NEESR-CR: Collapse Simulation of Multi-Story Buildings through Hybrid Testing

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This award is an outcome of the NSF 09-524 program solicitation "George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) Research (NEESR)" competition and includes Stanford University (lead institution), University of New Hampshire (subaward), University at Buffalo, The State University of New York, (subaward), and California State University, Sacramento (subaward). This project will utilize the NEES equipment sites at the University at Buffalo and the University of California at Berkeley. Intellectual Merit: The primary goal of earthquake resistant design is to protect life safety by preventing the collapse of the structure. Uncertainties in ground motion and in structural response to ground motion, together with economic constraints, impose the acceptance of a small probability of collapse. Assessment of this small probability of collapse requires the ability to predict, with sufficient confidence, the response of structures through collapse. This aspect of performance-based earthquake engineering poses major challenges, many of which have been addressed and partially solved through recent research. But what is lacking is experimental data of structures collapsing and confidence in analytical component and structure response predictions, which need to be fostered through evidence provided by careful validation using results from experimental studies. To validate collapse predictions and to evaluate phenomena that are not represented adequately in component tests, experimental tests at the structure level are needed. Shaking table (earthquake simulator) testing represents an excellent option. However, shaking table testing to collapse is very complex, very expensive, and potentially dangerous. Hybrid testing is becoming an attractive alternative because it can provide information on the response of the entire structure without having to physically test all the structure. This makes hybrid testing a versatile and cost-effective testing approach. This research will advance knowledge to improve our understanding of the response of structures as they approach collapse. The specific objectives are to: (1) conduct a comprehensive validation of hybrid simulation techniques to collapse, which includes tests with various collapse modes (e.g., ratchetting behavior-lateral deformations accumulating progressively in one direction); (2) significantly expand substructuring techniques used in distributed hybrid simulation to capture the effects of time-varying boundary conditions; (3) significantly expand the capabilities and reliability of hybrid simulation by developing and incorporating adaptive analytical models; (4) understand and identify the most important structural and ground motion parameters that cause ratchetting behavior leading to collapse; and (5) develop and implement innovative education, outreach, and technology transfer mechanisms to disseminate knowledge on structural responses to collapse. The successful completion of this study will transform the way in which collapse simulation of multi-story buildings is conducted through the development and validation of hybrid testing procedures that provide a more efficient and reliable quantification of the collapse potential of buildings. The main research contribution will be the creation and integration of new physical testing approaches and analytical simulation methods to develop a more in-depth understanding of the structural properties and ground motion characteristics that lead to collapse of structural systems. This research integrates multidisciplinary knowledge from the fields of earthquake engineering, structural dynamics, systems control, and information technology. Broader Impacts: This research will improve the ability to reliably estimate collapse probabilities, which will help minimize casualties, economic losses, and enhance the resiliency of buildings subjected to seismic events. Innovative testing methods and data will be made available to the earthquake engineering community through their implementation in the NEES shared use equipment, software, and data repository and through publications and presentations. An integrated outreach plan includes partnerships with schools and undergraduate institutions located in the east and west coasts of the United States, as well as innovative outreach activities to actively engage underrepresented students in engineering and research. Data from this project will be archived and made available to the public through the NEES data repository.