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Rice awarded $1.6 million to develop next generation of adaptive seismic protection systems
The George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) Research (NEESR) program of the National Science Foundation has awarded to the Rice University a $1.6 million grant (NSF-CMMI-NEESR-SG 0830391) to develop the next generation of adaptive seismic protection systems.
Conventionally designed structural frame systems develop significant inelastic deformations under strong earthquakes, leading to inelastic hysteretic behavior, stiffness and strength degradation, increased interstory drifts, and damage with residual drift. Passive seismic protection systems in the form of supplemental damping devices have emerged as an effective approach for reducing response and limiting damage by shifting the inelastic energy dissipation from the framing system to the dampers. However, such dampers do not generally provide self-centering stiffness capability or counter stiffness degradation. Recent investigations have shown that a combination of adaptive stiffness and damping (ASD) devices can provide substantial response modification, particularly during near-fault pulse-type earthquakes. ASD devices offer structural response modification capability by optimally varying the restoring forces (stiffness) linked to the frequencies of vibration and dissipative forces (damping) that govern the behavior of a structural dynamic system. To date, adaptive stiffness systems have received relatively little attention as compared to supplemental damping systems and thus represent a significant gap in earthquake engineering. Hence, development of new ASD devices is necessary to shift the energy dissipation and associated stiffness variations from the structural system to the ASD devices to reduce damage in frames, eliminate residual interstory drift, and provide self-centering capability.
The research vision of this project is to develop the next generation of seismic protection systems by combining a new class of self-centering adaptive stiffness systems with highly efficient energy dissipation. The goal is to mimic the behavior of actively controlled devices by developing self-contained semi-active ASD devices with feedback and passive ASD devices with internal hydraulic feedback. The core strategy involves a comprehensive analytical and experimental investigation of potential active, semiactive, and passive systems followed by the synthesis and development of practical adjustable passive systems and self-contained semi-active systems for implementation in practical structures. Such an approach is consistent with that adopted in the defense industry and is expected to result in widespread application of ASD systems in civil structures. The project is expected to advance the state-of-the-art of increased resilience through structural response modification, contributing to earthquake hazard mitigation and expedient post earthquake recovery (due to easy replacement of ASD systems). The project will broadly impact earthquake engineering practice through educational outreach and wide dissemination of research findings through the project web site. Additionally, the project will have a significant impact on students from underrepresented groups through active involvement of a Hispanic Serving Institution.
This project will utilize the University of Buffalo-NEES equipment site hosted by the Structural Engineering and Earthquake Simulation Laboratory (SEESL). The lab has state-of-the-art shake tables and advanced control systems with large-scale building and bridge models that the team can access remotely via the Internet.
The fifteen NEES sites (http://www.nees.org) provide a shared network of experimental facilities, earthquake simulation software and online collaborative tools that allow earthquake researchers across the country to perform large scale experiments remotely. The advantages are that (1) universities that do not have large scale facilities can perform them remotely at a NEES equipment site, and (2) costs of testing are borne by the NEES equipment site that is separately funded by NSF through an operations and maintenance agreement, thus allowing the researchers to use their entire NEESR grant for theoretical research and validation.
The project principal investigator is Satish Nagarajaiah, Professor of Civil and Mechanical Engineering, from Rice University. The Co-Principal Investigators are Andrei Reinhorn and Michael Constantinou, Professors of Civil Engineering, both from University of Buffalo; Michael Symans, Associate Professor of Civil Engineering from the Rensselaer Polytechnic Institute; Jian Zhang, Assistant Professor of Civil Engineering from the University of California at Los Angeles. The project includes participation from Thomas Attard, Assistant Professor at Hispanic Serving Institution California State University, Fresno, and Douglas Taylor, President of Taylor Devices (industrial partner), Buffalo, N.Y.
For more information contact Satish Nagarajaiah 713-348-6207, nagaraja@rice.edu.