Accounting for spectral shape in a simplified method of analyzing friction pendulum systems

摘要

This paper examines the effect of subduction zone and basin amplified motions on the accuracy of using a simplified method to analyze Friction Pendulum Systems, which is the basis for many international code pro-visions. This method estimates the maximum displacement demand for Friction Pendulum System isolated structures from analyzing a single degree of freedom system with equivalent period and damping coefficient. Friction Pendulum Systems with equivalent natural period between 1.5 s and 5 s and equivalent damping ratio from 16% to 32% were considered when subjected to over 400 motions. The considered ground motions include crustal and subduction zone motions, with and without basin amplification effect. Ratios of analysis-to-design maximum displacements corresponding to each ground motion are computed. A displacement-spectrum shape correction factor is proposed to improve the accuracy of the simplified method. This correction factor takes into account the irregularity of the 5% damped displacement spectrum that depends on the equivalent period and damping ratio at design displacement of the isolation system.