Influence Analysis Of Stairs On Seismic Performance Of Frame-shear Wall Structure

Reinforced concrete frame-shear wall structure, one of the top structures, is widely used at present. In the design of stair, the frame-shear wall structure generally is not input the staircase components, but through opening the floor and transferring vertical load to the frame beam and column or wall to consider staircase in the whole structure. The stairs are just calculated and reinforced in isolation, not considering the earthquake action. Summarizing all previous seismic data, however, it is easy to find, the stairs did not play its due role success in major earthquake disaster, sometimes even ahead of the main structure damage and hindering people escape or rescue.After the Wenchuan Earthquake, the revised code for seismic design of buildings(GB50011-2010)has made it clear that: using computer analysis of structure, the establishment of calculation model, the necessary simplified calculation and processing should be consistent with the structure of the actual condition, and calculation of stair effect should be considered.In reinforced concrete frame-shear wall structure, stair whether to participate in the structure modeling calculation has impact on the overall stiffness. This paper, by using the finite element analysis software Midas Gen, through response spectrum analysis and static elastoplastic analysis(Pushover analysis) and dynamic elastic-plastic time history analysis, systematically studies the stairs on seismic performance of frame-shear wall structure.In the setting of analysis model, consider the following requirement:(1)Stair whether to participate in the overall computing model;(2)The position of staircase;(3)The structure of the staircase.Through the comparison of models, we analyze main influence on the whole structure parameters(period, floor shear, floor displacement and displacement angle between the layers, etc.). And internal force of beam and column components are also analyzed and evaluated. In frequent earthquakes and rare earthquakes, it focuses on the stairs artifacts on seismic performance of frame-shear wall structure as a whole as well as the influence of the internal force of beams and columns structure.Here are the main conclusions:Under the seismic action, the participation of stairs increases stiffness of frame-shear wall structure. Natural vibration period of structure, the floor displacement, the interlayer displacement angle, floor shear and so on all have different degrees of influence and stair components must brace effect in the structure. In structure design, therefore, it needs to consider the effect of stair component to the overall structure.Under the seismic action, the position of staircase also has more obvious influence on seismic performance of frame-shear wall structure. Asymmetric arrangement of the stairs leads to the floor shear, the floor displacement and base shear being larger. So we in the structural layout, stair layout should be fully considered for the overall stiffness of the impact of uniform distribution.Under seismic action, stair structure change on seismic performance of frame-shear wall structure has important influence. Scissors stairs make natural vibration period, floor shear and base shear of overall structure significantly increased. So we need to fully consider the particularity of its structures which have the stairs similar to the scissors type structure. And we need to analyze the seismic performance impact according to the practical situation.The participation of the stairs to internal force of the structures also has had an impact. The existence of the staircase leads to structural stiffness larger, and then structure internal force of beams and columns changes accordingly. And the current in the design of stair simplified treatment obviously cannot accurately reflect the stairs in the earthquake effect on internal force of beams and columns structure. So it should be improved.