Analysis Of The Influence Of The Stairs On Seismic Performance Of Frame Structure

As we know, the stairs is an important vertical escape in the earthquake disaster.However, the investigators found that a lot of stairwelles were severely damaged andlost their role as vertical escape in the wenchuan earthquake, even the main structure isnot severely damaged and collapsed.In the design before, however, we open an hole at the location of the stairwell andapproximately simulating the load to consider the role of the stairs on the framework.This approach fails to consider the influence of the stairs to the whole structure rigidity,and fails to give full consideration of the stairs impact on the frame beams surroundingthe stairwell. After the wenchuan earthquake，the new seismic code modified thecorresponding problem. The code requested that “the impact of staircase componentsshould be considered in the calculation.” Related research suggested reduce the bracingeffect of the stairs and the atlas of the national standard (11G101-2) have given theprocess of the sliding bearing stairs. The study also found that stair destruction is verycomplex, one common form is the short column damage of the stairwell frame column.Therefore, it proposed using the stair column to separate the framework columns fromthe resting platform.Through structural analysis software SAP2000, we established eight frame structuremodel. Include two-layer, four-layer, six-layer framework model with and without stairs,six-layer framework model with sliding support stair, six-layer framework model withsliding support stair whose resting platform separated from the frame column. With theformer six models, we analyzed how general plate staircase effect on the seismicperformance of the framework structure with different layers. Besides, we analyzd theadvantages of the last two staircases.This paper draws the following conclusions through these analyzes:(1) The influence of the stairs on the rigidity of the framework structure can not beignored when it’s under the action of the earthquake.(2) To the framework with different layers, the influence of stairs is not the same. Theeffect of stair increases when the height of framework increased.(3) The influence of the stairs on the ground floor is most obvious, where the internalforce of the frame column and part of the frame beam around the staircase significantlylarger. It means that it’s not safe to simulate the stairs by the model without stairs. (4) The influence of the sliding support stair and sliding support stair whose restingplatform separated from the frame column on the structural seismic performance isnegligible, especially the latter one. The sliding support stair whose resting platformseparated from the frame column does not affect the internal force of the frame column,but still affect the internal force of the frame beam around the staircase.