The bridge model tests with rubber bearing

This paper is concerned with the mechanical properties and friction characteristics of rubber bearings and their interaction behavior with shear key under seismic loading. In Taiwan, the rubber bearings systems on the bridges are very different from those in the U.S and Japan.To understand the force transmitted from the supper-structure system to substructure, a series of experiments were performed, including cyclic loading tests of bearings, pseudo dynamic tests of a SDOF bridge model and shaking table tests of a scale-down simple supported bridge. In addition, a numerical model built in SAP2000 is used to simulate the test results and to understand the friction-sliding mechanism. The friction coefficient test results show that the friction coefficient of rubber bearing on the concrete surface is close to 0.24 in low velocity, and the one of PTFE-rubber bearing is close to 0.1; the effect on the deformed bearing should be considered to reduce nonlinear shear stiffness for better analysis. The pseudo dynamic test results show that the force transmit from upper part to substructure is a constant as friction force when the rubber bearing slides. Most of importantly, from shaking table tests, it is evident that the strains on the column which is below the bearing with lower friction are smaller than the ones measured on another because of the two different rubber bearing style on two columns. In addition, the strain of both two bridge columns will not be a constant obviously as the pseudo dynamic test result because of the influence of the cap bean inertia force, but it is still obvious that the strain-PGA curve will be gradual when the rubber bearing sliding behavior happens. The shaking table tests demonstrated the lessons learned from minor damaged bridges in Taiwan Chi-Chi Earthquake