Full-Scale Experimental Investigation of Second-Story Collapse Behavior in a Woodframe Building with an Over-Retrofitted First Story
Publication: Journal of Performance of Constructed Facilities
Volume 30, Issue 2
Abstract
Soft-story woodframe buildings have been identified as a disaster preparedness problem throughout California and are present in many other states of the United States. These buildings can be readily identified by their large openings at the ground floor, often for parking, which results in a soft and weak first story that is prone to collapse in moderate to severe earthquakes. This paper presents the hybrid test results of a full-scale collapse test program that was carried out on a 3-story soft-story woodframe building with an overretrofitted first story. The overretrofitted design was constrained to the soft story only, essentially representing a retrofit that would likely drive the soft-story failure mechanism into the upper stories. The objectives of the collapse testing were to (1) quantify the collapse shift into the upper stories when the first story is overstrengthened, (2) investigate the collapse mechanisms of a woodframe building constructed with archaic building materials and style in the upper level, and (3) investigate the collapse capacity of the unretrofitted structurally deficient upper stories composed of archaic building materials. The overretrofitted design and collapse testing with results are presented in this paper. Even when overstrengthened, a very high-intensity earthquake, approximately 125–150% of the maximum considered earthquake, is required to collapse the archaic assemblies found in the upper stories of soft-story woodframe buildings. This high-intensity earthquake caused a 6.7% residual drift in the upper two stories which resulted in multiple fastener push-outs and dramatic softening (as indicated by the change in fundamental period). The collapse capacity of the archaic and unretrofitted upper two stories was approximately 20-kN lateral strength and 8% lateral drift.
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Acknowledgments
The research reported in this paper is based upon work partially funded by the National Science Foundation through Engineering Education and Centers (EEC)-1263155, and through Civil, Mechanical, and Manufacturing Innovation (CMMI)-1314957 and the USDA Forest Products Laboratory, through a cooperative agreement with Colorado State University. The writers are extremely grateful to the entire NEES-Soft project team and contributors to the research reported in this paper, including co-principle investigator (co-PI) Michael Symans of Rensselaer Polytechnic Institute (RPI), Co-PI Mikhail Gershfeld of California Polytechnic State University (Cal-Poly) Pomona, and to all of the senior personnel; i.e., David Rosowsky of University of Vermont, Andre Filiatrault of State University of New York (SUNY) at Buffalo, Douglas Rammer of Forest Products Laboratory, Gary Mochizuki of Simpson Strong Tie, and David Mar of Tipping Mar. The writers would like to thank Cortese Construction for their contributions to the building construction, and ReUse Action for their contributions to the building demolition and recycling as much of the building as possible. Special thanks are extended to Steve Pryor, Tim Ellis, and Simpson Strong Tie for product donation, as well as to the SUNY at Buffalo Structural Engineering and Earthquake Simulation Laboratory (SEESL) staff for the continuous help throughout the duration of the research reported in this paper. The writers would also like to recognize and thank the four undergraduate research assistants [i.e., (1) Karly Rager, (2) Phil Thompson, (3) Rocky Chen, and (4) Gabriel Banuelos] for their hard work.
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Information & Authors
Information
Published In
Journal of Performance of Constructed Facilities
Volume 30 • Issue 2 • April 2016
Copyright
© 2015 American Society of Civil Engineers.
History
Received: Jun 25, 2014
Accepted: Dec 3, 2014
Published online: Jan 8, 2015
Discussion open until: Jun 8, 2015
Published in print: Apr 1, 2016
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