The research objective of this project is to develop improved methods for modeling and predicting the stability limit of elastomeric and lead rubber seismic isolation bearings. Elastomeric and lead-rubber isolation bearings are used for seismic isolation of building and bridge structures to reduce the damaging effects of strong ground shaking. The Elastomeric bearings consist of alternating layers of rubber bonded to intermediate steel shim plates and the lead-rubber bearings have an additional lead plug inserted into a central hole. During severe earthquake ground shaking, these isolation bearings are likely to be subjected to simultaneous large lateral displacements and axial compressive loads that could cause bearing instability. This research will identify the fundamental mechanism(s) causing bearing instability through detailed nonlinear finite element analysis and component level testing. These studies will aid in the development of an improved macro-model capable of capturing bearing instability and the derivation of a mechanics-based closed-form expression for predicting the bearing stability limit state.
The results of this research will provide tools to improve the assessment of bearing safety for the design of isolation systems composed of elastomeric or lead-rubber bearings. This research will also develop improved macro-models for rapid numerical earthquake simulation that will provide new knowledge about the performance of isolated structures under extreme earthquake loads. This new knowledge would lead to innovative solutions to modify and enhance the response of individual bearings to achieve a desired system performance. The results will be disseminated broadly to the research and design communities through journal publications, seminars, conference sessions and design recommendations. The project will provide advanced training to graduate students with professional development opportunities of presenting their work at technical meetings and conferences. This project will also recruit undergraduate students from diverse backgrounds to participate in structural engineering research and to pursue a graduate education in civil engineering through Penn State's Office of Engineering Diversity's Summer Research Program (SROP) program.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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Weisman, J.; Warn, G.P.. "Stability of Elastomeric and Lead-Rubber Seismic Isolation Bearings," J. Struct. Eng., v.138, 2012, p. 215.
Han, X., Kelleher, C.A., Warn, G.P. and Wagener, T.. "Identification of the controlling mechanism for predicting critical loads in elastomeric bearings," Journal of Structural Engineering, v.139, 2013, p. 04013016.
Han, X. and Warn, G.P.. "Mechanistic Model for Simulating Critical Behavior in Elastomeric Bearings," Journal of Structural Engineering, 2014, p. 04014140.
Weisman, J. and Warn, G.P. "Stability of Elastomeric and Lead-Rubber Seismic Isolation Bearings," Journal of Structural Engineering, v.138, 2012, p. 215.
BOOKS/ONE TIME PROCEEDING
Gordon P. Warn, Xing Han, Amarnath Kasalanati. "Dynamic stability testing of isolation systems composed of elastomeric bearings and implications for design", 09/01/2011-08/31/2012, , American Society of Ciivl Engineerings (ASCE) Structural Engineering Institute (SEI)"Structures Congress",  2013, "Warn, G.P., Xing, H., Kasalanati, A. Dynamic stability testing of isolation systems composed of elastomeric bearings and implications for design, 2013 ASCE/SEI Structures Congr".