Study On Optimization Of Cable Tension Of Completion State Under Dead Load For Hybrid Cable-Stayed Bridge

With the rapid development of the national economy and the increasingly rise of the traffic, the scale and number of bridges with long span increase daily. The cable-stayed bridge is a competitive bridge type of bridges with long span and super span bridges. The distributing of internal force of the cable-stayed bridge at completion stage is one of the important standards to evaluate the design quality. As for bridges at completion stage, the distributing of internal force is determined by the cable tension to a great degree. So it is the main purpose of this paper to study the optimization of cable tension.At the present time, there are various methods to optimize the cable tension. They can be sorted into optimization of cable tension with specified stress state,unconstrained optimization of cable tension and constrained optimization of cable tension. For instance, there are rigid support continuous beam method,minimal bending energy method,force balance method,minimal cable usage method and influence matrix method. In the practical applications, you should select the appropriate optimization method according to the fact.The girder of the hybrid cable-stayed bridge is composed of two materials along the length direction. The main span has large span ability. Based on the characteristics of the hybrid cable-stayed bridge, this paper brings forward an optimization model of cable tension at completion stage. It aims to minimize the maximum displacements of the girder and the main pylon of hybrid cable-stayed bridge. And it takes allowable stress of cable as a restriction. Otherwise, it also considers the restriction of joint bending moment between steel gilder and concrete girder. On the basis of the above model, the paper applies complex method to optimization of cable tension. In addition, the basic idea,arithmetic along with scope of application of simplex method and complex method are stressed. The solving steps of influence matrix are introduced in detail.Based on the Ronghu Bridge of Wuxi city, this paper uses finite element program ANSYS to establish the spatial model, and optimizes the cable tension by optimal analysis module with ANSYS. In addition to particular introduction of the ANSYS optimal analysis technique's fundamental,basic concepts and optimal analysis flow, the paper also compares the merits and flaws of zero order and first order optimal analysis method. At first, use zero order method to primarily get the optimal cable tension. Then, adopt first order method with gradient optimization to exactly confirm it.Finally, the paper introduces the functions of APDL parameter design language and writes program in this language to carry out the complex method. In this paper, use the program mentioned above to do the optimization of cable tension analysis of RongHu Bridge and educe the optimal cable tension under dead loads and completion stage. By comparing the results of first order analysis method and complex method, we can draw a conclusion as follows: when optimizing the cable tension of hybrid cable-stayed bridge with complex method, there is no use to obtain the differential coefficient of displacement function, so the operation is relatively simple, nevertheless the optimization result is feasible.