Seismic damage analysis and design suggestions for staircases in RC frame structures

Staircases,critically important for egress and access during emergency events,suffered severe damages in recent earthquakes at home and abroad in reinforced concrete(RC) frame structures.Staircases,acting as the first line of defense in earthquake,firstly yielded and failed,and were out the action of emergency access,they could not meet the seismic performance objectives.To realize the objective of acting as safe access under strong earthquakes,the current Chinese seismic design code for buildings specifies special requirement on the design of staircase.The comparison of numerical analysis of a typical RC frame structure under frequent earthquakes between considering and neglecting the effect of staircases was performed to study the influence of staircases on the structural behavior.The effect of staircases on the yielding and failure mechanism of RC frame structures was investigated with nonlinear static analysis.Accordingly,the damage reasons for in-situ cast staircase and precast staircase were analyzed.Finally,some suggestions to improve design of staircases were proposed according to the analysis results and the current design method.