NEESR-GC: Mitigation of Collapse Risk in Vulnerable Concrete Buildings

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

This multi-institution award is an outcome of the NSF 06-504 program solicitation "George E. Brown, Jr. Network for Earthquake Engineering Simulation Research (NEESR)" competition. One of the greatest overall seismic risks in the United States is the risk of collapse of older concrete buildings in a major urban earthquake, yet there are no solutions to how to address this in a cost-effective manner. Policy makers and building owners are frustrated by the costs of retrofitting large inventories of existing buildings. Engineers need tools to accurately assess the risk of individual buildings and to differentiate between adequate buildings and potentially hazardous ones, so building owners can prioritize mitigation expenses. Regulatory agencies need better information on the regional extent of the risk so that effective policy measures can be put in place to effect regional mitigation efforts. This project will study the collapse potential of older nonductile concrete buildings, which are pervasive and high risk, to improve and disseminate effective engineering assessment and retrofit tools and to define appropriate incentive or policy measures to mitigate the risk. The research will investigate four areas: 1) Exposure - a single urban region will be selected to serve as a model for other regions, and an inventory model suitable to study the regional collapse risk of older type concrete buildings will be developed; 2) Component and System Performance - laboratory and field experiments will be conducted on components, subassemblies, and soil-foundation-structure systems to better understand conditions that lead to collapse; 3) Building and Regional Simulation - models will be developed and implemented in nonlinear dynamic analysis software useful to earthquake engineers, and results will be extended through regional dynamic simulations to help understand the regional distribution of building collapses in a major earthquake; and 4) Mitigation Strategies - effective mitigation strategies and coalitions involving engineers, planners, policy experts, and stakeholders will be developed to promote action for risk reduction. The program features a significant education component aimed at increasing diversity in earthquake engineering, international collaborations, and outreach to disseminate results to a broad community. The intellectual merit lies in the multi-disciplinary challenge of understanding the conditions and mechanics of collapse under three-dimensional loading, implementing that understanding in software usable for individual building analysis, and extending the understanding to the regional level where the intersection among engineering science, economics, and public policy will provide a rational basis for recommending the best mitigation strategies. The broader impacts of the project are extensive. The research program tackles an important and challenging problem that will advance discovery and understanding of earthquake engineering. The education program will expose a diverse population of undergraduates to the program and promote top candidates into graduate research. The results of the research will be disseminated in several ways, including: by sharing results using the NEES resources, by involving earthquake professionals and urban planners, and by disseminating educational materials. The results will benefit society by helping define appropriate engineering and public policy solutions to address the problem of existing hazardous building construction. Better understanding collapse of buildings during earthquake will also contribute to knowledge on vulnerability and toughening of infrastructure against effects of explosive and impact hazards. Mitigation strategies developed in this project also can inform strategies to mitigate for other natural hazards such as hurricanes. This project uses the NEES equipment sites at the University of California, Berkeley, the University of California, Los Angeles, the University of California, Santa Barbara, and the University of Minnesota.