While woodframe structures have historically performed well with regard to life safety in regions of moderate to high seismicity, these low-rise structures have sustained significant structural and non-structural damage in recent earthquakes. The height of woodframe construction is currently limited to approximately four stories, due to the lack of understanding of the dynamic response of taller (mid-rise) woodframe construction, non-structural limitations such as material fire requirements, and potential damage considerations for non-structural finishes. Current building code requirements for engineered wood construction around the world are not based on a global seismic design philosophy. Instead, wood elements are designed independently of each other without consideration of the influence that their stiffness and strength have on the other structural components of the structural system. Furthermore, load paths in woodframe construction arising during earthquake shaking are not well understood. These factors, rather than economic considerations, have limited the use of wood to low-rise construction and have reduced the economical competitiveness of the wood industry in the United States and abroad relative to the steel and concrete industries. This project will develop a performance-based seismic design (PBSD) philosophy to safely increase the height of woodframe structures in active seismic zones of the United States as well as mitigating damage to low-rise woodframe structures. During year one, full-scale seismic benchmark tests of a two-story woodframe townhouse will be performed using the two three-dimensional shake tables at the NEES SUNY-Buffalo equipment site. As the largest full-scale, three-dimensional shake table test performed in the United States, the test results will serve as a benchmark for both woodframe performance and nonlinear models for seismic analysis of woodframe structures. These efficient analysis tools will provide a platform upon which to build the PBSD philosophy. The PBSD methodology will rely on the development of key performance requirements such as limiting interstory deformations. The method will incorporate the use of economical seismic protection systems such as supplemental dampers and base isolation systems in order to further increase energy dissipation capacity and/or increase the natural period of the woodframe buildings. A real-time hybrid test will be performed by linking the fixed-based townhouse structure on the Buffalo NEES shake table with a reduced scale base isolation bearing tested simultaneously on a smaller shake table at Rensselaer Polytechnic Institute. The societal impacts of this new PBSD procedure, aimed at increasing the height of woodframe structures equipped with economical seismic protection systems, will also be investigated. Once the PBSD philosophy for mid-rise woodframe structures has been developed, it will be applied to the seismic design of a mid-rise (five or six-story) multi-family residential woodframe apartment building. This mid-rise woodframe structure will be constructed and tested at full-scale in a series of shake table tests on the Japanese E-Defense shake table in Miki City, Japan. The use of the E-Defense shake table, the largest 3-D shake table in the world, is necessary to accommodate the height and payload of the mid-rise building. There will be a request in the United States and in the international earthquake engineering community for payload projects to be conducted during this series of tests. The intellectual merit of NEESWood is the development of a new design philosophy that will provide a logical, economical basis for the design of mid-rise woodframe construction. The broader impacts of NEESWood are that it will provide a seminal advancement in seismic design of woodframe construction as well as the full-scale seismic testing of structural systems including dynamic distributed testing between two sites. When this challenge is successfully met, mid-rise woodframe construction may be an economic option in seismic regions around the United States and the world.
