Seismic behavior of reinforced concrete frame staircase with separated slab stairs

To avoid the shear failure of the frame columns in staircase and improve the seismic performance, we propose a reinforced concrete frame staircase with separated slab stairs. In this study, we conduct reversed cyclic loading test of this staircase to investigate the failure mode, hysteretic behavior, ductility, stiffness degradation, and energy dissipation. Our test results show that the failure modes are the crushing damage of the stair beam-stair column joint and the cracking failure of the frame column, resulting in the reduction of energy dissipation capacity of the staircase. The ductility factor is approximately 2.9 and the maximum energy dissipation coefficient is 0.714, showing good seismic performance. Stairs as a diagonal strut can resist most horizontal load exerted on the staircase, but they also can cause uneven distribution of stiffness and torsional deformation in the staircase. In addition, we develop two finite element models to investigate the effect of stairs on the seismic performance of staircase. The lateral stiffness of the staircase with separated slab stairs is 53.46% higher than that of the frame model, and the separated slab stairs show a significant effect on the frame columns that are connected to them.