Presenting a new equation to calculate the damping of rubber bumper in base isolation systems to mitigate pounding hazard

Seismic isolation offers a simple and direct opportunity to control or even eliminate damage to structures subjected to ground shaking by simultaneously reducing deformations and acceleration demands. A base isolation system decouples the superstructure from the ground resulting in elongation of fundamental period of the structure and reducing the accelerations transferred to superstructure during ground shaking. However, increasing the fundamental period of the structure is mostly accompanied by increased displacement demands. In base isolated structures, this large displacement is concentrated at base level where seismic isolation devices are installed and designed to handle these large deformations without damage. A typical base isolated basement design requires a space in which the building is free to move sideways without hitting the surrounding structure. For this challenge, a sufficient separation distance between structures is logically considered to allow moving base of buildings. Nowadays, in order to mitigate impact force and increase energy absorption, rubber bumpers are widely used within contact zone of base level of isolated structures to dissipate energy and control base displacement. Bumpers are typically included special spring and damper, which control the value of impact force and dissipated energy during collisions. In this paper, through numerical simulation based on the results of experimental test, an impact is parametrically simulated and hysteresis loop of impact is mathematically calibrated. The aim of this study is to focus on the effect of damper to create a novel equation in order to calculate the value of damping using all effective parameters for square shape of rubber bumpers. The new formula is normally solved to determine the value of damping and the accuracy of the equation is investigated by the validation of numerical results against experimental results. The results of the study indicate that rubber bumper can mitigate the value of transferred impact force by absorbing energy during impact while the number of collisions is physically increased. In fact, using rubber bumper as an external element can be an accepted method to decrease negative effect of seismic excitations for base isolation system.