Hysteresis model of metal rubber bridge bearings

Abstract

Metal rubber bridge bearings have good durability and hold promising prospects for small and medium -span highway bridges. The seismic design of medium and small span bridges with metal rubber bearings involves the hysteretic model of bearings and the calculations of post-yield stiffness, initial stiffness and yield force. In this study, the formula for calculating the post-yield stiffness of metal rubber bridge bearings with circular section was derived based on the overlap area method. In the formula, the post-yield stiffness is directly proportional to the compressive stress and the diameter of the bearing, and inversely proportional to the height of the bearing. Considering the initial stress state of the bearing, the differential equation was established, and the theoretical formula for calculating the initial stiffness of the metal rubber bearing was derived. Based on the experimental results, the simplified formulas for calculating the initial stiffness and post-yield stiffness have been proposed for practical applications. Based on the shear yield displacement of the metal rubber bearings obtained from the test, the yield strain of the bearings was obtained, and the formula for calculating the yield force using this yield strain was presented. The relationship between the initial stiffness and the post-yield stiffness of metal rubber bridge bearings was investigated. The initial stiffness of metal rubber bearings can be expressed as the post-yield stiffness. The experimental hysteresis curve was compared with the bilinear hysteresis curve obtained from the formula. The hysteresis curves calculated by the formulas are in good agreement with the test hysteresis curves. The bilinear hysteresis model and its key parameter calculation formula can be effectively employed for seismic response analysis of metal rubber bearing bridges.