in the plugin.

3.3 Planning
There are several versions of prefabricated panels that vary depending on the manufacturer.
Clark Pacific currently has two products that use a back frame, GFRC and Infinite Panels. The
Infinite Panel system is a more standardized shape and is a complete building envelope system
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that exceeds current Title 24, sound, water, vapor, and fire code requirements. The California
State University Los Angeles project (introduced in Chapter Two) shows how it can be used.

There is a need to identify which type of system would be the best to partially automate. A
drawing set needs to be procured and diagrammed to understand the relationship between the
frame and panels/openings. The diagramming process will also help identify the different types
of panel sizes, HSS member types, opening types, connection types, and openings sizes.

3.3.1 Preparing Revit Native Geometry
One of the main outputs of the plug-in is the creation of a completed 3D model of a panel. This
consists of a precast panel, modeled connections systems, and a steel framework made of HSS
members.
It is assumed that the bare minimum a precaster can receive is a pdf file of drawings. They can
also receive 2D AutoCAD dwg floor plans that can be linked into Revit and use to model. The
best is a 3D model of the building created in Revit with basic walls, openings, and floors. There
can also side context made through direct modeling or importing the site from other software
programs.
A completed 3D model of the building containing basic walls, openings, and floors is created in
Revit to represent what would be the bare minimum received from an architecture firm.

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3.3.2 Preparing Revit Native Geometry – Families
In Revit, families are developed and built because of the reusability of components in multiple
projects. This allows architects, engineers, and contractors to re-use the same object in multiple
projects. This is advantageous in time, effort, and cost savings.
Families in Revit come in three types: system families, loadable families, and in-place families.
Most elements used in projects are system families or loadable families. The loadable families
can be loaded in one another/grouped to create nested and shared families. If there is a custom
element or a non-standard, then an in-place family is a better choice to use.

System families include basic elements one would assemble on a construction site. Common
examples include walls, roofs, and floors. They are predefined in Revit. The composition of the
walls and floor will need to be designed in Revit.

Loadable families are used to create building components (e.g. windows, doors, furniture),
system components (e.g. normally items installed in and around a building like a water heater or
a plumbing fixture), and annotation elements. Pieces of the panel that will be used in the loadable
families include windows and openings.

In-place elements are unique elements that are specific to a current project. They are created in
the project and dependent on the geometry of the model. This can include items such as custom
gutters, built-in furniture, or a special trim.

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For this plugin, the focus is on scalability and repeatability. Therefore, only loadable families
and system families are used. Loadable families are highly customizable in nature and are
created in external RFA (family files that are created on the hard disk of a computer). They can
be imported and loaded into projects. One loadable family can contain many types, in which can
be used to create type catalogs, which allows user to load only the type need for the project. For
example, there can be one single-flush door with many different types/sizes (Figure 3-3).

Figure 3-3 Door family showing multiple options (Author)

3.3.3 Preparing Revit Native Geometry – Family Flexing
When creating families in Revit, creating family parameters will allow flexing of the family.
Using the family editor, creating label dimensions and flexing the dimensions create a parametric
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relationship in the family. It is also possible to lock these dimensions to enforce these constraints
in the finished design. By using the family types tool, it is possible to create many types or sizes
for a family (Figure 3-4).

Figure 3-4 Family type designer (Author)

3.3.4 Preparing Revit Native Geometry – Titleblocks
Using the sheet composition command in Revit, a titleblock family is created.

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3.4 Programming
After creating the native geometry families in Revit. All of the these Revit components (walls,
floors, openings) will needed to be collected in a folder. This folder or dictionary will be need to
be packaged so it will come with the plugin.

Out of the box, Revit provides an amazing set of tools to develop and document complex
building models. To extend the functionality of Revit, these tools can be extended by using the
existing Revit Application Programming Interface and creating plugins with C# (Figure 3-5).

C# (pronounced as "C Sharp") is a general-purpose, modern, and object-oriented programming
language developed by Microsoft within the .Net initiative. C# is a popular language and used
for developing web applications and desktop applications. There currently exists copious
amounts of resources and support on the web. Also, as part of the .Net Initiative, C# written
applications run on the .Net framework (Autodesk 2019).
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Figure 3-5 Visual studio script showing how to place a group in Revit (Author)

3.4.1 Programming – API Setup
An API, or application programming interface, is a set of operations provided by a piece of
software, web application, or web service that allows other applications to interact with them.
This allows for different applications to talk with each other.

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A common way of thinking about an API is like a waiter in a restaurant. The kitchen is the
application, like Revit, and the customer is an external application. The only (logical) way to get
food from the kitchen is through the waiter (or API). For the customer to get an item from the
menu, request it via the waiter who would go to the kitchen, retrieve the article, and then bring it
to us. API's work in the same way (Figure 3-6).

Figure 3-6 Revit API (Author)

Revit is the platform selected since Revit is a popular software used by architects. Visual Studio
is one of the powerful coding and debugging tools. It has the ability to import Revit dll file,
which includes all the namespace and functions of Revit API, and helps users to code easier.
Also, Visual Studio allows users to debug by running Revit inside it, which helps users to
quickly find problems.

The Revit API comes with Revit and allows us to create applications with Revit through classes
and methods accessed through our plugins. For example, if one wanted to create a view from our
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plugin, one would access the view class in the Revit API and call the constructor methods to
construct a view.

The Revit API (application programming interface) is a library that developers can use to
integrate applications in Revit. It provides the codebase that interacts with Revit by making
calls/commands through methods that are provided by the Revit API. The Revit API supports
any language that is compatible with the. Net framework such as C#. By being able to access the
Revit API, developers can integrate new applications with Revit and extend the capabilities of
the software beyond the pre-installed functions.

3.4.2 Programming – Visual Studio API Setup
In order to develop plugins, it is necessary to use an IDE or an Integrated Developer
Environment. This is an environment where code can be written and is essentially a tool that
assists in writing and testing software. For this, Visual Studio Community 2019 will be used.
This is a free IDE from Microsoft.

The first step after installing Visual Studio is to create a new project. This is done by navigating
to the File menu and New > project.

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Figure 3-7 Visual Studio API Setup (Graham 2020)

When creating a project, Visual Studio offers many templates. For a Revit Plug-In, the template
used is a new class library. This will allow Revit to access the commands while building through
C# classes. The C# class template is found in the Visual C# section of the templates and marked
with the .Net Framework as Revit required plugins to target the .Net framework. Therefore,
select Class Library should be selected (Figure 3-8).

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Figure 3-8 Class Library (Graham 2020)

The plugin needs to target the .Net Framework as Revit utilizes this framework. The version of
.Net Framework that Revit uses varies between releases
The .Net framework is backward compatible so a plugin targeting .Net Framework version 4.7
will work for previous versions. The targeting framework is set at .Net Framework at 4.7 for
Revit 2022. The next step is to create a directory for solution.

In order to work with the Revit API, there is reference to the Revit API files. This allows us to
access the contents of Revit. The two files that are needed are :
• RevitAPI.dll :
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• RevitAPIUI.dll : provides Revit user interface which includes all the classes and
functions required to add interface elements.
Both of these files end with .dll meaning they are Dynamic Link Library files. These are files of
complied code and come with the Revit install. These files can be reference to the plugin, so that
the code is accessible in the project.

Through implementing, this means any class will inherit/adopt, the methods of an interface. The
interface basically acts as a blueprint for classes by providing a set of methods that a class needs
to implement or have in the.

3.4.2 Programming – User Interface
Using the interviews as a guide, create the user interface form. This is done using Windows
Form, a software designed by Microsoft (Figure 3-9). Consult with the engineers to ensure the
order of the steps. Determine which steps will need an override.

When coding, start with simple geometries first. The first plug-in will create a panel back frame
for a simple rectangle. Create a few simple panels for multiple sizes and create documentation.
At the same time, these documents are being verified, working on looking for an API that can
recognize window openings. After openings can be added, create a secondary user interface to
create the back frame tool. Make sure each step is robust and will not break the plugin.
At each step, consult with the engineers and have them work with the plug-in. Document any
problems and observations. Fine tune the software as time allows.

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Figure 3-9 Windows Form (Microsoft 2015)
3.4.3 Programming – Manifesting
When a code is built with no errors, it needs to be register for the command to show up in Revit
(Figure 3-9). This process is done through a manifest files. When Revit boots up, it will read
manifest files that is located in one or two specific files to determine what plugins to load and
with what options (Figure 3-10).
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Figure 3-10 Adding a manifest file (Graham 2020)
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Figure 3-11 Adding a manifest file (Graham 2020)

3.5 Validation
After creating the plug-in in Revit and it is deployed. The output is a completed 3D model of the
panel containing a wall family, connection families, anchor families, and openings. These are
generated in Revit and can be exported as an IFC model to be used in other software, such as
Autodesk Forge for fabrications. In order to validate the plugin is working properly, construction
documents of existing panels will be procured. The existing drawings will be used, and the back
frame design will be checked after the plugin. The completed model is also needed to create the
second tool which is a sheeting tool.

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3.6 Back frame Plug-In Methodology (Current versus Proposed).
In order to understand the new proposed methodology, it is important to understand the current
process that are being used for precast panels (Figure 3-11). Currently, the traditional workflow
requires multiple disciplines/users.
The architect provides the precasters/fabricators either a Revit model or AutoCAD drawings.
The main output that is needed for fabrication is a shop drawing that details the types of anchors
used, their locations, slots and tabs, and back frame. The Revit Model is then used by the
precasters’ BIM department that essentially strips the model of most items except the building
envelope, floors, and walls. A façade specialist will determine how panels are needed on this
project. Variables include what is currently being processed at the plant and what is able to be
processed. Generic models for the HSS members can be used but normally this process is used to
create AutoCAD drawings. The AutoCAD drawings used for the structural engineers to do
calculations. The calculations are then used back in the original drawings where an outside team
(contracted out work) draw the anchors, frame, and connections in AutoCAD. After the drawings
are received back, the drawings are compiled to make a 3D model in Forge. Autodesk Forge is
then used as a fabrication tool in order to model in the tabs and slots needed. Afterward, the
model is sent out to a third party that draws the tooling path. They end up creating a set of
DWGs that are taken back and labeled to be used for shop drawings. These are not a full
complete set of shop drawings but are sufficient enough for the fabrication team. It is important
to note that at this time, this process does not "draw" or "model" all current components need for
fabrication. For example, precast panels of this type need a 6”x6” wire mesh wire mesh that
cannot conflict with other connections. However, since it is not modeled (and not drawn in at
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times), it adds additional time. In this workflow, there is a chance for error since parts are
related. For example, if a structural calculation was incorrect, the entire process needs to be
started again.

Figure 3-12 Current workflow at Clark Pacific, Larger Image in Appendix A (Author)

As opposed to the way the current workflow works, the proposed workflow is based on
leveraging Revit platform. Currently, most architectural firms in US use Revit. Revit is also used
because software such as Tekla are priced higher and will require interoperability between Revit
and the second software. In the proposed workflow, different types of families are used. By
capitalizing on different types of Revit families, it increases the accuracy of the project model.
Revit families allows variations of types of the components. Revit family creation is important
because it saves, and time effort spent on recreating this data for future use. This is similar to
how blocks work in AutoCAD.
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Having a workflow that leverages on a 3D model will reduce the use of third parties and
decrease the number of steps (Figure 3-12).
Figure 3-13 3D model workflow (Author)
3.7 Back frame Methodology (Proposed)
Before using the plugin tool, there are several key steps that need to be done. First, the architect
needs to provide a Revit model or a set of drawings. The precaster BIM team can strip the Revit
model to only contain the walls and floors. The structural engineer/façade designer at the
precaster will need to do structural calcuations in order to decide how many panels to divide the
projects before being able to run the back frame plugin.
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After, it is possible to access the back frame plugin. The user interface of the back frame start
screen will have a load button that will load all the types of HSS families, connection families,
and anchor families (Table 2 -1). These families are packaged with the plugin and loaded using
the plugin. Afterward, the user is guided through a series of steps that will layout the back frame
(HSS families), connection famlies, and anchor families (Figure 3-12). The last step is the plugin
will look for the intersections of the HSS families to create points to place a tab-and-slot family.
This will create voids in the back frame.
78
Name Type Comments Image
Wall System
Families
May come
directly from
Revit, Family
comes from
Architect
Window System
Families
May come
directly from
Revit, Family
comes from
Architect
Floor Slab System
Families
May come
directly from
Revit, Family
comes from
Architect
79
Window to
Frame
Connections
Loadable
Families
Reference
Plane
Cast in Place
Connection
Loadable
Family
Connects to
Floor Slab
Nested Version with Plunger Connection:
Safety
Connection
Loadable
Families
Removed after
panel is
installed
80
Plunger
Connection
Loadable
Family
HSS Loadable
Families
Parametric
Length and
Width
Parameter
Pins Profile Does not work
properly.
Currently the
code uses a
block.
Table 2 -1 Families (Author)
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Figure 3-14 Relationship between programming and Revit geometry (Author)
After creating a 3D model, the second plug-in, a sheeting tool can be used to place materials.
3.8 Sheeting Tool Methodology
The sheeting tool follows a similar methodology as the plugin. In the research stage, typical
documentation and construction sets will be retrieved. During the planning portion, title blocks
and dimensions style will be created and loaded into Revit. During the programming, Visual
Studio will be setup in Revit and leverage the existing API to place the geometry on title blocks.
Lastly, in the validation process the plug-in drawings will be compared to the built drawings.
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Figure 3-15 Sheeting tool methodology diagram (Author)

3.9 Summary
This chapter is about the methodology, research, planning, programming, validation, back frame
plug-in methodology (current versus proposed), back frame methodology (proposed), and the
sheeting tool methodology.

Chapter 3 introduces the overall methodology based on four main modules – research, planning,
programming, and validation. Both plugins use a four-process workflow: research, planning,
programming, and validation. During research, the type of precast facades will be determined
and the different parts that will need to be part of the plugin. Interviews and a job site visit will
be done in order to understand the process. Drawings that are procured during the research stage
are analyzed for their rulesets. During planning is the preparation of any Revit geometry that
needs to be loaded into the software include wall panels, steel framework, connections and
anchors. In programming, the key parts of programming with the Revit API and Visual
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Studio/C# is introduced. Each revised step of the workflow is coded into the plugin. There is a
proposed user interface that details the steps of the back frame design tool and the sheeting tool.
Lastly, a validation method is used to compare the drawings produced with the 3D model and the
current AutoCAD process.

The sheeting tool also uses a four-process workflow: research, planning, programming, and
validation. During research, typical documentation and construction drawings will be retrieved.
During planning, items that will be needed for the sheeting tool such as titleblocks, dimensions
styles, and a 3d model will be acquired. Afterward in the programming stage, Visual Studio will
be used again with the Revit API in order to reference the 3d geometry model. The plugin will
create multiple elevations of the model and lay out the drawings onto sheets. In the validation, a
comparison of the built drawings and the plugin drawings will be compared.

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Chapter 4 TOOL DEVELOPMENT
The current precast concrete community lacks an existing 3D BIM design tool that can help
streamline production drawings that will belong to the stud framework that is going to belong to
precast concrete panels. This chapter provides an overview of the research project for the back
frame tool, the Revit geometry, the programming setup, and the validation method used. The
programming parts are done in Visual Studio. This explains parts of the source code. This
chapter is about the research methodology, the research between current and revised workflow,
planning/preparation of the Revit native geometries, programming, validation, back frame plug-
in code, and the sheeting tool code. Chapter 5 describes how to install the software and includes
an existing case study walkthrough on how to use the tool.

4.1 Research Methodology
During conservations with Clark Pacific, it was identified that the Infinite Facades system would
be a system that can be partially automated due to its rectangular nature. It also fits the business
goals of Clark Pacific. The goal of Clark Pacific's mission is to develop and standardize façade
goods and systems so that owners and design teams may focus on aesthetics while streamlining
design utilizing a standard approach. The Infinite Panel provides an endless palette of form and
finish options, ranging from standard and premium to unique, resulting in greater project value
for all stakeholders. The Infinite Façade system allows for better control and installing up to
seven building systems in a controlled environment.

The current system used most frequently is their Composite Architectural Precast Panel which
comes with the pre-glazing and pre-insulation installed. Another benefit of Infinite Façade is that
85

through independent studies, it was found to reduce heating energy by 30 percent compared to
typical construction assembly(Clark Pacific 2021).

4.2 Research – Current Workflow

In order to understand the new proposed methodology, it is important to understand the current
process used for precast panels. Currently, the traditional workflow requires multiple
disciplines/users (Figure 4-1). The currently being studied method is when production requires
the use of an out-of-house company. This method was used during the CSULA project
mentioned in Chapter 2.

The architect provides either a Revit model or AutoCAD drawings to the precaster. The
precaster's BIM department then uses the Revit model, essentially strips the model of most items
except the building envelope, floors, and walls. A façade specialist will determine how panels
are needed for this project. Variables include what is currently being processed at the plant and
what can be processed. Generic models for the HSS members can be used, but normally this
process is used to create AutoCAD drawings. The AutoCAD drawings are used by the structural
engineers to do calculations. The main output needed for fabrication is a shop drawing that
details the types of anchors used, their locations, slots and tabs, and back frame.

The calculations are then used back in the original drawings where an outside team (contracted
out work) draw the anchors, frame, and connections in AutoCAD. After the drawings are
received back, the drawings are complied to make a 3D model in Forge. Autodesk Forge is then
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used as a fabrication tool in order to model in the tabs and slots needed. Afterward, the model is
sent out to a third party that draws the tooling path. They end up creating a set of DWGs that are
taken back and labeled to be used for shop drawings. These are not a complete set of shop
drawings but are sufficient for the fabrication team. It is important to note that at this time, this
process does not "draw" or "model" all current components need for fabrication. For example,
precast panels of this type need a 6”x6" wire mesh that cannot conflict with other connections.
However, it adds additional time since it is not modeled (and drawn in at times). There is a
chance for error in this workflow since parts are related. For example, if a structural calculation
was incorrect, the entire process needs to be started again.

Figure 4-1 Current workflow at Clark Pacific, Larger Image in Appendix A (Author)

Unlike the current workflow, the proposed workflow is based on leveraging the Revit platform
(Figure 4-2). Currently, most architectural firms in the US use Revit. Revit is also used because
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software such as Tekla is priced higher and will require interoperability between Revit and the
second software.

In the proposed workflow, different types of families are used. By capitalizing on different types
of Revit families, it increases the accuracy of the project model. Revit families allow variations
of types of the components. Revit family creation is important because it saves and time effort
spent on recreating this data for future use. This is similar to how blocks work in AutoCAD.

Figure 4-2 Revised workflow (Author)

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4.2.1 Revised Workflow
After analyzing which steps could be automated, a revised workflow was established.
When manually modeling the panel in Revit, the revised workflow includes the following steps:

1. In Revit, create a wall panel. Assign materials
2. Load/Insert HSS Families
3. Choose Top/Bottom Edge of Panel, Offset HSS Family 10" off frame
4. Choose Side of Panel, Offset HSS 4" off frame
5. Array HSS Family between frame at 6" intervals
6. Group all HSS Families , offset 2" for airgap
7. Load/Insert Anchor, Load Flex Pin, Lateral Pin, Gravity Pin Families
8. Insert Flex Pin , # of intervals (e.g. 3 = divide the panel into 3 equal parts)
9. Insert Gravity Pin, # of intervals (e.g. 3 = divide the panel into 3 equal parts)
10. Insert Lateral Pin, # of intervals (e.g. 3 = divide the panel into 3 equal parts)
11. Load/Insert Connection Families
12. Insert Connection families where it is hanging to the building, create an angle that it can
hang it to
13. Add voids to the connections so there is something to bolt on (this should be in the
family)
14. Cut Thru Hole for the plate for the bolt to rest on
15. Tabs and Slots (Fabrication)
a. Explode the tube pieces of the frames

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When working with the plugin, several steps can be grouped together to minimize the number of
steps. For example, all families can be loaded at once reducing Step 2, 7, and 10 in one step.

1. Load/Insert
a. HSS Families
b. Anchor, Load Flex Pin, Lateral Pin, Gravity Pin Families
c. Void/Tab Family
d. Connection Families
2. Reference a wall panel geometry
a. Plugin will find Top/Bottom Edge of Panel, Offset HSS Family 10" off frame
3. Reference a wall panel geometry
a. Plugin will find Side of Panel, Offset HSS 4" off frame
4. Reference a wall panel geometry
a. Array HSS Family between frame at 6" intervals
b. Group all HSS Families , offset 2" for airgap
5. Reference a HSS Group Families
a. Place Flex Pins at # intervals (# of intervals (e.g. 3 = divide the panel into 3 equal
parts)
b. Place Gravity Pins at # intervals (# of intervals (e.g. 3 = divide the panel into 3
equal parts)
c. Place Lateral Pin, # interval (# of intervals (e.g. 3 = divide the panel into 3 equal
parts)
6. Reference a wall panel geometry
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a. Insert Connection families where it is hanging to the building, create an angle that
it can hang to
b. Load Tab and Slot Family (Void) at each Connection family
7. Tabs and Slots, Exploded the tube pieces of the frame

4.3 Planning - Preparing Revit Native Geometry – Families
The characteristics of the categories (e.g., wall, connections, openings) will determine if the
families need to be system families, loadable families, or in-place elements. It is unlikely that in-
place elements will be used due to their unique nature. The next sections will explain the creation
process of the families.

Name Type Comments Image
Wall System
Families
May come
directly from
Revit, Family
comes from
Architect

91

Window System
Families
May come
directly from
Revit, Family
comes from
Architect

Floor Slab System
Families
May come
directly from
Revit, Family
comes from
Architect

Window to
Frame
Connections
Loadable
Families
Reference
Plane

Cast in Place
Connection
Loadable
Family
Connects to
Floor Slab
Cast in Place

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Nested Version with Plunger Connection:

Safety
Connection
Loadable
Families
Removed after
panel is
installed

Plunger
Connection
Loadable
Family

HSS Loadable
Families
Parametric
Length and
Width
Parameter

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Pins Profile Does not work
properly.
Currently the
code uses a
block.
Table 4-1 Families (Author)
After creating these families, it is important to make a "dictionary," which is a catalog that holds
all these items for the plugin to read into. In this plugin dictionary, some loadable families are
premade and loaded with the plugin. In the section about the back frame code, the loading family
scripts take all the families into a folder and loads them like a dictionary.
4.3.1 Preparing Revit Native Geometry – Loadable Families – Wall / Floor
Different walls can be created that are different from system families. This is to create a 6x6”
inch wall grid (Figure 4-3). The same idea is used for the floors and any other geometry gathered
from the Revit model provided by the architect. This information will normally come from the
provided Revit file from the architect. The wall is treated as the panel for this plugin (Figure 4-
4).
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Figure 4-3 Wall Type Editor (Author)

Figure 4-4- Wall Systems (Author)

95

4.3.2 Preparing Revit Native Geometry – Parametric Families
The wall, floors, roofs, and windows geometry are retrieved from the architect Revit model. The
other families needed are packaged with the plugin. Some of them are parametric. Parametric
families are those that are controlled by parameters. These parameters are based on reference
planes that are dimensioned and labels.

For example, the HSS members will be parametric in length. This is a loadable family with a
length parameter. It is important that this member is able to stretch. The connections do not
change in shape are loadable families. The anchors are both loadable regular and parametric
families.

Figure 4-5 - Loadable Families (Author
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4.3.3 Openings
Openings will affect the offset of the structural back frame. The opening families come from the
architect’s Revit model. For this plug-in, the default windows were used. A catalog of openings
options are collected. Currently, this uses Revit default windows (Figure 4-6). Explained further
in Chapter 6, the code only is only able to reference windows that are coded into the plugin. This
means that if another type of window is used, the plugin would not recognize it and will build the
backframe on top of it. In Chapter 6, an alternative method that could be explored is using the
openings created by the windows.

Figure 4-6 Default Windows and Openings in Revit (Author)

All of these Revit components (walls, floors, openings) are collected in a folder on the desktop.
This folder or “dictionary” is packaged in the manifest file so it will come with the plugin.

4.2.5 Titleblock
When creating a new sheet, a titleblock needs to be loaded. A default Autodesk titleblock is
included in all versions of Revit. In the sheeting tool, the tool will read all titleblocks families
that is loaded into the file. Autodesk has a default titleblock that is supplied with Revit (Figure 4-
7).
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Figure 4-7 - Revit titleblock (Author)

4.4.1 Programming Setup
After creating the Revit geometry, the next step is the programming portion. First is to set up the
coding environment which is the same process for both plugin. This is where the methods are
coded. In order for a user to run the code, a user interface is used. Sections 4.6 and 4.7 will
explain the back frame code and the sheeting tool code in more detail.

4.4.1 Programming – Setting Up Coding Environment
The coding environment is setup in Visual Studio. There is also a Revit plugin Addin file. The
User Interfaces (UI) for the plugins are created using Window Forms. The UI form can use the
98

default rules or use the user input values and provide user controls, which runs the program. Two
UI forms are created, one of them for the back frame and one for the sheeting tool.

As mentioned in the previous chapters, in order to setup the environment for Revit plug-ins in
Visual Studio, the RevitAPI and RevitAPIUI references need to be added. These contains
information that allows the access to the Revit and allows the plug-in to override the Revit
Application (Figure 4-8).

Figure 4-8 API Reference API (Author)

In addition to coding in Visual Studio, an Addin manifest is needed to make the plugin work in
Revit. This file includes the name and path of the plug in, which allows Revit to gain access
when the plug in is initiated.

When working with the Visual Studio code, it is important to note which are classes that are
programmed and which are classes that come from the API. Using the API, an important method
is find the selected target element. This method can be done by using the API code. The gray
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method references to a namespace (the software database), then the class (method). An example
is showing how the the Autodesk.Revit.DB.XYZ point of the selected target element can be
selected (Figure 4-9). The method uses a if-else statement which is that if the variable is satisifed
(here is collection size is 1 panel), then it will choose a point. If there is more than 1 target
element, it will create a null condition and an error (in a string statement) that “You must select
one family instance from which the distance to panels will be measured”.

Figure 4-9 Revit API in Visual Studio (Author)

4.4.2 Programming – User Interface
One of the UI design platforms that can be used with Visual Studio is Windows Forms, which is
developed by Microsoft. It uses a graphic design dropdown as a toolbox which can make UI
design faster, instead of working with XML or CSS. The developer can drag the function that is
100

needed to the toolbox such as the label and textbook and put them on the desired location on the
base form. Functions such as click button will need extra code to tell the program on what is do.

Using the revised workflow from section 3, the Windows Form Interface is created. The
workflow is copied here.

1. Load/Insert
a. HSS Families
b. Anchor, Load Flex Pin, Lateral Pin, Gravity Pin Families
c. Void/Tab Family
d. Connection Families
2. Reference a wall panel geometry
a. Plugin will find Top/Bottom Edge of Panel, Offset HSS Family 10" off frame
3. Reference a wall panel geometry
a. Plugin will find Side of Panel, Offset HSS 4" off frame
4. Reference a wall panel geometry
a. Array HSS Family between frame at 6" intervals
b. Group all HSS Families , offset 2" for airgap
5. Reference a HSS Group Families
a. Place Flex Pins at __ intervals
b. Place Gravity Pins at __ intervals
c. Place Lateral Pin, __ interval
6. Reference a wall panel geometry
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a. Insert Connection families where it is hanging to the building, create an angle that
it can hang it to
b. Load Tab and Slot Family (Void) at each Connection family
7. Tabs and Slots, Exploded the tube pieces of the frame

A visualization of the steps is created to show the difference in the code (Figure 4-10). For the
windows, the HSS are calculated, then the openings are geometry referenced. After that, the HSS
is moved again before proceedings for the next steps.

Figure 4-10 Visualization of the steps (Author)
After the windows form was created in Windows Form. This creates the buttons to allow the user
to interface with the plugin (Figure 4-11). The code (Figure 4-13) must match the properties
window (Figure 4-12). A final version of the UI interface is the result (Figure 4-14).
102
103

Figure 4-11 Visual Studio Interface using Windows Form (Author)

Figure 4-12 Properties Window (Author)
104

Figure 4-13 Windows Form for Back frame plugin (Author)
105

The code comprises of using XML in order to link a button to a command that is coded in C#.
Button 1 is previewed as “Continue” but is a true statement that validates that each item is
correct (Figure 4-14). This creates an EventHandler that creates the panel in Revit.

// button1
//
this.button1.Location = new System.Drawing.Point(529, 704);
this.button1.Name = "button1";
this.button1.Size = new System.Drawing.Size(75, 23);
this.button1.TabIndex = 0;
this.button1.Text = "Continue";
this.button1.UseVisualStyleBackColor = true;
this.button1.Click += new System.EventHandler(this.button1_Click);

Figure 4-14 Event Handler Button (Author)
The same method of using setting up and user interface through Windows Form is used for the
Sheeting Tool.

4.5 Validation
During validation, different panel drawings were received from Clark Pacific. After designing
the panel, a comparison was done to check what were issues. For example, the panel designed by
Clark Pacific used the sweep on the panel to calculate to separate frame assembly. This creates
two frameworks (Figure 4-15). In the code, it can only calculate one panel at a time (Figure 4-
16). The workaround was to create the panel twice (Figure 4-17), which was considered an
unrealistic modeling practice. The double panel would allow the center point of the project to be
calculated twice and thus provide a more accurate framework (Figure 4-17).

106

Figure 4-15 Clark Pacific Double Panel (Clark Pacific)

Figure 4-16 Revit Plugin Panel (Author)

107

Figure 4-17 Remodeling it using double panel (Author)

4.6 Back frame Plug-In Code
The back frame code comprises several methods. Several of the methods are repeated for the
different families. This section is to provide an overview of the code.

108

4.6.1. IExternalCommand Method
An IExternalCommand method allows for the implementation of a Revit add-in command. This
is coded first in order to ensure that the plug-in can be opened (Figure 4-13).

public class Command : IExternalCommand
{
#region IExternalCommand Members Implementation
///
/// Implement this method as an external command for Revit.
///
/// An object that is passed to the external
application
/// which contains data related to the command,
/// such as the application object and active view.
/// A message that can be set by the external application
/// which will be displayed if a failure or cancellation is returned by
/// the external command.
/// A set of elements to which the external application
/// can add elements that are to be highlighted in case of failure or
cancellation.
/// Return the status of the external command.
/// A result of Succeeded means that the API external method functioned as
expected.
/// Cancelled can be used to signify that the user cancelled the external
operation
/// at some point. Failure should be returned if the application is unable to
proceed with
/// the operation.
public Autodesk.Revit.UI.Result Execute(ExternalCommandData commandData,
ref string message, Autodesk.Revit.DB.ElementSet elements)
{

// try to initialize necessary data to create framing
FrameData data = FrameData.CreateInstance(commandData);
// display UI for user's input
using (CreateFrameForm framingForm = new CreateFrameForm(data))
{
if (framingForm.ShowDialog() == DialogResult.OK)
{
// create framing
FrameBuilder builder = new FrameBuilder(data);
builder.CreateFraming();
}
else
{
// cancel the command
return Autodesk.Revit.UI.Result.Cancelled;
}
}

return Autodesk.Revit.UI.Result.Succeeded;
}
#endregion IExternalCommand Members Implementation
}
}

Figure 4-18 External Method (Author)

109

4.6.1 Load Families
In order to access the correct non-system families (walls, floors, other geometry from the Revit
model). A directory folder is added and is connected to the first load button in XML (Figure 4-
14). This allows Revit to load all the families from a pre-determined folder in the user’s
computer. This folder path must match exactly (Figure 4-15). This code is reliant on the Family
name is repeated multiple times for the different types of connections. For example, there needs
to be one for the HSS families, one for the connections, and another for the anchors.

This code is also used for three other purposes:
• Retrieve a specific family to check whether it has been loaded into the project
• Retrieve a specific family symbol to check whether it has been defined in the project
• Retrieve a specific material to apply it to a family symbol

110

Figure 4-19 User Interface , Load Families (Author)

111

Figure 4-20 Load Families Code (Author)

4.6.2 Filtering Elements
Out of the many methods for filtering, quick filters are highly preferred, since they enable
filtering of elements without loading the entire element information into memory. Slow filters
are also effective, since they enable checking of element properties inside the Revit memory
space before the element information is marshalled and transferred out into the .NET universe.
The slowest filtering is achieved by post-processing the element data in .NET after extracting it
from Revit.

112

Since there are not a lot of families in this model, using a filter element collector method is also
possible (Figure 4-16). Another method is using it by a database element, which is only useful if
the family name is exact (Figure 4-17).

Figure 4-21 Load FilterElementCollector (Fast) Author

Figure 4-22 Loading by Database Element (Author)
4.6.1 User Inputs Overrides
In most instances all components have two load commands. One that used the pre-defined rules
and another that works using user inputs. In the red boxes are overrides that allows a user to put
in integer number. This number is then used in the list or calculation method as an override. The
113

method is called a catch method. This means that if the value is an integer, it will be used as an
override.

Figure 4-23 User Overrides (Author)

114

private void distanceTextBox_Validating(object sender, CancelEventArgs e)
{
double value;
try
{
value = double.Parse(distanceTextBox.Text);
m_frameData.Distance = value;
}
catch (FormatException formatEx)
{
Debug.WriteLine(formatEx.Message);
TaskDialog.Show("Revit", "Please input a integer.");
e.Cancel = true;
}
catch (ErrorMessageException msgEx)
{
distanceTextBox.Text = m_frameData.Distance.ToString();
TaskDialog.Show("Revit", msgEx.Message);
e.Cancel = true;
}
}

Figure 4-24 User Input Validation Box (Author)

4.6.2 Loading Windows Forms Inputs

After a user fills out the forms or uses the defaults (the defaults are pre-entered through the
Windows Form), the data is collected in “FrameData” (Figure 4-20). The public class FrameData
is loaded through WindowsForm through the ExternalCommand (Figure 4-21).

115

Figure 4-25 External Command, take data from UI form for Builder (Author)

Figure 4-26 User input data to Frame Builder (Author)
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4.6.2 Accessing Placed Instances
The DocumentChangedEventArgs instance is passed to the event handler, which has a method
GetAddedElementIds that returns all newly added element ids. Use the DocumentChanged
event to get the newly produced elements added to the model by calling
PromptForFamilyInstancePlacement. This is used to place family instance.

Note that each time this method is called each time a placement is completed, so a single
PromptForFamilyInstancePlacement function may contain numerous calls for various
placements. Each call will focus on a different component of the sample, which will be marked
in red on the form (Figure 4-27).

Because every event handler or other reactor introduced to a system adds overhead, it makes
logical to utilize event handlers as little as possible. This can be readily accomplished in this
situation by adding the handler just before prompting for instance placement and deleting it just
after.
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Figure 4-27 Placed Instances (Author)

4.6.3 Methods for Placing Instances

The first method is to create the basic boundary which uses a matrix reference to create a grid in
the rectangular panel. These are referred to as the interior HSS. This creates the boundary HSS
condition (Figure 4-28). Inside the HSS, there is an array. The array is reference of the boundary
HSS (interiorHSS class) (Figure 4-29).

118

Another method that is used is referring to the location line in order to place a new family
instance. The example looks at using a BeamSymbol (similar to a profile) and uses a line to
extrude it. This is an alternative method to creating a flexible family.

Figure 4-28 Creating initial boundary HSS (Author)
119

Figure 4-29 HSS interior array (Author)

Figure 4-30 Family Instance Placement (Author)
4.6.3 Moving Frames

After creating the initial framework, the frame needs to be grouped. This is done by grabbing
each family instance in Revit (Figure 4-31). The elements are moved in the next steps through
translation methods. For example, if there is an opening and the entire framework needs to be
120

moved, it can use the horizontal plane method (Figure 4-32) or RotateDegree method (Figure 4-
33).

Figure 4-31 Moving entire backframe as a group (Author)

Figure 4-32 Translation Method (Author)

Figure 4-33 Translation Method (Author)

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4.6.3 XML code
Below is the XML code that is used to link the addin to the Revit. In order to add a .XML File
for PackageContents, click on the solution and add new item. Choose "XML File" and rename it
"PackageContents". Take the code below and copy paste it to the toolbar. Each addin needs a
separated Id in order to prevent a clash with an existing add-in.

PreCast2022
PreCast2022.dll

973072FB-3FEB-4A5E-924B-484403452463

PreCast2022.Command
Command
Frame Tool
Victoria Dam
Frame Tool
NotVisibleWhenNoActiveDocument

Figure 4-34 Addin information (Author)
4.7 Sheeting Code

The Sheet View Creator also has a similar development to the back frame tool. The first is the
creation the windows form that acts as a user interface (Figure 4-35). The generated code is
created through XML (Figure 4-36).

122

Figure 4-35 Windows Form for Sheeting Tool (Author)

Figure 4-36 Windows Forms generated code (Author)
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4.7.1 Referencing Geometry
The sheet tool also uses an external command. If there is a view and sheet that exists, it will
create a null and not open.

Figure 4-37 User Interface External Command (Author)

4.7.1 Sheet Generation
Generating a new sheet that has all the selected views placed in. This updates and retrieving
properties of a selected viewport.
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Figure 4-38 Box orientation (Author)

The length of the label is normally defaulted to Revit. The code takes that information in order to
update the label line length (Figure 4-39).
125

Figure 4-39 Label lengths (Author)

The next part of the code collects all the views that are in the document by using the
FilteredElementCollector (Figure 4-40). If the view template is invisible in the project browser, it
is skipped. If it is visible, it is inserted and a sheet is created.
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Figure 4-40 Get name of drawings (Author)

After, the title block name is generated. It takes an existing Titleblock and adds a variation
(F.Name) such as Sheet 1, Sheet 2. A FilterElementCollector is used again retrieve all the
avaliable title blocks in the documents (Figure 4-41).
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Figure 4-41 Get title blocks for placement (Author)

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4.8 Summary
The current precast concrete community lacks an existing 3D BIM design tool that can help
streamline production drawings that will belong to the stud framework that is going to belong to
precast concrete panels. This chapter provides an overview of the research project for the back
frame tool, the Revit geometry, the programming setup, and the validation method used. The
programming parts are done in Visual Studio. This explains parts of the source code. This
chapter is about the research methodology, the research between current and revised workflow,
planning/preparation of the Revit native geometries, programming, validation, back frame plug-
in code, and the sheeting tool code. Chapter 5 describes how to install the software and includes
an existing case study walkthrough that belongs to how to use the tool.

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Chapter 5 INSTALLATION AND TUTORIAL
This chapter is about the plug-in package preparation and includes a case study tutorial. The two
tools developed in Chapter 4 are the back frame tool and the sheeting tool. This chapter explains
how to install and use them. This chapter introduces how to use the plugin through the
installation process and includes a case study tutorial walkthrough. The panels used for this
chapter were modeled after examples received from Clark Pacific. Limitations of both of the
tools are explained further in Chapter 6.

5.1 Plug-in Package and Preparation
Both tools are packaged together as a zip file. The file needs to be unzipped by the user into a
local C drive. The addin should be a dll package that is loaded into the Revit install location.
Within the folder, there is a ReadMe file, an example Revit project, multiple family files, the dll
files and addin files. The example Revit project allows the user to get familiar with the software.
It also should have all the Revit families preloaded.

Figure 5-1 Contents of package (Author)
The package contains two plug-ins. A backframe tool that is used for rectangular panels with no
windows and a rectangular panel with windows. There is also a sheeting tool that can take any
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3D geometry and creates sheets. For example, if a house was modeled in Revit, the sheeting tool
can make plans, and elevations of the project. It will also assign a defaulted titleblock. In the
main program folder, there is also a cs file, the window form file /user interface file, and the dll
file.

The user needs to place the addin files in the Revit Addin file in order to launch them in Revit.
This needs to be done for each version of Revit. The file path is Autodesk-> Revit -> Addins-
>2022 (Figure 5-2). When placing the addin file, “Show Hidden Files” must be clicked on in
order to see the program data file (Figure 5-3).

Figure 5-2 Addin (Author)

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Figure 5-3 Hidden folder (Author)

5.1.1. Revit Interface
After placing the addin files in the install locations in Revit, the user needs to restart their
computer and relaunch Revit to use the plugin. When initiating Revit, several warning windows
will pop up to ask for the user’s permission to load the plug in into Revit. Click “Always Load”
to enable Revit to load the tool each time when opening Revit.

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5.2 Case Study
The case study buildings are existing completed Clark Pacific projects. These examples use a
panel that is already modeled in Revit. In the Appendix B , there are examples of multiple ways
to model a precast panel in Revit. These can be referred to if a precaster receives a PDF drawing
from the architect.

5.2.1 Running Backframe and Sheeting Tool – Rectangle (Defaults)
The default steps are in highlighted in red (Figure 5-4), which uses the rule-of-thumb
calculations. These are not highlighed red when running the plugin. When running this tool, the
load families need to be loaded once. The “Type of Concrete” is default to the type of panel, and
there currently is a dropdown menu with no other options to select from.

After modeling a panel, select “panel” from ghe menu. This Load button will change the panel to
concrete if it is not already concrete. Next, click HSS / Drop Tubes Load and it will default and
create a HSS family that is 10 inches from the back to frame and 4 inches to the back of the
skins. The default arrays is set to 3 divisions.

133

Figure 5-4 Default drawings (Author)

Since the plugin relies on previous information that is stored, the finished panel is not modeled in
parts. Instead, click all the items, and it will create a panel. A null error will pop up if there is no
Revit panel picked.
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In this case study, the panel is being model based on an existing panel from a real project
completed by Clark Pacific (Figure 5-5).

Figure 5-5 Clark Pacific Drawing (Clark Pacific)
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When preparing a panel, the two methods for obtaining the 3d geometry are either to model it in
Revit or use an existing panel. In this example, a wall panel was modeled using a wall and reveal
system (Figure 5-6). The Appendix C shows multiple alternative methods to model a precast
panel.

There are several methods an architect might model a Revit Precast Panel. Before going into the
methodology of the Revit API, it is important to know the possible input that is loaded and how
that might affect the output. While they may all look the same, the way a panel is modeled
affects what types of "tags" are being associated with them. When running the plugin, the code is
looking for associated tags to match up.

Figure 5-6 Wall panel (Author)

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By using the defaults (labeled red in Figure 5-7), it automatically creates a 3D panel. The pin
connections currently do not stretch properly and instead a box is used as a geometrical
representation.

Figure 5-7 Revit Plugin - Rectangular (Author)

In order to see this project a bit clearer, one can click the External Tools (Figure 5-8). Click the
Sheet addin. This will create a second dialog box that opens the Sheet Tool (Figure 5-9).

Figure 5-8 External Tools (Author)
137

Figure 5-9 Sheet Tool in Revit (Author)

The Sheet tool uses a default titleblock. In this example, there is only one Level. Two views are
also selected (Figure 5-10).

138

Figure 5-10 Sheet Tool in Revit (Author)

As a result, the panel is placed on sheets. There is manual manipulation needed to move the
views if the panels are too large (Figure 5-11).
139

Figure 5-11 Pick a panel (Author)

5.2.2 Running Back frame and Sheeting Tool – Rectangle Reveal, default, 2 inches

A second case study uses a panel that has a reveal (Figure 5-12). In this example, the defaults
were lowered to 2 inches. When working with a project that has a reveal, the panel tool needs to
be run twice. This allows the center point to be calculated twice.

140

Figure 5-12 Clark Pacific Panel (Clark Pacific)

When modeling this panel using the plugin, the sweeps are not calculating it as separate panels.
Instead each panel needs to be done individually (Figure 5-13). During validation, different
construction sets were received from Clark Pacific. After designing the panel, a comparison was
done to check what were issues. For example, the panel designed by Clark Pacific used the
sweep on the panel to calculate to separate frame assembly. This creates two frameworks (Figure
5-13). In the code, it can only calculate one panel at a time (Figure 5-13). The workaround was
to create the panel twice (Figure 5-13), which was considered an unrealistic modeling practice.
The double panel would allow the center point of the project to be calculated twice and thus
provide a more accurate framework (Figure 5-13).
141

Figure 5-13 Double panel sweep method (Author)
142

Figure 5-14 Double panel in Revit, without using two systems (Author)

5.2.3 Running Back frame and Sheeting Tool – Windows
An example was used with a large window using the defaults (Figure 5-15).

143

Figure 5-15 Windows option, rendered (Author)

5.3 Summary
This chapter explained to install the plug-in package and preparation and showed case studies on
how to use the tools. The back frame tool and the sheeting tool are the two tools developed in
Chapter 4. This chapter describes how to set them up and use them. It detailed the installation
procedure and a case study tutorial walkthrough for using the plugin. The panels were created
based on examples provided by Clark Pacific. In Chapter 6, the limitations of both technologies
are discussed in further detail.

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Chapter 6 – Discussion and Future Work
Currently, the traditional 2D design techniques used to create precast panels do not meet the
customer's needs for both quality and speed. The layout of precast panels by the precasters can
be a tedious process that consists of multiple people and an inefficient workflow of switching
from 2D to 3D and back to 2D. As a result, many industries have already transitioned from 2D to
using building information modeling software programs. The objective was to create plug-ins in
C# for simple or complex tasks by using the Revit API. Precast design could take advantage of
building information modeling and custom tools to help in the design process of panels. While
two plug-ins were developed, a combination of lack of software skills, time, and lack of
structural knowledge, made the prototype tool only usable for few standard conditions.

This chapter summarizes the discussion of the work done, evaluation and limitations, and future
work. It details the current workflow performed during the development of the back frame tool
and the sheeting tool. Several limitations of the current workflow are described and evaluated.
Finally, the chapter proposes improvements to deal with existing limitations and discusses the
future potential of developing the two tools into a more advanced product for assisting precast
frame design.

6.1. Discussion
After discussion with engineers and contractors at a local precast concrete plant, Clark Pacific, it
was decided to identify a back frame system that can be automated. The original intention before
talking to Clark Pacific engineers was to design a framework system for GFRC panels because
the GFRC material lends itself well to irregular profiles. After discussions, it was decided to use
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the Clark Pacific’s Infinite Façade system as the basis for the design rules in the code because it
is a more standardized way of creating panels.

6.1.1 Workflow
A four process workflow was developed in order to design the back frame plug-in. The
developed Revit plug-in uses a a four-process workflow: research, planning, programming, and
validation (Figure 6-1).

Figure 6-1 Methodology diagram for back frame tool (Author)

In the back frame research process, investigation about the current typical precast process was
conducted through interviews, publications, and visiting a precast plant. In the initial interviews,
it was learned that the in-house process slow because it was constant switching between 2D and
3D and 2D coordination (Figure 6-2). The precast team was also not able to draw or model all
the current components needed for current fabrication. A revised workflow was proposed that
would limit down the number of steps and people involved in the process (Figure 6-3). This was
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successful because it could limit errors since the team could be working from one consolidated
model than working with 2D drawings, partially completed 3D model, and fabrication sheet
drawings.

Figure 6-2 Current workflow (Author)

Figure 6-3 Proposed workflow (Author)

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6.1.2 Creation of objects and tool
After gathering information about the back frame process, the planning stage consists of creating
the materials to make one complete building information model. Revit families, templates, and
material information were created (Table 6-1).
Name Type Comments Image
Wall System
Families
May come directly from Revit,
Family comes from Architect

Window System
Families
May come directly from Revit,
Family comes from Architect

Floor Slab System
Families
May come directly from Revit,
Family comes from Architect

Window to
Frame
Connections
Loadable
Families
Reference Plane

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Cast in Place
Connection
Loadable
Family
Connects to Floor Slab

Nested Version with
Plunger Connection:

Safety
Connection
Loadable
Families
Removed after panel is installed

Plunger
Connection
Loadable
Family

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HSS Loadable
Families
Parametric
Length and Width Parameter

Pins Profile Does not work properly.
Currently the code uses a block.

Table 6-1 Families created (Author)

Sample drawings that were procured during the research stage are analyzed for their rulesets.
The original rulesets that were discovered were:

• HSS : 10 inches back to the frame, 4” off the side of the skins
• HSS: There are consistent arrays between the panels
• Minimum of 6 connections, maximum of 8 connections on larger panels

After creating the necessary objects in planning stage, these items were to be programmed using
C#. The Revit API is setup using Visual Studio. A user interface was designed first and
implemented in order to guide the user through the use of the plugin. The precast team at Clark
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Pacific revised the order of the steps in order to align with their way of thinking. This meant that
the programming was being done in a slightly different order than the way the tool would operate
for the user. The original intention was that the user could see each item being modeled
individually as they click through the app. For example, in the traditional workflow, HSS design
requirements were added first, then openings were considered, and the HSS were shifted. While
it is possible to group items in Revit and shift them, it was a consistent shift. It might be that only
one HSS member needed to be moved. Instead, in the programming, it used a reference geometry
code to considered shifts. This data was copied in lists and stored to prevent user errors from
manually clicking the HSS and windows. Due to this, the user was only able to see a completed
panel and not step by step.

There are multiple ways to model a precast panel in Revit. For example, one method involves
using a reveal or sweep to create a break in the wall (Figure 6-3) . Another method is using a
split gap (Figure 6-4). An architect can also use a generic model to model a panel. All of these
require different reference geometry classes in the code, some of which currently is not
automatically stored in a list.

151

Figure 6-3 Reveal modeling (Author)

Figure 6-4 Split with gap (Author)

The final tool uses a windows form as the user interface (Figure 6-5). The output is a completed
3d panel that can be loaded into the next sheeting tool (Figure 6-6). The steps are in created in
sequential order of how the precaster will use the tool. Chapter 4 discusses how the code was
created and Chapter 5 discusses how to use the tool.
152

Figure 6-5 Interface of back frame tool (Author)
153

Figure 6-6 Back frame tool output (Author)

6.1.3 Sheeting tool
When the first two example panels were successful, the sheeting tool was being developed while
waiting to get more panel drawings. The sheeting tool takes the 3d model and places it on a sheet
with a title block. The tool used the same four step methodology as the back frame tool (Figure
6-7). This was more successful in that it would take any existing geometry and layout it out in a
sheet. It currently though lay a project out in a similar fashion as a building with such as floor
plans, sections, elevations but in the future work, the titles can be adapted in a way that makes
more sense for precast back frame layout.

154

Figure 6-7 Methodology diagram for sheeting tool (Author)

The final interface is a form that can be accessed inside Revit (Figure 6-8).

Figure 6-8 Final sheeting tool interface (Author)
155

After using the sheeting tool, the output is a sheet with drawings on it (Figure 6-9). Refer to
chapter four for a discussion of the code and chapter five for how to use the tool.

Figure 6-9 Sheeting tool output (Author)

6.1.4 Problems with validation
The process of revising the code involved receiving sample panel drawings from a non-design
person at Clark Pacific and using the tool to design and draw the back frame, then comparing this
result with the actual design of the real built drawings as created by the design and engineering
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team at Clark Pacific. Many of the rules that were established in the initial interviews did not
match up with the panel drawings.

At this point, a discussion ensued, recognizing that some of the panels were not regular typical
wall panels but rather were corner pieces. More examples of non-corner panels were requested,
but there was also trouble with having the Revit plugin and construction drawings. The drawings
provided were from multiple projects which made it more difficult to understand what hard rules
and soft rules from the original guidelines were. An example of a hard rule is that a HSS member
occurs at the bottom of each panel. An example of a soft rule is that the tool should create a
boundary curve.

At one point, it was further revealed that some of the panel examples were completed by a third-
party drafting company and that these panel examples might be a bit different form the standard
way the design is carried out. There were also drawings of example panels that had additional
unexpected bracing that was not initially explained. This made it more difficult to understand the
rule of thumbs when it came to designing a panel back frame layout. For example, a soft rule was
having the bracing in the center array and some of these example panels did not include this.

The plugin tool ended up including numerous user overrides for special cases, and this made it
difficult for the list to compute. For example, some of the special case user overrides were

• Changing the spacing of the arrays
• The offset of the entire HSS group
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• Number of anchors

In spite of these problems, some of the panels designed with the help of the tool were very
similar to the real cases. The panels that were successful are most similar to the first two panels
which are the what the code is based off of. The more closely the examples matched the
originally submitted layout and rules were the ones that achieved more success in using the tool.
Panels that are rectangular work better with this tool because this type of panel was what was
used to create the tool. Panels that are rectangular and with windows that do not extend out of the
panel also work well.

6.2 Evaluation and Limitations
The current tool has limitations in the type of panels that could be designed. The four significant
limitations are panels with multiple reveals, frames that extend outside the panels, non-standard
windows, and stiffener ribs situations. Panels that are most successful is using the tool are
rectangular panels and rectangular panels with windows for which the opening is entirely
contained inside the panel (Figure 6-10). The current workflow also designs each panel
individually when in reality it should also consider the connection the adjacent panel. A better
method would be to have a tool that considers the panelization the entire façade before using this
tool. It should be able to reference the HSS members on the adjacent panels and readjust
accordingly.

158

Figure 6-10 Standard panel with windows completely inside panel. A- input, B- geometry
Revits reads , C- output with back frame (Author)

There are currently four main limitations with the current version of the back frame tool:
• Panels with multiple reveals
• Frame extends outside the panels. This is common with large windows.
• Non-standard windows
• Stiffener Ribs situations

6.2.1 Limitations of the back frame tool – Panels with multiple reveals
Panels often include reveals or breaks. There are multiple ways to model this kind of break in the
panel. Sometimes a break or reveal is added for structural reasons and sometimes they is
modeled for aesthetics. There was not sufficient time and communications to understand which
ones were added and which were considered for structural or aesthetic purposes.
159

In Revit, the reference geometry reads a panel with a reveal as one single wall (Figure 6-11). It
does not read as one wall split with a reveal. Therefore it calculated the geometry from the center
of the full panel. The code relies on calculating the geometry from the center of each split, and
the tool needed to identify two centers to be able to code it properly with a reveal (Figure 6-12).
An alternative method to address this problem is to model them separately, but this method also
caused issues because the HSS members at the top should be continuous across the full panel and
not stop for the reveal (Figure 6-13).

Figure 6-11 Panel with reveal (input geometry), Revit API cannot read reveals and sees it as panel (Author)

160

Figure 6-12 Panel with center points (Author)

Figure 6-13 Panel with a sweep (Author)
161

6.2.2 Limitations of the back frame tool – Frame extends outside the panel
Since each panel is individually designed, it does not consider the placement of the HSS for the
adjacent panels. For some panels, such as those with large windows, the HSS extends outside the
geometry of the frame (Figure 6-14). Since the HSS is a host family in Revit, it needs some host
geometry and thus the tool cannot design boundary shape. In these instances, it is necessary to
manually adjust the model inside the tool which can be a tedious and time-consuming process.

Figure 6-14 HSS Panel that over the frame (Author)

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6.2.3 Limitations of the back frame tool – openings
As currently configured, the codes only can only recognize standard Revit windows for
openings. If a non-standard window was added, the code ignored it and created a HSS family
(Figure 6-15). A way to possibly fix this is explored in the future work section.

Figure 6-15 Nonstandard vs standard windows (Author)

6.2.4 Limitations of the back frame tool – Stiffener Ribs
Stiffener ribs are an additional member that is used to strengthen the frame. This normally
happens because of a special condition.

These conditions typically happen at two times:
• Presentation of a window system (Figure 6-16)
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• Uneven number of arrays of HSS members. (Figure 6-16 and Figure 6-17)

At both of these conditions, the HSS needs to be recalculated. Since the tool does not redo
calculations based on uneven arrays, it did not host them properly. The stiffener rib also needs to
be called out separately. Since this is also a HSS member geometry, it does not have a separate
element tag in Revit.

Figure 6-16 Window stiffener ribs (Clark Pacific/Author)
164

Figure 6-17 Window stiffener ribs (Clark Pacific/Author)

6.2.5 Limitations of the back frame tool – Uneven arrays
The code will only calculate and design consistently spaced arrays. When trying to create one
example panel, it was unable to space it out properly (Figure 6-18). This was a drawing done by
the third party and the code was unable to figure out the logic with this piece. Being unable to
understand where it was on the building also made it difficult to understand if this was a special
panel or if it was a repeated panel that happened several times.

165

Figure 6-18 Window stiffener ribs (Clark Pacific/Author)

6.3. Future Work
Having a better understanding of the Revit API, coding limitations, and structural layout would
be helpful in further developing both plug-ins. Among the most important future work items are
the back frame – openings, the sheeting tools, the use of GFRC, and the paneling tool.

6.3.1 Future Work – Back frame - Openings
The windows “opening” also uses family based elements to access openings. There are no
standard pre-glazed window systems in the Infinite Facades systems, and this presents a problem
for standardizing the process. A better alternative method might be to try linking the “Openings”
class in Revit to try to have multiple different choices of windows being programmed in (Figure
6-19).
166

Figure 6-19 Future work, openings (Author)

There was some success in using family elements to access openings. Figure 6-20, it shows how
sample display openings can be used to create model lines (in red) on edges. It is currently
displaced in view. The classes that need to be implemented are: Vector, UCS, Line2D, Line3D,
LineSketch, ObjectSketch, WireFrame (for little mini graphics system), Opening Property,
Opening Info (Figure 6-12). This is a modification of the software development code (Figure 6-
12)

Time constraints and modest coding skills made it difficult to include recognition of windows
and doors with the openings. A possible method to resolved this would be to use an element filter
to grab the windows and door, and then use that to pick up the edges of the HSS frame. This
method is extremely computer intensive.

167

Figure 6-20 Openings (Author)

6.3.2 Future Work – Sheeting Tools
The sheeting tool places items on generic elevations and generic sheets. It also places these
views without consideration of how large or small the drawings are (Figure 6-21). A better
method would be to create a set scale for the drawings in advance. This can ensure that the
collection of views do not extend off the sheet.

168

Figure 6-21 Sheeting errors, lack of dimensions and sizing errors (Author)

Another method might to use a named scope box that the code can reference and place the views
(Figure 6-22).
169

Figure 6-22 Scope box (Author)

A valuable additional feature would also be to have Revit auto tag and dimension the panels.

6.3.3 Future Work – GFRC
Future work could include a more developed structural system by incorporating more rulesets for
the Infinite Facades system. Currently, the code is optimized for rectilinear shapes. There is also
the possibility of it working with non-uniform shapes and can be adapted for the use other
precast products that use a framework, such as GFRC. In the future, it would be preferred to
develop software that can handle more complex shapes and can also incorporate the use of
GRFC. GRFC also uses a back frame (Appendix C).

6.3.3 Future Work – Paneling tool
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Creating a paneling tool that can assist with dividing the façade into workable panels based on
what a precaster can build in their plant would be useful (Figure 6-23). A paneling tool can be
developed to address panels that overhang with each other. It can also create an index of the
panels that can be linked in the sheet to create a schedule (Figure 6-24).

Figure 6-23 Paneling tool (Skindesigner 2020)

A paneling tool can be developed to address panels that overhang with each other.

171

Figure 6-24 Panel schedule (Author)
6.4. Conclusion
This chapter is a discussion about the current limitations of the workflow, evaluation and
limitations, and future work for the Revit tool for creating back frames based on a rectangular
panel with an opening using the Infinite Frame by Clark Pacific as an example. Two plugins
were developed, a back frame tool and a sheeting tool. They have the potential to make
precasters’ work quicker and more accurate although currently there are many limitations with
the current tool.

The discussion of some of the limitations with the current workflow is also provided and
evaluated. The tools successfully work for the simpler and more straightforward panels such as
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rectangular panels with no reveals and panels with the window fully enclosed inside them. The
current workflow also designs each panel individually when in reality it should also consider the
connection the he adjacent panel. There are currently four main limitations with the current
version of the back frame tool: panels with multiple reveals, frame extends outside the panels
(e.g. large windows), non-standard windows, and stiffener ribs. Limited structural knowledge
and coding ability made it code for every possible situation. For the sheeting tool, the addition of
adding a scope box could help with placing oversized views. Adding dimensions capabilities can
also added it to be more useful.

There is potential in developing the two tools into a more advanced product for assisting precast
frame design. Some of the fundamental sections of the code should be revised to make it easier
to layout for different situations. Currently, the code is optimized for rectilinear shapes. There is
also the possibility of it working with non-uniform shapes and can be adapted for the use other
precast products that use a framework, such as GFRC.

The two Revit plug-ins developed, a back frame tool and a sheeting tool, are just the beginning
of ways that customized tools can add to the precast concrete business. With a 3D model, other
plugins can assist with fabrciation such as a layout tool, scheduling tool, or a cost estimation.

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Appendices
Appendix A- Current workflow at Clark Pacific

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Appendix B:
There are several methods an architect might model a Revit Precast Panel. Before going into the
methodology of the Revit API, it is important to know the possible input that is loaded and how
that might affect the output. While they may all look the same, the way a panel is Model affects
what types of "tags" are being associated with them. When running the plugin, it is looking for
associated tags to match up.

B.1 Method – Split with Gap
Normally a precast wall is Model as continuous but as an architect go into more developed or
detailed design, the precast wall is split into individual panels (Figure B-1). The easiest way is
use ‘Modify  Split with Gap’. Specify the joint gap dimension then click the location on the
precast wall where the split should be. At wall joins, use 'Disallow Joins" to separate the panels
at the corners. Right click on the end of the wall (in plan) to disallow joins/prevent the walls
from wanting to join together. The benefit of this method is that is very easy, creates accurate
gap dimensions, and each panel is a separate wall (which is useful for tagging individual panels),
and works for both vertical and horizontal split. The con with is that it is only useful for simple
panels.

Figure B-1 Split Method with Gaps (Author)
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B.2 Method – Precast Panels Using Reveals
Another method is to model precast panels (Figure B-2) is by going into Section or Elevation
view. Using Structures tab, click the drop down on the wall and select Wall: Reveal.

Figure B-2 Reveals (Author)

Figure B-3 Reveals (Author)
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Then choose what type of placement (vertical or horizontal), and then click in the wall the
location where you want the joint. Select the wall sweep and edit the type properties. Here there
is an option to choose a profile for the panel joints (Figure B-4).

Figure B-4 Type properties (Author)

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In order to create a profile such as the "200 Precast Panel Butt Joint", start with the ‘Profile’
family template.

Figure B-5 Reveal profile (Author)

While this is an easy method to create accurate gap dimensions, profiles, vertical and horizontal
joints, it poses a major issue in panel design. It is one continuous wall so the plug in is not able to
tag each panel. It also requires the need to create a profile which is an extra step in comparison to
the first method.

B.3 Method – Precast Panels Using Parts
An seldom use method but one can also create Precast panels using ‘Parts’. This allows the wall
to remain the same but in each view, you can choose to show the ‘Parts’ (in this case Panels) you
create or the original wall. The steps to do this is select the Precast walls then click the ‘Parts’
button under ‘Create’ on the Modify Walls Tab (Figure B-6).

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Figure B-6 Parts interface in Revit (Author)
Afterward, click on the ‘Divide Parts’, then ‘Edit Sketch’. There you can sketch the location of
the panel joints (Figure B-7).

Figure B-7 Edit sketch (Author)

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In the properties bar, you can specify adding a Gap dimension to each joint and the option of
applying a profile if needed (Figure B-8).

Figure B-8 Division Geometry (Author)
To create a profile family, start with the "Division Profile" family template (Figure B-9).

Figure B-9 Division profile (Author)

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Also specify each view that you want to show the Parts (panels), show the original wall, or both.
This method provides a few benefits. It is simple to do and creates accurate gap dimensions. You
can also apply gap profiles. Panels can also be tagged, and each panel has its own shape handle
so it can provide different thickness. It is cumbersome that for each view, it is needed to specify
the Visibility of Parts (Figure B-10).

Figure B-10 Parts Visibility in Revit interface (Author)

B.4 Method - Revit Precast Panels Using Curtain Walls
This method is creating a ‘Precast Curtain Wall’ (Figure B-11). Choose a ‘curtain panel’ to be a
precast wall or concrete wall with correct thickness. Then set up the horizontal and vertical grids.
For example, if the panels to be a maximum of 2.9 ft wide, the vertical grid layout should be set
to "maximum spacing" and the space to "2.9 ft". Another method is using the ‘Curtain Grid’ tool
to specify your own Grids.

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Figure B-11 Precast panels curtain walls (Author)

To make the joints, create a ‘Curtain Wall Mullion’ with the width being the required gap
dimension. Then Hide the Curtain Wall Mullions in view and what is left is the panel with
the correct gaps. Then ‘Edit Profile’ to create voids or different wall profiles (Figure B-12).

185

Figure B-12 Curtain walls dialog box (Author)

This method is also somewhat easy to set up and creates accurate gap dimensions. It also allows
for a set fixed or maximum width for the panels. The panels can be individual tagged (though
using the curtain panel tag). This method also allows for wall openings or edit profile to create
186

voids. The issue with this is that the Panel gap is an a curtain wall mullion that needs to be
hidden. It will not appear properly. Also, reinforcement cannot be Model in the panel.

B.5 Method - Revit Precast Panels Using Voids
This method is generally used for more complex panels that are made of one Precast wall. In this
example, the designer created one ‘in-place void’ that can represent all openings. This is done
via creating a 'Model in-place component', found in the ‘Structure Tab’ on the ‘Component’ drop
down (Figure B-14):

Figure B-14 Model in-place component (Author)

Next, select a category (Generic Model is most commonly use) and give it a name like “PreCast
Openings”. Create a ‘Void extrusion’ in ‘Elevation’ or ‘Section’ view (Figure B-14).

187

Figure B-15 Void extrusion (Author)

Then sketch in all the openings and panel joints as needed. Once done, confirm and select Cut-
Geometry. It is important to pay attention to where the void passes through and cuts the wall
(Figure B-15). Simply click on the Void that is created, then on the wall you want split (Figure
B-16).
188

Figure B-15 Voids modeled (Author)

Figure B-16 Voids Result (Author)
This is an easy to control method. The sketch tool allows to create any shaped void. Multiple
openings are controlled by one in-place void, and this is good for slight complex panel systems.
The cons with this are that one continuous walls so it cannot tag each panel. It is also hard to
change thickness.
189

B.6 Method - Using Wall Openings
The last method is good for panels with lots of voids. Use ‘Wall Openings’ to create rectangular
voids, either to separate the panels/gaps (Figure B-17). This can also be used to create windows
(or doors) openings. This is done by selecting the precast wall, then selecting ‘Wall Opening’ on
the ‘Modify Wall Tab’. This creates a rectangular opening, that can be further edited by pushing
and pulling down the arrows to create temporary dimensions (Figure B-18).

Figure B-17 Wall openings (Author)
190

Figure B-18 Wall openings (Author)
The issue is that the openings are singular and this only allows rectangular voids Also there an
inability to use the sketch tool.

As explained above, there are many methods to model a precast panel in Revit. Though there are
multiple methods to come to the same visual/aesthetic outcome, only some of them come with
the proper "elements" that allow the code to read and identify it.

191

Appendix C: GFRC
This appendix is about Glass Fiber Reinforced Concrete. There is a possibility of creating a
GFRC back frame panel tool. This information gives basic information about the material and its
assembly.

Another type of Precast Concrete that needs a steel back frame is GFRC. "GFRC" is the acronym
for "Glass Fiber Reinforced Concrete." GFRC is a Portland cement-based composite with
alkaline-resistant glass fibers randomly dispersed throughout the sand/cement matrix. The fibers
are used in the same way as reinforcing steel in reinforced concrete in tensile stress zones.
Architectural panels manufactured by GFRC are robust, durable, and lightweight because the
glass fibers add flexural, tensile, and impact strength. GFRC is normally used as exterior façade
materials, with each panel custom designed from the specific application. The largest dimensions
can be vertical or horizontal, and panels can be 400 feet larger if needed.

The skin of GFRC is normally ½ to ¾ thick. The skin is anchored to a frame consisting of cold-
framed / galvanized steel members. The GFRC "skin" is panelized on steel stud frames and
weighs 20-25lb per square foot. The GFRC skin transfers the loads to the frame, then transfers
the loads to the building structure. The sizing and spacing of the backup frame members depend
on the overall size of the panel and the loads to which it is subjected. The steel frame adds
rigidity to the thin wall concrete skins, thus allowing the large panels to be fabricated, de-
molded, and shipped to the job site without damage.

192

The skin is hung 2 inches or more away from the face of the frame using bar anchors. There is a
gap between the skin, and the frame allows for differential movement between the skin and the
frame, which essentially during the period when the fresh concrete in the skin shrinks as the
water evaporates.

The fabrication of GFRC Panels is the following:
1. Preparing the mold
2. Applying the mist Coat
3. Applying the GFRC Mix
4. Frame Placement ( After the GFRC spray is completed, a cold-formed steel support
frame is placed against the skin, leaving the required distance between the skin and the
frame.)
5. Apply bonding pads
6. Removing the panel from the mold and curing

When comparing GFRC to typical Precast Concrete, GFRC is much more elastic and dense. The
cement ratio to stand for GRFC is 1:1, while it is 1:6 for typical precast concrete. The GFRC is a
true curtain wall because it is a non-load-bearing exterior cladding. It is used to use typical
Precast panels. This means that the panels were needed to supply structural supports.
GFRC panels are also popular for renovation or recladding of existing buildings because they
add a minimal superimposed load to the existing structure and foundations. In many cases,
GFRC panels can be installed directly over the old claddings with minimal impact on the
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building structure. These lighter-weight panels can also be installed with ligher, less expensive
crames, making installation cheaper and faster.

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Appendix D: Code
D.1 Back frame code

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D.2 Sheeting code

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Abstract (if available)

Abstract Precast design can take advantage of building information modeling and custom tools to help in the design process of panels. Currently, the traditional 2D design techniques used to create precast panels do not meet the needs of the customer in both quality and speed. As a result, many industries have already made the transition of moving from 2D to using building information modeling software programs. Revit is a common program used by many professionals in the architecture, engineering, and construction industry. The software can be further approved by developing plug-ins in C# for simple or complex tasks by working with the interface of the software (Revit API).
Most thin-shell precast panels are rectangular in design. The precast's weight is supported by a steel back frame made of HSS tubes and anchors that connect to the building. Several design rules that the façade engineers use can be programmed into an app for repetitive tasks. The facade engineers can receive different deliverables from an architect, such as 2D plans or a 3D Revit model. The plugin comes with modeled families to assist with creating a basic architectural model in Revit. After having a base architectural model, the façade skin is panelized. The plugin is then used to reference the geometry of a panel. After getting the boundary shape of the panel, it will create the initial frame offset. If the wall is generic, the plugin can also override the materials settings for a type of precast panel. The next step will create the max spacing and array of the frame. After that, it will find the connection points of the frame to the floor. It will also load the anchor families and find the points. It will also load the pins, and it is parametrically increase into the wall. When a window is added, the panel will recalculate the back frame and move the related connections, anchors, and pins. This plugin automates less complex panels and allows the façade engineers to alleviate some of their work.
A second Revit plug-in helps with documentation by quickly and easily making shop drawings and enabling the configurations of shop drawing templates. After the panels are framed, the shop drawings are set up.

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Asset Metadata

Creator Dam, Victoria (author)

Core Title Streamlining precast back-frame design: automated design using Revit plugin

School School of Architecture

Degree Master of Building Science

Degree Program Building Science

Degree Conferral Date 2022-08

Publication Date 05/09/2022

Defense Date 04/20/2022

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag building information modeling (BIM),envelopes,facades,OAI-PMH Harvest,precast concrete,Revit API

Format application/pdf (imt)

Language English

Contributor Electronically uploaded by the author (provenance)

Advisor Noble, Douglas E. (committee chair), Kensek, Karen M. (committee member), Seal, Steven (committee member)

Creator Email damv@usc.edu,msvictoriadam@gmail.com

Permanent Link (DOI) https://doi.org/10.25549/usctheses-oUC111307051

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Format application/pdf (imt)

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