NEESR-SG: Self-Centering Damage-Free Seismic-Resistant Steel Frame Systems

Lehigh University, Bethlehem PA

Investigators

Abstract

PROJECT SUMMARY The proposed project will investigate a family of innovative self-centering (SC) steel frame systems with the potential to withstand the currently accepted design basis earthquake (DBE) for buildings without damage. The project goals are: to develop fundamental knowledge of the seismic behavior of SC steel frame systems; to conduct integrated design, analysis, and experimental research on SC steel frame systems, using the enabling facilities of the George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES); to develop performance-based, reliability-based seismic design procedures and criteria for SC steel frame systems; and to educate students and practitioners with fundamental and practical knowledge about SC steel frame systems. Unlike conventional earthquake-resistant steel frame systems that are designed to develop significant inelastic deformations under the DBE, resulting in significant damage as well as residual drift, the innovative SC steel frame systems developed by the project have the potential to avoid structural damage under the DBE as a result of several features: the lateral force-drift behavior softens without inelastic deformation of the structural members, and, therefore, without the resulting structural damage and residual drift; the softening behavior is created by gap opening at selected post-tensioned connections (e.g., a separation at the beamcolumn interfaces of the frame); the ductility capacity of the lateral force-drift behavior can be quite large and is not controlled by material ductility capacity; and energy dissipation under seismic loading is not from damage to main structural members, but from energy dissipation elements that are specified in the design process and can be replaced if damaged. The project scope includes nine research tasks and a number of educational, outreach, and dissemination activities focused on SC steel frame systems. The research team will develop reliability-based seismic design procedures, system concepts and details, and energy dissipation elements for SC steel frame systems; will develop sensor networks to monitor and assess SC steel frame systems; and will design prototype buildings using SC steel frame systems, perform nonlinear analyses of these prototype buildings, and conduct large-scale laboratory simulations on specimens derived from the prototype buildings. The project requires the use of the Real-Time Multidirectional Testing Facility for Seismic Performance Simulation of Large-Scale Structural Systems (RTMD) NEES equipment site at Lehigh for large-scale earthquake simulations to achieve its goals.The hybrid (pseudo-dynamic) testing method will be utilized, and when needed, the real-time hybrid testing method and real-time capabilities of the RTMD will be used as well. The project team is multi-organizational, involving Lehigh, Princeton, and Purdue Universities, multidisciplinary and diverse. The team includes international participation from the National Center for Research on Earthquake Engineering (NCREE) in Taiwan, and will be advised by a board of individuals from engineering firms well known in the US and international earthquake and structural engineering communities. Intellectual Merit.. Prior research on SC steel systems has demonstrated their potential, however, comprehensive knowledge of their seismic behavior and performance is lacking. Prior NSF-funded research on SC precast concrete systems has produced knowledge that is enabling these innovative systems to move into practice; similar knowledge is needed for SC steel systems. The proposed project will provide the needed fundamental knowledge on the behavior and performance of SC steel systems, as well as practical knowledge needed for implementation into design, fabrication, and construction practice. The main innovations of SC steel systems are: initial stiffness similar to conventional systems, with softening under earthquake loading, but without main structural member damage, residual drift, and the related post-earthquake repair costs; and energy dissipation by design, not by main structural member damage. In addition, innovative project features include the development of reliability-based, comprehensive design procedures and criteria for SC steel systems in parallel with the development of the systems themselves, and the development of sensor networks for damage monitoring and assessment to avoid costly post-earthquake inspection processes. Broader Impacts.. The new SC steel frame systems have the potential to withstand the DBE without damage, as well as to be economical in initial cost. Thus, by advancing knowledge about SC steel frame systems, the project is anticipated to have significant societal benefits by reducing the often-enormous post-earthquake damage costs of conventional earthquake-resistant systems. In addition, the project will impact the earthquake engineering workforce by educating graduate and undergraduate students participating in the proposed project, students enrolled in the course developed by the project, and students reached by the project web site. Practitioners will be educated through the dissemination plan and project web site.