Internal Force Calculation And Seismic Performance Analysis Of Staircase In A Concrete Frame Structure

ABSTRACT:As important vertical escape exits, a lot of stairs were destroyed before the body structures at Wenchuan Earthquake, which did not perform their proper functions and resulted in large numbers of people injured. So newly "criterion of architecture asseismatic design" not only puts forward some specific construction measures, but also points out that establishment、simplified calculation and result processing of model should satisfy real structural work condition, which means that the influence of stairs should be considered. So many scholars studied the whole frame structures affected by stairs with finite element software, they found that the stiffness and torsion of whole structure rose considering stairs, and the influence of structure changed according to different location of stairs. Although they provide corresponding design proposals, the ways of calculating specific forces of stairs under horizontal seismic ground motion are still not mentioned yet.This paper verifies the impact of stairs to whole frame structure with PKPM software, and D-method is used in this paper for calculating simplified model with stairs in order to amend lateral stiffness of structure. Shear stresses of beams and the internal forces of stairs on each floor can be calculated after modified lateral stiffness, compared with the results of SAP2000, it is clear that those forces are plenty big not to be ignored; structural beams connected to landing slab have different shear stresses between the top and the bottom, what is more, shear stresses in the bottom is bigger than that at the top. This paper suggests that two different simplified model considering stairs should be used to calculate the internal forces of frame structure with modified D-method, and reinforcement assembly of structure can be designed after the combination between gravity load and horizontal earthquake action.Taking account of concrete material nonlinearity, this paper does a nonlinear static analysis on the staircase model with Midas Fea. The research focuses on the location of crack caused by horizontal earthquake action, which satisfies the computer simulation technology too.