Earthquake-resistance Performance Study On Irregular L-shaped Plane Frame Structure With Stairs Under Rare Earthquake

With the development of urban construction,buildings of complex shape are more and more be favored,a lot of irregular plane structures are being constructed.The stairs as part of the structure,can provide structure with large stiffness,should work together and the overall structure.But in the practical structure design,structural model tend not to set up the stairs,pay little attention to seismic performance of stairs.Scholars at home and abroad who study on irregular plane frame structure most did not consider the stairs,and for much of the stair’s research is based on the plane frame structure more rules,study on nonlinear seismic behavior of irregular plane frame structure with stairs is still relatively small.This paper uses the perform-3d software,established 6 different stair arrangement of "L" plane irregular frame structure models,selected the EL-Centro seismic wave,Taft seismic waves and an artificial seismic wave as seismic load for dynamic elastic-plastic analysis.To study the influence on the stairs of the L plane irregular frame structure seismic performance under rare earthquake.Using performance-based seismic design method to evaluate structural performance.Set different performance goals to different components under the different earthquake levels,find out the yield mechanism of the structure,determine the weak parts of the structure under strong earthquake,compare structure seismic performance under the different seismic wave.The results showed that(1)The stairs have a large influence on the cycle of the structure,the period of the structure with staircase is reduced by about 6% to 26%.Improper placement of the stairs will make the structure of the torsion effect intensified,leading to torsional vibration mode to the first mode;(2)The yield mechanism of the structure is that beams and ladder of staircase yield occurred fastest,corner pillars of the staircase occurred short column failure,a small number of beam near the staircase also yield.(3)The elastic-plastic displacement angle of the structure with stair under different seismic wave can be reduced by about 15% ~ 30%.The floor displacement of the structure with no stair increases about 1.3 times than that of the staircase model.The vertex displacement of structure with the staircase can be reduced by 10% to 30%.The floor shear of the structure with stairs reduced more.The maximum shearing force of the second layer is smaller than that of the non-staircase structure,the X-direction decreases from 9% to 24%,and the Y direction is about 7% to 14%.(4)Under pre-set LS(life safety)performance objectives,ladder column and ladder beam failed to achieve the desired objectives,but the number of destroyed components ofthe main frame structure is small,the overall structure achieves the expected performance goals of life safety.Finally,based on the conclusions of the study,some suggestions are given for the design of the existing staircase.