Seismic-isolation characteristics of double concave friction pendulum bearings for bridge and building structures

Abstract

Friction pendulum system (FPS) is known to be one of the most effective and frequently used seismic isolation devices for seismic design and retrofit of civil infra-structures. In this dissertation, isolated structures with a double concave friction pendulum (DCFP) bearings are studied. A DCFP bearing consists of two sliding surfaces with different friction coefficients and radii of curvature. The purpose of this dissertation is to investigate the behavior of bridges and buildings with a DCFP bearing, particularly in conjunction with the friction and restoring properties of two sliding surfaces under various levels of earthquake excitation. The radii of curvatures and coefficients of friction of two sliding surfaces can be chosen to be different, which results in tri-linear behavior of the DCFP bearing. Therefore, different restoring and energy dissipation characteristics in tri-linear DCFP bearing may be achieved for moderate, strong and extreme earthquakes. A simple nonlinear time history analysis technique is developed to investigate the complicated tri-linear behavior. Behaviors of DCFP bearing and base isolated structure are discussed for various ground accelerations regarding the intensity of the earthquake motion.