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University of Southern California Dissertations and Theses
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A proposed wood frame system for the Philippines
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A proposed wood frame system for the Philippines
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INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand comer and continuing from left to right in equal sections with small overlaps. Each original is also photographed in one exposure and is included in reduced form at the back of the book. Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6” x 9” black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directiy to order. UMI A Beil & Howell Information Company 300 North Zed) Road, Ann Arbor MI 48106-1346 USA 313/761-4700 800/521-0600 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Copyright 1996 A PROPOSED WOOD FRAME SYSTEM for the PHILIPPINES by Dominador C. Daplas A Thesis Presented to the FACULTY OF THE SCHOOL OF ARCHITECTURE UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree MASTER OF BUILDING SCIENCE May 1996 Dominador C. Daplas Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number: 1383555 UMI Microform 1383555 Copyright 1997, by UMI Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. UMI 300 North Zeeb Road Ann Arbor, MI 48103 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UNIVERSITY OF SOUTHERN CALIFORNIA SCHOOL OF ARCHITECTURE UNIVERSITY PARK LOS ANGELES, CA 90089-0291 Tftis tfiesis, written By ____________ D o m in a d o r C. D a p l a s ________ under tfie directum o fd i s Hiesis Committee, and approved By a ll its m e m B e rs , Bos Been pre sented to and accepted B y tfie 'Dean o f Hie graduate S c f io o C , in partial fulfillm ent o f tfie requirements fo r tfie d eg re e o f Dean Date H- N + r c L W C . THESES COMMITTEE Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGMENTS Upon the completion of this thesis, I find myself truly blessed by God, the Almighty, for giving all the people around me who have helped me a lot in giving me encouragement and motivation. To Him, my undying faith and gratefulness. First, my deepest gratitude to my parents, who have provided me with all the support that I needed. I don’t think I can thank them enough. Professor G. Goetz Schierle, at the School of Architecture, University of Southern California, who has provided me with all the support, help and feedback not only towards the completion of this work but in everything that I have undertaken. My sincere thanks to him. Professor Marc E. Schiler, Director of the Building Science Program, School of Architecture, University of Southern California, with his inspiring, and encouraging support toward us all in the Building Science Program. To him, my deepest appreciation and honor that I have the opportunity to be under his administration. Professor Dimitry Vergun, at the School of Architecture, University of Southern California, with his constructive comments and suggestions towards the completion of the tests that I have undertaken, I can’t thank him enough. Robert Bueche, Test Lab Superintendent, at the School of Civil Engineering, University of Southern California, to his open hand in helping me operate the testing machine and giving me unlimited access to the testing laboratory. I thank him a lot. ii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Special thanks to everyone in the Building Science Program, to the faculty and classmates, for making me feel part of a family. To my friends, thank you for all their encouragement and inspirational support that they have provided me. iii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS ACKNOWLEDGEMENTS ii LIST OF FIGURES vi ABSTRACT x PART I: BACKGROUND RESEARCH INTRODUCTION 1 CHAPTER 1 WOOD AS A BUILDING MATERIAL 3 1.1 Natural Structure of Wood 3 1.2 Wood and Other Wood Products 7 PHYSICAL PROPERTIES 1.3 Moisture Content 14 1.4 Shrinkage and Swelling 16 1.5 Thermal Properties 17 1.6 Defects in Wood 18 MECHANICAL PROPERTIES 1.7 Strength of Wood 22 1.8 Grading of Lumber 22 1.9 Orientation of Forces 30 CHAPTER 2 FUNDAMENTALS OF TIMBER CONSTRUCTION 2.1 General Description 34 2.2 Development of Wood Structures 35 2.3 Types of Timber Framing 38 2.4 Traditional Wood Connections 42 CHAPTER 3 FABRICATION OPERATIONS 3.1 General Definition 52 3.2 Prefabrication Operations 52 3.2.1 Design Consideration 52 3.2.2 Production Methods and Equipments 53 3.2.3 Subassemby Operations 54 3.2.4 Plant Assembly Operations 54 3.2.5 Painting Operation 55 3.2.6 Inspection for Quality Control 55 3.2.7 Storage and Shipment of House Parts 56 IV Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 3.2.8 Site Assembly 56 CHAPTER 4 CODE REQUIREMENTS (acc. to Phil. Nat. Bldg. Code) 4.1 Sypnosis 4.2 Lateral Forces 4.2.1 Earthquake Forces 4.2.2 Wind Pressure 57 57 57 59 PART O: DESIGN AND ANALYSIS CHAPTER 5 LOAD BEARING TEST 5.1 Built-up Cross Column System 5.1.1 General 5.1.2 Description 5.1.3 Methodology 5.1.4 Observations 5.1.5 Test Results 5.2 Dovetail Connection 5.3 Braced Shear Wall Frame 63 63 63 66 67 68 90 102 CHAPTER 6 PROTOTYPE STRUCTURE, DETAILS AND ANALYSIS 6.1 General Description 112 6.2 The Structural System 112 6.3 Detail Connections 117 6.4 Structural Analysis 121 CHAPTER 7 PROPOSED PREFABRICATION OPERATIONS 7.1 General Description 7.2 Prefabrication Operations 137 138 CHAPTER 8 RECOMMENDATIONS AND FURTHER WORK 8.1 Conclusions 8.2 Recommendations 144 145 BIBLIOGRAPHY 147 v Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LISTS OF FIGURES Figure 1.01 Cross Section of a Log 3 Figure 1.02 Transverse Section of a 9 year-old Stem 5 Figure 1.03 Radial and Tangential Section of a Log 6 Figure 1.04 Growth of Springwood and Summerwood 7 Figure 1.05 Lumber Types 8 Figure 1.06 Assembly of Laminated Beams 9 Figure 1.07 Composition of Construction Plywood 1 1 Figure 1.08 Composition of Furniture Panels 12 Figure 1.09 Bar Chart Showing Different MC Conditions 15 Figure 1.10 Shrinkage Components 16 Figure 1.11 Tearing of Timber due to Shrinkage 17 Figure 1.12 Slope of Grain 19 Figure 1.13 Edge Knots and Center Knot 23 Figure 1.14 Checks, Shakes and Splits 24 Figure 1.15 Types of Warps 25 Figure 1.16 Compression Parallel to Grain 30 Figure 1.17 Compression Perpendicular to Grain 31 Figure 1.18 Tension Parallel to Grain 32 Figure 1.19 Tension Across the Grain 32 Figure 1.20 Bending and Shear 33 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 2.01 Early Form of Wood Frame Structure 35 Figure 2.02 Comer Sill Joints for Stave Structures 36 Figure 2.03 Typical Bent Frame Structure 37 Figure 2.04 Traditional Framing 38 Figure 2.05 Girder on Column 38 Figure 2.06 Tie-Beam Connection 39 Figure 2.07 Split Girder 39 Figure 2.08 Split Column 40 Figure 2.09 Types of Rib Construction 41 Figure 2.10 Butt Joint Fastened with a Key 43 Figure 2.11 Simple Splayed Joint 44 Figure 2.12 Half Lap with Splayed Shoulders 45 Figure 2.13 Notched Heel Joint 45 Figure 2.14 Beveled Slot Mortise and Tenon 46 Figure 2.15 Angled Lap Joints 47 Figure 2.16 Simple Bridle Joints on Post and Beams 48 Figure 2.17 Mortise and Tenon Joints 48 Figure 2.18 Simple Cross Lap and T-shaped Lap Joint 49 Figure 2.19 Simple Doweled Cogged Joint 49 Figure 2.20 Tongue and Groove Joints 50 Figure 2.21 Double Spline and Groove Joint 51 Figure 5.01 Built-up Cross Column 64 vii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 5.02 Cross Sections of Columns 65 Figure 5.03 Baldwin Compression-Tension Test Machine Load Adjuster and output Computer 66 Figure 5.04 Baldwin Compression-Tension Test Machine Compression Table 67 Figure 5.05 Solid Square Column (scale 1:8) 69 Figure 5.06 Solid Cross Column (scale 1:8) 71 Figure 5.07 Built-up Cross Column with Dowel @ 6” spacing (scale 1:8) 73 Figure 5.08 Built-up Cross Column with Dowel @ 12” spacing (scale 1:8) 75 Figure 5.09 Built-up Cross Column with Dowel @ 18” spacing (scale 1:8) 77 Figure 5.10 Solid Square Column (scale 1:4) 79 Figure 5.11 Solid Cross Column (scale 1:4) 81 Figure 5.12 Built-up Cross Column with Dowel @ 6” spacing (scale 1:4) 83 Figure 5.13 Built-up Cross Column with Dowel @ 12” spacing (scale 1:4) 85 Figure 5.14 Built-up Cross Column with Dowel @ 18” spacing (scale 1:4) 87 Figure 5.15 Built-up Cross Column, 2nd Configuration (scale 1:4) 89 Figure 5.16 Dovetail Joint and Direction of Load 90 Figure 5.17 Dovetail Test No. 1, Joint @ 30° Inclination 93 Figure 5.18 Dovetail Test No.2, Joint @ 20° Inclination 95 Figure 5.19 Dovetail Test No.3, Joint @ 10° Inclination 97 Figure 5.20 Dovetail Test No.4, Lateral Shear (sideways) 99 Figure 5.21 Dovetail Test No.5, Lateral Shear (frontal) 101 Figure 5.22 Braced Wall Frame 102 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 5.23 Wall Test No. 1, Glued Connection in Compression 105 Figure 5.24 Wall Test No.2, Doweled Connection in Compression 107 Figure 5.25 Wall Test No.3, Glued Connection in Tension 109 Figure 5.26 Wall Test No.4, Doweled Connection in Tension 111 Figure 6.01 Ground Floor Plan 113 Figure 6.02 Second Floor Plan 113 Figure 6.03 Structural Plans 114 Figure 6.04 Section through Gable End 115 Figure 6.05 Typical Eave Section 116 Figure 6.06 Column to Foundation Connection 117 Figure 6.07 Typical Cross Joint Connection 118 Figure 6.08 Typical T-Joint Connection 119 Figure 6.09 Typical Comer Joint Connection 120 Figure 7.01 Schematic Diagram of Prefabrication Operations 137 Figure 7.02 Erection of Columns 141 Figure 7.03 Installation of Beams and Girders 142 Figure 7.04 Installtion of Floor Joist 142 Figure 7.05 Installation of Rafters and Purlins 143 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT Like many of the developing countries where construction techniques are still to be learned, the Philippines is still a couple of steps back in standardizing its construction industry. Although many innovative techniques have been adapted for steel and concrete structures, nothing much has been done with regard to timber structures, thus making the latter not very competitive as a building system. This thesis aims to develop a proposed wood frame structural system for the Philippines to utilize wood and other related materials more efficiently, so that production may be stimulated and more economical houses produced. The purpose of this study is to facilitate the construction of durable, permanent houses with consideration to design, materials, and fabrication methods. Through detailed design analysis and load-bearing test of structural components and joints, a prototype structure of a two-story residential building was designed and analyzed. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. INTRODUCTION Wood being known as the only renewable building material has a widespread use in the construction of building in both economic and aesthetic aspect, it should achieve more and more use as a material of choice in the preliminary structural building frame. The ability to use wood in the construction of buildings requires minimal amount of equipment that kept the cost of wood frame buildings competitive with other types of construction. The warm qualities of wood brings out the desire to design and build timber structures. As Frank Lloyd Wright once said: “ There is a need to bring forth the beauty of wood, the beauty being its intrinsic property .’ ’(Goetz, K-R, p. 1 , 1989) The following are advantage of wood as a building material : * Wood has good strength in bending, compression and tension. * Wood is a comparatively lightweight material. * Wood is simple to work with, both during construction and finishing stages. * Structural components made of wood can be assembled in may ways. * Wood has a good insulating value, a physical property essential in building. With all the advantages of wood as a building material, there are also factors that we should look up to that are disadvantageous. Since wood is a natural material, it is subject to a number of imperfections or limitations that affects its strength and final use. Strength is not uniform in all direction. Different species differ in their properties. Trees of the same species and parts of the same tree may vary depending on the growth conditions prevailing when the wood was formed. Natural defects such as knots, shakes and splits also affects the strength of wood. There are also blemishes that mars the 1 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. appearance of wood. Not to mention wood as a combustible material. Thus one of the roles of a wood designer is to leam the natural characteristics of wood and to overcome its defects, but also to capitalize on its strength. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 1: Wood as a Building Material i.l Structure of Wood There are two types of wood: hardwood and softwood. Hardwoods are the broadleafed deciduous trees and softwoods are the narrow, needlelike leaves, known as conifers (Breyer, D . E., 1988:107). Most structural lumber is from the softwood species. Structural timber is derived from tree trunks. The live trunks perform three functions: they support the crown of the tree, carry nutrients from the roots to the crown, and store these nutrients. In hardwoods, these functions are performed by three different types of wood cells. Of the three, those which form tubular fibers are primarily arranged in the longitudinal direction of the trunk. In conifers, which have a simple regular structure, a single cell type performs all the tree functions: conducting and storing fluids and providing strength. Wood is composed of elongated, round or rectangular tubelike cells which are essentially parallel with the length of the tree (Fig. 1.01). Figure 1.01. Cross Section of a Log Source: Breyer (1988) 3 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Annual rings are divided into two sector, the earlywood or springwood and the latewood or summerwood. The earlywood or springwood has large thin-walled cells that are formed at the beginning of the growing season. Latewood or summerwood has smaller cells with thicker walls that are deposited on the outside of the annual ring toward the end of the growing season (Breyer, D.E., 1988:108). Annual rings occur only in trees located in the climate zones which have distinct growing seasons. In tropical zones, trees produce wood cells which are essentially uniform throughout the entire year. Summerwoods are denser than springwoods, they are stronger and more solid material per unit volume, with greater strength of wood. Hearthwood is the darker center portion of the log. It represents wood cells which are dead. They provide strength and support for the tree. Sapwood is the lighter portion of the wood near the exterior of the log. It represents the living cells of the wood. The strengths of heartwood and sapwood are essentially the same. Heartwood is more decay-resistant and sapwood more readily accepts penetration by wood-preserving chemicals (Breyer, D.E., 1988:109). If one cut a portion perpendicular to the trunk, the naked eyes can readily discern the structure of conifer woods in three main sections (Fig. 1.02.): * Transverse Section * Radial Section * Tangential Section 4 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Transverse Section: In this section (Fig. 1.02), which is cut perpendicularly to the axis of the trunk, the following layers can be seen (G oetz, K -H ., 1989:15): a. Bark. Composed of outer and inner bark. b. Wood. Composed o yearly cell growth. The annual rings which is the yearly limit of growth of a tree can be readily seen by the naked eye. c. Pith. Dead core tissue surrounded by annual rings. Annual rings Resin ducts - Inner bark O uter bark Transverse cross section - Pith Springwood Summerwood W ood rays Radial section Tangential section Figure 1.02. Transverse Section of a 9 year-old Stem Source: Karl-Heinz, Goetz [et al], (1989) 5 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Radial Section In this section (Fig. 1.03 a), which is cut along the axis of the tree, the annual rings appear as stripes parallel to the axis, while the wood rays appear as radial lines. The wood rays serve as horizontal conduits and storage for nutrients. Initially, formed at the pith, they radiate to the back, and shine when cut longitudinally in a radial section (Goetz, K -H ., 1989:15). (a). Radial Section 1 Wood rays 2 P H h d u c r 3 Annual rings (b) Tangential Section Figure 1.03. (a) Radial Section, (b) Tangential Section Source: Karl-Heinz, Goetz [et all, (1989) Tangential Section The annual rings in this section appear as curved or wavy lines (Fig. 1,03b). Major wood rays cut at right angles appear as spindle-shaped dark stripes. 6 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1.04. Growth of Springwood and Summerwood Source: Karl-Heinz, Goetz [et al|, (1989) Growth and Annual Rings The growth of a tree occurs when cells divide within the cambium layer that envelops the wood core. During this process more new wood cells are produced on the inside of the layer than bark cells on the outside. Early cells are thin-walled tubes with large diameters, In conifers they have a lighter color than the thicker cells of later growth, which are smaller in diameter (Fig. 1.04). The early springwood cells lead the nutrients from the roots to the leaves, while the later summerwood growth, mainly strengthens the trunk (Goetz, K-H., 1989:15). 1.2 Wood and Other Wood Products Wood is categorized as: lumber, laminated beams and other wood products such as: plywood, chipboards, and particle boards. As with all building materials, certain characteristics of wood govern its utility in whatever form it is used. 7 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Lum ber is defined as the product manufactured by saw and planing mill and is cut in specific forms such as: common boards (unedged), sawn lumber, round end boards, end boards, and round end boards (edged) (Fig. 1.05). It is generally delivered rough-sawn, unless planed lumber is used in construction, which has to be expressly indicated in the specifications (G oetz, K-R, 1989:21). T hu/s*s\n\iv wzim Sawn lumber in spaced slacks Common boards, unedged Round end End boards Round end boards, boards edged Figure 1.05. Lumber Source: Goetz, Karl-Heinz [et al],p.21, (1989) The term “ grain" is generally used in connection with appearance lumber. It is used in referring to annual rings, the direction in which fiber runs as straight, spiral, interlocked, curly and wavy grain; and the relative size of the pores and the fibers as open and close grain. The term “ texture” expresses the relative size of pores and fibers or the relative amounts of springwood and summerwood, as “coarse” or “fine” texture, “even” or “uneven” texture. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Lam inated beams (Fig. 1.06) are defined as two or more boards glued together along their wider sides. Boards less than 20 cm wide are arranged in such a way that left and right sides of the boards are glued together, with only the right sides facing the exterior. This arrangement is necessary in order to minimize transverse tension stresses in wood and in the joints due to variations in climate. For members wider than 20 cm. it is necessary to use at least two boards for each laminated layer. Butt joints in each layer must be offset. Boards wider than 20 cm must contain two longitudinal relieving groves on each face (Goetz, K-R, 1989:21). Width b £ 20 cm Width b > 20 cm a. Relieving grooves s 35mm fl/5 to VQ a thickness a Figure 1.06. Assembly of Laminated Beams. Depending on specified size, laminated beams can be manufactured in any length and depth, limited only by the length of the shop, the length of the gluing bed and transportation facilities. In modem laminating plants nearly all preparation of the boards is automated and all ends are finger jointed. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The compensating properties of wood lamination allow the use of the quality grades required by design to be limited to only the outer 15% of depth in the tension and compression zone of the members subject to bending, but to no less than two outer boards. Wood Products There are three limitations to the use of solid timber: the relatively small sizes of beams that can be obtained from the tree stems, the anisotropic properties of wood, and the different shrinkage or swelling properties of wood, in longitudinal and transverse directions. This limitation has led to the development of wood panels which are made in varying widths. They have more uniform strength and deformation properties, and better dimensional stability than solid wood under conditions of variable humidity. The panels are prepared by pressing together many smaller wood particles with adhesives. Three types of panels can be identified, depending on the size of the particles: 1. Plywood 2. Chipboard 3. Particle board Panels can be used as load-carrying members, as stiffener, or as non-load-bearing covering of walls and floors intended for insulation or sound proofing. The plywood category encompasses all panels having at least three layers of wood glued together, the grain of each layer being at a right angle to that of the adjacent layer. It is fabricated from thin layers of wood, called veneers, which are obtained by sawing, cutting, or stripping timber. 10 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Construction plywoods are boards in which all layers are made from veneers which are glued transverse to each other. The elastic and mechanical properties of plywood depend on the grain directions. They are different for each main direction and for each direction at right angle to the surface veneer. Generally, the direction of the surface veneer is considered as the main direction (Fig. 1.07). Furniture panels consist of at least two surfaces of veneers and a core made from wood strips placed adjacent to each other. The direction of grain of each layer is normal to that of adjacent layers (Goetz, K-H., 1989:22). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Surface veneers ^ 2.5 mm Three-lover Jnside veneers ^ 3.7 mm Figure 1.07. Composition of Construction Plywood. Source: Karl-Heinz, Goetz [et al], (1989) 11 Furniture panels are differentiated according to the following types: 1. Core made from small wood strips glued together and placed normal to the panel surface. The strips are made from circularly stripped veneers (Fig. 1.08a) 2. Core made from larger wood strips varying in width and glued together parallel to the panel surface (Fig. 1,08b). 3. Core made from the same type of wood strips as above, but not glued together. Glued Glued Figure 1.08. Composition of Furniture Panels. Source: Karl-Heinz, Goetz [et al], (1989) Chipboards are fabricated from wood chips and similar fiber materials, such as bagasse, flax, or hemp, which are customarily mixed and pressed together with hardening resins. Chipboards with mineral binders have recently gained in importance. When chips are made exclusively from wood, the boards are called wood-chip boards. Fabrication of chipboards follow certain steps. After tree stems have been debarked, they are splintered in large tearing machines, which splinter the wood into chips 12 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. of various sizes. Then chips are dried and sorted. Two practical fabrication procedures are available; they produce chipboards which differ by the layout of the chips in the board. In flat-pressing procedure, the resin-coated chips are spread on form liners and thus they tend to be parallel to the panel surface. A multi-layered buildup is achieved by successfully spreading various types of chips. The forms are then pressed together and panels are formed under heat and pressure. Extrudedpressboards are made by pressing the resin-coated chips into forms by means of an extruding device which moves inside the forms within the cross section of the panel. Deposited in this way, the chips are placed normal to the plane of the panel. The heat in the forms and the speed of deposition are adjusted such that, combined with the applied pressure, the core is produced in continuous formation. Extruded pressboards have lower bending strengths than multilayered flat-pressed panels (Goetz, K-H., 1989:23). Particle boards are wood products made up of wood reduced to fibers or bundles of fibers. Randomly placed, they are formed into a new material with or without the help of binders and fillers. In this product the wood structure can no longer be recognized. However, since there are wood chipboards fabricated from very fine ground chips, there is an area of transition between chipboards and particle boards. In the fabrication of particle boards, the raw materials can consist of softwood and bark of the lowest quality. Hardwoods are suitable only as additives because of their short fibers. Other plant fibers, such as straw, wood shavings, jute or coconut, can also be added. The raw material are ground to splinters, humidified and mechanically reduced to the fibers in a defibrator. In order to homogenize the composition, ground fibers are 13 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. mixed with water and thoroughly stirred in large containers. The strength and water- repellent properties of the end product are regulated by admixtures of chemicals and binders. The pulp is dried on long sieves, partially by gravity and partially by vacuum and rolling cylinders. The final handling depends on the type of panels to be produced. In the newest drying procedure, in which air replaces water for mixing and gluing, several layers of panels may be prepared, and the panels may be smooth on both sides. Wood-particle boards are differentiated mostly by hardness (strength) or surface treatment (Goetz, K -H ., 1989:24). Physical Properties 1.3 Moisture Content and Shrinkage of Wood The solid portion of wood is made of a complex cellulose-lignin compound. The cellulose comprises the framework of the cell wall, and the lignin cements and binds the cells together. In addition to the solid material, wood contains moisture. The moisture content (MC) is measured as the percentage of water to the dry weight of the wood. moist weight - dry weight MC = ---------------------------------- x 100 (%) dry weight For most species, the moisture content of a tree can be two times the weight of the solid material making it as high as 200 percent. The average moisture content that lumber assumes in service is known as the equilibrium moisture content (EMC). Depending on atmospheric conditions, the EMC of structural framing lumber in a covered structure (dry 14 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. conditions) will range somewhere between 7 to 14 percent. In most cases, the MC at the time of construction will be higher than the EMC of a building. Moisture is held within wood in two ways. Water contained in the cavity between cells is known as free water. Water contained within the cell is known as bound water. As wood dries, the first water to be driven off is the free water. The moisture content that corresponds to a complete loss of free water is known as the fiber saturation point (FSP). In Figure 1.09 shows the moisture content in lumber in comparison with its solid weight. The values indicate that the lumber was fabricated (pt. 1) at an MC below the fiber saturation point. Some additional drying occurred before the lumber was used in construction (pt.2). The EMC is shown to be less than the MC at the time of construction which is typical in most building (Breyer, D.E., 1988:109). M C itJ Figure 1.09. Bar Chart Showing Different MC Conditions Source: Breyer, D.E, p.l 10 (1988) 15 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1.4 Shrinkage and Swelling Shrinkage and swelling are represented by dimensional changes due to variation of moisture content. The removal of cell-wall moisture causes shrinkage and increases wood’s strength and elastic properties and the addition of moisture in dry-cell causes swelling as well as the reduction of strength and elastic properties (G oetz, K -H., 1989:26). Shrinkage and swelling are reversible processes and vary considerably according to various directions of the yearly growth rings and the grain of wood. Dimensional changes are largest tangentially to the annual rings, half as large radially and are negligible in the direction of the grain (longitudinally). Shrinkage components are shown in Fig. 1.10. Six tfTtf 5HKIUK166. Figure 1.10. Shrinkage Components Source: Breyer (1988) Lighter wood is less prone to dimensional changes cause by the changes in moisture. This is due to the fact that the higher percent change in moisture are, the more material there is in the cell wall. Thus, shrinkage and swelling rates depend on the unit 16 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. weight of wood. Fig. 1.11 shows the characteristic shrinkage and distortion of flats, squares, and rounds as affected by the direction of the annual rings (Hoyle, R.J., 1989:26). Figure 1.11. Tearing of Timber due to Shrinkage Source: HoyIe,RJ., p.26 (1989) 1.5 Thermal Properties The thermal properties of wood within the normal temperature range of -25 to + 60 °C encountered in buildings, generally determine its suitability as a structural material or as a material for interior finishes and insulation. Thermal Expansion: The effect of temperature on the length of lumber is very small. For softwoods, the longitudinal expansion coefficient is about 18 x 10'5 in. per inch per degree F. For hardwoods, the coefficient is larger, about 25 x 10'5 in. per inch per degree F. When wood is heated, moisture is driven off. The size change is a combination of thermal expansion and contraction due to drying. In most situation for wood with 3 to 4 % moisture content, the shrinkage due to moisture loss will exceed the expansion due to 17 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. temperature, resulting is a net reduction size. At intemediate moisture levels, about 8 to 20 %, wood will first expand when heated and then shrink to a smaller volume, the net effect being negative (Hoyle, R.J., 1989:27). Thermal Conductivity Wood is superior to most common structural materials as an insulator. This insulating effect should not be overlooked in design, as it contributes to the operating economy of buildings. Heat transfer losses depend on surface area. The direction of heat transfer is usually across rather than along the grain. The low thermal conductivity of wood makes expansion due to temperature change very slowly. The total thermal contraction of beams exposed to winter weather at their ends is much less for wood than for steel. When fire raises the temperature, unprotected metal beams respond very much faster than wood, both in terms of expansion and in terms of strength loss (Hoyle, R.J., 1989:27). 1.6 Defects in Wood Wood with a straight grain without knots, holes, or cracks has the highest strength possible for its species. Such a piece of wood is available only in very limited dimension. The reality of wood as a natural material is that it is full of growth characteristics that affect the appearance and strength of the material. Visual stress grading correlates the size, quantity, and location of the variety of defects with their strength-reducing effects. Each piece of lumber that is visually graded is examined for all of these defects and assigned a grade and a set of strength based on the most limiting of the defects. 18 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. When a log is cut into pieces of lumber, each piece exhibits certain lines along its length called grain. The grain is never in perfectly straight lines because trees do not grow perfectly straight. Slope o f grain (Fig. 1.12) is the deviation of the line of fibers from a straight line parallel to the sides of the piece (Halperin, D. A., 1994:7). A piece nth o ratio of 1 to 20 M e horizontal ratio forage line of the M o n of mod fibers Figure 1.12. Slope of Grain Source: Halperin/Bible, p.09 (1994) In figure 1.12 the line of the fibers deviate from the side of the piece by an inch over a length of the piece in 12 inches. This slope is referred to as 1 in 12. The strength of wood in tension and compression is greater in the direction of the grain. If the grain aligns exactly with the sides of the piece, a piece of wood will have the greatest available strength, particularly when loaded in compression, tension, or bending. Thus, lumber with a smaller slope of grain will have greater strength. Slope of grain can arise from two sources. Most trees grow by laying down the wood cells at a slight angle to the axis of the tree. The cells spiral around the tree, resulting in spiral grain. The other possible cause of slope of grain comes from manufacturing, where lumber may be sawn at a right angle to the axis of the tree. The 19 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. two forms of slope of grain may coexist. For the purpose of grading and assigning strength, their effects are the same. A knot is a portion of the branch or limb that has become incorporated in a piece of lumber. Knots reduce the strength the wood in two ways. They replace the wood of the trunk with the wood of the knot, which we assume has no strength. This is particularly true for loose knots, but is a good assumption even for knots that are tight. The other consequence is that the grain of the wood winks around a knot, leaving an area with a local deviation of grain. The larger the knot, the larger will the deviation of the grain; as a consequence, the greater will be the reduction of strength (Halperin, D . A., 1994:9). The National Grading Rule lists the allowable knot sizes for all grades of lumber 2 to 4 in. thick. The rule recognizes that the location of the knot is an important factor in determining the strength reduction. Lumber loaded in bending, such as joists, will have the maximum stress in the extreme fibers at the top and bottom edges. A knot in this location has a greater impact on the strength than does a similar-size knot in the middle of the piece. Table 2.1 lists the maximum allowable knot sizes for the edge of the wide face and for the centerline wide face. 20 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 2.1. Grades and Limiting Characteristics Characteristic Maximum Permissible Select Structural No. 2 Strength (as a percentage of clear wood strength) Slope of Grain Knots Knot size Edge of wide face Centerline wide face Unsound knot Splits Shake Checks Wane Pitch Streaks Pitch or Bark pockets Rate of Growth Stain Skips 65% 1 in 1 2 Sound, firm, encased, and pith knots if fight and well spaced, are permit ted in sizes not to exceed the follow ing, or equivalent displacement 1 7/ 8 in. 2 5 /g in. 1 ' / 4 in. Equal in length to the width of the piece ( 1 0 in.) If through at ends, limited as splits. Surface shakes up to 2 ft. long. Surface seasoning checks not limited through checks at end are limited as splits. V 4 the thickness, ' / 4 the width, full length; provided that wane not exceed ' / 2 the thickness or V3 the width for ' / 4 the length. Not limited Not limited Not limited Stained sapwood, firm heart stain or firm red heart limited to 1 0 % of pieces Hit and miss in 10% of pieces Warp l / 2 o f medium 45% 1 i n 8 Well-spaced knots of any quality are permitted in sizes not to exceed the following or equivalent displace ments. 3 '/A in. 4 V4 in. 2 ‘ / 2 in. Equal in length to 1 ' / 2 times the width (15 in.) If through at ends, limited as splits. Away from ends through shakes up to 2 f t long, well separated. If not through, single shakes shall not exceed 3ft. long or ' / 4 the length whichever is greater. Seasoning checks not limited; through checks at end are limited as splits V 3 the thickness, V3 the width, full length; provided that wane not exceed 2/ 3 the thickness or ’ / 2 the width for ' / 4 the length. Not limited Not limited Not limited Stained sapwood, firm heart stain or firm red heart not limited Hit and miss with a maximum of 5% of the pieces containing hit or miss or heavy skip not longer than 2 ft Light (S o u rce: N a tio n a l G ra d in g R u le.) 21 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Mechanical Properties of Wood 1.7 Strength of Wood The mechanical properties of wood, pertaining to the design specifications which contain information of the strength about commonly used species and grades of wood, strengths of connectors and standard engineering principles. Strength is a general term related to those properties that enable a material to resist forces. Generally, it is preferable to refer more specifically to the strength property being considered, such a strength in bending, shear or compression parallel to the grain. Allowable properties of visually stressed-graded lumber are based on the measured characteristics of clear, straight-grained, unseasoned wood. The commonly used visual stress-grading system involves assesing the effects of knots, knotholes, sloping grain, and other permitted strength-reducing characteristics on each property of each grade, as a percentage of the clear wood strength. These percentage are called strength ratios. A process of combining basic, unseasoned, clear, and straight-grained wood strength with the strength ratios of the grade and adjusting these values for moisture content and several factors to account for the differences between laboratory test results and in-service performance yields the allowable properties of design (H oyle, R.J., 1989:31). 1.8 Grading of Lumber One major step in turning a natural material into an engineered product is the grading of lumber. The basis of grading is to establish a relationship between the defects in wood and the strength of the wood (Halperin, D.A., 1994:10). 22 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. For joists and plonks the size of a knot on the vide face is the ovg. between the largest and smallest diameters The size of a knot on the edge of the w ide face is its w idth between lines parade! to the edge of the piece ( a > B=mndmum ollonoble knot size on the wide face C=mdnmum aHovabie knot size on the norm* face in the middle third of the length of the beam Maximum size of knot in the middle third ncreoses from C to B at the center of the mde face Maximum size of rife face knot ri the outer third increases from C to 2C (but not to exceed B] ot the ends (b ) Figure 1.13. Edge knot and centerline knot: (a) measuring knots and, (b) maximum size of knots Source: Halperin/Bible (1994) Wood splits are another form of natural wood defects which occur for a variety of reasons. Splits are defined and measured depending on their orientation with respect to 23 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. the growth rings. There are three types of wood splits (Fig. 1.14). Splits and shakes occur only at the ends of lumber (Halperin, D.A., 1994:10). measure average penetration measure average penetration in joists and planks, and beams and splits ore measured as the stringer^ shake is measured at the end penetration of the split from of the piece between lines parallel to the the end of the piece and wide faces . . . . . . (a) (W parallel to the edges of the piece (0 Figure 1.14. (a) Checks, (b) Shakes, and (c) Splits. Source: Halperin/Bible (1994) Splits, checks, or shake at the ends will reduce the shear capacity of a piece of wood. These defects, particularly checks, are a result of dying and may increase after the lumber has been graded and has left the yard. The NDS (National Design Specification) therefore assumes that all pieces have the worst possible combination of splits, shake, and checks: namely, a split completely through the piece at the end. The allowable shear strengths listed in the NDS may be adjusted upward if there are smaller splits than assumed. Checks away from the ends have little effect and are not considered. Checks are separations of the wood normally occurring across or through the rings of seasoning. Shake is a lengthwise separation of the wood which usually occurs between or through the rings of annual growth. Shake between rings, called ring shake, is most common. It is caused principally by the severe stressing of the living tree due to wind 24 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. storms. Splits are separations of the wood due to tearing apart of the wood cells (Halperin, D.A., 1994:10). Wane is another form of wood defect. It is known to be a bark, or lack of wood, on the comer edge of the board. Wane occurs as a result of the sawing process when a board is cut too close to the edge of the tree. It does not diminish the strength of the wood, but it obviously does result in less wood area than a full-size piece. Its edge, so that nails used to hold up on plywood or other sheathing will have less penetration into the wood and less “bite” (Halperin, D.A., 1994:10). Warp is any deviation from a true plane of surface, including bow, crook, cup, and twist, or any combination (Fig. 1.15). So* is a deviation flatwise from a straight line drawn from end to end of a piece. It is measured at the point of greatest deviation. («) Cup is a deviation in the foce of a piece from a straight line drawn edge to edge of a piece. It is measured a t the point of greatest deviation. <c> W ) Sweep is a deviotion edgewise Irom o straight She drown from one end of a piece, parallel to original line of the piece. Crook is a deviation edgewise from a straight line drawn from end to end. It is measured at the point of greatest deviation. Figure 1.15. Type of Warps, (a) Bow, (b) Sweep, (c) Cup, and (d) Crook Source: Halperin/Bible (1994) 25 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Warp is a result primarily of unequal shrinking as the material dries. Warp has more of an effect on construction than on strength-warped wood does not fit into straight buildings. Wood that is warped can be stressed while being straightened, leaving less available strength to carry the applied loads. Each grade has limits as to the amount of warp that is allowed. Compression wood is abnormal wood that forms on the underside of leaning and crooked coniferous trees. In addition to its distinguishing pale color, it is characterized by being hard and brittle and by its relatively lifeless appearance. It is not permitted in readily identifiable and damaging form in stress grades (Halperin, D.A., 1994:10). The succeeding tables are averages of the strength of various species of wood used in construction in the Philippines at three different stress grades. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 3.1 Working Stresses for Visuality Stress-Graded Unseasoned Structural Timbers of Philippine Woods Species common and botanical names Bending and tension parallel to grain 80% Stress Grade Modulus of elasticity in bending Compression parallel to grain Compression Shear perpendicular parallel to grain to grain x 103 lbs./in2 lbs./in2 lbs./in2 lbs./in2 lbs./in2 Acacia (Samanea saman (Jacq.)Merr.) 1700 560 1068 560 190 Agoho (Casuarina equise- tifolla L.) 3750 1800 2120 1000 265 Almaciga (Agathis phili- ppinensis Warb.) 1700 1120 950 250 132 Almon (Shorea almon Foxw.) 2000 1250 1180 335 132 Anang (Diospyros sp.) 2800 1400 1600 475 200 Apitong (Dipteroscarpus sp.) 2360 1600 1400 375 160 Bagtikan (Parashorea plicata Brandis) 2500 1320 1500 335 170 Benguet pine (Pinus Insularis Endl.) 2240 1320 1250 335 170 Binggas (Terminalla citrina) 3150 1500 2240 850 265 Bitaog (Calophyllum sp.) 2360 1900 1400 425 180 Bok-Bok [Xanthophyllum excelsum (Blume) Bakh.] 2800 1400 1600 500 180 Dangula [Teijsmannladendroa ahemianum (Merr). Bakh] 4500 2000 3150 1700 300 Guijo (Shorea sp.) 3000 1800 1800 630 212 Kamatog [Erythrophloeum depsiflorum(Elm)Merr. ] 3150 1600 1800 670 224 Kakilma (Diospyros nitida Merr.) 3350 1800 1900 600 136 Lanipau (Teminalla cope- landil Elm.) 2000 1250 1250 300 132 (Source: Philippine National Building Code, 1992) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 3.2 Working Stresses for Visuality Stress-Graded Unseasoned Structural Timbers of Philippine Woods Species common and botanical names 67% Stress Grade Bending and tension parallel to grain Modulus of elasticity in bending Compression parallel to grain Compression perpendicular to grain Shear parallel to grain lbs/m2 x 103 lbs./in2 lbs./in2 lbs./in2 lbs./in2 Acacia (Samanea saman (Jacq.)Merr.) 1400 530 900 450 190 Agoho (Casuarina equise- tifolla L.) 3150 1700 1800 800 265 Almaciga (Agathis phili- ppinensis Warb.) 1400 160 800 200 132 Almon (Shorea almon Foxw.) 1700 1180 1000 265 132 Anang (Diospyros sp.) 2360 1320 1320 375 200 Apitong (Dipteroscarpus sp.) 2000 1500 1180 300 160 Bagtikan (Parashorea plicata Brandis) 2120 1250 1250 265 170 Benguet pine (Pinus Insularis Endl.) 1900 1250 1060 265 170 Binggas (Terminalla citrina) 2650 1400 1900 670 265 Bitaog (Calophyllum sp.) 2000 1250 1180 335 180 Bok-Bok [Xanthophyllum excelsum (Blume) Bakh.] 2360 Dangula [Teijsmannladendroa 1320 1320 400 180 ahemianum (Merr). Bakh] 3750 1900 2650 1320 300 Guijo (Shorea sp.) 2500 1700 1500 500 212 Kamatog [Erythrophloeum depsiflorum(Elm)Merr. ] 2550 1500 1500 530 224 Kakilma (Diospyros nitida Merr.) 2800 1700 1600 475 136 Lanipau (Teminalla cope- landil Elm.) 1700 1180 1060 236 132 (Source: Philippine National Building Code, 1992) 28 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 3.3 Working Stresses for Visuality Stress-Graded Unseasoned Structural Timbers of Philippine Woods 56% Stress Grade Species Bending Modulus Compression Compression Shear common and botanical and tension of elasticity parallel perpendicular parallel names parallel to grain in bending to grain to grain to grain lbs./in2 x 103 lbs./in2 lbs./in2 lbs./in2 lbs./in2 Acacia (Samanea saman (Jacq.)Merr.) 1180 475 750 450 160 Agoho (Casuarina equise- tifolla L.) 2650 1500 1500 800 224 Almaciga (Agathis phili- ppinensis Warb.) 1180 950 670 200 112 Almon (Shorea almon Foxw.) 1400 1060 850 265 112 Anang (Diospyros sp.) 2000 1180 1120 375 170 Apitong (Dipteroscarpus sp.) 1700 1320 1000 300 132 Bagtikan (Parashorea plicata Brandis) 1800 1120 1060 265 140 Benguet pine (Pinus Insularis Endl.) 1600 1120 900 265 140 Binggas (Terminalla citrina) 2240 1250 1600 670 224 Bitaog (Calophyllum sp.) 1700 1120 1000 335 150 Bok-Bok [Xanthophyllum excelsum (Blume) Bakh.] 2000 Dangula [Teijsmannladendroa 1180 1120 400 150 ahemianum (Merr). Bakh] 3150 1700 2240 1320 250 Guijo (Shorea sp.) 2120 1500 1250 500 180 Kamatog [Erythrophloeum depsiflorum(Elm)Merr.] 2240 1320 1250 530 190 Kakilma (Diospyros nitida Merr.) 2360 1500 1320 475 200 Lanipau (Teminalla cope- Iandil Elm.) 1400 1060 900 236 112 (Source: Philippine National Building Code, 1992) 29 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1.9 Orientation of the Forces To understand fully the values in the proceeding tables, it is best to analyze the different forces acting on the material. Wood fiber is composed of wood cells. These cells are composed of cellulose, which are like fibers, and lignin, which glues the cellulose fibers together. The orientation of the cells is generally such that the axis of the cell aligns with the axis of the tree (Fig. 1.16). Because the cells are strongest in their long direction, wood exhibits a high strength in compression when loaded along the axis of the tree. This strength is referred to as compression parallel to grain (Halperin, D.A., 1994:5). Because the tube shape of the cells is much weaker in the direction perpendicular to its axis, wood exhibits much less strength when compressed across the grain. Wood is weaker in compression perpendicular to the grain. Wood is loaded in compression 30 Figure 1.16. Compression Parallel to Grain (Fc ) Source: Halperin/Bible (1994) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. perpendicular to grain (Fig. 1.17) when it is used in bearing, such as at the end of a beam (Halperin, D. A., 1994:7). Figure 1.17. Compression Perpendicular to Grain (Fc ) Source: Halperin/Bible (1994) Lignin bonds the cellulose together and thus bonds cell to cell. Because of its strength, wood can perform well under tension loads when applied parallel to the grain of the wood along the axis of the tree (Fig. 1.18). This strength is referred to as tension parallel to grain (Halperin, D.A., 1994:7). The strength of wood in cross-grain tension is so small that it is considered to have no tensile strength perpendicular to grain. All wood design codes forbid using wood in such a way that it will be loaded in tension perpendicular to grain (Fig. 1.19). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. f t & f t Figure 1.18. Tension Parallel to Grain (Ft) Source: Halperin/Bible (1994) f Figure 1.19. Tension Across the Grain Source: Halperin/Bible (1994) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. A member that is subject to bending forces must be able to resist both tension and compression with relatively equal ease. Because wood has good strength characteristics in both tension and compression it is an ideal bending member. The bending strength is usually controlled by the ability to carry tension. Any beam that is loaded perpendicularly to its long axis will develop both bending and shear stress. Shear is composed of a vertical and horizontal component. Wood has far less capacity to resist horizontal shear than it does vertical shear. Horizontal shear (Fig. 1.20) causes the wood to split along the grain. It is common in some wood members, particularly short beams, that shear will govern the design (Halperin, D.A.,1994:7). Applied load Horizontal S h e a r Figure 1.20. Bending and Shear. Source: Halperin/Bible (1994) 33 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 2: Fundamentals of Timber Construction 2.1 General Description The widespread use of wood in the construction of building has both economic and aesthetic basis. The ability to construct wood buildings with a minimal amount of equipment has kept the cost of wood frame buildings competitive with other types of construction, not to mention the development of new techniques in wood and timber construction such as new types of connections and combining lumber with derivative wood products. The heart of early buildings was the timber frame in which most parts of it are cut on the ground and linked into sections called bents, then raised into place with the bents linked together by plates and sill beams. A bent is a framework usually designed to carry both lateral and vertical load which is transverse to the length of the frame structure (Sobon, J., 1984:1). Where architectural considerations are important, the beauty and warmth of exposed wood is difficult to match with other materials. It is essential to introduce the subject of timber design as applied to wood-frame building construction. However, the present wide range of timber construction is due mostly to advanced engineering techniques which rest on principles proven and refined over many years. During the recent past, stud framing has been widely used for wood construction because it is easier and faster to work with and requires less special skills to construct. Today, the availability of power tools, play a role in lowering cost of timber frame construction. 34 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2.2 Development of Wood Structures The oldest existing roof structure dates from about 1000 AD. Various wooden building fragments that have survived from the 4th century provide us with information on earlier methods of wood construction. A basis for understanding even earlier structures can be found in art, in notched openings left in masonry where roof beams once rested, in stone imitations of wood construction and in wood remnants preserved in water and bogs. 2.2.1 Pole, post and palisade buildings The earliest dwellings in Japan were hollows in the ground that were covered with a roof, the supporting stakes were staked to the ground (Fig. 2.01), a technique that was used in European pole and post buildings. At about the same time, palisade structures were built in Europe, with walls constructed of vertical trunks set side by side in the ground (Graubner, W., 1992:11). Figur 2.01. Early form of Wood Frame Structure Source: Wolfram Graubner, 1992 35 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2.2.2 Stave Buildings Stave construction, a refinement of post building, developed by the vikings in northern Europe during the 4th century. Wood columns up to 33ft. long extended to the foot purlins and ridge purlin, making it possible to build purlin roof trusses with relatively large spans. This framework of columns were crowned by rectangular plates housed in open mortises cut in the upper ends of the comer posts, or staves (Fig. 2.02). The intermediate column ends were housed in a groove in the plate. On the lower end, a sill was tenoned between the columns with a groove on its upper edge to receive the vertical wall planks (Graubner, W., 1992:12). Figure 2.02. Comer Sill Joints for Stave Structures Source: Wolfram Graubner (1992) 36 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2.2.3 Bent Wood Frame Structures This method of construction predominated in Europe between the 8th and 11th centuries (Fig. 2.03). In Bent construction, two upright wall post are joined with a horizontal beam and a pair of rafters to form a bent (Sobon, J., 1984:12). I I 9 Figure 2.03 A typical Bent Frame Structure Source: Karl-Heinz Goetz, 1989 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2.3 Framing Types: 2.3.1 Traditional Building Frames (14th to 18th Centuries) - in this type ofbuilding, the frame consist of columns (pillars, post, studs) and main beams (girders, headers, sleepers, or sills) (Goetz, K-H., 1989:179). Figure 2.04 Traditional Framing Source: Goetz .Karl-Heinz, [et al], 1989 2.3.2 Post and Beam Construction - structures of this type consist of posts which rest on girders. All girders are parallel; secondary girders, beams, or planks are placed normal to them (Goetz, K-H., 1989:179). (a) Single Storey (b) Two Stories Figure 2.05 Girder on Column Source: Goetz ,Karl-Heinz, [et all, 1989 38 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2.3.3 Tie-Beam Construction - the main girders are set as tie beams into continuous columns with identical details in four directions. All interior and exterior connections occur on the same level (G oetz, K -H ., 1989:180). Figure 2.06 Tie-Beam Connection Source: Goetz ,Karl-Heinz, [et alj, 1989 2.3.4 Twin-Girder Framing - continuous twin girders span between continuous columns and are attached to their sides. Floor beams or planks are supported by the twin girders. The advantage o f this system is that both post and girders are continuous and vertical pipes or ducts can pass between beams (Goetz, K-H., 1989:180). Figure 2.07 Split Girder Source: Goetz, Karl-Heinz [et al], 1989 39 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2.3.5 Split-Column Framing - continuous girders are placed between split columns. Twin columns represent a reversal of twin girder framing (Goetz, K-H., 1989:180). Figure 2.08 Split-Column Framing Source: Goetz, Karl-Heinz, [et all, 1989 2.3.6 Rib Framing - this type of construction is mainly used in the United States under the names of balloon framing and platform framing. The load-carrying members of a rib structure consist of nominally 2”x4” lumber studs(Goetz, K-H., 1989:180). In balloon construction (Fig. 2.09a) the wall studs continue through all floors. Upright planks are cut into the studs as sills at every floor, the joist resting on them are nailed sidewise to the studs. In platform construction (Fig. 2.09b) continuous floor sills rest of top of wall studs; the joists of the next floor rest on sills. A new deck is laid on the joist and forms a new platform. 40 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. % \ \ (a) Balloon Framing (b) Platform Framing Figure 2.09 Types of Rib Construction Source: Goetz, Karl-Heinz, [et al], 1989 41 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2.4 Traditional Wood Joint Connections Traditional connections includes multiple hand-cut connections which have been developed through centuries of experience. The use of wood joint connections is an opportunity to continue an old tradition and to develop new alternatives on how to manufacture them using modem technology and to give a new appreciation of the quality and value of wood. Such joinery actually restrains wood from its natural characteristics of warping and contracting. There are certain drawbacks with the use of traditional joint connections primarily the weakening of the timber due to mortises and notches created, and the high degree of workmanship and difficult assembly or elements. These drawbacks can be compensated for by alternative solutions. The weakening of timber could be compensated for by larger sections of timber, and the degree of workmanship can be utilized more efficiently by the use of mechanized power tools, with the proper planning of cutting and material preparation. Different joint forms were not developed exclusively for a particular function, and it is not self-evident which joint should be used in which part of construction. The great majority of wood joints came into existence as generations of craftsmen developed and adapted existing joints in response to changing conditions and demands. Thus, simple lap joints and mortise and tenon joints have evolved into complex joint forms that can withstand stresses from all sides. Joints are made where supporting and supported elements meet, where timbers must be spliced together, supported or braced and where boards have to be joined together, or secured to prevent warp. 42 with permission of the copyright owner. Further reproduction prohibited without permission. A wood joint is basically the mating of two or more surfaces to form a solid unit that serves a specific purpose. To choose the most appropriate joint for a building, it is important to consider carefully the different forces acting on the structure. The characteristics of the wood used should also be taken into account (Graubner, W., 1992:25). Depending on the position of the mating timbers, joints must be made both with the grain and across the grain. Joints are presented in the following order: 2.4.1 Splicing joints for lengthening horizontal and vertical members. This type of joint is used whenever the natural length of a timber is shorter than that needed for horizontal member such as beams, sills, purlings, girts, and joist. They are also used to extend the length of rafters (Graubner, W., 1992:28). Type of splicing joints: 2.4.1a. A butt joint (Fig. 2.10) is a commonly used joint that is always secured with a key or wedge across the ends of two mating parts. Gluing a butt joint is effective only if the pores on the end-grain surfaces are first filled with thinned adhesive (Graubner, W., 1992:30). Figure 2.10 Butt joint fastened with a key Source: Graubner, 1992 43 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2.4.1b, Splayed joints (Fig 2.11) are similar to butt joints but the area of mating surfaces is greatly increased by angling the cuts. This provides a better gluing surface, which makes splayed joints more common than butt joints for cabinetmakers (Graubner, W „ 1992:31). Figure 2.11 Simple Splayed Joint Source: Graubner, 1992 2.4.1c. Lapped scarf joints (Fig.2.12) are made with mating members that are cut to half thickness members at their ends. Lap joints can be cut in various ways to enable them to withstand forces of compression and help to prevent vertical shifting. However, half the thickness of the mating members being removed to make the joint, the wood is weakened in cross section. As a result, lap joints can be used only where vertical loads on the joint are insignificant or where they are adequately supported from below (Graubner, W., 1992:32). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. z 1/ 7 Figure 2.12 Half Lap with splayed shoulders Source: Graubner, 1992 2.4.2. Oblique joints are for joining timber at angles less than 90°. This type of joint is of secondary imprtance in Japanese wood construction, but in the West, by contrast, oblique joints are used extensively in the construction of roofs, houses and bridges (Graubner, W„ 1992:64). Types of Oblique joints: 2.4.2a. The notched heel (Fig.2.13) joint is the basic form of the oblique joinery. The angle of the front shoulder is critical and is bisecting the adjoining member (Graubner, W„ 1992:365). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. IV Figure 2.13 Notched Heel Joint Source: Graubner, 1992 45 2.4.2b. A slot mortise and tenon (Fig.2.14) can be used instead of a notched joint. The advantage of this joint is that it can withstand lateral stress. Although the mortised beam is not weakened as much as in simple notched joint, the load bearing capacity of the brace’s slot tenon is about three times less. Slot mortise and tenon are often used on knee braces between posts and the top plate, where the load is not too great. A disadvantage of this joint is that it can open when the wood shrinks or twists (Graubner, W., 1992:67). Figure 2.14 Beveled Slot Mortise and Tenon Source: Graubner, 1992 2.4.2c, Angled lapped joints (Fig. 2.15) are used to connect king posts and their supporting braces. For rigid bracing, where both compression and tension must be resisted, angled half-dovetail lap joints are often used. Collar ties and rafters are also joined with half dovetails (Graubner, W „ 1992:79). 46 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Angled Lap Joint Angled lap joint on a collar tie Figure 2.15 Angled Lap Joints Source: Graubner, 1992 2.4.3. Corner joints for connecting timbers at right angles. Right-angled joints take the form of comer joints, T-shaped joints and cross joints. The basis form of all right-angled joints is the fork, or groove, into which is inserted a perpendicular mating member (Graubner, W., 1992:82). Types of Comer and Cross Joints 2.4.3a. The bridle joint (Fig. 2.16) is one of the simplest form of a right angled joint and has been known in the West since the time of the first Viking stave buildings and is still used in modem construction. A horizontal beam is housed in a fork cut in the end of a vertical support. The joint is secured by bolt or peg (Graubner, W„ 1992:83). 47 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 2.16 Simple Bridle Joints for Post and Beams Source: Graubner, 1992 2.4.3b. Mortise and tenon joints (Fig. 2.17) are one of the most common joint form used for right angled joints. The ease of construction and ability ot withstand forces from several directions makes it well suited joint for connecting post, beams, wall plates, sills and other members in timber-frame structures (Graubner, W„ 1992:86). (a) Haunched Mortise and Tenon (b) Through Mortise and Tenon Figure 2.17 Mortise and Tenon Joints Source: Graubner, 1992 48 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2.4.3c, Lap joints (Fig. 2.18), like mortise and tenon, have a large number of variations that are derived from a simple, basic form. The basic lap-joint design has ends of two pieces of wood overlap, or one member crosses another (Graubner, W ., 1992:101). Figure 2.18 Simple Cross Lap and T-shaped Lap Source: Graubner, 1992 2.4.3d. Cogged joint (Fig. 2.19) differ from common lap joints in that the surfaces of the cogged members are not flush and the members are always horizontal. The advantage of the cogged joint is that it does not significantly weaken the cogged timbers, because of its shallow groove (Graubner, W „ 1992:115). Figure 2.19 Simple Doweled Cogged Joint Source: Graubner, 1992 49 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2.4.4. Edge joints for joining boards edge to edge. Also within this category are joints that are made by inserting sliding battens perpendicular to flat boards to prevent warp (Graubner, W„ 1992:124). Types of Edge Joints 2.4.4a. The tongue and groove joint (Fig. 2.20) is a very old edge joint that has a multitude of applications, whether as a glued joint or unglued. These type of joints are found in plank construction, flooring, wall paneling and frame-and-panel construction. The tonge should be about one-third the thickness of the board. The groove’s cheeks are the weak points of the joint (Graubner, W„ 1992:127). Figure 2.20 Tongue and Groove Joints Source: Graubner, 1992 50 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2.4.4b. The spline-and groove joint (Fig. 2.21), or loose spline, was used widely in the plank ceilings of Romanesque stone churches. One advantage of the splined joint is that it saves wood; another is that it saves time for the craftsman, because it is not necessary to cut two different profiles on the edges of the boards to be joined (G raubner, W „ 1992:125). Figure 2.21 Double Spline-and-groove Joint Source: Graubner, 1992 51 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 3: Prefabrication 3.1 General Definition The U.S. National Bureau of Standards defines prefabricated houses as those having floors, walls, ceiling, or roof composed of sections, or panels, of varying sizes which have been fabricated prior to erection on the building foundation. This is in contrast with conventionally built houses that are constructed piece by piece on the site (FPL., 1947:211). Basically, its primary objective was to place as much as possible of the building operations in a factory for better quality control and away from the vagaries of weather conditions. Advantages of prefabrication, other than the avoidance of delays due to weather, include economies possible through the use of jigs, power cutting tools, and other equipment, and to eliminate waste of material. 3.2 Prefabrication Operations 3.2.1 Design Consideration The most important factor in the design process of prefabrication is modular coordination. Depending on the type of house and the builder’s approach, the cardinal principle of all assembly line fabrication is the production of large numbers of identical units. The houses must be reduced to a minimum number of different parts, each so designed that it can be interchangeable with others of its particular size and construction and will fit ito its 52 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. proper place in any house of like design. To achieve such identity and interchangeability call for a system of design. There are three types of design system approach for prefabricated houses (FPL., 1947:213): 3.2.1a. Ready-cut H ouse - is a system in which framing, sheathing, fastenings, and other materials usually are prepared and stenciled, by the material supplier, with the identifying part marked according to established house designs. Actual construction and assembly is done on the site by methods similar with those by which conventional houses are built. 3.2.1b. Panelized Construction - is a system in which the panel is the basic unit of most systems of prefabricated house construction. A panel is an integral construction unit consisting of both load-bearing and covering materials which also contains insulation and moisture barriers. 3.2.1c. Factory-made Panels with Framing o f Conventional Size - panels can be fabricated with a framework and sheathing of sizes common in conventional site construction. The panels are capable of carrying all the loads. Usually, plywood is nailed or glued on one or both sides of the studding and to the top and bottom plates of wall panels. Using plywood, fabricating time is reduced and a panel is produced that has greater resistance to racking loads than is achieved with lumber sheathing which are rarely used today. 3.2.2 Production Methods and Equipments Whatever the product, the basic principle of its manufacture is to utilize the methods of machines most suited to the materials and parts to be made. This discussion 53 a.f • with permission of the copyright owner. Further reproduction prohibited without permission. is the review of production methods and equipment in use for house prefabrication. The methods and machines involved must be best for the particular task involved, either from the standpoint of production economy or that of quality fo the final product. To make the production process efficient in this type of production, storage of materials, plant equipments, and jigs must be taken into consideration. 3.2.2a. Storage o f Materials - Volume production of houses requires extensive storage facilities for lumber, plywood, wallboard, insulations, and other materials. 3.2.2b. Plant Equipments - The equipment of prefabricating plants may range, depending upon size and volume of output, from a few simple jigs, hand trucks, and dollies to highly integrated conveyor system. 3.2.2c. Jigs - Jigs are used in all prefabricating plants to insure accurate assembly of parts. The jigs governs the dimensions of the finished part to a degree of precision depending somewhat upon its constructions. 3.2.3 Subassembly Operations Subassembly operations are considered to be those that prepare materials for and necessarily precede the final assembly of panels, trusses, box girders, and other sectionalized parts of prefabricated houses in the factory. Priority among these preliminary operations are grading, machining, gluing operations, treating with preservative, and wood and plywood bending. 3.2.4 Plant Assembly Operations The basic assembly operations involved in production of panelized construction usually includes: 54 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 3.2.4a. Assem bly o f Framework - the principal factor involved is to match all framing joints as precisely as possible, so that the surfaces to which covers will be attached are in a single plane at all joints. The need for precision varies with the type of construction. 3.2.4b. Installation o f Electrical and M echanical services - all necessary electrical wiring, backup plates for switches and other electrical fixtures, ducts, water and plumbing pipes, gas lines and similar household equipment must be installed before the covers are attached to the panels. 3.2.4c. Installation o f Insulation - the principles and functions of insulation and information on installation requirements are to be considered for this process. 3.2.4c. Installation o f Cover Materials - this involves the attachements of covering materials over framing to provide protection against weather. Coverage includes sheathing, building paper, siding, shingles, or other roofing, lath, plaster, paint, and wall paper. 3.2.4e. Installation o f Doors and Windows - a matter of attaching door and window framing in place in a properly framed panel. 3.2.5 Painting This part of the fabricating process is optional to a lot of plants surveyed within the United States. Some have applied priming and first coating of paints in the plants but otherwise, finishing paints are done at the building site after the house is completed. 3.2.6 Inspection for Quality Control In general, inspection does not create quality; however, it helps to insure that quality will not fall below the standard called for by the design. Hence, inspection is 5 5 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. essential to the satisfactory service of the product by its users and can contribute greatly to the reduction of waste. Inspections are done for raw materials, manufacturing, dimensional accuracy, workmanship, gluing, and services. 3.2.7 Storage and Shipment of House Parts In storing and shipping panels, millwork, and other parts of prefabricted houses, it is necessary to take precautions against the possibility of damage from various causes. Aside from economic considerations, the need for storage of prefabricated house parts depends primarily upon the type of construction. The principal reason for this storage is to permit glue to cure adequately. Shipment must be done with outmost care to prevent damages of house part for easy and accurate assembly. For site storage, the safest way to escape damage is to avoid storing house part in the open. Builders usually plan their construction schedules well in advance to avoid leaving house parts in the open field. 3.2.8 Site Assembly Site assembly operations consist in general of foundation, erection of wall, ceiling, and roof panels, together with interior panels, all interior and exterior finish, application of roofing, installation of electrical plumbing, heating, and other fixtures; painting and other finishes. The scope of these tasks is determined by the amount of work done in the factory (FPL., 1947:241-84). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 4: Requirements of the Philippine National Building Code 4.1 Sypnosis The Philippines lies within the Pacific earthquake belt and also in an area frequently visited by typhoons, the most severe ones usually occuring during the months of October and November. The tremendous losses of life and property due to these forces have prompted the Philippine Goverment to review existing regulations and formulate new ones to avoid repetition in the future. The help of relevant international institutions with facilities and expertise like UNESCO was sought by the goverment to produce a National Building Code incorporating the best practice in design and construction of buildings and structures to withstand WIND AND EARTHQUAKE FORCES. 4.2 Lateral Forces 4.2.1. Earthquake Forces 4.2.1a. General. The UBC requirements for lateral force are intended to provide minimum standards as design criteria toward making buildings and other structures earthquake resistant. The provisions of this Section apply to the structures as a unit and to all parts thereof, including the structural frame walls, floors, roof systems and other structural features. 4.2.1b. Minimum Earthquake Forces for Structure 1. Total lateral force and distribution of lateral forces. Every structure shall be designed and constructed to withstand minimum lateral seismic forces assumed to act non- concurrently in the direction of each of the main axes of the structure in accordance with the following formula: 5 7 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. where: Z I C v = w Rw V = Base shear - total design lateral force or shear at the base Z = seismic zone factor (UBC Table No. 23-1) Z = .075 for seismic zone 1 Z = . 15 for seismic zone 2a Z = .2 for seismic zone 2b Z = .3 for seismic zone 3 Z = .4 for seismic zone 4 I = importance factor (UBC Table No. 23-L) I = 1.25 Essential facilities (hospitals, fire station, etc.) I = 1.0 for all other structures C = numerical coefficient C = 1.25 (S)/TA .666 Cnux=2.75 S = 1.0 for rock-like material S = 1.2 for dense or stiff soil (200’ deep) S = 1.5 for soft to medium stiff soil (20’ deep) S = 2.0 for soft clay W = total dead load R « r= structure system coefficient (UBC Table No. 23-0, 23-Q) Rw= 8 for plywood walls for structure 3 stories or less Rw = 8 for all other light-framed walls Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4.2.2 Wind Pressure 4.2.2a. General. Every building or structure and every portion thereof shall be designed and constructed to resist wind effects determined in accordance with the requirements of this section. Wind shall be assumed to come from any horizontal direction. No reduction in wind pressure shall be taken for the shielding effect of adjacent structures. Structures sensitive to dynamic effects, such as building with a height-to-width ratio greater than five, structures sensitive to wind-excited oscillation, such as vortex shedding or icing, and buildings over 400 feet in height, shall be, and any structure may be, designed in accordance with approved national standards (UBC., 1991:153). Buildings or structures shall be designed to withstand the minimum horizontal and uplift pressures set forth in this section allowing for wind from any direction. The wind pressure set forth in this figures are minimum values and shall be adjusted by the Building Officials for areas subjected to higher wind pressures. When the form factor, as detemined by wind tunnel tests or other recognized methods, indicates vertical or horizontal loads of lesser or greater severity than those produced by the loads herein specified, the structure may be designed accordingly. 4.2.2b. Horizontal Wind Pressure. For purpose of design, the wind pressure shall be taken upon the gross area of the vertical project of the portion of the building or structure measured above the average level of the adjoining ground. 4.2.2c, Uplift Wind Pressure. Roofs of all enclosed buildings or structures shall be designed and constructed to withstand pressure acting upward normal to the surface 59 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. equal to three-forths of the values set forth for the height zone under consideration. An enclosed building shall be defined as a building enclosed at the perimeter with solid exterior walls. Openings are permitted in the solid exterior wall provided, they are enclosed buildings, roof over-hangs, architectural projections, caves, canopies, cornices, marquees, or similar structures unenclosed on one or more sides shall be designed and constructed to withstand upward pressures equal to one and one-fourth times those values set forth. Upward pressure shall be assumed to act over the entire roof area. 4.2.2d. Anchorage Requirements. Adequate anchorage of the roof to walls and columns, and of walls, and columns to the foundations to resist over-turning, uplift, and sliding, shall be provided in all cases. 4.2.2e. Moment of Stability. The overturning moment calculated from the wind pressure shall in no case exceed two-thirds of the dead load resisting moment. The weight of earth superimposed over footings may be used to calculate the dead load resisting moment. 4.2.2f, Combined Wind and Live Loads. For the purpose of determining stresses, all vertical design loads except roof live load and crade loads shall be considered as acting simultaneously with the wind pressure. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4.2.2g. Design Wind Pressure Design wind pressures for structures or elements of structures shall be determined for any height in accordance with the following formula: P = C. C, q, I where: P = design for wind pressure Ce= combined height, exposure and gust coefficient (UBC Table No. 23-G) Cc =1.13 exposure C at 20 ft. in height Cq= pressure coefficient for the structure (UBC Table No. 23-H) Cq = 1.3 for structures 40 feet or less on vertical projected area. q, = wind stagnation pressure at the standard height of 33 ft. (UBC Table No. 23-F) q, = 36.9 psf at wind speed of 120 mph I = importance factor (UBC Table No. 23-L) I = 1.0 for standard occupancy structure 61 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 4.01 Wind Zone of the Philippines Zone 1 V = 200 KPH 125 MPH p 300 ksm 60 psf, h above 100 ft. p 250 ksm 50 psf, h 30 ft. to 100 ft. p 200 ksm 40 psf, h 0 ft. to 30 ft. Zone 2 V = 175 KPH 108 MPH P 250 ksm 50 psf, h above 100 ft. P 200 ksm 40 psf, h 30 ft. to 100 ft. P 150 ksm 30 psf, h 0 ft. to 30 ft. Zone 3 V = 153 KPH 96 MPH P 200 ksm 40 psf, h above 100 ft. P 150 ksm 30 psf, h 30ft. to 100 ft. P 100 ksm 20 psf, h 0 ft. to 30 ft. 62 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. PART II: DESIGN AND ANALYSIS CHAPTER 5: Load Bearing Test 5.1 Built-up Cross Column System 5.1.1 General The subject of this report is a load bearing column system for wood structures consisting of built-up component units of 1 pc. 4” x 4” core and 4 pcs. of 2” x 4” at nominal dimensions. The fasteners to be used are basically wood dowels spaced in three different configuration, namely: spaced at 6”, 12, and 18” apart. It is recommended to use the column with 6” dowel spacing because it held the most load. The object of the test is to determine the load bearing capacity of the column for compression and buckling by means of applying load based on design loads and continue up to the breaking point. The buckling tests were supplemented with different configurations (Table 5. la, Table 5.1b) to fumish information regarding the strength and load bearing capacity of these configuration to determine the practicability of handling, assembling, and installing such column. 5.1.2 Description The following columns were prepared for the tests at two diffent scales. The following items are used in the test assembly: Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4” x 4” wood - was basically used as a central core of the cross built-up column which are cut at a length of 8 ft. and 16 ft. respectively to accomodate the scale factor of 1:4 and 1:8 used for the test run. 2” x 4” wood - was attached to the four sides of the 4” x 4” column thus making a cross column configuration. l”d. wood dowels - were used as connector of the built-up column components spaced at three different configuration described in table 5. la and 5. lb. The tests are summarized in the following table: Figure 5.01 Built-up Cross Column Table 5.1a Model Scale: 1:8 scale Test no. Description of Test Item 1 Solid Square Wood Column @ 8” x 8” x 16’ 2 Solid Cross Wood Column @ 8” x 8” x 16’ 3 Built-up Cross Column with Dowel Connections @ 6” spacing 4 Built-up Cross Column with Dowel Connections @ 12” spacing 5 Built-up Cross Column with Dowel Connections @ 18” spacing 6 4 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 5.1b Model Scale: 1:4 scale Test no. Description of Test Item 6 Solid Square Wood Column @ 8” x 8” x 8’ 7 Solid Cross Wood Column @ 8” x 8” x 8’ 8 Built-up Cross Column with Dowel Connections @ 6” spacing 9 Built-up Cross Column with Dowel Connections @ 12” spacing 10 Built-up Cross Column with Dowel Connections @ 18” spacing 11 Built-up Cross Column (type-2) with Dowel Connection @ 12” spacing Note: Test item nos. 3-5, 9-10 are composed of 1-pc. 4” x 4” core and 4-pcs. 2”x 4” Test item no. 1 1 are composed of 1-pc. 4” x 8” core and 2-pcs. 2” x 4” The loads applied to the columns are based on the actual design load of the structure (roof load and floor loads combined), which is at 12,384 lbs. The duration of the load for each individual columns were applied at design load, 2 times the design load, 4 times the design load, up to its breaking point. The general cross sections of the test items before and after the loads were applied are shown in figure 5.02. Q Solid Square Column Solid Cross Column Built-up Cross Column Figure 5.02. Cross Sections of Columns Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 5.1.3 Methodology The Baldwin Tension and Compression machine (Fig. 5.03) was used in the test to apply load on the columns that were tested for buckling. And an extensiometer set at midpoint at two different sides of the column was used to measure the deflection of the column. Figure 5.03 Baldwin Compression Tension Test Machine (a) Load Adjuster and Output Computer Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 5.04 Baldwin Compression Tension Test Machine (b) Compression Table 5.1.4 Observations The built-up column with 6” dowel spacing was found to be capable of supporting the load of the structure with a minimal deflection of 2.4 in. along the entire length of the column. A series of test were done comparing the performance of the cross built-up columns to standard solid-sawn square columns, the result is somewhat similar to both configuration varying around 300 lbs. in each configuration. The dowel connections have performed well as a fastener for the built-up columns and not even in one of the configurations and spacing did the dowels separated from its connections. 6 7 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. S.l.S Test Results and Charts 5.1.5a Column Test at Scale 1:8 Test No. 1: Solid Square Column (Force Scale 1:64) Test No. 1 Model Load (lbs) (1:64) Actual Load (lbs) Model Deformation (1:8) Actual Deformation (in.) Design Load 194 12,384 0.007 0.056 Load x2 388 24,832 0.010 0.08 Load x4 766 49,024 0.020 0.16 Breaking Point 3,262 208,768 0.32 2.56 Test No.1: Solid Square Column 8" x 8" (scale 1:8) 3500 3000 2500 2000 1500 1000 500 i .. .... “ ' - ■ « . r : “ - . : - '.i ■ v -- r-' - < ■ • • • • / •' > ■ -• * ■ > . . . . r- V : ■ '• ' / r. - * ?• -■ a V.’ ' ' > “ ; . V - > » ■ ; • • • • T ■ :* '.2. - .M - < ■ ■« - • T :•* / '• .1 'A t < ■ ", -• : v- • i. T A V ' -• o.'; v* : . * , * ■ ■ t - .V, •V r- ■ V / \ * . ■ * r'.' n- .* ■ • •• 7 £ s V . ?:r '•T t A r*'' 4" r* - ... • ■ > • ' iV < ■ ■ H .i' • . - J - V V? : '■ • • : V : •> ■ : £ Tj- • • - ■ • *' '■i ‘ A V A - - V; /-• > : • T / ■ r : 7 •V , ’ < -? y*. ... ■ z - ■ - s r- .- •V* - ; “ / * .. V ; r." r - ■ - ■ ' -i £ •- A * '• ' ; \. * . ; - ■ - / - >' r - .s > ■ - - •: ■ a ■ / > ■ f. V ■ I v ..i - i- ?; V :* V k ; / ■ r '' -• v; ■ :• • • • • i / * • • .• “ > - ■ V * ■ 7 1 > - < - - ■ - ’ •.r • > f •> I- w v * 'I ' ■ v • * * * I * ‘ ‘ A • ; • • • • • .• - ■ V • • ... ... . V > T “ ' ♦ I : r . V > • - -• • : •-* . ; iA < ■ ~ ? ° P T ~ V v- 7 ■ J •f: c . j ‘"r ,V' < . — • :: : '' V .« ... • • • • • " X . 71’i «• ■ A - -- r- , < > -'t :• * • . : a * > ' ■ .; , 0.05 0.1 0.15 0.2 0.25 0.3 L a te ra l D e fo rm a tio n (in c h e s ) 0.35 0.4 0.45 0.5 68 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (a) Solid Square Column before loads are applied. (b) Solid Square Column after 3,262 lbs. had been partially applied, the column deflected about 0.32 in.(model scale) at this point. Figure 5.05 Test No.l: Solid Square Column 6 9 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Test No. 2 : Solid Cross Column (Force Scale 1:64) Test No. 2 Model Load (lbs) (1:64) Actual Load (lbs) Model Deformation (1:8) Actual Deformation (in.) Design Load 194 12,384 0.010 0.08 Load x2 388 24,832 0.020 0.16 Load x4 766 49,024 0.027 0.216 Breaking Point 2,525 161,600 0.4 3.2 Test No. 2: Solid C ro ss Column (scale 1:8) 3500 3000 .2525. 2500 W n 2000 • o a 1500 Q. a < 1000 500 0.45 0.5 0.35 0.25 0.3 0.4 0.15 0.2 0 .0 5 0.1 0 L atera l D e fo rm a tio n (in c h e s ) 70 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (a) Solid Cross Column before load s are applied. (b) Solid Cross Column after 2,525 lbs. had been applied with a maximum deflection of 0.4 in. in model scale. Figure 5.06 Test No. 2 Solid Cross Column 71 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Test No. 3 : Built-up Cross Column (Dowel Connection @ 6” spacing) Force Scale 1:64 Test No. 3 Model Load (lbs) (1:64) Actual Load (lbs) Model Deformation (1:8) Actual Deformation (in.) Design Load 194 12,384 0.005 0.04 Load x2 388 24,832 0.006 0.048 Load x4 766 49,024 0.010 0.08 Breaking Point 1,988 127,232 0.3 2.4 T est No. 3: Built-up Cross Column (Dowel C onnections @ 6" spacing) 3500 3000 2500 VI A 2000 XI ( O o I 1500 Q. CL < 1000 n 6 fr 500 ■ a p e 0.45 0.5 0.35 0.4 0.15 0.2 0.3 0.05 0.1 0.25 0 L ateral D e fo rm a tio n ( in c h e s ) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (a) Built-up Cross Column before load s are applied. (b) Built-up Cross Column after 1,988 lbs. had been applied with a maximum deflection of 0.3 in. in model scale. Figure 5.07 Test No.3: Built-up Cross Column Dowel Spacing @ 6” 73 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Test No. 4 : Built-up Cross Column (Dowel Connection @ 12” spacing) Force Scale 1:64 Test No. 4 Model Load (lbs) (1:64) Actual Load (lbs) Model Deformation (1:8) Actual Deformation (in.) Design Load 194 12,384 0.030 0.24 Load x2 388 24,832 0.040 0.32 Load x4 766 49,024 0.048 0.384 Breaking Point 1,625 104,000 0.50 4.0 Test No. 4: Built-up C ross Column (Dowel C onnection @ 12" spacing) 3500 3000 2500 §- 2000 T > a o _ J ■ a at ■ ■ = 1500 c . a . < 1000 500 • . : ' - >r - ■ r - > •: 1 : • ... •v s* > ; - r. > ■ : • • •4* . . r •• ; ■ • i ; ..s ... S . j.. if • • > '.■ • v - i X' 9 r ■a a > •• • * t r . -J A .*• .• - - v e * * J ; r ? ; > ' •V V ** *3 »■ •rx - ■r- * - - w V •V V ... t.. v : - , !. ; S .* - ■ • j : •N. > •:v > *:: & •v F: - ■ ■ .: : ■ - v -■ :••• •- - ':: •• ■ ■ : -- r r^. > -7 - ■- ■ X .- ■ y. - •• - " - • -■ 7 ' * v ; - :'3 i- J ' • - • V - •i • • • ••• : ' •• :;v I : * L - . •• •V - : • :> 1 .u - * . • -V ' •> X <• ■ r | ir>. :■ x ■- •.:> ... r r 'V: r ■ »: .> ■; .* r ’ •• | .i ' : -V X ; x. •; i V : ••• .V ... ■ > :• - [ ... - #• ” ; 1 . * - t- - I < •- “ ( .. '• ■ r ’ • > . ( 1 ■ r J.'.' - - V :• - > • ! : , .< • •• Y - : j .v - ... , :• .. - .. L > .. - V • • • * ■ : =, '• - * .■ j : ■ < ; f ... - 1625 0.05 0.1 0.15 0.2 0.25 0.3 0.35 L a te ra l D e fo rm atio n (in c h e s ) 0.4 0.45 0.5 74 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (a) Built-up Cross Column before load s are applied. (b) Built-up Cross Column 1,625 lbs. had been applied with a maximum deflection of 0.5 in. in model scale. Figure 5.08 TestNo.4: Built-up Cross Column Dowel Spacing @ 12” 75 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Test No. 5 : Built-up Cross Column (Dowel Connection @ 18” spacing) Force Scale 1:64 Test No. 5 Model Load (lbs) (1:64) Actual Load (lbs) Model Deformation (1:8) Actual Deformation (in.) Design Load 194 12,384 0.010 0.08 Load x2 388 24,832 0.014 .112 Load x4 766 49,024 0.016 1.28 Breaking Point 2,100 134,400 0.4 3.2 3500 3000 2500 o i = ■ 2000 ■ o a o = 1500 Q . a. < 1000 500 0 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 L a t e r a l D e f o r m a t i o n ( i n c h e s ) 76 Test No. 5: Built-up Cross Column (Dowel Connection @ 18" spacing) ... . . jE £ E — ... 7 T 0 r“ 7 . : : _ x P ~ • • ; • F T 7 * • v 7 ■ a 7 7 T " • _ £ ; r y r- - { 7 7 “ T ... 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E '.. ■ ; " T £ 7 —“ X X X X r * —■ — r — 7 "T 7 • f . 7 E 7 7 £ E ■ “ TT T * “ • ' i E 7 E .'fr S £X I 7 7 E xj 7 T X 7 7 m X £ r E m * “■ T ; : r- T X 7 7 X : V 7 7 E E ?Y r" T • x , 7 " E 7 T L : rr T 1 * 1 . ii E E Z z 7 Z • x X 7 r £ 7 " T E 7 ~ i E , T £ E T " E i. 7 ” £ > z 7 7 J - I - 7 £ z 7 E £ 1 2 ■ * r E z i£ X i X . E 7 7 E t 1- • • _ _ _ 7 z — E z z ' E E ■ w _ _ ~ _ _ _ _ _ Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (a) Built-up Cross Column before load s are applied. (b) Built-up Cross Column 2,100 lbs. had been applied with a maximum deflection of 0.4 in. in model scale. Figure 5.09 Test No.5: Built-up Cross Column Dowel Spacing @ 18” 77 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 5.1.5b Column Test at Scale 1:4 Test No.6 : Solid Square Column (Force Scale 1:16) Test No. 6 Model Load (lbs) (1:16) Actual Load (lbs) Model Deformation (1:4) Actual Deformation (in.) Design Load 774 12,384 0.032 0.128 Load x2 1,548 24,672 0.048 0.192 Load x4 3,096 49,536 0.048 0.192 Breaking Point 22,937.5 367,000 0.2 0.8 Test No. 6 : Solid Square Column (scale 1:4) 25000 20000 15000 a 10000 5000 0.45 0.5 0.4 0.35 0.25 0.3 0.2 0.15 0.1 0.05 0 L a te ra l D e fo rm a tio n (in c h e s ) 78 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (a) Solid Square Column before load s are applied. (b) Solid Square Column 23 kips had been applied with a maximum deflection of 0.2 in. model scale. Figure 5.10 Test No.6: Solid Square Column Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Test No. 7 : Solid Cross Column (Force Scale 1:16) G Test No. 7 Model Load (lbs) (1:16) Actual Load (lbs) Model Deformation (1:4) Actual Deformation (in.) Design Load 774 12,384 0.011 0.044 Load x2 1,548 24,672 0.012 0.048 Load x4 3,096 49,536 0.015 0.06 Breaking Point 18,625 298,000 0.4 1.6 Test No. 7 : Solid Cross Column (scale 1:4) 25000 20000 « 15000 £ * D < 9 O a. 10000 < 5000 - -• - ■ ■ V ~ > • ?! .. • " 7 ■ ' - ... r • n .A > - . : V. l:. ... .7 % ‘S f; • - 7 V ? r : •f -i. :■ > y 7 .; T ’ T . ; ‘ s' > “I - r ■ £- 7: W S r. -y V > A - ' ' • ■ t * 7 • . ■ * '.r . ✓ »: b X • > ■ ■ • * ■: ■y rr : :i » • L :» • ; -■ ' r y • . , .. V •: * * - •• s. > 'i V c : • • ,v - V ' V - . . : • "V *- ‘j . * : • ; . ■ < : : ■ ■ ■ ■ > " :• • • . • X- '• ; - ; - -- if .7. 7 ' •v • i. • :• i : I;: •i ' y ■ * : T; iV ;v -V V V . " V > -X * ••• .A •r ,r; ■ ■ * ► ; ■ ■ \ 7 ■ ■ ■ A >; ■ ‘1 ; • ; 9. r - • r. :• - ■ .a > X ; - ■ : •; ✓ 7 ■ ; fz .. - - ■r 15 V r' ■ ' ' n r i : ■ ■ ■ ' j- 0.05 0.1 0.15 0.2 0.25 0.3 0.35 L a te ra l D e fo rm a tio n (in c h e s ) 0.4 0.45 0.5 80 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (a) Solid Cross Column before load s are applied. (b) Solid Cross Column after 18.6 kips had been applied with a maximum deflection of 0.4 in. model scale. Figure 5.11 Test No.7: Solid Cross Column 81 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Test No. 8 : Built-up Cross Column (Dowel Connection @ 6” spacing) (Force Scale 1:16) Test No. 8 Model Load (lbs) (1:16) Actual Load (lbs) Model Deformation (1:4) Actual Deformation (in.) Design Load 774 12,384 0.019 0.076 Load x2 1,548 24,672 0.030 0.12 Load x4 3,096 49,536 0.041 0.164 Breaking Point 10,562.5 169,000 0.35 1.4 Test No. 8 : Built-up Cross Column (Dowel Connection @ 6” spacing) • i 20000 2 15000 a a . 10000 5000 0.5 0.45 0.4 0.35 0.25 0.3 0.2 0.15 0.1 0.05 0 L a te ra l D e fo rm a tio n (in c h e s ) 82 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. - m (a) Built-up Cross Column before load s are applied. (b) Built-up Cross Column after 10.5 kips had been applied with a maximum deflection of 0.35 in. model scale. Figure 5.12 Test No.8: Built-up Cross Column Dowel Spacing @ 6” Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Test No.9 : Built-up Cross Column (Dowel Connection @ 12” spacing) (Force Scale 1:16) Test No. 9 Model Load (lbs) (1:16) Actual Load flbs) Model Deformation (1:4) Actual Deformation (in.) Design Load 774 12,384 0.013 0.052 Load x2 1,548 24,672 0.016 0.064 Load x4 3,096 49,536 0.017 0.068 Breaking Point 11,187.5 179,000 0.3 1.2 Test No. 9 : Built-up Cross Column (Dowel Connection @ 12" spacing) 2 S 0 0 0 20000 1 ; * • i I _i 15000 10000 5000 0.45 0.35 0.5 0.3 0.4 0.15 0.2 0.25 0.05 0.1 0 L a te ra l D e fo rm a tio n (in c h e s ) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (b) Built-up Cross Column after 11.1 kips had been applied with a maximum deflection of 0.3 in. model scale. Figure 5.13 TestNo.9: Built-up Cross Column Dowel Spacing @ 12” 85 Reproduced with permission ofthe copyright owner Fi.rth* PV m owner. Further reproduction prohibited without permission. Test No. 10 : Built-up Cross Column (Dowel Connection @ 18” spacing) (Force Scale 1:16) I" Test No. 10 Model Load (lbs) (1:16) Actual Load (lbs) Model Deformation (1:4) Actual Deformation (in.) Design Load 774 12,384 0.012 0.048 Load x2 1,548 24,672 0.017 0.068 Load x4 3,096 49,536 0.018 0.072 Breaking Point 11,212 179,392 0.25 1.0 Test No. 10 : Built-up Cross Column (Dowel Connection @ 18” spacing) 25000 20000 « > ' 15000 £ • o ■ o O . 10000 5000 3096 0.35 0.4 0.45 0.5 0 0.05 0.1 0.15 0.25 0.3 0.2 L a te ra l D e fo rm a tio n (in c h e s ) 86 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (a) Built-up Cross Column before load s are applied. (b) Built-up Cross Column after 11.2 kips had been applied with a maximum deflection of 0.25 in. model scale. Figure 5.14 Test No. 10: Built-up Cross Column Dowel Spacing @ 18” 87 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Test No. 11: Built-up Cross Column (2nd Configuration) (Force Scale 1:16) Test No. 10 Model Load (lbs) (1:16) Actual Load (lbs) Model Deformation (1:4) Actual Deformation (in.) Design Load 774 12,384 0.008 0.032 Load x2 1,548 24,672 0.013 0.052 Load x4 3,096 49,536 0.025 0.1 Breaking Point 11,550 184,800 0.2 0.8 T est No. 11 : Built-up C ross Column (2nd Configuration) 25000 20000 “> 15000 a ■ a < 3 O _ J 550 T J i : 10000 < 5000 1548 0.5 0.35 0.4 0.45 0.3 0.15 0.2 0.25 0.05 0.1 0 L atera l D e fo rm a tio n (in c h e s ) 88 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. i) Built-up Cross Column before load s are applied. b) Built-up Cross Column after 11.5 kips had been applied with a maximum deflection of 0.2 in. model scale. Figure 5.15 Test No. 11: Built-up Cross Column Dowel Spacing @ 12”(2nd Configuration) 89 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 5.2 Dovetail Connection (for stud and base sill connection) 5.2.1 General The subject of this report is to test the maximum uplift force a dovetail connection is capable of withstanding and also for the lateral shear of such connection on its sideway and frontal direction (Fig. 5.16). Figure 5.16 Dovetail Joints and Direction of Load The uplift and lateral shear tests were supplemented with different joint configurations (Table 5.2) to furnish datas regarding the strength and capacity of such joint. 5.2.2 Description The scale factor used for the joints are 1:1 on a 2” x 4” wood member. The maximum penetration of the dovetail joint to the sill is 3/4”. The wood used in this test is a No. 1 Douglas Fir-larch. The dovetail joints are glued to its connections with three different configurations for the inclination of its joints, at 10°, 20°, and 30°. 90 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The tests are summarized in the following table: Table 5.2 Model Force Scale: 1:1 scale Test No. Description of Test Item 1 Dovetail Joint @ 10° inclination, test for uplift 2 Dovetail Joint @ 20° inclination, test for uplift 3 Dovetail Joint @30° inclination, test for uplift 4 Dovetail Joint test for lateral shear at sideway direction 5 Dovetail Joint test for lateral shear at frontal direction 5.2.3 Methodology The Baldwin Tension and Compression machine (Figures 5.1 & 5.2) was used to conduct this test, applying load on the joints that were tested for withdrawal and lateral shear. 5.2.4 Obsevations The joints that were tested for its maximum uplift force were found to be capable if applied to structure with a safety factor of 2 which is quite low for wood which typically have a safety factor of 4. In test no. 1 and 2, joints with inclination of 20° and 30°, failure of the joints resulted from shearing of the wood on the joints inclination. The safety factor of the joints was compared to the computed allowable tension for joints with penetration of 3/4” which was 500 lbs. And for lateral shear on its sideways direction, based on the test results, the joints were very capable to withstand loads up to 5 kips of pressure, and for lateral direction, the joint can withstand loads up to 2 kips. 91 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 5.2.5 Test Results 5.2.5a Withdrawal Test Dovetail Test No. I: @ Joint at 30° Inclination Applied Load (lbs.) Displacement (inches) 0 0 500 0 800 0.125 900 0.5 987.5 (breaking point) 0.75 Uplift T est No.3: Dovetail Jo in t @ 30° inclination 1200 1000 800 (A a o > u w O u. 5 600 Q . 3 • O Si Q . « 400 500 200 0.9 1 0.8 0.7 0.6 0.4 0.5 0.3 0.1 0.2 0 U plift D isp lac e m e n t ( in c h e s ) Reproduced with permission of the copyright owner Further reproduction prohibited without permission. (a) Dovetail Joint before applying pull-out pressure (left). (b) Joint after its breaking point. Notice the end grain had sheared off from the tail of the joint (below). Figure 5.17. Dovetail Test No. 1 @ Joint at 30° Inclination 93 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Dovetail Test No. 2: @ Joint at 20° Inclination Applied Load (lbs.) Displacement (inches) 0 0 500 0 700 0.5 800 0.675 837.5 (breaking point) 0.75 Uplift T est No.2: Dovetail Joint @ 20° inclination 1200 1000 800 u ) a 93 U w a u. 600 a 3 T O a a. a. < 500 200 0.8 0.9 0.5 0.6 0.7 1 0.2 0.3 0.4 0 0.1 U p lift D is p la c e m e n t (in c h e s) 94 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (a) Dovetail Joint @ 20° inclination before uplift loads have been applied f'-.t Z. * tj..w .U l, (b) Dovetail Joint after uplift pressure had been applied. End grain had sheared off from the tail of the joint. Figure 5.18 Dovetail Test No. 2 @ Joint at 20° Inclination 95 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Applied Uplift Force (lb s .) Dovetail Test No. 3:@ Joint at 10° Inclination Applied Load Qbs.) 0 500 600 700 800 900 1000 1012.5 (Breaking Point) Displacement (inches) 0 0 0.125 0.25 0.375 0.5 0.675 0.75 Uplift Test No.1 : Dovetail Jo in t @ 10° Inclination 1200 1000 800 600 500 400 200 0 1 0.8 0.9 0.7 0.6 0.5 0.3 0.4 0.2 0.1 U plift D is p la c e m e n t ( in c h e s ) 9 6 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (a) Dovetail Joint @ 10° inclination before uplift loads have been applied D m c ta il I'csl 5 : u 10" ilu v c la il c u l. V ," tlc p lh (b) Dovetail Joint after uplift pressure had been applied. End grain did not sheared off from the tail of the joint. Figure 5.19 Dovetail Test No. 3 @ Joint at 10° Inclination 97 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 5.2.5b Lateral Test Dovetail Test No.4: Lateral Shear Test (Sideways) Applied Load Displacement Obs.) (inches) 0 4000 4500 5000 0 0.125 0.25 0.5 5062.5 (breaking point) 0.675 Dovetail T e st No.4 : Lateral Shear {Sideway Direction) 5000 4000 3000 2000 1000 0 0.9 1 0.8 0.7 0.5 0.6 0.4 0.2 0.3 0.1 0 L a te ra l D is p la c e m e n t (in c h e s) 98 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. text 4: Lateral liiir(r iM «trn (a) Before applying load (b) After load had been applied Figure 5.20 Dovetail Test No. 4 Lateral Shear (sideways) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Dovetail Test No. 5: Lateral Shear Test (Frontal) Applied Load (lbs.) 0 1850 2000 2112.5 (breaking point) Displacement (inches) 0 0.125 0.5 0.75 Dovetail T est No.5: Lateral Shear (Frontal Direction) 5000 4000 3000 ]j 2000 < 1000 0.8 0.9 0.7 1 0.6 0.5 0.3 0.4 0.2 0.1 L a te ra l D is p la c e m e n t (in c h e s ) 100 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (a) Before applying load (b) After load had been applied Figure 5.21 Dovetail Test No. 5 Lateral Shear (frontal) 101 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 5.3 Braced Shear Wall Frame 5.3.1 General The subject of this report is a braced shear wall frame system (Fig. 5.22) for wood frame structure. The wall frame is braced diagonally from one comer to the other with a 1” x 6” wood. The connections of studs, base sill and top plate are of dovetail joints. The objective of the test is to determine the maximum shear capacity of the wall frame by applying concentrated load to the upper comer of the frame. It is also the objective of the test to determine the maximum lateral deflection of the frame. Figure 5.22 Braced Wall Frame 5.3.2 Description The braced wall frames were prepared for lateral shear test at a force scale factor of 1:4. The frame is 8’ x 8’ and made o f 2” x 4” wood with a 1” x 6” diagonal bracing. 102 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The studs were spaced at 16” apart. The diagonal brace are fastened to the wall frame in two different manner, such as: glued and doweled connections. The runs were summarized in the following table: Table 5.3 Test No. Description 1 Wall Frame with Glued Connection (Tested for Compression) 2 Wall Frame with Dowel Connection (Tested for Compression) 3 Wall Frame with Glued Connection (Tested for Tension) 4 Wall Frame with Dowel Connection (Tested for Tension) 5.3.3 Methodology The Baldwin Compression and Tension machine (figures 5.1 & 5.2) was used to conduct this test with a frame jig attached sideways, were the frames were placed so the load will be applied laterally to the frame. 5.3.4 Observations For all the tests, the walls started to deflect with an applied concentrated load of 70 lbs. Due to the uniformity of the load the walls started to deflects, it was observed that the bracing did not actually make much difference in stiffening the wall. For the walls that were tested in compression, the joints of the wall failed. It seemed that the diagonal bracing punched through the connections that made the joints to fail. For the frames that were tested for tension, the joints did not fail but both walls started to twist before reaching the maximum breaking point. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 5.3.5 Test Results 5.3.5a Braced Wall in Compression Wall Test No. 1: Glued Connection (in compression) Scale 1:16 Model Load Actual Load Model Deflection Actual” Deflection (lbs.) (lbs.) (inches) (inches) 0 0 0 0 70 1120 0.05 0.2 80 1280 0.25 1.0 90 1440 0.5 2.0 100 1600 1.0 4.0 Wall 1: Braced Wall Frame - Glued Connection (Compression Test) 200 180 160 140 1 2 0 5 100 100 c 4 ) U c o O ■ a a. a < 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 L a te ra l D e fle ctio n (in c h e s ) 104 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (a) Before applying load (b) At breaking point, joint connection failed Figure 5.23 Braced Wall Test No. 1 Glued Connection in Compression 105 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Wall Test No. 2: Doweled Connection (in compression) Scale 1:16 Model Load Actual Load Model Deflection Actual Deflection (lbs.) (lbs.) (inches) (inches) 0 0 0 0 70 1120 0.05 0.2 80 1280 0.125 0.5 90 1550 0.25 1.0 100 1600 0.375 1.5 110 1760 0.5 2.0 120 1920 0.6 2.4 Wall 2: Braced Wall Frame - Dowel Connection (Compression Test) 200 1 8 0 160 3 120 100 • a 1 0.8 0.9 0.7 0.6 0 .5 0.4 0.2 0.3 0.1 0 L a t e r a l D e f l e c t i o n ( i n c h e s ) 106 w gaw ..' ___ . Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (a) Before applying load ,\\mvW STT.ST> (b) At breaking point, joint connection failed Figure 5.24 Braced Wall Test No.2 Doweled Connection in Compression 1 0 7 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Wall Test No.3: Glued Connection ( in tension) Scale 1:16 Model Load Actual Load Model Deflection Actual Deflection (lbs.) (lbs.) (inches) (inches) 0 0 0 0 70 1120 0.05 0.5 100 1600 0.125 0.5 130 2080 0.25 1.0 160 2560 0.375 1.5 190 3040 0.5 2.0 Wall 3: Braced Wall Frame - Glued Connection (Tension Test) L a te ra l D eflectio n (in c h e s ) 108 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (a) Before applying load (above) (b) At breaking point. As load is being applied to the frame, no sign of breaking in all its joints but the frame have twisted (left). Figure 5.25 Braced Wall Test No.3 Glued Connection in Tension 109 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Wall Test No. 4: Doweled Connection (in tension) Scale 1:16 Model Load Actual Load Model Deflection Actual Deflection (lbs.) (lbs.) (inches) (inches) 0 0 0 0 70 1120 0.025 0.1 80 1280 0.05 0.2 90 1440 0.125 0.5 100 1600 0.25 1.0 110 1760 0.375 1.5 120 1920 0.5 2.0 Wall 4: Braced Wall Frame - Dowel Connection (Tension Test) 200 180 160 m * 140 3 120 100 ■ D 0.7 0.8 0.9 0.6 1 0.1 0.2 0.5 0 0.3 0.4 L a te ra l D e fle c tio n (in c h e s ) 1 10 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (a) Before applying load (above) (b) At breaking point. As load is being applied to the frame, no sign of breaking in all its joints but the frame have twisted (left). Figure 5.26 Braced Wall Test No.4 Glued Connection in Tension i l l Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 6: Prototype Structure, Details and Analysis 6.1 General The prototype is a two story, three bedroom, residential buiding with a floor area o f2064 sq.ft. The construction is post and beam framing with light wood shear wall for all the portions above grade and poured concrete for the ground floor slab on grade and footings. A complete set of structural calculations are provided in this section for the wood components. 6.2 The Structural System The materials used for the wood frame are: Joist, rafters and stud: Tangile Girders and Columns: Guijo Roof sheathing 1/2:” Structural Marine Plywood Floor Decking 1 ” Hardwood Floor Ceiling 1/2” Gypsum Board Some of the Criteria used for the structural design are as follows: Floor Live Load 40 psf (NBC Table 1.04-A) Roof Live Load 16 psf (reduced to Slope) 20 psf (NBC Table 1.05-A) Wind Zone 2, 30 ft. reference height, Exposure C. Seismic Zone Zone 4 1 1 2 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 6.01 Ground Floor Plan Figure 6.02 Second Floor Plan 113 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2"x 8” Floor Joist 12" spacing (a) Roof Framing Plan 0 ® © i - 0 - 2"x 3" Purlins ■ 2”x 6” Rafters ~ 2-2”x 10” Roof Beam _ -P i -3 ) (b) 2nd Floor Framing Plan Figure 6.03 Structural Plans 114 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. I. Roof Structure: Corr. G.L sheer, 3/8” roof sheathing, 2”x3" purlins, 2”x6” rafters. 2-2”xl0” Ridge Beam 2 Post Anchor 2. Interior Wall: gypesum board, 2”x4” stud, insulation 3. Roor structure: I” thk. hardwood floor. 2”x8” joist, insulation 4”x l2 ” girders Figure 6.04 Section though Gable End Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Detail A c t f a Detail A Figure 6.05 Typical Eave Section Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 6.3 Detail Connections 6.3.1 Column to Foundation Connection The column is connected to the concrete foundation by a custom-made foundation anchor designed to fit a cross column configuration. The bracket is then connected to the column by 5/8” bolts (Fig. 6.06). The minimum penetration of the column anchor to the concrete foundation will be 6”. The column sits on a metal plate within the anchor to prevent the wooden column to have direct contact with concrete. 0 0 0 £ 1 4 • I 4 * , i- . 4 • Figure 6.06 Column to Foundation Connections 117 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 6.3.2 Column and Beam Connections 6.3.2a Typical Cross Joint Connections For this connections, the built-up column is notched at four sides where the beams connect (Fig. 6.07a). The beams are then installed through the notch on the column (Fig. 6.07b). (a) Typical Cross Joint Notched Column Figure 6.07 (b) Cross Joint Connection (Post & Beam) 118 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 6.3.2b T-Joint Connection This connection is typical at the exterior-middle part of the frame structure. Three sides of the built-up column is notched (Fig. 6.08a) and the unnotched part faces the exterior part of the frame. The girders connects to the notches of the column ( Fig. 6.08b). (a) Typical T-Joint Column Figure 6.08 (b) T-Joint Connection 119 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 6.3.2c Corner Joint Connection This type of connection is typical on comers of the proposed frame structure, where two comers of the column (Fig. 6.09a) is notched to connect with the two girders which are at right angle to the comer column (Fig. 6.09b). (a) Typical Comer Column Figure 6.09 (b) Comer Joint Connection 120 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 6.4 Structural Analysis 6.4.1 Design of Roof Structure The roof structure consist of structural marine plywood sheathing on rafters spaced at 48 inches apart. The rafters span from the exterior bearing walls to the ridge beam that is supported by the interior bearing columns and are inclined at a slope of 3 in 12, or approximately 15°. 6.4.1a Design of Rafter Design Loads: Dead Load Roofing Material 1.0 psf Sheathing 1.5 psf Purlin 0.5 psf Rafter 1.0 psf Insulation 1.5 psf Ceiling 3.0 psf Total Dead Load 8.5 psf Live Load (reduced for Slope) 16.0 psf Total Load 24.5 psf Computing for Tributary Load: Tributary load = Total Load x Tributary Area w = 24.5 psf x 4 ft. w = 98 plf Computing for Shear: Rafter overhanging in one support uniformly distributed load. EM = 0 Ri + R2 =0 1 2 1 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. = 523 lbs. = V, 12 Ri - 98(6)(12) + 98 (2)(4) = 0 7056 - 784 Rt = ----------- 12 Ri = 98(16) - 523 = 1045 lbs. V2 = wa = 98(4) = 392 lbs. V3 = 98(12) - 523 = 653 lbs. Computing for Shear Stress: Using 2” x 6” Douglas Fir-Larch F(shear force) Shear Stress (Fv ) = ---------------------- A (section area) 653 lbs. Fv = --------------= 79.15 psi < 95 psi 8.25in2 *-X = SJ*rJ| w = M p|f 5231b. ISZk. ( ■ I F U l r b Shear Moment 1 0 .8 f t. Computing for Maximum Bending Moment: Using Shear Area Method Vix 523 (5.3) Mi = — = 1386 Ib-ft. V2 a 392 (4) M2 = ----------= = 784 lb-ft. 2 2 Computing for Allowable Deflection at x A = - WX (L4 -2LV+Lx3 -2a2 L2 +2aV) 24EIL _ 98(5.3) (10724) 0-728) = { 2{ m 24(1320000) (20.8) Q.2 Note: The number 1728 is (12in/ft)3 , used to make the units come up right. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. In the design of rafter using the allowable stresses of the lumber Tangile, the values are as follows: Fb = 2240 ps Fv =150 psi E = 1,320,000 psi Computing for required Section Modulus M 1386 ( 12) S = --------- = = 7.42 in3 Fb 2240 Computing for Cross-sectional Area 1.5 (V) 1.5 (653) A = ------------- = = 6.53 in2 Fv 150 Computing for Moment of Inertia 1= - — - (L4 -2L 2 x2 +Lx3 -2a2 L2 +2a2 x2 ) 2 4 EdL 98(5.3) (10724) (1.728) . 4 = — - — —------- — - = 20.92 in 240.320000) (L21) 0.2 Note: The number 1728 is (12 in/ft)3 , used to make the units come up right. The required lumber property for a 2” x 6” are: S = 7.56 in3 > 7.42 in3 A = 8.25 in2 > 6.53 in2 I = 20.8 in4 < 20.92 in4 123 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 6.4.1b Design of Ridge Beam Total rafter reactions are loads on beam 1045(5) Raitcr Reaction W = = 435 plf. 12 1045 1045 1045 0145 1045 Computing for Shear (Simply supported beam) wl 435(12) V = = 2610 lbs. Computing for Bending Moment wl2 435(12)2 M = --------= --------------- = 7830 lbs. 8 8 Computing for Allowable Deflection 2610 lbs. •2610 .bs. 7830 lbs. A = 1 240 12(12) 240 /f A Uhv A ..................... .................... I k = 0.6 in. For the design of the ridge beam, the maximum allowable stresses of the wood “tangile” was used and as follows: Fb = 2240 psi Fv= 150 psi E = 1,320,000 psi Computing for the required Section Modulus M 7830 ( 12) S = -------- = ----------------= 41.9 in3 Fb 2240 124 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Computing for Cross-sectional Area 1.5 (V) 1.5(2610) A = ------------- = = 26.1 in2 Fv 150 Computing for Moment of Inertia (maximum deflection created by live load only) f _ 9*1* _ 5x20CL2)yl24 X l7 2 8 _ {>| { ^ fa4 384Ed 3 8 4 x 1 3 2 0 0 0 0 x 0 .4 Note: The number 1728 is (12 in/ft)3 , used to make the units come up right. The required lumber properties for a 4” x 10” wood member are: S = 49.9 in3 >41.9 in3 A = 32.4 in2 > 26.1 in2 I = 230.8 in4 >141.4 in4 6.4.2 Design of Floor Structure The floor structure consists of 1 ” thk. Hardwood flooring on 2” x 8” floor joists spaced at 16” on center. The joists span from the exterior girders to the interior girders supported by the columns. 6.4.2a Design of Floor Joist Design Loads Dead Load Flooring Mat’l (1” thk. Hardwood) 4.0 psf Framing (2” x 8” fir. Joist @ 12”o.c.) 2.0 psf Ceiling 3.0 psf Total Dead Load 9.0 psf Live Load 40.0 psf Total Load 49.0 psf 125 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Computing for Tributary Load: Tributary Load = Total Load x Tributary Area w = 49 psf x % = 65.33 plf Computing for Shear Computing for Bending Moment _ 6 M 3 M f „ U M M > 8 8 Computing for Allowable Deflection a 1 12(12) „ „ . A = ------ = —— = 0.4 in 3 6 0 3 60 In the design of floor joist, using the select wood specie (tangile) with the following allowable stresses: Fb= 2240 psi Fv = 150 psi E = 1,320,000 psi Computing for the required Section Modulus s = j!L = 1176(12), ^ 3 Fb 2 2 4 0 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Computing for Cross-sectional Area - ( y ) - ( 3 9 2 A = -2------= -2-------- =3.92 in2 Fv 1 50 Computing for Moment of Inertia (maximum moment created by the live load only) Strl* 5 x 4 0(L33)xl24 x l 7 2 8 . 4 I = 46.83 in 3 8 4 Ed 3 8 4 X 1 3 2 0 0 0 0 X 0 .4 Note: The number 1728 is (12 in/ft)3 , used to make the units come up right. The required lumber properties for a 2” x 8” wood member are: S = 13.1 in3 > 6.3 in3 A = 10.9 in2 > 3.92 in2 I = 47.6 in4 > 46.83 in4 6.4.2b Design for Girder Design Load Dead Load Total Dead Load (joist) 9.0 psf Girder (4” x 12”) 1.5 psf Total Load 10.5 psf Live Load 40.0 psf Total Load 50.5 psf Computing for Tributary Load Tributary Load = Total Load x Tributary Area w = 50.5 psf x 12 ft = 606 plf 127 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Computing for Shear Wl 606(12 V = — = — - — = 3636 lbs. 2 2 Computing for Bending Moment M - S £ - S 2 f f l £ _ , 0 9 0 I M , 8 8 Computing for Allowable Deflection A I 12(12) . . . A = ----- = - - - - = 0.4 in 3 6 0 3 6 0 In the design of girder, using the select wood specie (tangile) with the following allowable stresses: Fb= 2240 psi Fv= 150 psi E = 1,320,000 psi Computing for the required Section Modulus £ _ 1 0 9 0 * 1 2 = 5 8 4 jn J F b 2240 Computing for Cross-sectional Area 3 3 -(y ) — (3636) A = 2 = 2---------- = 36.36in2 F„ 150 Computing for Moment of Inertia (maximum moment created by the live load only) I = = ^ 0 ( 1 2 ^ 1 2 ^ 1 7 2 8 = 4 2 4 H .n4 384Ed 3 8 4 x 1 3 2 0 0 0 0 x 0 .4 Note: The number 1728 is (12 in/ft)3 , used to make the units come up right. i Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The required lumber properties for a 4” x 12” wood member are: Design for Column: P = 12,384 lbs. 1 = 9 ft. Fc = 1250 psi. E = 1,320,000 psi Calculating for 1/d ratio: 1 9(12) = ------------= 17.4 (intermediate column) d 5.5 k = 21.8 therefore: 11 < 17.4 < 21.8 Computing for allowable force 1 S = 73.8 in3 > 58.4 in: A = 39.4 in2 > 36.36 in2 I = 415 in4 < 424.14 in4 where: k = .671 1 13200C k = .671,1---------- V 1250 1320000 Fc’ = 1081 psi 129 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Therefore: Calculating for the Allowable Load: P = Fc’ x A = 1081(5.5)2 = 32.700 lbs. Calculating for the area of Column: P 32,700 A = — = ---------= 30.24 in2 Fc’ 1081 therefore: use 6” x 6” column. Note: From the tested built-up cross column with dowel connections spaced at 6”, the maximum load applied at breaking point is 127,232 lbs. Comparing it with the designed load and allowable load with a safety factor of 2.5. The tested column is still in the safety zone. Design load < allowable load < tested column load 12,384 lbs. < 32,700 lbs. < 50,893 lbs. Seismic Analysis: I. Weight of Building. Roof Assembly Roof material 1.0 psf Sheathing 1.5 psf Purlin (2”x3”) 0.5 psf Rafter (2”x6”) 1.0 psf Ridge beam (4”xl0”) 1.0 psf Insulation 1.5 psf Ceiling (gypsum) 3.0 psf Total 9.5 psf Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2nd Floor Assembly Flooring Mat’I. (1” hardwood) 4.0 psf Framing (2”x8”) 2.0 psf Ceiling (gypsum) 3.0 psf Total 9.0 psf Ground Floor Concrete Slab 12.5 psf Interior Walls 1/2” Gypsum Bd. (both sides) 3.0 psf 2”x4” stud wall @ 16”o.c. 1.0 psf Insulation 1.5 psf Total 5.5 psf Exterior Wall 7/8” stucco 10.0 psf 3/8” plywood 1.2 psf 2”x4” stud wall @ 16” o.c. 1.0 psf Batt Insulation 1.5 psf 1/2” gypsum bd. 1.5 psf Total 15.2 psf Plan Areas and Weight: Roof: (28 x 32) + (16 x 20)l/cosl5° = 1922 sq.ft. x 9.5 psf = Ground Floor: (16 x 24) + (24 x 24) + (12 x 12) = 1054 sq.ft. x 12.5 psf = 2nd Floor Floor: (24 x 24) +(12 x 12) = 720 sq. ft. x 9.0 psf = Interior Walls: Total Area =1.040 sq.ft. x 4.0 psf = Exterior Wall: Total Area = 2,368 sq.ft. x 15.2 psf = Total Weight ........................................................................ 18,254 lbs. 13,125 lbs. 6,480 lbs. 4,160 lbs. 35,994 lbs. 78,013 or 78 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Computing for Base Shear: ZIC V = -------------W B U (0.4X1X2.75) V = ----------------------------- 7 8 k i p s 8 V = 10.72 or 11 kips where: Z = 0.4 (Zone 4) 1= 1.0 Standard C = 4.55 use Cm w = 2.75 Rw=8 where: S = 1.2 (dense soil) T = Ct(h)A .75 = 0.02(20)A .75 = 0.189 C = 1.25(S)/TA .666 = 1.25(1.2)/0.189‘ 6 6 6 = 4.55 Computing for the Force per floor. where: (V - Ft) wx hx Fx = n 2 (wjhj) 1=1 where: whip force Ft on top of building is computed as: Ft = .07 TV = ,07(. 189)(11) = 0.145 /. Ft is considered 0 where T < 7 sec. Level W j / w x hi / hx w.h; / wx hx Force Roof 40,344 psf 20 ft. 807 kips 7.05 kips 2nd Floor 37,656 psf 12 ft. 452 kips 3.94 kips Total 1,259 kips Fx = Fx = (11 -0) 807 kips 1,259 kips (11-0) 452 kips 1,259 kips = 7.05 kips (Roof Level) = 3.94 kips (2nd Level) 132 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Wind Analysis: Wind Direction 8’ - 6” 9’ - 0 ” 24’ -0 ” 40’ - 0 ’ Wind Load = 100 mph Computing for Roof: P = Ce Cq qJ For Roof Level @ 20 ft. height P = CeCq^tl = (1.13)(1.3)(25.6)(1.0) - 37.6 psf Therefore: Exposure C where: P = design wind pressure Ce = combined height, exposure and gust factor coefficient (1.13) Cq = pressure coefficient (1.3) q. = wind stagnation pressure (25.6) I = importance factor (1.0) F = 37.6 psf ( 7 ft.) = 379.44 lb/ft 133 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Computing for Roof Longitudinal Force: * R i R2 ri « - R . * Ri 24’ - 0 ” '■ * R * 263.24 lb/ft x 12 ft. Ri — R* — = 1,579.44 lbs. say 1.6 kips * Rs R2 = R3 = 1.6 kips x 2 = 3.2 kips (wind force at the roof) Computing for Transverse Force: Same as Longitudinal Force where: Ri = R3 = 1.6 kips R2 =3.2 kips 134 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Computing for Second Floor @ 9 ft. height: P = Ce C,qiI = (1.06)(1.3)(25.6)(1.0) = 35.27 psf therefore: F = 35.27 psf x 8.5 ft. = 299.7 lb/ft. Computing for longitudinal force: 299.7 lb/ft x 12 ft. Ri = Ki = ------------------------= 1.8 kips 2 R2 = R3 = 1.8 kips x 2 = 3.6 kips Computing for transverse force: 299.7 lb/ft x 16 R. = - -- = 2.4 kips 299.7 lb/ft x 12 R2 = + 2.4 kips 2 = 4.2 kips 299.7 lb/ft x 12 R t = = 1.8 kips 299.7 lb/ft x 12 R3 = + 1.8 kips = 3.6 kips * Ri t Ra t R3 «-Ri «-R3 « -R . * R 4 135 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Comparison of Wind and Seismic Forces Level Direction Wind Seismic Roof Transverse 3.2 kips 7.04 kips Longitudinal 3.2 kips 7.04 kips Second Transverse 4.2 kips 3.94 kips Floor Longitudinal 3.6 kips 3.94 kips Note: Since there is a greater base shear factor in seismic, therefore seismic governs. 136 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 7: Proposed Prefabrication Operations 7.1 General Description For the purpose of having a better quality control and more efficient production of structural component parts for wood frame structure, a proposed prefabrication operation was developed and discussed in this chapter. The operation is divided into three category (fig. 7.01): PREFABRICATION^ OPERATIONS DESIGN MANUFACTURING ERECTION Equipment & Tools Foundation H Material Handling ^ Coluinns " j Cutting Operations ^ B e a m s i Storage Joists " j Transport ■^Rafters "K Walls ■ i Finishes Figure 7.01 Schematic Diagram of Prefabrication Operation 137 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 7.2 Prefabrication Operations 7.2.1 Design Systems The term “design”, is limited to the architectural and engineering phases of design. The emphasis is upon consideration to the type of building system to be used, whether a split beam-continuous column or continuous beam-spliced column frame system is to be used. Depending of the designer’s approach. Basically, the system must be reduced to a minimum number of different parts, each so designed that it will be used interchangeably with others of its particular size and construction and will fit into its proper place in any house of like design. This system provides for an economical frame that can be fabricated by any small timber construction enterprise without special equipment. 7.2.2 Manufacturing Process The basic concept of these process is to utilize the use of machines suited to the materials and parts to be made. 7.2.2a Equipment and Tools The equipment for a prefabrication plant range from standard wood cutting machines such as table and band saw, simple jigs, and shaper cutters for joint cutting. With the use of special saw blades, like carbide tip blades, the use of planing machines are minimized or eliminated, because this type of blades produces smooth surface as they cut the wood. 7.2.2b Material Handling Simple conveyor system must be provided for better handling and transporting of components parts within the factory. 138 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 7.2.2c Cutting Operations Component parts must be cut identically according to the actual size given in the design. Precision is the key factor for this part of the operation. Properly adjusting the cutting machines to the exact size of the parts to be cut will produce a precise cut. 7.2.2d Storage of Component Parts After all component parts were cut to their exact size and dimensions. It is necessary to store them in proper storage inside the factory before they are delivered to the site. All component parts are also treated with preservatives at this point of the operation to protect the wood members from decay. Marking down and numbering each part would be very helpful to identify which part goes where. 7.2.2e Shipment of Component Parts Structural component parts will be shipped by truck to the site. Loading of parts to the truck should be designed and fitted for safe loading of parts. Two types of loading can be used, racking and stacking. Where racking consist of loading prefabricated panels vertically, the bottom edges of the panels are seated between blocks permanently fixed to the truck floor. Stacking consists of flat piling necessary for precut component parts. The piling is so planned that a given number parts are bundled together with straps. The object of properly loading the parts is to reduce waste of space to the minimum. Shipment is to be done after the foundation and slab have already set and structural framing parts are ready to be installed. 139 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 7.2.3 Site Assembly A systematic erection sequence is also necessary as a guide to simplify erection and installation of structural component parts at the site of the timber frame building. Site assembly operations consist in general of (a) foundation; (b) erection of columns; (c) installation of girders and roof beams; (d) installations of floor joist; (e) installation of roof rafters; and (f) installation of walls and finishes. All these component parts to be installed at the site, except the foundation, are prefabricated in the factory and delivered to the site for assembly. Excluding the time required to construct the foundation, this assembly operations is planned to get the frame structure erected in a three day period or less. 7.2.3a Foundation Construction Requisites of a good foundation are adequate footings and walls to carry the loads of the structure. Complete and thorough supervision is necessary at this point of the construction to align all column anchorage perfectly as they are embedded in the concrete foundation. Even a minor misalignment of this anchors could cause difficulties in the erection of the columns for the frame structure. After the footings and wall footings are laid -out and poured with concrete, the next step is to pour the concrete for the floor slab of the ground floor. Structural component parts for the wood frame structure will not be transported at the site unless the foundation and floor slab have already set and ready to be installed. This is to prevent harmful effects to the wood parts when exposed to bad weather. 140 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 7.3.2b Erection of Columns After the foundation and floor slab had set, and structural parts delivered at the site, the first structural components to be erected are the columns. The columns are erected at the pre-installed columns anchors embedded in the foundation as shown in the line diagram (Fig.7.02). All column parts are numbered at the factory to make it easier for the workers on the site to follow where each components are to be erected. Figure 7.02 Erection of Columns 7.2.3c Installation of Girders and Roof Beams After the columns are set in place, girders and roof beams are installed to position. The columns already have notches and splices to accommodate the intersecting beams and girders (Fig.7.03). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 7.03 Girders and Beams Installed 7.2.3d Installation of Floor Joist The next step is installing the floor joists at the second floor of the frame building. This will make it easier to install the remaining component parts at the upper level of the structure (Fig. 7.04). Figure 7.04 Floor Joist Installed 142 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 7.2.3e Installation of Rafters and Purlins Rafters and purlins are the next component parts to be installed after the flooring was installed (Fig.7.05). Figure 7.05 Rafters and Purlins Installed 7.2.3f Walls and Finishes After all the prefabricated and precut components parts of the timber frame building were erected, walls and finishes are then installed to the structure. The wall and finishes may be handmade or prefabricated. 143 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 8: Recommendations and Further Work 8.1 Conclusion This thesis has been completed to prove the load bearing capacity of a new built up column using wood dowels as fasteners, and to demonstrate the uplift strength of dovetail joints and the lateral stability of a frame wall system make up of dovetail joints. This thesis also exhibit the effectiveness of prefabricating structural component parts and the effeciency of a systematic method of assembly of a frame structure. We understand that the old practice of fabricating built-up columns are by mechanically laminating a series of smaller pieces or by fastening pieces with bolts and nails. Therefore, we recognize that this is a new method of assembling built-up columns with the aim of proving its load bearing capacity. To demonstrate the strength of the column, different configurations were tested through series of load bearing and compression tests. There it was observed that the stiffness and strength of such members are less than that of solid members of the same size, but considerably greater than the sum of the load capacities of the individual members treated as independently sharing the load. Since the results from the test have been proven to be very promising, it appears that well-fastened columns of this type will perform to capacities above the averages for either solid members or unconnected laminations. It will also anticipate the use of traditional method of fastening wood members, whereby minimizing the use of the more expensive mechanical fasteners and lamination. 144 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. As for the uplift strength of a dovetail joint, we recognize that cutting dovetail joint on a tenon makes pullout of a joint impossible. Although dovetail joints are weak in tension because of the short grain at the edges of the tails, but this problem may be compensated by careful selection of wood to reduce the risk of shear failure. It must be recommended to use straight-grained wood for this type of joint and as far as possible, only wood with very low moisture content should be used. The method of fabricating this type of columns and joints may seem to be labor intensive if done manually, that is why the system was abandoned many years ago and mechanical fasteners and metal brackets are more widely used. But with the availability of machineries, jigs, and other wood working tools, the fabrication of this type of joints will be a lot faster. 8.2 Recommendations Since the proposed structural frame system is to be adapted for the Philippines, it is necessary to repeat the test using wood species available in the country. It is also to be recommended that the column configuration be tested at a normal scale to produce a more accurate and dependable result. Also a greater number of configration, dowel spacings and wood species should be tested. It is also proposed that the method of prefabrication and site assembly be demonstrated in actual manufacturing to facility the effectiveness of the system. 145 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Not only the system be adapted for columns, there is also the potential application of this method to different component members of a wood frame structure, such as beams and girders. There is a lot of potential in the adaptation of this proposed structural frame system for wood buildings. However, to be able to establish itself as a recognized system, it will have to undergo extensive testing on a real prototype building. With the actual construction of a timber frame structure using this system, a comprehensive joint assembly using traditional methods could be developed. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. BIBLIOGRAPHY AITC (American Institute of Timber Construction, Timber Construction Manual, John Wiley and Sons, Inc., Second Edition, 1974 Ambrose, J., Simplified Design o f Building Structures, John Wiley and Sons, Inc. 1979 Breyer, D. E., Design o f Wood Structures, McGraw-Hill Book Company, Second Edition, 1988 Graubner, W., Encyclopedia o f Wood Joints, The Taunton Press, Inc., 1992 Goetz, K-H./Hoor, D./ Moehler, K./ Nattarer, J., Timber Design and Construction Sourcebook, A Comprehensive Guide to Methods and Practice, McGraw-Hill Publishing Company, 1989 Halperin, D. A./Bible, G. T., Principles o f Timber Design fo r Architects and Builders, John Wiley and Sons, Inc., 1994 Hoyle, R. J. Jr./ Woeste, F. E., Wood Technology in the Design o f Structures, Iowa State University Press/Ames, Fifth Edition, 1989 PAPI, Philippine Architecture, Engineering, and Construction Records, PAENCOR, Inc., April 1978 PLG, The National Building Code o f the Philippines, Vicente Foz, 1992 Ramsey/Sleeper, Architectural Graphic Standard, John Wiley and Sons, Inc., Eigth Edition, 1988 Salvan, G. S., Architectural Building Materials, JMC Press, Inc. 1986 Sobon, J./ Schroeder, R., Timber Frame Construction, Garden Way Publishing, 1984 Sloane, E., Age o f Bams, Ballantine Book Company, New York, 1974 FPL (U.S. Forest Product Laboratory), Manual on Wood Construction fo r Prefabricated Houses, Washington D.C., 1947 147 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
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Asset Metadata
Creator
Daplas, Dominador Cajulis
(author)
Core Title
A proposed wood frame system for the Philippines
School
School of Architecture
Degree
Master of Building Science / Master in Biomedical Sciences
Degree Program
Building Science
Publisher
University of Southern California
(original),
University of Southern California. Libraries
(digital)
Tag
Architecture,OAI-PMH Harvest
Language
English
Contributor
Digitized by ProQuest
(provenance)
Advisor
Schierle, G. Goetz (
committee chair
), Schiler, Marc E. (
committee member
), Vergun, Dimitry (
committee member
)
Permanent Link (DOI)
https://doi.org/10.25549/usctheses-c16-10135
Unique identifier
UC11341420
Identifier
1383555.pdf (filename),usctheses-c16-10135 (legacy record id)
Legacy Identifier
1383555.pdf
Dmrecord
10135
Document Type
Thesis
Rights
Daplas, Dominador Cajulis
Type
texts
Source
University of Southern California
(contributing entity),
University of Southern California Dissertations and Theses
(collection)
Access Conditions
The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the au...
Repository Name
University of Southern California Digital Library
Repository Location
USC Digital Library, University of Southern California, University Park Campus, Los Angeles, California 90089, USA