Seismic behavior of prefabricated reinforced concrete stair isolated by high damping rubber bearings

To alleviate the detrimental diagonal bracing effect of the traditional rigid-connected reinforced concrete (RC) flight to the boundary frame under lateral inputs, the study proposes an innovative low-damage stair system: prefabricated RC stair isolated by high damping rubber (HDR) bearings. The remarkable properties of the HDR bearings are firstly verified by material tests. To understand the behavior of the novel system, a quasi-static test is conducted on two full-scale stair systems, and a parametric study of the design parameters of the HDR bearings is carried out. Test results confirm that the proposed system could mitigate the detrimental diagonal bracing effect of traditional RC flight by the HDR bearings. Consequently, no crack can be observed in the RC flight at the inter-story drift ratio (ISDR) of 2.0%, and only three horizontal cracks are detected at the bottom of the RC flight under the ISDR of 4.0%. Moreover, benefitting from the sliding mechanism of the developed stair system, the novel stair system is characterized by stable hysteretic responses and energy dissipation capacity at each loading stage and has about twice the equivalent viscous damping ratio to the traditional stair system. The parametric study shows that the rubber thickness of the HDR bearings has a remarkable effect on improving the seismic performance of the developed stair system, while the shear modulus and rubber hardness of the HDR bearings have a slight contribution to enhancing the lateral bearing capacity of the system.