NEESR-CR: Performance-Based Design for Cost-Effective Seismic Hazard Mitigation in New Buildings Using Supplemental Passive Damper Systems

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).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 Lehigh University, California State Polytechnic University, Pomona (Cal Poly Pomona), and California State University, Northridge. This project will utilize the NEES equipment site at Lehigh University.Intellectual Merit: The vision for this research is a validated probabilistic, performance-based seismic design procedure for buildings with passive damping systems. In this procedure, the design of the damping system is integrated with the design of the associated seismic load resisting frames. The uncertainties that influence the level of damage caused by ground motions at different seismic input levels are treated explicitly using probabilistic methods. The procedure considers multiple performance objectives, with each objective associating a different level of damage with a different seismic hazard level. The project will design two steel-framed prototype buildings as the context for the research. Several types of dampers will be studied. Tests at the Lehigh NEES equipment site will characterize the dampers; analytical models for the dampers will be calibrated and validated. Extending previous work, a practical performance-based design procedure, and an associated design assessment procedure for buildings with passive dampers will be developed. These procedures treat inherent uncertainties using partial safety factors. The performance-based design procedure will be used to produce several design cases for each prototype building. The strength of the steel frames and the damper type will be varied among the design cases. Then, each design case will be assessed with a rigorous, probabilistic assessment procedure developed by the project. This assessment uses nonlinear dynamic analyses, and considers the possible damage states of the building while rigorously treating uncertainties in building properties, damping systems, and ground motions. The procedure estimates the probabilities that these damage states are reached at different seismic hazard (input) levels. Large-scale, real-time hybrid simulations at the Lehigh NEES equipment site will validate the rigorous assessment procedure as well as the results of the practical performance-based design procedure. The hybrid simulations will have two phases: Phase 1 uses three individual large-scale dampers as the lab specimens, while the remainder of the building is modeled as an analytical substructure; Phase 2 uses a large-scale, three-story steel frame with dampers as the lab specimen, while the remainder of the building is modeled as an analytical substructure. Phase 1 simulations will be particularly efficient, by enabling numerous ground motions to be applied to the building, resulting in various levels of damage, without the need to repair the test specimens, since the damage will be within the analytical substructures. Phase 2 simulations will validate the overall project approach. This research will produce a validated, rigorous, probabilistic seismic performance assessment procedure for buildings with passive damping systems which addresses significant uncertainties in building performance. This research will also produce a validated, practical, multi-level, probabilistic, performance-based seismic design procedure for buildings with passive damping systems. Full-scale damper characterization test data sets will be produced. Validated analytical models for passive dampers, suitable for numerical simulations, will also be produced. Reliable and well-documented data sets from large-scale, real-time hybrid seismic simulations of buildings with passive dampers will be produced and used to validate the design and assessment procedures. Broader Impacts: This research will produce the knowledge needed to move the performance-based seismic design procedure into practice. Instructional materials for university classes will be developed, and a workshop for practicing engineers will be conducted to help transfer the design procedure into practice. Data from this project will be archived and made available to the public through the NEES data repository.