Seismic performance of reinforced concrete stairs with new sliding support

Abstract

Cast‐in‐suit stairs and precast stairs were damaged seriously during many earthquakes in recent years. Stairs with new sliding support were put forward in order to avoid the failure of stairs, landing slab in the half floor was divided into two parts and sliding support was placed between stair beam and landing slab. Down‐scaled model of stairs with new sliding support was produced, and reversed cyclic loading test was conducted to investigate the failure mode, hysteretic behavior, ductility, stiffness degradation and energy dissipation. The failure mode was crushing damage of frame column and stair components remained intact. The new sliding support had good working properties and landing slab separated from stair beam under the pull condition. In addition, seven finite element models of staircase were developed to investigate the seismic performance of staircase, and seven finite element models of frame structure were developed to investigate the effect of stairs on the seismic performance of main structure. Lateral stiffness of the staircase was asymmetrical affected by common stairs, so torsional deformation of staircase was large, and stairs with new sliding support had no effect to the lateral stiffness of staircase. Compared with frame structure, the natural period of vibration decreased approximately by 5% and the first vibration mode also changed direction when common stairs was considered, the natural period of vibration and the first vibration mode were not change when sliding support was adopted. Stairs were not damaged and did not affect the seismic performance of main structure when new sliding support was used.