Development of a Performance-Based Seismic Design Philosophy for Mid-Rise Woodframe Construction (NEESWood)
While woodframe structures have historically performed well with regard to life safety in regions of moderate to high seismicity, these types of low-rise structures have sustained significant structural and nonstructural damage in recent earthquakes. To date, the height of woodframe construction has been limited to approximately four stories, mainly due to a lack of understanding of the dynamic response of taller (mid-rise) woodframe construction, nonstructural limitations such as material fire requirements, and potential damage considerations for nonstructural finishes. Current building code requirements for engineered wood construction around the world are not based on a global seismic design philosophy. Rather, wood elements are designed independently of each other without considering the influence of their stiffness and strength 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, thereby, have reduced the economical competitiveness of the wood industry in the U.S. and abroad relative to the steel and concrete industry. This project sought to take on the challenge of developing a direct displacement based seismic design philosophy that provides the necessary mechanisms to safely increase the height of woodframe structures in active seismic zones of the U.S. as well as mitigating damage to low-rise woodframe structures. This was accomplished through the development of a new seismic design philosophy that will make mid-rise woodframe construction a competitive option in regions of moderate to high seismicity. Such a design philosophy falls under the umbrella of the performance-based design paradigm.
In Year 1 of the NEESWood Project, a full-scale seismic benchmark test of a two-story woodframe townhouse unit that required the simultaneous use of the two three-dimensional shake tables at the University of Buffalo’s NEES node was performed. As the largest full-scale three-dimensional shake table test ever performed in the U.S., the results of this series of shake table tests on the townhouse serve as a benchmark for both woodframe performance and nonlinear models for seismic analysis of woodframe structures. These efficient analysis tools provide a platform upon which to build the direct displacement based design (DDBD) philosophy. The DDBD methodology relies on the development of key performance requirements such as limiting inter-story deformations. The method incorporates 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.
The societal impacts of this new DDBD procedure, aimed at increasing the height of woodframe structures equipped with economical seismic protection systems, is also investigated within the scope of this NEESWood project. Following the development of the DDBD philosophy for mid-rise (and all) woodframe structures, it was applied to the seismic design of a mid-rise (six-story) multi-family residential woodframe condominium/apartment building. This mid-rise woodframe structure was constructed and tested at full-scale in a series of shake table tests on the E-Defense (Miki) shake table in Japan. The use of the E-Defense shake table, the largest 3-D shake table in the world, was necessary to accommodate the height and payload of the mid-rise building.
National Science Foundation - NEESWood Capstone Test
Structural Engineering and Earthquake Simulation Laboratory (SEESL) website
Videos of the NEESWood Shake Table testing at the University at Buffalo
Seismic Test of a Full-Scale Two-Story Light-Frame Wood Building: NEESWood Benchmark Test, by I.P. Christovasilis, A. Filiatrault, and A. Wanitkorkul, MCEER-09-0005.
Direct Displacement Procedure for Performance-based Seismic Design of Multistory Woodframe Structures, by W. Pang and D. Rosowsky, MCEER-10-0001.
Simplified Direct Displacement Design of Six Story NEESWood Capstone Building and Pre-test Seismic Performance Assessment,by W. Pang, D. Rozansky, J. van de Lindt and S. Pei, MCEER-10-0002.
Integration of Seismic Protection Systems in Performance-based Seismic Design of Woodframed Structures, by J. Shinde and M. Symans, MCEER 10-0003.
Seismic Testing of a Full-Scale Mid-Rise Building: The NEESWood Capstone Test, by S. Pei, J.W. van de Lindt, S.E. Pryor, H. Shimizu, H. Isoda and D. Rammer, MCEER-10-0008.
Numerical and Experimental Investigations of the Seismic Response of Light-Frame Wood Structures, I. Christovasilis and A. Filiatrault; MCEER-11-0001.
Filiatrault, A., Christovasilis, I.P., Wanitkorkul, A. and Van de Lindt, J.W. 2010. “Experimental Seismic Response of a Full-Scale Light-Frame Wood Building,” ASCE Journal of Structural Engineering, Vol. 136, No. 3, 246-254.
Van de Lindt, J.W., Pei, S., Liu, H. and Filiatrault, A. 2010. “Three-Dimensional Seismic Response of a Full-Scale Light-Frame Wood Building: A Numerical Study, ASCE Journal of Structural Engineering, Vol. 136, No. 1, 56-65.