SGER/Payload Project to NSF Award CMMI-0324522: Earthquake Hazard Reduction for Critical Facilities

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This Small Grant for Exploratory Research (SGER) project will utilize the experimental test set-up of the NSF-funded project CMMI-0324522 entitled "Development of a Seismic Design Methodology for Precast Floor Diaphragm" at the NEES outdoor shake table at the University of California, San Diego (UCSD) during 2007. The UCSD NEES shake table is operated as a shared use facility through NSF award CMMI-0402490 to NEES Consortium, Inc.Intellectual Merit: This project addresses three questions related to the seismic protection of critical subsystems, i.e., equipment isolated systems (EIS) found in hospitals, data, and communication centers: (1) What is the maximum level of seismic protection that rolling-pendulum type isolated systems can provide to fragile equipment for near-fault ground motions and far-fault motions? (2) What is the sensitivity of rolling EIS to the large displacement demands of near-fault ground motions? (3) Can elastomeric or frictional damping effectively attenuate payload accelerations and isolator drift? Nonstructural systems, telecommunications equipment in particular, can be particularly fragile to seismic effects. To mitigate the seismic risk posed to shock and vibration-sensitive equipment, isolation systems have been installed within hundreds of data centers, hospitals, and emergency response centers. Typically these EIS are of a friction pendulum, or rolling-pendulum type, and consist of sets of shallow steel dishes containing a hard steel ball. Rolling EIS perform extremely well during low-level seismic events. Current seismic qualification standards for such equipment protection systems, however, do not require long-period excitation and hence the seismic risk of these systems under this loading is unknown. The NEES UCSD long-period, high-velocity shake table and the large-scale, multi-story, precast concrete test structure to be built by project 0324522 provide a cost-effective opportunity and the technical capability to investigate this seismic risk. The precast concrete structure will be the host structure for testing various equipment rolling isolation systems subjected to high-velocity pulse motions. By placing the EIS near or on the top level of the precast concrete structure, the EIS will be tested under realistic floor motions, including linear and nonlinear dynamic amplification effects at long periods and high velocities. Input motion will include selected historic and/or synthetic time histories, with appropriate time and scaling amplitude factors.Broader Impacts: This project will develop curricular materials for an engineering course at Duke University and for the new Scientific Computation program at North Carolina Central University. The PI will work with several organizations for incorporation of the research results into practice. The experimental data derived from this project will be archived in the NEES central data repository in accordance with data archiving and sharing policies posted at http://www.nees.org. This award is part of the National Earthquake Hazards Reduction Program.