Design and Costing Workbook

Transcription

1 Wood Works! is a project of the Canadian Wood Council Design and Costing Workbook SINGLE STOREY COMMERCIAL WOOD STRUCTURES

2 DESIGN AND COSTING WORKBOOK A guide to single storey commercial wood structures Canadian Wood Council Conseil canadien du bois

3 1999 Copyright Canadian Wood Council Conseil canadien du bois 1400 Blair Place, Suite 210 Ottawa, Ontario, Canada K1J 9B8 tel: ISBN M99-4 Photographs courtesy of: D.E. Schaefer Architect Ltd. Design and production: Accurate Design & Communication Inc. Printing: Lomor Printers Ltd. Printed in Canada on recycled paper. ii

4 Preface In Canada, wood is well suited to commercial buildings of one to four storeys. Recent code changes have expanded the permitted use of wood and new engineered wood product systems with greater spans and carrying capacities. These two factors, combined with this Design and Costing Workbook, should provide many new opportunities for wood specifiers. The Design and Costing Workbook is a series of publications intended to demonstrate the steps for designing a cost effective wood-frame building. This workbook is for a single storey commercial building typical of retail or industrial buildings up to m 2. The Canadian Wood Council has a complete set of publications and design tools to facilitate designing and building with wood. These include the Wood Design Manual 1995, referenced in the example, and the complete software for wood design, WoodWorks Design Office 99. WoodWorks Design Office 99 includes SIZER, CONNECTIONS and SHEARWALLS to assist in the design process. A demo version of the software can be viewed at The latest software, CodeCheck, is a feasibility tool allowing the user to easily determine conformance of wood buildings to building codes, based on fire safety requirements. This free applet, or downloadable software, is available at Providing valuable design aids is an important goal of the Canadian Wood Council. A feedback form for this series is available at to collect your comments. In addition to economic factors, environmental concerns may play a role in construction project decision making. In this area, wood has the following advantages: Wood is the only major building material that is renewable Wood produces less pollution during manufacturing and use than other building materials Wood boasts superior energy savings because of its thermal performance Every effort has been made to ensure the data and information in this publication are as accurate as possible. The Canadian Wood Council does not, however, assume any responsibility for errors or omissions in the publication nor for any designs or plans prepared from it. The Canadian Wood Council acknowledges the contributions of the following in the preparation of this workbook. John Pao, P. Eng., Bogdonov Pao Associates Ltd., Ed Lim, P. Eng., Cloverdale Truss Co. Ltd. iii

5 Table of Contents 1.0 Introduction Layout Building Elevations Floor Plan Roof Plan Building Geometry Site Specifications Dead Loads Preliminary Design Roof Truss Tables Engineered Wood Products Tables Stud Wall Tables Material Count Cost Summary Table Components Summary Table Design Snow Loading Wind Loading External Pressure External and Internal Pressures Specified Wind Loads Lateral Wind Load Summary Seismic Loading Seismic Calculations Seismic Load Summary Lateral Loading Results Roof Diaphragm Design Diaphragm Design Chord Design Splice Design Shearwall Design Shearwall Design Base Plate Anchorage Overturning Chord Design Wall Line Loads Stud Wall Design Built-up Beam Design (B1) LVL Beam Design (B1) Built-up Column Design (C1) Conclusion v

6 1.0 Introduction This Workbook is intended to assist in determining the feasibility and cost competitiveness of wood in commercial construction and provide a step-by-step guide to the design of these structures. The popularity of single storey commercial projects, coupled with the wide availability of wood in Canada presents designers with many opportunities to use wood economically in these applications. Preliminary design tables and a design example are provided to demonstrate wood s suitability for engineered construction. This publication is a design and costing tool for single storey commercial wood structures. It will assist in evaluating the feasibility and cost effectiveness of wood structures and includes the following: Costing tables to determine feasibility and cost competitiveness A step by step design example to assist in the initial design The workbook is subdivided as follows: 1. INTRODUCTION gives background information. 2. LAYOUT introduces the building example including typical elevations, plan views and roof framing layouts. Climatic loads, building dimensions and geometry are also presented. 3. PRELIMINARY DESIGN provides tables with a range of spans and loading conditions to assist in determining the material quantities and a cost estimate for a single storey commercial structure. The costing details and material quantities of the example are presented here. Tabulated values are included to allow the user to rapidly determine material quantities and estimate costs for a customized building. 4. DESIGN provides a detailed design example of one of each structural member used in the single storey building. In the left margin, references will be noted as follows: d Wood Design Manual 1995 a CSA O Engineering Design in Wood (Limit States Design) b National Building Code of Canada c User s Guide NBC 1995 Structural Commentaries (Part 4) The design example features typical framing members and systems for a commercial wood building, including lumber, studs, columns and beams, wood trusses, structural composite lumber (SCL) and sheathing. 5. CONCLUSION Wood structures offer many advantages for commercial buildings. This publication will allow the user to quickly evaluate a wood option for their projects. In addition, wood offers a range of choices that include the following: Competitive material costs Availability of labour Ease of installation and material handling Shortened construction schedules Finishing options Ability to create complex building shapes with relative ease 1

7 2.0 Layout Section 2 introduces the building example in this document. It provides dimensions, typical elevation and plan drawings, details of the truss roof framing, climatic data, and materials and their corresponding dead loads and design implications. A generic building type was purposefully chosen to demonstrate flexibility and versatility found in wood construction projects. Users can adapt the modular format of this sample building to their projects by using the Tables of Section 3 for a range of spans and loading conditions. The use of many wall openings in a relatively demanding seismic zone demonstrates the flexibility of wood frame construction. The example chosen is a typical strip mall application, although the tables can be used for any one storey building. 2.1 Building Elevations Three elevations are shown depicting the features of the example. Features include 75% openings in the front bays, side windows, back loading entrances, and standard dimensions. An economical 4/12 hip roof configuration is chosen for the structure. The front and side sections are covered with cantilevered roof trusses to shelter the display windows. Figure 2.1 Building elevations SOUTH ELEVATION (FRONT) NORTH ELEVATION (BACK) Dimensions are in meters BACK EAST & WEST WALL ELEVATIONS FRONT 3

8 2.2 Floor Plan The building is subdivided into four bays of m 2 ( sq ft), each having front windows and rear service access. No supporting walls are required allowing maximum flexibility for merchant space. Dimensions used are typical for this application. Figure 2.2 serves as reference for dimensions and positions of highlighted members designed in Section 4. Costing values are based on Figure 2.2. Figure 2.2 Floor plan N PROJECT NORTH C7 B3 C7 C7 B3 C7 C7 B3 C7 C7 B3 C TYP TYP TYP TYP. C6 C5 C5 C6 B4 B4 B TYP TYP C6 C5 C5 C6 B4 B4 B N-S Shearwall C C2 C1 C2 TYP. C4 C3 C4 C4 C3 C4 TYP. C2 C1 B1 B1 B2 B2 B2 B2 B1 B Dimensions are in meters Partition Wall The center wall is a shearwall Partition Wall

9 2.3 Roof Plan The roof plan shows the positioning of the hip trusses and their configuration. The overhangs extend m (6 ft) beyond the building on three sides. Special attention should be given to cantilevered trusses and their reactions on supporting beams. Consideration should also be given to lateral bracing of trusses and proper transfer of lateral forces to the shearwalls. Figure 2.3 Roof plan Corner set trusses require special attention as they are typically installed as a unit with special fastening details. Dimensions are in meters Girder truss Cantilevered jack trusses N PROJECT NORTH

10 2.4 Building Geometry The location for the design was selected as a typical case. This particular case uses moderate snow loading, high seismic loading and light wind loading. Users can adapt their projects by making changes to this example. Building Geometry Roof slope: Pitch: 4:12 Height to eave: m (12 ft) Building width: m (40 ft) Building length: m (110 ft) No. of stories: 1 Figure 2.4 Standard building HEIGHT ROOF SLOPE BUILDING WIDTH BUILDING LENGTH 2.5 Site Specifications Design data as per the National Building Code of Canada 1995, Appendix C Climatic Information for Building Design in Canada Location for design data: Surrey, British Columbia Specified Loads: Snow Ground snow load (1/30 return) S s = 2.20 kpa (45.9 lb/ft 2 ) Associated rain load S r = 0.30 kpa (6.26 lb/ft 2 ) Wind Reference velocity pressure q 1/10 = 0.36 kpa (7.52 lb/ft 2 ) (1/10 return) Reference velocity pressure q 1/30 = 0.43 kpa (8.98 lb/ft 2 ) (1/30 return) Reference velocity pressure q 1/100 = 0.52 kpa (10.9 lb/ft 2 ) (1/100 return) Seismic Acceleration-related seismic zone Z a = 4 Velocity-related seismic zone Z v = 4 Zonal velocity ratio v =

11 2.6 Dead Loads The loads represent typical construction materials used in Canada for this application. However, each application is different and the user can modify the design case to match their conditions. Roof Corrugated steel W D /Cos (18.43) kpa (1.54 lb/ft 2 ) W D = kpa (1.46 lb/ft 2 ) 12.5 mm plywood or OSB sheathing W D /Cos (18.43) kpa (1.65 lb/ft 2 ) W D = kpa (1.57 lb/ft 2 ) Batt insulation, 175 mm kpa (0.73 lb/ft 2 ) Roof trusses (by supplier) kpa (2.00 lb/ft 2 ) 12.5 mm dry wall ceiling kpa (2.61 lb/ft 2 ) Mechanical & Electrical kpa (3.03 lb/ft 2 ) Miscellaneous kpa (2.00 lb/ft 2 ) Total wrt. horizontal projection: 0.65 kpa (13.57 lb/ft 2 ) Exterior Walls Aluminum siding kpa (1.46 lb/ft 2 ) 12.5 mm plywood or OSB sheathing kpa (1.57 lb/ft 2 ) 38x140 mm 406 mm o.c kpa (1.46 lb/ft 2 ) Batt insulation, 140 mm kpa (0.58 lb/ft 2 ) 12.5 mm dry wall kpa (2.61 lb/ft 2 ) Total wrt. wall surface: 0.37 kpa (7.68 lb/ft 2 ) These specified dead loads are used for design The above listed dead loads represent some of the typical construction materials. All values may be substituted with materials from pp. 571 of the d. One such example would be to use asphalt shingles at 0.12 kpa instead of kpa for corrugated steel for the roofing finish. 7

12 3.0 Preliminary Design Scope Section 3 features tables and a detailed costing example. The first two sets of the tables, roof tables and stud wall tables allow the user to select a solution based on building geometry and loading. A detailed costing example, derived from the design requirements of Section 4, is provided to illustrate the complete process of design and costing. A summary table is presented highlighting total structural costs of each component and the overall structural cost. A Components Summary Table demonstrates the structural requirements of the example under three loading scenarios. Cost Parameters This publication can assist in estimating quantities and costs of the basic structure along with cost tables. An estimator can use the building area, height, width and location to quickly estimate a cost for a project with ease. Two sets of tables are available: one for roofs and one for walls. Roofs and walls represent the bulk of the costs in a single storey building. Prompt determination of feasibility is a key factor in specifying construction materials. This workbook will shorten this process and aid in determining the effects of changing building parameters. This approach makes use of simplifications to average costs for a structural system. The tables are recommended for the purpose of preliminary costing, i.e., class D estimates. In the tender process there is a need to determine final costs, which are subject to local, regional and market fluctuations. How to Use the Tables The costing tables allow the user to determine the implications of varying length, width, height, roof type and pitch. Changing the width of building or using an existing design in a new location with different loads will have an effect on the preliminary cost estimate. The first step is to obtain a cost index from each of the material suppliers, as follows: l Truss Supplier $/Board Foot Measure l Lumber Supplier $/Board Foot Measure l LVL Supplier $/Board Foot Measure l Sheathing Supplier $/Square foot The board foot measure (BFM) is a unit used in the lumber industry to measure quantities. A board foot is the nominal width times the nominal thicknesss (in inches) divided by 12 times the length in feet. It is used here to represent the material requirement of a particular structural solution, i.e., a 13.4 m (44 ft) truss may require 150 board feet. Furthermore, the cost of a board foot in a truss includes the cost of design, manufacturing and material. For example, $1.50 could be the cost per board foot in a truss, making this truss cost $ However, for lumber, sheathing and engineered wood products, the BFM more closely represents material costs. The dollars per BFM or cost indices rely on certain assumptions. These are listed beside each table that refers to them. When requesting costs based on these indices, it is important that the material supplier understands the assumptions. Each region will have different costs associated with different materials, therefore, a regionspecific cost index should be obtained. Specific and proprietary component design values must be obtained from manufacturer s specifications if they are used to replace generic products. Caution is suggested when estimating, as the intent is to provide preliminary costing. The responsibility lies with the user to determine accurate cost for each of the material categories in their particular project. 9

13 3.1 Roof Truss Tables The following are truss tables showing 'board foot (BF) of trusses per horizontal roof area' (sq ft). These numbers can be converted to cost of trusses per square foot of horizontal roof area by applying the cost index ($1.50 per BFM in this case, for this example). This cost index can generally be obtained from the local or regional truss supplier, and should include material, shop labour, design and overhead. These unit costs are subject to local, regional and market fluctuations. Typically, several grades and sizes are used in a single truss. In order to simplify the estimating process an average material cost is assumed in the cost index. For a more detailed cost, the truss supplier will quote for a specific project. Two styles of roof systems are tabulated here: I) trusses of various shapes and, II) engineered wood products for shallow flat roofs where storey clearance is important. The tables include a 1.2 m (4 ft) cantilever in the truss. The user, for budget purposes, may substitute cantilevered values with clear spans with negligible change. The removal of a vertical web bearing member may approximate the effects of the additional structural requirements of a 1.2 m (4 ft) longer clear span. Example: How to use the Truss Tables The costing example uses configurations of the design example The grey areas represent the solution of the design example from Section 4 The first group of tables ( ) gives a board foot requirement per square foot and the second group of tables ( ) gives the costs per square foot of horizontal roof area Step In The Example 1 Select roof system type Trusses 2 Select roof profile Hip trusses from Table Select from Hip Truss Table 3.1 Span is 13.4 m (including 1.2 m cantilever), span, specified load and pitch. specified roof load is 2 kpa, the pitch is 4/12 4 Determine from Table 3.1 BF required Reading the highlighted number, obtain per sq ft of horizontal roof area 1.70 BF/sq ft of horizontal roof area 5 Determine cost index from truss supplier. For this example use $1.50 per BFM See above for explanation. 6 Multiply cost index by board foot/ sq ft 1.70 BF/sq ft x $1.50 gives $2.55 per square foot of horizontal roof area from Table Multiply $2.55 by building area $2.55 x (44 ft x 110 ft) gives $12,342 for the roof system 8 For entire building calculation carry area: 4840 sq ft, total BF: 4840 x 1.70 = 8228 building area, total board footage and and index: $1.50 cost index to Cost Summary Table on page 25 Note: This is a preliminary cost estimate 10 D e s i g n a n d C o s t i n g W o r k b o o k

14 Table 3.1 Board foot per horizontal roof area (sq ft) for hip trusses Truss Board Foot Requirement Tables Specified Roof Loads HIP TRUSSES 1 kpa (20 psf) 2 kpa (40 psf) 3 kpa (60 psf) pitch 4/12 6/12 8/12 4/12 6/12 8/12 4/12 6/12 8/12 span 10.4 m (34 ft) m (44 ft) m (54 ft) m (64 ft) Notes: The user will note that at 16.5 m (54 ft) the efficiency is maximized. The use of a lower slope will also decrease the material requirement especially for the 16.5 m (54 ft) spans Table 3.2 Board foot per horizontal roof area (sq ft) for gable trusses Specified Roof Loads GABLE TRUSSES 1 kpa (20 psf) 2 kpa (40 psf) 3 kpa (60 psf) pitch 4/12 6/12 8/12 4/12 6/12 8/12 4/12 6/12 8/12 span 10.4 m (34 ft) m (44 ft) m (54 ft) m (64 ft) Notes: The user will note that at 16.5 m (54 ft) the efficiency is maximized The use of a lower slope will also decrease the material requirement especially for the 16.5 m (54 ft) spans 11

15 Table 3.3 Board foot per horizontal roof area (sq ft) for mansard trusses MANSARD TRUSSES Specified Roof Loads 1 kpa (20 psf) 2 kpa (40 psf) 3 kpa (60 psf) span 10.4 m (34 ft) m (44 ft) m (54 ft) m (64 ft) Table 3.4 Board foot per horizontal roof area (sq ft) for low slope trusses Specified Roof Loads LOW SLOPE TRUSSES 1 kpa (20 psf) 2 kpa (40 psf) 3 kpa (60 psf) pitch 0.5/12 0.5/12 0.5/12 span 10.4 m (34 ft) m (44 ft) m (54 ft) m (64 ft) Table 3.5 Board foot per horizontal roof area (sq ft) for mono and girder truss arrangement MONO TRUSSES Specified Roof Loads ON GIRDER TRUSS 1 kpa (20 psf) 2 kpa (40 psf) 3 kpa (60 psf) pitch 4/12 4/12 4/12 system span 20.7 m (68 ft) Notes: This table assumes a 7.32 m (24 ft) girder truss supporting two m (34 ft) mono trusses 12 D e s i g n a n d C o s t i n g W o r k b o o k

16 Table 3.6 Cost per horizontal roof area (sq ft) based on index of $1.50 for hip trusses Truss Cost Tables These tables give the user a cost per square foot based on the the cost index of $1.50 from the example. The user should obtain a specific cost index from their particular truss supplier as these values can fluctuate. Specified Roof Loads HIP TRUSSES 1 kpa (20 psf) 2 kpa (40 psf) 3 kpa (60 psf) pitch 4/12 6/12 8/12 4/12 6/12 8/12 4/12 6/12 8/12 span 10.4 m (34 ft) $2.19 $2.47 $2.70 $2.44 $2.68 $2.91 $2.77 $2.88 $ m (44 ft) $2.55 $2.55 $2.82 $2.55 $2.79 $3.09 $3.06 $3.11 $ m (54 ft) $2.46 $2.93 $3.52 $2.50 $3.05 $3.60 $3.03 $3.37 $ m (64 ft) $2.72 $3.10 $3.04 $3.13 $3.23 $3.62 Notes: The user will note that at 16.5 m (54 ft) the efficiency is maximized. The use of a lower slope will also decrease the material requirement especially for the 16.5 m (54 ft) spans Table 3.7 Cost per horizontal roof area (sq ft) based on index of $1.50 for gable trusses Specified Roof Loads GABLE TRUSSES 1 kpa (20 psf) 2 kpa (40 psf) 3 kpa (60 psf) pitch 4/12 6/12 8/12 4/12 6/12 8/12 4/12 6/12 8/12 span 10.4 m (34 ft) $2.19 $2.37 $2.58 $2.44 $2.68 $2.81 $3.00 $2.88 $ m (44 ft) $2.55 $2.55 $2.82 $2.55 $2.79 $3.09 $3.06 $3.11 $ m (54 ft) $2.40 $2.93 $3.52 $2.42 $3.05 $3.60 $3.00 $3.37 $ m (64 ft) $2.52 $3.10 $3.11 $3.13 $3.23 $3.62 Notes: The user will note that at 16.5 m (54 ft) the efficiency is maximized. The use of a lower slope will also decrease the material requirement especially for the 16.5 m (54 ft) spans 13

17 Table 3.8 Cost per horizontal roof area (sq ft) based on index of $1.50 for mansard trusses MANSARD TRUSSES Specified Roof Loads 1 kpa (20 psf) 2 kpa (40 psf) 3 kpa (60 psf) span 10.4 m (34 ft) $2.37 $2.68 $ m (44 ft) $2.55 $2.79 $ m (54 ft) $2.93 $3.05 $ m (64 ft) $3.10 $3.13 $3.62 Table 3.9 Cost per horizontal roof area (sq ft) based on index of $1.50 for low slope trusses Specified Roof Loads LOW SLOPE TRUSSES 1 kpa (20 psf) 2 kpa (40 psf) 3 kpa (60 psf) pitch 0.5/12 0.5/12 0.5/12 span 10.4 m (34 ft) $2.37 $2.68 $ m (44 ft) $2.55 $2.79 $ m (54 ft) $2.93 $3.05 $ m (64 ft) $3.10 $3.13 $3.62 Table 3.10 Cost per horizontal roof area (sq ft) based on index of $1.50 for mono and girder truss arrangement MONO TRUSSES Specified Roof Loads ON GIRDER TRUSS 1 kpa (20 psf) 2 kpa (40 psf) 3 kpa (60 psf) pitch 4/12 4/12 4/12 system span 20.7 m (68 ft) $3.34 $4.16 $4.57 Notes: This table assumes a 7.32 m (24 ft) girder truss supporting two m (34 ft) mono trusses Truss Table Assumptions These costs are based on typical situations with 1,2 & 3 kpa specified roof loads. Snow drifts and mechanical loads have not been considered since cases can vary widely The trusses are installed on 610 mm centers Each span includes a 1.2 m (4 ft) cantilever The tables are based on the footprint of the trusses for area calculations The BFM cost index includes the complete cost of an undelivered truss The truss cost index is assumed to be $1.50 per board foot per square foot of horizontal roof coverage or area 14 D e s i g n a n d C o s t i n g W o r k b o o k

18 3.2 Engineered Wood Products Tables Another option for a flat roof building is the use of engineered wood products as demonstrated below. If the requirements of your project require increased useable storey height these products may be advantageous. Table 3.11 Engineered wood products solutions I-JOIST OR O WEB TRUSS span Specified Roof Loads 1 kpa (20 psf) 2 kpa (40 psf) 3 kpa (60 psf) 10.4 m (34 ft) 406 mm (16 ) mm (22 ) L mm (23 ) TJL OW 13.4 m (44 ft) 559 mm (22 ) L mm (28 ) TJL OW 965 mm (38 ) TJLX OW 16.5 m (54 ft) 610 mm (24 ) H mm (40 ) TJLX 1016 mm (44 ) TJS OW 19.5 m (64 ft) 940 mm (37 ) TJLX OW 1143 mm (45 ) TJS OW 1118 mm (40 ) TJH OW Table 3.12 Engineered wood products costs per horizontal roof area (sq ft) I-JOIST OR O WEB TRUSS span Specified Roof Loads 1 kpa (20 psf) 2 kpa (40 psf) 3 kpa (60 psf) 10.4 m (34 ft) $1.58 $1.59 $ m (44 ft) $1.59 $2.47 $ m (54 ft) $2.30 $2.87 $ m (64 ft) $2.65 $3.63 $5.35 Notes: These examples were supplied by Trus Joist MacMillan for preliminary costing purposes. The user should contact their supplier to obtain representative costs as there are many manufacturers with varied products and configurations. In Table 3.11, the word series has been omitted after the structural solution. Engineered Wood Products Tables Assumptions These costs are based on typical situations with 1,2 & 3 kpa specified roof loads. Snow drifts and mechanical loads have not been considered since cases can vary widely Engineered wood products are installed on 610 mm centers The tabled spans include a 1.2 m (4 ft) cantilever. Therefore the clear span is 1.2 m (4 ft) less than the system span To span the full system without a cantilever span the user should contact a local engineered wood product manufacturer A 0.67 kpa (14 psf) dead load was used to create these tables 15

19 3.3 Stud Wall Tables The following are stud wall tables showing size, height and cost per lineal meter for various configurations. The Stud Wall Requirements Tables list the cost associated with a particular height and stud spacing for a variety of cases. The most Economical Structural Wall System Tables list the most economical solution and cost per lineal meter given building width and specified roof load using a cost of $0.50 per board foot. This cost index should be obtained from the local lumber supplier for the job in question and is subject to local, regional and market fluctuations. Stud Wall Requirements Tables Table mm stud wall requirements 89 mm 2 x 4 Spacing Height BF/m of wall $/m of wall mm (in) m (ft) 3.05 (10) 32.8 $ (12) 3.66 (12) 37.2 $ (14) 43.7 $ (16) 48.1 $ (10) 27.3 $ (16) 3.66 (12) 30.6 $ (14) 36.1 $ (16) 39.4 $ (10) 21.9 $ (24) 3.66 (12) 24.1 $ (14) 28.4 $ (16) 30.6 $15.31 Table mm stud wall requirements 140 mm 2 x 6 Spacing Height BF/m of wall $/m of wall mm (in) m (ft) 3.05 (10) 49.2 $ (12) 3.66 (12) 55.8 $ (14) 65.6 $ (16) 72.2 $ (10) 41.0 $ (16) 3.66 (12) 45.9 $ (14) 54.1 $ (16) 59.1 $ (10) 32.8 $ (24) 3.66 (12) 36.1 $ (14) 42.7 $ (16) 45.9 $ D e s i g n a n d C o s t i n g W o r k b o o k

20 Table mm stud wall requirements 184 mm 2 x 8 Spacing Height BF/m of wall $/m of wall mm (in) m (ft) 3.05 (10) 65.6 $ (12) 3.66 (12) 74.4 $ (14) 87.5 $ (16) 96.2 $ (10) 54.7 $ (16) 3.66 (12) 61.2 $ (14) 72.2 $ (16) 78.7 $ (10) 43.7 $ (24) 3.66 (12) 48.1 $ (14) 56.9 $ (16) 61.2 $30.62 Table mm stud wall requirements 235 mm 2 x 10 Spacing Height BF/m of wall $/m of wall mm (in) m (ft) 3.05 (10) 82.0 $ (12) 3.66 (12) 93.0 $ (14) $ (16) $ (10) 68.4 $ (16) 3.66 (12) 76.6 $ (14) 90.2 $ (16) 98.4 $ (10) 54.7 $ (24) 3.66 (12) 60.1 $ (14) 71.1 $ (16) 76.6 $38.28 Notes: 1. Cost is given in dollars per lineal meter 2. The second column represents board feet per lineal meter of wall 3. These tables are for 38 mm thick studs 17

21 Stud Wall Requirements Tables Assumptions The costs are based on a cost index of $0.50 per board foot Stud walls include a double top plate and single bottom plate with a maximum blocking spacing of 1.2 m These tables list results from gravity and wind loads. Shearwall design considerations have not been accounted for Example: How to use Structural Wall Tables The grey areas represent the solution of the design example from Section 4 Step In The Example 1 Select the table from 3.17 to 3.20 that 12.2 m (40 ft) from Table 3.18 corresponds to your building width 2 Select the wall height and the 3.66 m (12 ft) wall height, 2 kpa (40 psf) specified roof load specified roof load 3 Find intersection of 3.66 m and 2 kpa under Solution read 16, use 38 x mm spacing 4 Determine the cost of 38 x 140 mm under BF/m read 45.9 board feet per 406 mm spacing meter, under cost/m read $22.97 per lineal meter Note: This is a preliminary cost estimate 18

22 Most Economical Structural Wall System Tables building width m overhang Table 3.17 Most economical structural wall system for 9.1 meter wide structures Building Width 9.1 m (30 ft) Specified Roof Load 1 kpa 2 kpa 3 kpa (20 psf) (40 psf) (60 psf) Stud Length Solution BF/m Cost/m Solution BF/m Cost/m Solution BF/m Cost/m 3.05 m (10 ft) $ $ $ m (12 ft) $ $ $ m (14 ft) $ $ $ m (16 ft) $ $ $39.37 Table 3.18 Most economical structural wall system for 12.2 meter wide structures Building Width 12.2 m (40 ft) Specified Roof Load 1 kpa 2 kpa 3 kpa (20 psf) (40 psf) (60 psf) Stud Length Solution BF/m Cost/m Solution BF/m Cost/m Solution BF/m Cost/m 3.05 m (10 ft) $ $ $ m (12 ft) $ $ $ m (14 ft) $ $ $ m (16 ft) $ $ $39.37 Notes: is a 38x89 mm 305 mm spacing is a 38x140 mm 305 mm spacing is a 38x140 mm 406 mm spacing is a 38x184 mm 305 mm spacing is a 38x184 mm 406 mm spacing is a 38x184 mm 610 mm spacing 19

23 Table 3.19 Most economical structural wall system for 15.2 meter wide structures Building Width 15.2 m (50 ft) Specified Roof Load 1 kpa 2 kpa 3 kpa (20 psf) (40 psf) (60 psf) Stud Length Solution BF/m Cost/m Solution BF/m Cost/m Solution BF/m Cost/m 3.05 m (10 ft) $ $ $ m (12 ft) $ $ $ m (14 ft) $ $ $ m (16 ft) $ $ $39.37 Table 3.20 Most economical structural wall system for 18.3 meter wide structures Building Width 18.3 m (60 ft) Specified Roof Load 1 kpa 2 kpa 3 kpa (20 psf) (40 psf) (60 psf) Stud Length Solution BF/m Cost/m Solution BF/m Cost/m Solution BF/m Cost/m 3.05 m (10 ft) $ $ $ m (12 ft) $ $ $ m (14 ft) $ $ $ m (16 ft) $ $ $39.37 Notes: is a 38x89 mm 305 mm spacing is a 38x140 mm 305 mm spacing is a 38x140 mm 406 mm spacing is a 38x184 mm 305 mm spacing is a 38x184 mm 406 mm spacing is a 38x184 mm 610 mm spacing Most Economical Structural Wall System Tables Assumptions Wind loads for lateral pressure used a q 30 of 0.5 kpa and a q 10 of 0.4 kpa The combined load duration is assumed to be short The service condition is assumed to be dry with no treatment The studs are pinned and laterally restrained by sheathing which also prevents weak axis buckling The wall meets criteria of a Case 2 system The building width is considered the distance from exterior wall to exterior wall The tables allow for a m (2-6 ft) overhang The costs are based on a cost index of $0.50 per board foot 20 D e s i g n a n d C o s t i n g W o r k b o o k

24 3.4 Material Count The lumber material count is a detailed example of the quantity estimates for the design example. Each component is calculated exactly and the document leaves it up to the estimator to add an additional percentage for cutoffs, waste, bracing and heavier opening framing. Total wall/roof surface areas To calculate wall areas for stud quantities, the area of each wall is calculated, from which each opening is subtracted to determine an exact wall area. This calculation is used for both sheathing area and stud quantities. Exterior North wall area: x = m 2 South wall area: x = m 2 East wall area: x = 44.6 m 2 West wall area: x = 44.6 m m 2 Interior Shear wall area: x = 44.6 m 2 Party wall area (x 2): x x 2 = 89.2 m m 2 Windows North wall area: loading bays x x 4 = 37.2 m 2 man doors x x 4 = 7.8 m m 2 South wall area: end window/door bays x x 2 = 28.6 m 2 mid. Window/door bays x x 2 = 22.1 m m 2 East wall area: window bay x = 16.9 m 2 West wall area: window bay x = 16.9 m 2 Total window area: m 2 Total area for wall 12.5 mm Sheathing: m 2 21

25 The roof area is calculated for the hip roof configuration given in the example. An exact three-dimensional calculation is done for all four panels of the roof. Their total makes up the roof sheathing requirements. Once again the onus is on the estimator to factor in extra plywood for the particular roof configurations. Roof for 4/12 pitch roof (18.43 ) the calculation is as follows: east and west pitches: 2( 0.5 ( x 7.71)) = m 2 north and south pitches: 2( 0.5 ( ) x 7.71) = m 2 total roof area: m 2 alternatively ( x ) / cos (18.43) = m 2 Total area for roof 12.5 mm Sheathing: m 2 Stud walls Using the area of the covered wall, the total length of required studs is calculated. In the case of the example, the shearwall and party walls use a spacing of 610 mm versus the 406 mm spacing for the exterior walls. 406 mm o.c. Exterior wall surface area (less windows): = m 2 Total length of 406 mm o.c / = m 610 mm o.c. Interior wall surface area: m 2 Total length of 610 mm o.c / = m Total length of 38x140 mm (2x6) studs: m 22

26 Columns Column and beam calculations are relatively straightforward. Material requirements are obtained by multiplying the number of elements in the structural member by the lengths of the members. Column C1 38x140 mm (5 plies) quantity = 2 total length of 38x140 mm: 2 x 5 x = 36.6 m Column C2 38x140 mm (3 plies) quantity = 4 total length of 38x140 mm: 4 x 3 x = 43.9 m Column C3 38x140 mm (5 plies) quantity = 2 total length of 38x140 mm: 2 x 5 x = 36.6 m Column C4 38x140 mm (3 plies) quantity = 4 total length of 38x140 mm: 4 x 3 x = 43.9 m Column C5 38x140 mm (4 plies) quantity = 4 total length of 38x140 mm: 4 x 4 x = 58.6 m Column C6 38x140 mm (2 plies) quantity = 4 total length of 38x140 mm: 4 x 2 x = 29.3 m Column C7 38x140 mm (3 plies) quantity = 8 total length of 38x140 mm: 8 x 3 x = 87.8 m Total length of 38x140 mm (2x6) columns: m 23

27 LVL Beams Beam B1 45 x 302 mm (2 plies) quantity = 4 total length of 45x302 mm: 4 x 2 x = 25.7 m Beam B2 45 x 302 mm (2 plies) quantity = 4 total length of 45x302 mm: 4 x 2 x = 19.3 m Beam B3 45 x 302 mm (2 plies) quantity = 4 total length of 45x302 mm: 4 x 2 x = 26.6 m Total length of 45x302 mm (1-3/4 x 11-7/8) LVL beams: 71.6 m Sawn Lumber Beams Beam B4 38 x 286 mm (3 plies) quantity = 6 total length of 38x286 mm: 6 x 3 x = 52.6 m Total length of 38x286 mm (2 x 12) sawn lumber beams: 52.6 m The results of this quantity estimate are brought forward to the Cost Summary Table for project cost calculations. 24

28 3.5 Cost Summary Table This table sumarizes the amounts of each component, and using a typical cost index calculates project cost. The user should obtain their own cost index per quantity for specific estimation purposes. These quantities are more accurately determined from a complete design process which will give the user exact dimensions and quantities. However, using roof and stud wall tables, the user can estimate these components with relative confidence. The estimation of beams and columns can be derived from tables in the Wood Design Manual 1995 with some simple calculations. Sheathing requirements can be calculated from area calculations. The user, however, should go through a detailed design to determine shearwall and diaphragm requirements. Once material quantities are determined, costing based on cost indices should be obtained from the respective material suppliers. Table 3.21 Cost summary table Structural Member sizes Required Board 1 Cost Index Components quantity footage (per BF) Cost Stud Walls No.1/No.2 SPF 38x mm m 2381 $0.50 $1, Column C1 No.1/No.2 SPF (5) 38x140 mm 36.6 m 120 $0.50 $60.02 Column C2 No.1/No.2 SPF (3) 38x140 mm 43.9 m 144 $0.50 $72.00 Column C3 No.1/No.2 SPF (5) 38x140 mm 36.6 m 120 $0.50 $60.02 Column C4 No.1/No.2 SPF (3) 38x140 mm 43.9 m 144 $0.50 $72.00 Column C5 No.1/No.2 SPF (4) 38x140 mm 58.6 m 192 $0.50 $96.10 Column C6 No.1/No.2 SPF (2) 38x140 mm 29.3 m 96 $0.50 $48.05 Column C7 No.1/No.2 SPF (3) 38x140 mm 87.8 m 288 $0.50 $ Cripple studs No.1/No.2 SPF (2) 38x140 mm m 810 $0.50 $ m 4295 BF $2, Double top plates No.1/No.2 SPF (2) 38x140 mm 184 m 604 $0.50 $ Bottom plates No.1/No.2 SPF (1) 38x140 mm 92 m 302 $0.50 $ Blocking No.1/No.2 SPF (1) 38x140 mm 184 m 604 $0.50 $ m 1509 BF $ Beam B1 LVL (2) 45x302 mm 25.7 m 169 $3.00 $ Beam B2 LVL (2) 45x302 mm 19.3 m 127 $3.00 $ Beam B3 LVL (2) 45x302 mm 26.6 m 174 $3.00 $ m 470 BF $1, Beam B4 No.1/No.2 SPF (3) 38x286 mm 52.6 m 345 $0.50 $ Shear walls Roof sheathing 52.6 m 345 BF $ mm plywood or OSB 100 o.c. with 75 mm nails SPF studs m ft 2 $0.75 $2, mm plywood or OSB 75 o.c. with 75 mm nails SPF studs m ft 2 $0.75 $4, m ft 2 $7, Roof trusses Hip roof 4/12 pitch 4840 ft BF $1.50 $12, $12, Total Cost: $24, Building Area Interior 40 X ft 2 $5.50 per square ft Note: 1. A board foot is the nominal width times the nominal thickness (in inches) divided by 12 times length in feet. eg m of 38 x 140 mm studs = x 3.28 x (2 x 6)/12 = 2381 BF In this example the result is a $5.50 cost per square foot or $59.20 per square meter which is very competitive for this type of building 25

29 3.6 Components Summary Table This final table shows how the design example changes with varying specified roof loads. It is a summary of the detailed design example with three loading scenarios. Table 3.22 Components summary table Member Design Example 1 kpa Snow Load 2 kpa Snow Load 3 kpa Snow Load Stud Wall 38 x 140 No.1/No.2 38 x 140 No.1/No.2 38 x 140 No.1/No.2 38 x 140 No.1/No oc 610 oc 610 oc 487 oc Beam B1 (2) 45 x 302 LVL (2) 45 x 302 LVL (2) 45 x 302 LVL (2) 45 x 302 LVL Beam B2 (2) 45 x 302 LVL (3) 38 x 286 (2) 45 x 302 LVL (2) 45 x 302 LVL ` No.1/No.2 SPF Beam B3 (2) 45 x 302 LVL (3) 38 x 286 (2) 45 x 302 LVL (2) 45 x 302 LVL No.1/No.2 SPF Beam B4 (3) 38 x 286 (2) 38 x 286 (2) 38 x 286 (3) 38 x 286 No.1/No.2 SPF No.1/No.2 SPF No.1/No.2 SPF No.1/No.2 SPF Column C1 (5) 38 x 140 (5) 38 x 140 (5) 38 x 140 (6) 38 x 140 No.1/No.2 SPF No.1/No.2 SPF No.1/No.2 SPF No.1/No.2 SPF Column C2 (3) 38 x 140 (3) 38 x 140 (3) 38 x 140 (4) 38 x 140 No.1/No.2 SPF No.1/No.2 SPF No.1/No.2 SPF No.1/No.2 SPF Column C3 (5) 38 x 140 (4) 38 x 140 (5) 38 x 140 (5) 38 x 140 No.1/No.2 SPF No.1/No.2 SPF No.1/No.2 SPF No.1/No.2 SPF Column C4 (3) 38 x 140 (2) 38 x 140 (3) 38 x 140 (3) 38 x 140 No.1/No.2 SPF No.1/No.2 SPF No.1/No.2 SPF No.1/No.2 SPF Column C5 (4) 38 x 140 (4) 38 x 140 (4) 38 x 140 (4) 38 x 140 No.1/No.2 SPF No.1/No.2 SPF No.1/No.2 SPF No.1/No.2 SPF Column C6 (2) 38 x 140 (2) 38 x 140 (2) 38 x 140 (3) 38 x 140 No.1/No.2 SPF No.1/No.2 SPF No.1/No.2 SPF No.1/No.2 SPF Column C7 (3) 38 x 140 (3) 38 x 140 (3) 38 x 140 (3) 38 x 140 No.1/No.2 SPF No.1/No.2 SPF No.1/No.2 SPF No.1/No.2 SPF Diaphragm 12.5 mm plywood 7.5 mm plywood 9.5 mm plywood or 12.5 mm plywood or or OSB w/ 2 1/2" or OSB w/ 2" OSB w/ 2 1/2" nails OSB w/ 2 1/2" 150 oc oc 100 oc (with blocking) Shearwalls 12.5 mm plywood 9.5 mm plywood 12.5 mm plywood or 12.5 mm plywood or or OSB w/ 3" or OSB w/ 2 1/2" OSB w/ 3" nails OSB w/ 3" 100 oc oc 64 oc Notes: 1. All dimensions are in mm unless otherwise noted 26

30 4.0 Design Scope Section 4 features a design example of a typical single storey commercial building such as a plaza, restaurant, strip mall or shop. The example was defined after a review of common buildings of this type across North America. Its characteristics were chosen so that they could be easily adapted to any single storey building. The example shows detailed calculations to design a single storey wood structure with references to structural formulae, building codes and commentary. The forces applied to structural elements are derived from a typical loading scenario found in Canada. Building Parameters The design example is both flexible and economical. It offers modular 12.2 m (40 ft) X 16.8 m (55 ft) bays that can be oriented in various ways. The features include cantilevered cover sections over the display sides and cargo loading doors in the rear of each bay. The building example is a generic NBCC Part 4 single storey design. It represents a popular and economical use of wood in a commercial setting. The loads were chosen to provide a full range of load conditions and to demonstrate the versatility of wood structures. The location represents typical Canadian design wind pressures. Seismic loads, however, govern in this example. The design example is a step by step design of each structural component found in this type of building. Commentary has been added to footnote many assumptions, formulae and decisions. To create a different design, the example may also be used as a template for the design process. How to Use the Example The example begins with the calculation of applied forces based on a defined building. The process is detailed so that the calculations may be used for other designs. A complete gravity load, wind pressure and seismic force analysis is presented and the results are tabulated in logical steps. The user can also adapt the calculations for their design conditions and record their results. After applied loads are calculated, the example leads the user through a typical design of the roof diaphragm, a shearwall, a chord, a stud wall, a beam and a column. Many engineered wood products are proprietary in nature and design values must be obtained from the manufacturer. The design example uses generic design values. Substitution with proprietary values requires consultation with manufacturers regarding costs and design parameters. The assumptions on which design values are based are given where necessary. The left margin has been reserved to reference appropriate sections of the design from the following sources: d Wood Design Manual 1995 a CSA O Engineering Design in Wood (Limit States Design) b National Building Code of Canada c User s Guide NBC 1995 Structural Commentaries (Part 4) 27

31 b (1) b Appendix C b Appendix C b (1) b (3) b Sentences (4, 5, 6) 4.1 Snow Loading Location for design data: Surrey, British Columbia S = S s (C b C w C s C a ) + S r Ground snow load (1/30 return): S s = 2.2 kpa Associated rain load: S r = 0.30 kpa Basic roof snow load factor: C b = 0.8 Wind exposure: C w = 1.0 Roof slope factor: 15<a<60 (60-a)/45 = C s = 0.92 (Slippery roof condition) Is roof slippery (yes/no) yes Roof slope a (degrees)= b (7) b (1) Accumulation factor: 1. Full loading: (Load Case 1) C a = 1.00 b (2) S = 2.2 x (0.8 x 1.0 x 0.92 x 1.0) = 1.93 kpa 2. Partial loading: (Load case 2) 0.25+a/20 = C a = 1.17 S = 2.2 x (0.8 x 1.0 x 0.92 x 1.17) = 2.20 kpa These specified live loads are used for design (see figure 4.1) Figure 4.1 Snow load cases a 12 4 NBCC requires that the building be designed for both of these load cases (full loading and partial loading) as follows. SNOW LOAD S = 1.93 kpa (40.2 psf) SNOW LOAD S = 2.20 kpa (46.0 psf) 28

32 Load Case 1: Loads based on horizontal projection Figure 4.2 Wall reactions due to gravity loads of Case m 12.2 m 1.21 m 0.61 m R1 R2 Specified Roof Dead Load = 0.65 kpa R1 1D = 4.28 kn/m R2 1D = 5.23 kn/m Specified Snow Live Load = 1.93 kpa R1 1L = kn/m R2 1L = kn/m W = (D + L) = kn/m W = (D + L) = kn/m W f = (1.25D + 1.5L) = kn/m W f = (1.25D + 1.5L) = kn/m Note: The first subscript for reactions determines load case, the second uses D for dead load, and L for live load Load Case 2: Loads based on horizontal projection Figure 4.3 Wall reactions due to gravity loads of Case m 12.2 m 1.21 m 0.61 m R1 R2 Specified Roof Dead Load = 0.65 kpa R1 2D = 4.28 kn/m R2 2D = 5.23 kn/m Specified Snow Live Load = 2.20 kpa R1 2L = 2.42 kn/m R2 2L = kn/m W = (D + L) = 6.70 kn/m W = (D + L) = kn/m W f = (1.25D + 1.5L) = 8.98 kn/m W f = (1.25D + 1.5L) = kn/m 29

33 Load Case 3: Loads based on horizontal projection Figure 4.4 Wall reactions due to gravity loads of Case m 12.2 m 1.21 m 0.61 m R1 R2 Specified Roof Dead Load = 0.65 kpa R1 3D = 4.28 kn/m R2 3D = 5.23 kn/m Specified Snow Live Load = 2.20 kpa R1 3L = kn/m R2 3L = 4.03 kn/m W = (D + L) = kn/m W = (D + L) = 9.26 kn/m W f = (1.25D + 1.5L) = kn/m W f = (1.25D + 1.5L) = kn/m Summary of Roof Loads on Walls & Columns: Figure 4.5 Governing wall reactions due to gravity loads 0.61 m 12.2 m 1.21 m 0.61 m kn/m Unfactored reactions kn/m W = D + L Case 1: R1 1 = kn/m R2 1 = kn/m Case 2: R1 2 = 6.7 kn/m R2 2 = kn/m Case 3: R1 3 = kn/m R2 3 = 9.26 kn/m Factored reactions W f = 1.25D + 1.5L Case 1: R1 1 = kn/m R2 1 = kn/m Case 2: R1 2 = 8.98 kn/m R2 2 = kn/m Case 3: R1 3 = kn/m R2 3 = kn/m LOAD CASE 1 (FULL LOADING) GOVERNS For quick estimating and initial conservative designs, the maximum line load may be used for the design of the all of the stud walls, beams and columns. 30

34 4.2 Wind Loading The information in this section is derived from NBCC and NBCC External Pressure (for shearwalls and diaphragms) b (1) p = qc e C g C p Location for design data: Surrey, British Columbia b Appendix C b (4) b (5) b (6) c Commentary B Reference velocity pressure: q = 0.43 kpa (1/30 return period) 1 Exposure factor: C 5 e = (h /10) 0.90 Gust factor: C g = C p C g are obtained from the tables of Commentary B of NBCC 1995 External pressure coefficient: C p = Building Geometry: Calculated building geometry: (NBCC Commentary figure B-7) Roof slope: a = 18.4 Reference height: h = 4.68 m Height to eave: H = 3.66 m End zone Z : Z = 1.22 m Building width: B = 12.2 m End zone Y : Y = 6 m Note: The internal pressures generally act in equal and opposite directions on opposing walls and hence have no effect on the overall lateral loads imposed on the structure. 31