Application Of Structural Topology, Shape And Size Optimization Method In The Design Of Cable-stayed Bridge Girders

Cable-stayed bridge is a kind of high-order statically indeterminate structure. The cable-stayed bridge girder is one of the key load-carrying members and its elevation and cross-section form directly influence the stresses, traveled condition and economic performance of the whole system, so its structure form and security are very important. But the design of the girder depends on experience of the designers and need pilot calculations for many times. It is difficult because the girder stresses are complex. In order to reduce the designers' cockamamie workload, the optimum design to the cable-stayed bridge girder is studied.In this dissertation the transverse topology, longitudinal shape and size optimization of the cable-stayed bridge girder are researched and examples for Junshan Yangtse Rive Bridge are calculated. The main contents are as follows:(1) A kind of astringency-based Bi-directional Evolutionary Structural Optimization method is proposed which can assure the topology optimization converging fast to the best solution and be easy to program.(2) Using this kind of astringency-based Bi-directional Evolutionary Structural Optimization method for the transverse topology optimization of the cable-stayed bridge girder and it is proved that box girder is the best cross-section for steel large-span cable-stayed bridges. This also shows that the astringency-based Bi-directional Evolutionary Structural Optimization method is practical and feasible.(3) The longitudinal shape and size optimization of the cable-stayed bridge girder is studied and the structural model consists of spatial plate, beam and pole cells. The results of the study show that the longitudinal ribbed slabs' space between and their position greatly effect the stresses and displacements of the top and the below plates of the girder. If the space betweens were too large, the thicknesses of the top or below plate would also be large in order to meet the stresses, displacements and other challenges.(4) The optimum cable tension distribution for completion state of the cable-stayed bridge is studied because it is necessary to calculate the girder stresses and displacements when the structural model is spatial. The results of the study show that choosing the minimum cross section area of structure as the objective function of shape and size optimization can reduce the material usage of the cables. And the optimization of cable tension makes them more uniform.