The NEESWood project in review

The NSF-funded NEESWood Project was a four-year, five-university research project whose objective was to develop a performance-based seismic design philosophy for mid-rise woodframe construction. The project began in 2005 and, by the end of 2006, the benchmark testing of a two-story townhouse structure had taken place at the University at Buffalo's SEESL shake table facility. This test included several shear walls designed with fluid dampers. A series of sub-assembly tests on shear walls with toggle-braced damping systems and half-scale base isolation tests followed. From 2005-2008, non-linear time history analysis software was developed that was based on existing concepts and software, and improved upon as part of the NEESWood effort. This software package, called SAPWood, had the dual purpose of being a research and design tool for later testing within the project as well as being available for use by practitioners. It was extended to include six degrees-of-freedom at each story and tri-axial excitation. In parallel, a detailed two-dimensional numerical model that enables the static and dynamic response analysis of two-dimensional light-frame wood buildings under unidirectional horizontal and vertical earthquake shaking was developed. From 2006-2008, the Direct Displacement Design (DDD) approach was extended to multi-story woodframe buildings, which is a key outcome of the project. The DDD approach was also extended for application to woodframe buildings with sliding seismic isolation systems. From 2007-2009 the effect of design code changes on societal risk were investigated within the project by using Los Angeles, CA as a test bed. Finally, in order to validate the DDD approach, the world's largest shake table test was conducted at Japan's E-defense laboratory in collaboration with numerous researchers and industry participants from the U.S., Japan, and Canada. The 1350 square meter, seven-story building was designed using the DDD concept, the development of which was completed in 2008. Shear transfer and continuous steel rod holdowns were designed based on probabilistic concepts using SAPWood. The building, termed the Capstone Building, was subjected to three levels of seismic intensity including a design-basis earthquake (DBE) and a maximum credible earthquake (MCE). This paper provides an overview of the entire NEESWood Project along with a discussion of key contributions to the seismic design of mid-rise (and low-rise) woodframe buildings and a candid assessment of the pros and cons of increasing the height of woodframe buildings.