Analysis Of The Interaction Between Stair And Frame Under Horizontal Earthquake Action

The WenChuan earthquake of 12 May 2008 is the most destructive earthquake in China, causing great property damage and human losses. In the investigation after earthquake, it was found that some stairs appeared to be failure before main structure. Stair did not play the due role in natural disaster but delayed the people evacuation and caused a great obstacle for the wok of rescue personnel. In addition, the existing of stair changed the rigid distribution of whole structure, which led to the problem that internal forces distribution of the main structural members connected with the stair appeared significant change under earthquake and then had a significant influence on the safety of whole structure.After WenChuan earthquake, a series of papers about the interaction between stair and whole structure under earthquake were published by domestic experts and scholars. In these papers there is a consensus that stair had a great effort on the working performance of whole structure so that it should not be ignored in practical structure design. In July 2008 Ministry of Construction added local revised items of seismic design code in which it is referred that"the influence of stair components should be considered in structure computation". Subsequently, domestic current structure design software, PKPM08 provided the solution of considering the stair influence in computation.On the base of the summary of seismic damage for staircase in WenChuan earthquake,this paper set an imaginary frame structure with stair as an example. The models with and without stair were built by PKPM08 and SAP2000 respectively. Vibration mode, period, base shear, displacement and the force condition of stair and frame component around of four models were obtained through modal analysis and spectrum analysis respectively in this paper.The research work in this paper mainly involves:(1) Analyze and summarize the stair influence on the work performance of frame structure under horizontal earthquake. (2) Through making a comparison between the computation results of SAP2000 and PKPM08, Discuss the accuracy of the computation solution of the frame with stair modeled by PKPM08.(3) Analyze and summarize the force characteristic of stair component under horizontal earthquake. Combining the practical seismic damage for stair structure in WenChuan earthquake, the main factors that result in stair failure in earthquake were inductive.(4)Some pertinent suggestions on construction treatment and seismic design of stair were given, which can provide reference for structure design in future.