Impact of structures with double concave friction pendulum bearings on adjacent structures

The double concave friction pendulum bearing is a new kind of friction pendulum bearing that consists of two sliding surfaces. To study the seismic responses of three-dimensional base-isolated structures using double concave friction pendulum systems during impact with adjacent structures, after deriving the coupled differential equations of motion, a computer program was developed in order to obtain the time history response of base-isolated structures under earthquake excitations. In the first part of this paper, the seismic response of three-dimensional base-isolated structures using double concave friction pendulum bearings considering tri-linear and bi-linear behaviours without adjacent structures is investigated. The advantages and disadvantages of tri-linear over bi-linear behaviour, considering the principal parameters, are scrutinised. It is demonstrated that using tri-linear double concave friction pendulum bearing behaviour rather than the bi-linear one can decrease the base shear up to 48%. However, tri-linear double concave friction pendulum bearings cause larger displacements of sliding surfaces than bi-linear ones, by up to 57%. The second part of the paper studies the effects of essential parameters such as separation distance, stiffness of impact elements, isolation period and the behaviour of double concave friction pendulum bearings on the seismic response of base-isolated structures using double concave friction pendulum systems during impact with adjacent structures. Numerical simulations demonstrate that base shear force increases significantly and, vice versa, bearing displacement decreases considerably due to impact of the isolated structure with adjacent structures. In addition, the hysteretic curve of the bearing affects the responses of the isolated structure during impact with adjacent structures.