Seismic Behavior Analysis Of Long Span Cable-stayed Bridge With Double Deck And Steel Truss Beam

With the quick development of our nation’s railway and highway traffic cause, more and more larger span double deck bridge constructed. The highway-railway cable-stayed bridge is one of common structure forms, which not only can give full play to the railway bridge and road bridge for vertical and lateral stiffness of complementary advantages, also can make full use of resources such as land, rivers and space. Large span highway-railway cable-stayed bridge is usually located in the key position of highway traffic network, whether in politics, economy, national defence are important. Therefore, reach a conclusion of regularity from the study of seismic response analysis to guide bridge design is very necessary.In this paper, taking the Haitan strait railway and highway bridge (75+165+450+165+75m) for engineering background, studying the seismic response of the large span steel truss girder double-layer cable-stayed bridge. The background bridge had been established double deck model and single deck model through a large general-purpose finite element analysis software ANSYS10.0, and analyzing its dynamic characteristic analysis, response spectrum analysis and time history analysis respectively. The main content is as following aspects:First, Describes the development of double steel truss girder bridge and seismic response analysis of long-span bridge, and explains the research objectives and content of this article.Secondly, the modeling process of the large span cable-stayed bridge with double deck and steel truss beam is described in detail. Establishing the single deck model based on double deck model. Comparative analysis the dynamic characteristics of single deck model and the double deck model, that there frequency difference is not big, but some modes appear in different order. On the influence of dynamic characteristics of single deck model factor parameter analysis, draw that beam elastic modulus and the quality of single deck are major factors affecting the dynamic behavior of single deck model, initial cable force of cable effects can be neglected.Then, Introducing the earthquake fortification level and response spectrum analysis theory, theory earthquake response spectrum and combination methods are briefly introduced. According to the geological conditions of the Haitan Straits Highway and Railway Bridge, with reference to the relevant norms, the double deck model and single deck model were analyzed respectively by response spectrum through seven different input directions, and the internal force of pier-tower bottom and displacement of tower top and girder mid-span were obtained. The results show that part of the axial force calculation results has larger difference.Finally, for double deck model and single deck model seismic time history response analysis, it is concluded that cable-stayed bridge has obvious three dimensional coupling characteristics,3 d seismic input response value larger than a 2 d. The most unfavorable earthquake combination should been choose in the seismic design. The bottom of pier and tower internal force value for Double deck model and single deck model are close, and meanwhile path curve is also very anastomosis. But the displament of main gird are different. So if the design stage demands high calculation accurary, useing single deck model to replace double deck model calculation is not a good choice.