Study On The Failure Probability Of Staircase Of Frame Structure Under Earthquakes

Staircase as one of the building’s vertical transportation hubs, as well as the vertical escape route when earthquake occurs, should not have subjected to damage before the failure of the main frame structure. However, the staircase of frame structure actually serves as the first line of defense to resist the earthquake through investigations on several major earthquakes at home and abroad. Conventionally, the design of staircase of frame structures is not involved in the main frame structure seismic design. Although some design calculation provisions about the staircase have been added to the current seismic codes, studies on the seismic performance of each member of the staircase of frame structure are not thorough enough. In order to study seismic performances of staircase members in the frame structure, this following work was carried out in this paper:(1) Based on damage data of several major earthquakes at home and abroad, the damage situations of each member of the staircase were investigated. What’s more, the failure models were summed up and the damage mechanisms were studied.(2) Two six-floor frame structure models, one with stairs and one without stairs, are built by SAP2000. The modal analysis and the response spectrum analysis were carried out, and effects of the existence of staircases on the frame structure were discussed through the model.(3) A typical staircase model of frame structure was built. The failure probability of each member of the staircase under the inverted triangle load was studied according to their failure models. Furthermore, the failure probability of each member of the staircase under rare earthquakes was studied through the shear amplification coefficient of the rare earthquake to the small earthquake, calculated through displacement-based seismic design method.(4) Methods and measures to reduce failure probability of each member of staircases under rare earthquake were discussed.