Bi-directional implementation of multiple-slider surface bearing to girder bridges: simplified 3-D modelling and seismic performance assessment

The uplifting slide shoe (UPSS) bearing, consisting of multiple sliding surfaces, is a new type of bearing which has been proposed to achieve reduced displacement under strong earthquakes without losing advantage of the slide bearing to deal with the thermal effects on bridges girders. In the present study, bi-directional implementation of the UPSS devices is proposed to achieve effectiveness in controlling the bi-directional seismic response of girder bridges induced by bi-directional ground motions. A simplified multi-spring model of the bi-directional UPSS, considering the coupling effect of the friction mechanism and the geometric contact condition of the slider, is established to assess the bi-directional bridge response including the integrated nonlinear interaction between the longitudinal and transverse components. Numerical simulations demonstrate that the bi-directional UPSS is effective in reducing the pier response in the transverse direction compared with the conventional UPSS. The seismic performance of the bridge with the application of the bi-directional UPSS is shown to be superior to that of the functionally discrete bearing (FDB) systems in effectively reducing both the bearing displacement and the pier response ductility factor.