Study On Design Method Of Portal Frame With Interlayer Under Earthquake Action

With the wide application of the portal frame structure system,considering the maximum use of the internal space and the combination of various functions,it is often necessary to add interlayer in the portal frame,thus forming portal frame structure with interlayer.Compared with the ordinary portal frame structure,the portal frame structure with interlayer often uses the concrete floor,and the selfweight load of the interlayer is much larger than that of the other parts.The whole structure center of mass and stiffness will change greatly,which changes the characteristics of the original In-plane force.Further research of the effect of the earthquake action and the torsional effect on the structure needs to be studied.At present,most of the seismic design methods for this kind of structure are mainly based on the portal frame in-plane seismic analysis,perpendicular to the portal frame direction,depending on experience,adopting structural measures to strengthen.And some people also put forward the method of integral modeling analysis and calculation.However,relative to the original plane standardization modeling,the overall modeling analysis brings the modeling engineering quantity to the designer.There is no doubt that there is a lot of increase,and there is no clear expression of the difference between the whole and the analysis results of the plane modeling,so the seismic design method for the portal frame needs to be further studied.In this paper,the domestic finite element software PKPM and 3D3S are used to analyze the wind load and the in-plane seismic action of the portal frame with full span,half span and local interlayer,and the results of the two software analysis are compared.At the same time,the spatial three-dimensional analysis of the portal frame structure with full span,half span and local sandwich is established by using 3D3S,the model is subjected to horizontal seismic analysis of two principal axis directions,taking into account the effects of mutual coupling.The following research has been completed:(1)PKPM and 3D3S software are applied to the analysis of the internal force of the portal frame structure with interlayer.The results of the internal force and displacement calculation of the main control points of the two software under the left wind 1 load are basically stable.Under the left earthquake,the bending moment of the portal frame column of the PKPM and 3D3S at the upper end of the interlayer is different,and the comparative analysis shows that the results of 3D3S calculation are relatively accurate.The internal force of the portal frame structure with interlayer is relatively small under vertical seismic action.(2)It is found that the arrangement range of interlayer affects the vibration characteristics of the structure.The wider the arrangement of interlayer is,the earlier the main vibration mode of the structure appears.The vibration mode before the main mode is mostly the partial vibration of the oblique beam.(3)the three-dimensional model of portal frame structure with interlayer was established by 3D3S and the horizontal seismic action was analyzed.At the same time,it was compared with the results obtained by the two-dimensional modeling in the horizontal earthquake.It was found that the bending moment of the portal frame column obtained by the three-dimensional modeling analysis was relatively small,the lateral displacement of frames obtained by two-dimensional plane analysis is slightly smaller than that of three-dimensional modeling.According to the calculation results,it is known that the 3 kinds of portal frame structure analyzed in this paper can be satisfied with the structural stress requirements by using 2-D plane calculation analysis and design.(4)In the overall modeling and analysis of the portal frame with interlayer,the influence of the coupling of two-way seismic action on the force of the rigid frame is smaller.Under the action of the direction of the column distance(Y direction),the displacement stiffness of the interlayer is relatively weak in this direction and the displacement of the seismic action is larger.It is advisable to arrange the support between the sandwich columns in the proper position to improve the longitudinal lateral stiffness.