Engineering Guide Woodfram PDF

Canadian Wood CouncilConseil canadien du bois Engineering Guide for Wood Frame Construction 2009 Edition . Engineering Guide for Wood Frame Construction 2009 Edition Canadian Wood Council Conseil canadien du bois . Ottawa. Ontario.© 2009 Copyright Canadian Wood Council Conseil canadien du bois Ottawa.. ON . Canada ISBN 978-0-9783213-4-5 Printed in Canada Design and production: Accurate Design & Communication Inc. builders.H. technical bulletins and case studies. “Housing and Small Buildings. National Research Council of Canada. Guidance on the National Building Code of Canada Part 9 prescriptive requirements can be found in Part C “Supplementary Guidelines on Applicability and Scope” of the Guide. Design Requirements are provided in Part B of the Guide and Supplementary Design Tables are provided in Part D of the Guide.4.1.Engineering Guide for Wood Frame Construction V Preface The Canadian Wood Council (CWC) is the national federation of forest products associations responsible for development and communication of technical information about the use of wood products in construction.1 of the 2005 National Building Code of Canada references the “Engineering Guide for Wood Frame Construction. University of New Brunswick Steve Copp Construction Ltd. location or configuration of the building. in this 2009 Edition. and (b) due to the size. however. researchers and industry representatives. Canadian Construction Materials Centre CertiWood™ Technical Centre RCG Developments Consultant . building designers. software. This edition of the Guide was developed with technical input from a committee of engineers. accurate fabrication and adequate supervision of construction. builders. building officials. The CWC does not. building regulators. in order to conform to changes in the 2010 edition of the National Building Code of Canada. It is intended that the Guide be used in conjunction with competent engineering design. Article 9. This is the third edition of the Guide and it supersedes the previous editions published in 2001 and 2004. Chui Steve Copp Bruno DiLenardo Paul Jaehrlich Keith Jansen Dominique Janssens BC Institute of Technology University of Western Ontario Blackwell Engineering Quaile Engineering Simpson Strong-Tie Canada Ltd.” of the National Building Code of Canada. engineering design is required in order to augment the prescriptive requirements in Part 9 (See the Foreword for additional explanation).” published by the Canadian Wood Council as an example of good engineering practice for the design of Part 9 structural members and their connections. Every effort has been made to ensure that the data and information in the Guide are accurate and complete. on the structural design of wood elements and connections for wood frame buildings that: (a) fall within the scope of Part 9. and students of these disciplines. The Guide was revised. Ensuring that this information is in tune with technical changes and users’ needs is accomplished through the publication and updating of CWC manuals. assume any responsibility for errors or omissions in the Guide nor for designs or plans prepared from it. The Engineering Guide for Wood Frame Construction has been produced by CWC to provide guidance to engineers. The Canadian Wood Council gratefully acknowledges the contribution of the following people: Thomas Abbuhl Michael Bartlett David Bowick Steve Boyd Brent Bunting Y. Canadian Codes Centre With the permission of Canadian Standards Association. For additional technical information or to receive more information on CWC design tools. which is copyrighted by Canadian Standards Association. While use of this material has been authorized. Toronto. . M9W 1R3. material is reproduced from CSA Standard CAN/CSA-O86-09.ca. National Research Council of Canada.. 178 Rexdale Blvd. Engineering Design in Wood.cwc. call this toll-free number 1-800-463-5091 or visit the CWC web site at www. Ontario. CSA shall not be responsible for the manner in which the information is presented. nor for any interpretations thereof.VI Preface Robert Kok Kenneth Koo Frank Lam Chun Ni Thor Tandy Cathleen Taraschuk Brockport Home Systems Ltd FPInnovations – Forintek Division University of British Columbia FPInnovations – Forintek Division UNISOL Engineering Ltd. .. B-30 Column Design .......D-121 Diaphragm Design Tables ............................................................................................................................................................................................................................... B-17 Floor Design........................................................................................D-73 Wall Design Tables ............................................................................................. B-3 Definitions and Symbols .................D-35 Design Tables Roof Design Tables ............................... B-7 Objectives and Design Requirements ...................................................... B-36 Shearwalls ..............................D-83 Beam and Column Design Tables ...................................................................................................... B-12 Roof Design ........................................................................................................................................................................................ B-23 Wall Design ..D-9 Seismic Load Tables .............D-3 Wind Load Tables ........................................................................................................................................................................Engineering Guide for Wood Frame Construction VII Table of Contents A B Foreword Design Requirements Scope ................................................................................................................................ B-35 Diaphragms ...........................................................D-135 Shearwall Design Tables ................................................................D-149 ................................................................................................................................................................... B-62 Supplementary Guidelines andScope Supplementary Guidelines on Applicability and Tables C D Supplementary Tables Load Tables Gravity Load Tables .................................................................................................................. B-47 General Construction Details ....................................... B-10 Loads ...................................................D-61 Floor Design Tables ........................................................................................................................................................................................................................... VIII Wood Frame Construction Guide . Engineering Guide for Wood Frame Construction Foreword A . A-2 Forward . walls and floors are generally constructed using systems of repetitive wood members spaced no more than 600 mm on centre. Part B. Supplementary information is included in the sections: Part C – Supplementary Guidelines on Applicability and Scope. 3 stories or less in building height and 600 m2 or less in building area. The Design Requirements and Tables in Parts B and D of the Guide have been written on the assumption that structural design will be carried out by a Professional Engineer who is qualified for such design. durability. The provisions and solutions provided in the Guide address structural design considerations. business.4 kPa. It is recommended that all post-disaster buildings essential to services in the event of a disaster also be designed in accordance with Part 4 of the NBCC. • wall. • clear spans of wood members are limited to 12. Structural design provisions are provided in the Design Requirements. mercantile and some industrial buildings. These solutions apply to conditions where the element or building being designed is within the scope of this Guide. and roofs. The Guide also contains supplementary information to assist in identifying situations. and provide structural solutions for designs that are beyond the prescriptive solutions in Part 9. and Part D – Supplementary Tables Builders. sheathed or braced on at least one side. Buildings or building elements beyond the scope of Part 9 and the Guide are designed in accordance with Part 4 of the NBCC. For design requirements related to other issues such as fire.. Housing and Small Buildings. .c. The Design Requirements in Part B of the Guide are based on design calculations that reflect the prescriptive provisions of Part 9 where appropriate. 600 m2 or less in building area. regulatory authorities and building designers may wish to consult the section on “Supplementary Guidelines on Applicability and Scope” as a guide to determining whether a building or element falls outside the assumptions on which the Part 9 prescriptive requirements are based.2 m. roofs and floors are clad. of the Guide.Engineering Guide for Wood Frame Construction A-3 Foreword The objective of the Engineering Guide for Wood Frame Construction is to provide acceptable structural design solutions for wood elements and connections in wood frame buildings that are 3 stories or less in building height. Part 9 and Wood Frame Construction Part 9 includes prescriptive solutions for wood systems where. “HOUSING AND SMALL BUILDINGS” General Part 9 of the NBCC is a set of primarily prescriptive requirements covering the design of residential. PART 9 OF THE NATIONAL BUILDING CODE OF CANADA. and additional information is provided to supplement the prescriptive wood frame construction requirements in Part 9. personal service. where engineering analysis is required and structural solutions in the Guide are appropriate. sound transmission and building envelope refer to the NBCC. • walls. of the 2010 edition of the National Building Code of Canada (NBCC). roof and floor planes are generally comprised of repetitive wood structural members spaced no more than 600 mm o. and • the floor live load does not exceed 2. Some. The Design Requirements and Tables in Parts B and D of the Guide use an engineering mechanics approach to assess the lateral resistance of a wood frame building.A-4 Forward The solutions were developed as a simple set of minimum requirements that could be used without the assistance of an architect or engineer. though not all. Examples of elements in Part 9 that are based mainly on performance history include: • notching and drilling limitations • bearing requirements for rafters.. The span tables in Part 9 are based on gravity loads . and • column sizes. calculations include performance considerations. Section 9. The Engineering Guide for Wood Frame Construction specifies lateral loads and lateral design solutions. mercantile and medium or low hazard industrial buildings. business.dead loads. i. Examples of elements in Part 9 that are explicitly based on calculations include: • dimension lumber floor joists • dimension lumber and glulam floor beams • dimension lumber roof rafters • dimension lumber roof joists • dimension lumber ceiling joists • trusses designed in accordance with TPIC procedures • dimension lumber lintels. Non-structural elements that contribute to the overall building performance are . elements such as roof rafters and roof trusses that are designed for gravity loads also withstand lateral loads without being explicitly designed for that purpose. personal service. The Part 9 requirements for wood frame construction are based on a combination of calculated designs and solutions based on performance history. and trimmer joist sizes • hip and valley rafter size and connection • wall plates • stud size and spacing. There is some overlap between these two categories. In addition. and • anchor bolt connections. of the elements sized by calculation in Part 9 would be larger if they were sized in accordance with Part 4 due to both load differences and differences in design assumptions. with some simplifying assumptions for practical purposes. Consistent with Part 9.e. In some circumstances new products are introduced into Part 9 solutions using engineering design. 3 stories or less in building height and 600 m2 or less in building area. the roof systems and floor systems are assumed to act as diaphragms to transfer the lateral forces to wall systems acting as shearwalls. In this approach. occupancy loads and balanced snow loads. The NBCC 2010 introduced prescriptive requirements for lateral resistance of Part 9 buildings. and the section on Applicability and Scope includes a framework for considering where the lateral load provisions in the Guide may be applicable. the Engineering Guide for Wood Frame Construction applies to the design of residential. Gravity loads in the Guide are consistent with loads in Part 9 of the NBCC and may be used to design repetitive framing members and their supporting members. The gravity loads used in Part 4 are in some cases higher than the gravity loads used in Part 9 calculations.4 of the NBCC allows Part 9 structural members and connections to be designed according to Part 4 using the loads and deflection and vibration limits specified in Part 9 or Part 4. joists and beams • header joist. Boughton and Reardon.4 of the NBCC • Wind and earthquake loads from Part 4 of the NBCC. The performance of wood light frame systems is enhanced by the load sharing and composite actions. diaphragms and connections based on CSA Standard O86. However. 2002. Traditional wood-frame construction is difficult to model mathematically due to the many load paths in the indeterminate structural system and the contributions of “non-structural” elements. Paevere. closets and cabinetry also contribute to the lateral resistance of the building. WOOD FRAME CONSTRUCTION – PART 9 AND THE GUIDE The Part 9 structural requirements for wood frame construction are derived from a combination of calculated designs and solutions based on performance history. to date. shearwalls. Using this approach. The Guide calculations use: • Gravity loads based on Section 9.Engineering Guide for Wood Frame Construction A-5 disregarded. 2005). calculations are used to develop structural requirements. 1982. The overturning resistance of a wall is enhanced through “corner effects” that engage adjacent walls. including walls parallel and perpendicular to the direction of loading that normally may not be considered in design. performance history indicates that this is not the case. and • Resistances for lumber members. if adequately connected. Other non-structural elements such as stairs. Non-loadbearing partitions stiffen and strengthen the structure so that the building acts as a rigid box rather than a series of diaphragms and shearwalls. The numerous wood frame buildings throughout Canada and elsewhere represent countless “prototypes” subject to field-testing over many decades. Although to a large extent the structural stability of Part 9 buildings relies on these non-structural elements. sheathing. Lateral Design . The performance history of small wood frame structures cannot be explained completely by Part 4 structural calculations using simple 2-dimensional load path assumptions. Roof and floor diaphragms. 3. 2001. many wood frame buildings based only on the Part 9 prescriptive requirements would appear to be inadequate for resisting lateral loads. Various aspects of building performance have been investigated experimentally during the past fifty years (for example Dorey and Schriever 1957. 4. however. Most of these studies have focused on one. this action has not been quantified in a systematic manner suitable for use in structural design. Fischer et al. some wood frame buildings covered by Part 9 differ sufficiently from the norm that they cannot be counted on to demonstrate similar performance if their design is based only on the prescriptive provisions of Part 9. will transfer lateral wind and earthquake loads to all supporting walls. 2. roofs and walls sheathed with structural wood panels (alone or combined with gypsum board in the same wall or combined with gypsum board within a storey) are considered in the engineering calculations. Doudak. 1990.and two-story structures on rigid foundations. These reports gave more insight into the mechanisms of structural deformation including the importance of load sharing among the structural and “non-structural” elements within the structure: 1. Both the ultimate load capacity and the lateral stiffness are improved by the addition of architectural components. In the Guide. Only adequately anchored floors. I-joists. 1988. Ceccotti. UWO 2002. Boughton. Interior finishes and many types of exterior cladding contribute to the lateral resistance of the structure. structural composite lumber. Engineering Design in Wood with some modifications. ” (Canadian Commission on Building and Fire Codes.6.7 because of the low risk of loss to individual owners. the Structural Commentaries to the National Building Code state. is essentially covered by NBCC Article 9. It is. Jablonski. important to provide key construction details for the safety of building occupants…. structural damage is usually related to the roof system. Structural damage to wood frame construction in this earthquake was attributed to site conditions or non-conformance with building codes. Major damage occurs at gradient wind speeds of 70 m/s or greater and minor damage occurs at gradient wind speeds below 50 m/s (Sparks and Bhinderwala. Based on observations made in Canadian tornadoes. Keith and Rose. Openings for doors in the ground floor of multiple storey buildings created “weak storeys” which led to damage of the buildings. 2. Most of the serious structural failures that occurred to residential construction were due to deficiencies prohibited by California building codes and reflected in the 1985 Uniform Building Code (UBC). Neither the National Building Code nor this guide is intended to provide design solutions against the direct force of tornadoes. 1992. (Crandell.A-6 Forward Performance of wood frame construction under high wind loads The wind design provisions in the National Building Code of Canada and the Engineering Guide for Wood Frame Construction are intended to simulate peak gusts in storms having a 1 in 50 probability of occurring every year. gable end details and attachment of roof framing to walls are critical. “It is generally not economical to design buildings for tornadoes beyond what is currently required by NBCC Subsection 4. 1993. 1990). 3.” Similar observations were made following the 1994 Northridge earthquake in California (NAHB Research Center. however. 1994). Wolfe. 1994. When it occurs. Sheathing attachment. (Douglas. 1992. Studying the damage from hurricane force winds in other parts of the world provides insight into how wood frame construction behaves under high wind loads. leading to the following observations concerning the performance of wood frame construction: 1.anchorage of home floors. Riba and Triche. . The authors concluded: “Nominal lateral resistance in the UBC is achieved by specifying minimum percentages of shear panels in the walls. Damage to walls and foundations are rarer. 1994) The damage to housing in hurricanes and tornadoes shows that: 1. Allen 1986. 1984. Law and Allen.1.1 for normal housing with permanent foundations. 1993) 3. (Allen. 1993). Foundation walls weak in racking resistance—such as cripple-stud walls—led to failure of buildings. The damage from the 1989 earthquake in the San Francisco area was studied by Canadian researchers (Rainer. American Forest and Paper Association. Sheffield. Laatsch. Similar forms of damage have been reported in wood frame houses exposed to the direct paths of tornadoes. 2010) Performance of wood frame construction under earthquake loads Canada has not experienced an earthquake that has caused widespread damage to wood frame buildings. Gibson.23. Nowak and vanOvereem. 1993) 2. Dagliesh and Allen. The dead loads in the Guide reflect actual construction and are provided for floors with normal weight finishes and concrete toppings. 1999) the authors concluded that. Part 4 of the NBCC. both from the perspective of life safety and incidence of damage. Sometimes only a small portion of a building will have higher loads and engineering may be required to address an element supporting a combination of loads. designers and building officials have sought guidance in using these products with Part 9 requirements. The Guide may be used with proprietary wood products that are manufactured in accordance with a quality assurance program supervised by an independent third-party certification organization with design values developed in accordance with Clauses 13 and 14 of CSA Standard O86 and are designed and installed in accordance with the manufacturer’s material evaluation report. Gravity Loads The prescriptive requirements in Part 9 are limited to buildings with occupancy loads of 2.” Lateral Resistance in the Guide The section on “Applicability and Scope. where required.9 kPa even though Part 9 may apply to occupancies which have specified live floor loads up to 2. laminated strand lumber and proprietary wood framed roof and wall systems and their connections.2 m for interior studs and 3. Snow loads in the Guide are calculated in accordance with Part 9 or. floor trusses. The Guide provides design solutions for small wood frame buildings with occupancy loads up to 2. The stud design procedures and stud tables in the Engineering Guide for Wood Frame Construction have been developed using wind load data and considering the composite action of wall elements. proprietary wood products such as wood I-joists.4 kPa.” provides guidelines that are additional to the Part 9 prescriptive requirements of the NBCC. . longer studs are used. laminated veneer lumber. parallel strand lumber. wood frame buildings incorporate engineered.Engineering Guide for Wood Frame Construction A-7 In a survey of wood frame building construction from around the world (Rainer and Karacabeyli.4 kPa and the floor joist.6 m for exterior studs. wood frame construction has performed exceedingly well. “…despite some specific shortcomings and resultant failures. In the Design Requirements. such as entrances and gable end walls. In some situations. One of the objectives of the Engineering Guide for Wood Frame Construction is to clarify load requirements for engineered wood products used in small wood buildings. lintel and floor beam span tables in Part 9 apply only to residential loads of 1. The detailed design information in the Guide can be used where a full lateral design to resist wind and earthquake loads is considered necessary. Design of Individual Elements Studs NBCC Part 9 stud provisions are limited to stud lengths of 4. lateral design for wind and earthquake loads includes the design of fully detailed roof and floor diaphragms supported on shearwalls. Builders.4 kPa. New Materials Increasingly. header and lintel tables for built-up wood members supporting uniform loads. . The Guide provides design solutions for built-up wood members supporting point loads. The Guide section on “Applicability and Scope. headers and lintels supporting point loads Part 9 provides beam. In addition. the Guide provides structural design solutions for hip and valley rafters.A-8 Forward Beams. The Guide provides rafter design for rafters with raised ties.4 kPa occupancy load. In addition. Roof rafters Part 9 rafter spans are limited to rafters tied at the eave. Floor members The Guide may be used to design floor support members supporting non-residential floor loads.” provides guidance on limits to the Part 9 prescriptive requirements and the “Design Requirements” provide column design solutions for a broad range of loads and sizes. a maximum tributary width of 5 m and a maximum of 2. Column design Part 9 prescriptive requirements for columns are limited to columns supporting 2 floors. the Guide may be used for designing header and trimmer joists for openings larger than allowed with the prescriptive requirements of Part 9. APA Report T92-21. Part 2 Wood Building Analysis and Recommendations. F. Allen. B. Washington DC Boughton. CUREE Publication No.S. Building Research Note 222. 669. G. University of Melbourne. PhD thesis. Canada Ceccotti. D. Canada. No. A. Florence University. 1992). R. National Research Council of Canada. Jablonski. D. (2002) “Full-scale Testing. 1992. Gibson. Canada Canadian Commission on Building and Fire Codes. American Plywood Association. Paevere. National Building Code of Canada. Richmond. vanOvereem. Dipartimento di Ingegneria Civille. W-06. CA. D. B. Dorey.A. Structural Behavior of Timber Constructions in Seismic Zones.M. 1984. W. (1988) “Full scale structural testing of houses under cyclonic wind loads” Proceedings of the 1988 International Conference on Timber Engineering. Hurricane Andrew – Structural Performance of Buildings in Southern Florida (August 24.T. Internal Report No. Canadian Commission on Building and Fire Codes. McGill University. G.H. 2005. Modeling and Analysis of Light-Frame Structures Under Lateral Loading”. Pub. Boughton. Uniform Building Code.D. E. F. User’s Guide . W. N. PA. 82-88. July 1984. Tacoma. Philadelphia. Ottawa. May 1985. E.A. Australia. 12. Tornado Damage in Aylmer. Tornado Damage in the Barrie/Orangeville Area. Australia. American Society for Testing and Materials. 1994. Statistically-Based Evaluation of Homes Damaged by Hurricanes Andrew and Iniki.D.NBCC 2005 Structural Commentaries. National Research Council of Canada. Quebec on August 4.. and Seible. Queensland.T. Rainer. Folz. and D. International Conference of Building Officials. (2001) “Shake Table Tests of a Two-Story Wood-fame House. CUREE... Canada. Nowak and J.E. G. American Wood Council. N. Ph. Rose. 427 pp. New York. Whittier. K. Crandell. 1986. Thesis. California. . and J. Canada. 1994.K. Dalgliesh. National Research Council of Canada.. Allen. 1990. (Ed. Earthquake Damage in the San Francisco Area and Projection to Greater Vancouver. Douglas. Keith. Hurricanes of 1992: Lessons Learned and Implications for the Future. Vol. National Research Council of Canada. Hurricane Andrew. C-M. 2005. Allen. Laatsch. D.E. The Northridge Earthquake – A Preliminary Report. 210. Seattle. James Cook Cyclone Testing station. 1994. WA. New York. M. Tornado Damage at Blue Sea Lake and Nicabong. A. J. QC. Ontario. Building Research Note 240. A Special Report of the National Forest Products Association Fischer. A. Uang. (1982) “Simulated wind test on a house: Part 1 -Description” Tech. (1957) “Structural test on a house under simulated wind and snow loads.” Special tech.M.. G.. Doudak. Townsville.H. Ottawa. 1993. 1. Ottawa. American Society of Civil Engineers. and Schriever. Montreal. Commission of the European Communities and Florence University. Filiatrault. J. 1994. Institute for Research in Construction. No. Ottawa. Italy. Washington. International Conference of Building Officials. Law and D. and Reardon. Field Determination and Modeling of Load Paths in Wood Light-Frame Structures. Rep. Division of Building Research. Quebec. Canada Mortgage and Housing Corporation. Department of Civil and Environmental Engineering.Engineering Guide for Wood Frame Construction A-9 REFERENCES Allen. National Research Council of Canada. 2005.L. P.. Ottawa.E.E. Ottawa.) 1990. 1992. Canada. B. American Forest and Paper Association.. M. “Mitigating housing losses in extreme natural events”. Triche. Rainer. 1999. Forintek Canada Corp. Sparks. J.M. Performance of Wood frame Building Construction in Earthquakes..R. New York. R. 2002. University of Western Ontario. Karacabeyli. Wind Resistance of Conventional Light-Frame Buildings. R. American Society of Civil Engineers.W. 1994. Canada (on CD). New York. Special Publication SP 40. Bhinderwala. 1993. Canada Sheffield. New York.S. Vancouver. American Society of Civil Engineers.A. Assessment of Damage to Residential Buildings Caused by the Northridge Earthquake. U. . Office of Policy Development and Research. New York.W. Riba and M. Toronto. 1993. and E. ON.A-10 Forward NAHB Research Center. 1993. J. New York. Hurricanes of 1992: Lessons Learned and Implications for the Future. UWO. Wolfe. Department of Housing and Urban Development. Proceedings of Workshop. Hurricanes of 1992: Lessons Learned and Implications for the Future.H. P. Hurricanes of 1992: Lessons Learned and Implications for the Future. American Society of Civil Engineers. A Survey of Building Performance in Hurricane Iniki and Typhoon Omar. and S. 2 & 3 December 2002. New York. Relationship Between Residential Insurance Losses and Wind Conditions in Hurricane Andrew.