Design Models of Light Frame Wood Buildings under Lateral Loads B. Kasal, A.M.ASCE 1 ; M. S. Collins, A.M.ASCE 2 ; P. Paevere, A.M.ASCE 3 ; and G. C. Foliente, A.M.ASCE 4 Abstract: In this paper, different methods of lateral force distribution and design are described and compared with the results of experiments on a full-scale woodframe test house, and with a detailed three-dimensional analysis using a Finite Element FE model. The primary motive for this analysis and investigation is to provide the basic understanding required for the development of improved design procedures for light-frame wood buildings subjected to lateral loads. Improved procedures for lateral load distribution should be analytically correct in their philosophy, and offer reasonable trade-offs between the uncertainties and omissions in the design process and simplicity for the end-user. In this paper, eight methods are used to predict the distribution of design wind forces to the walls of an example L-shaped single-story woodframe house, in a moderate hurricane prone environment. The results are compared and the differ- ences in the predictions between the various methods are highlighted. Four of these methods are further compared against the results of physical experiments conducted on a full-scale test house. The FE model was generally the most accurate in predicting the experimentally measured load distribution, followed by the ‘‘plate method’’ and the ‘‘rigid beam method’’ described herein. DOI: 10.1061/ASCE0733-94452004130:81263 CE Database subject headings: Wooden structures; Lateral loads; Load distribution; Framed structures; Full scale tests; Models. Introduction Accurate design tools, for predicting the performance of wood- frame buildings in natural disasters such as hurricanes and earth- quakes, are important to provide the consistent and reasonable levels of safety expected by the large numbers of people who live in these buildings. Accurate prediction of building performance is also needed for other design considerations such as damage con- trol to mitigate the economic impact of natural disasters. Continu- ing housing developments in high natural hazard areas such as California and the U.S. coastlines mean that the development of improved design tools, based on an improved understanding of whole house response to natural hazard loads, is both worthwhile and urgent. Such design tools should be analytically correct, and offer reasonable tradeoffs between the uncertainties and omis- sions in the design process e.g., impact of finishes and simplic- ity for the end-user. The Residential Structural Design Guide: 2000 Edition NAHBRC 2000, published by the U.S. Department of Housing and Urban Development, provides the state-of-the-practice in en- gineering design of light-frame homes, apartments, and town- houses in the United States. This guide outlines the steps required to design a building’s lateral force resisting system LFRS, and indicates the importance in the design process of determining the distribution of lateral loads within the building. The guide identi- fies and describes the three most common methods of lateral force distribution in order of popularity: 1. The tributary area method—based on an assumption that the horizontal diaphragms are ‘‘flexible’’ compared to the shear walls; 2. The total shear method—based on designer judgment of the load distribution; and 3. The relative stiffness method—based on the assumption that the horizontal diaphragms are ‘‘rigid’’ compared to the shear walls. The guide ‘‘highlights the advantages and disadvantages of the various approaches to lateral force distribution but, in the ab- sence of a coherent body of evidence, makes no attempt to iden- tify which approach, if any, may be considered superior.’’ In this paper, these and other methods of lateral force distribu- tion and design are described and compared with a detailed three- dimensional analysis, using a finite element FE model, and with the results of experiments on a full-scale L-shaped woodframe test house. Fig. 1 shows the floor-plan and configuration of the test house. Further details are given in Paevere et al. 2003. The work described herein addresses design predictions in lateral loadings up to a design wind load in a hurricane prone climate with a suburban environment i.e., Exposure ‘‘B’’ based on ASCE 7-98 ASCE 1999. It is anticipated that the results presented herein will contribute to the ‘‘body of evidence’’ required to de- velop recommended methods for lateral force distribution in light-frame wood buildings. 1 Professor, Dept. of Wood and Paper Science, North Carolina State Univ., Raleigh, NC 27695-8005. E-mail: bo – kasal@ncsu.edu 2 Graduate Student, Dept. of Wood and Paper Science, North Carolina State Univ., Raleigh, NC 27695-8005. E-mail: mscollins@eos.ncsu.edu 3 Research Scientist, CSIRO Manufacturing and Infrastructure Tech- nology, PO Box 56, Highett, 3190, Australia. E-mail: phillip.paevere@csiro.au 4 Team Leader and Principal Research Scientist, CSIRO Manufactur- ing and Infrastructure Technology, PO Box 56, Highett, 3190, Australia. E-mail: greg.foliente@csiro.au Note. Associate Editor: David V. Rosowsky. Discussion open until January 1, 2005. Separate discussions must be submitted for individual papers. To extend the closing date by one month, a written request must be filed with the ASCE Managing Editor. The manuscript for this paper was submitted for review and possible publication on May 22, 2002; approved on March 13, 2003. This paper is part of the Journal of Struc- tural Engineering, Vol. 130, No. 8, August 1, 2004. ©ASCE, ISSN 0733- 9445/2004/8-1263–1271/$18.00. JOURNAL OF STRUCTURAL ENGINEERING © ASCE / AUGUST 2004 / 1263 J. Struct. Eng. 2004.130:1263-1271. Downloaded from ascelibrary.org by CSIRO INFO TECH SERVICE BRANCH on 09/18/14. Copyright ASCE. For personal use only; all rights reserved.