Seismic Performance Analysis Of Long-span Steel Truss Roof Structure

With the rapid development of economy,people's requirements for living environment have been raised,and large-span spatial structures have emerged with their unique charm.It has the advantages of light weight,large span,various forms,beautiful appearance and good performance,but its development is also limited by many factors,especially the impact of earthquake.Earlier researchers believed that horizontal earthquakes were the main cause of building damage.Later,a large number of earthquake damage investigations showed that the vertical seismic action had a significant impact on large-span structures.The study of vertical earthquakes on large-span structures is a crucial step in the history of the development of such structures.In this paper,SAP2000 finite element software is used to establish the overall model of long-span steel truss roof.The modal analysis is used to analyze the characteristics of structural mode and natural vibration period.Then the response spectrum analysis and elastic time history analysis are carried out to obtain the deformation and stress response characteristics of the structure under different seismic combinations.Finally,the elastic-plastic time history analysis is carried out to analyze the plastic development of the structure.The main contents are as follows:The modal analysis shows that the main mode of the structure is vertical vibration,which has the characteristics of complex mode and dense frequency.The response spectrum analysis of the structure under three seismic combinations(horizontal two-way earthquake,vertical earthquake and horizontal two-way and vertical seismic coupling)shows that the X-direction displacement,peak acceleration of 5.530mm and 3.359m/s~2 occur under horizontal two-way earthquake,and the vertical displacement and peak acceleration of 2.004mm and 1.177m/s~2occur only under vertical earthquake.The dynamic internal force coefficient of the structure is about 10%,which shows that the vertical earthquake has a significant impact on the overall structure,especially on the two ends of the roof and the lower chord members.By choosing three kinds of vertical seismic waves to analyze the elastic time history of the structure,it can be seen that the response values of the same component under different seismic waves will differ greatly,but the variation law still shows consistency.The maximum response of the structure under Taft wave is 2.279mm and 1.583m/s~2 in vertical displacement and acceleration.By comparing the results of response spectrum analysis and elastic time-history analysis,it can be seen that the response value of elastic time-history analysis is larger,the maximum difference between them is 15%,and the dynamic internal force coefficients are maintained at about 10%.Vertical earthquakes can be seen in the influence of large-span structures.Therefore,the effect of vertical earthquake should not be neglected in the seismic design of this kind of long-span structure,and it must be considered as an important factor.Finally,the elastic-plastic time history analysis of the structure under rare earthquakes shows that the plastic development of the structure is not high.Under the selected three kinds of seismic wave input,only a small number of web members at the supports produce plastic hinges,accounting for 1.4%of the total number of members,and the overall structure does not appear obvious damage.