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原文传递 Performance Estimates for Seismically Isolated Bridges.

题名：	Performance Estimates for Seismically Isolated Bridges.
作者：	warn, g. p. whittaker, a. s.
关键词：	ground motion, excitation, vibration isolators, structural analysis, testing, simulation, performance evaluation
摘要：	This report presents an analytical study investigating the performance of an isolated bridge structure subjected to seismic excitation. Here performance is being assessed using the following descriptors: maximum horizontal displacements and cumulative energy dissipated by an individual seismic isolator. Twenty different isolation systems are considered with varied parameters, namely, characteristic strength (Q (sub d)) and second-slope stiffness (K(sub d)) Unidirectional and bi-directional response-history analysis was performed considering nonlinear systems and eight bins of earthquake ground motions. Results of the response-history analysis are being used to: (1) determine the increase in maximum horizontal displacement of a seismic isolator due to bi-directional seismic excitation utilizing a coupled plasticity model with a circular yield function to represent the seismic isolator elements, and (2) review the accuracy of the current AASHTO equation for the calculation of displacements in isolated bridge structures which assumes unidirectional seismic excitation and linearly increasing displacements for periods greater that 1-second, and (3) develop prototype testing requirements for seismic isolators in terms of an equivalent number of harmonic cycles to the maximum displacement and an equivalent testing frequency based on the observed energy demand imposed on individual isolators and isolation systems from numerical simulation of maximum earthquake events. / NOTE: Technical rept. / Supplementary Notes: See also PB99-140485. Sponsored by Multidisciplinary Center for Earthquake Engineering Research, Buffalo, NY. and Federal Highway Administration, Washington, DC. / Availability Note: Available on CD-ROM and in color paper copy only. Order this product from NTIS by: phone at 1-800-553-NTIS (U.S. customers); (703)605-6000 (other countries); fax at (703)605-6900; and email at orders@ntis.gov. NTIS is located at 5285 Port Royal Road, Springfield, VA, 22161, USA.
总页数：	u0821；336p
报告类型：	科技报告