Research On The Optimal Design Of Tied Arch Bridge Based On Substructure Contribution

With the development of modern structural optimization theory,it has also been widely used in the field of bridge structural optimization.The traditional bridge structural optimization relies on the experience of the designers to select a group of discrete variables for contrastive analysis,and this may lead to many limitations.When the mathematical optimization method is introduced into the bridge structural optimization,the optimal solution cannot meet neither the requirements of displacement and internal force simultaneously,nor the feasibility of construction,engineering cost and aesthetic requirements.Therefore,on the basis of mathematical optimization method,this paper proposes a structural optimization method based on sub-contribution,which overcomes the limitations of traditional bridge structural optimization and obtains a feasible solution with a certain bandwidth compared with the mathematical optimization method.Tied-arch bridge is widely used in construction because of its structural form diversity.The study on optimization of cable-tied arch bridge at home and abroad is mainly focused on the local section parameter optimization,while the research on the hanger arrangement of sparse cable-tied arch bridge is rather inadequate.Therefore,this paper selects a 230-m-span basket-tied arch bridge and conducts the design of the initial scheme,uses genetic algorithm to optimize the size of the bridge,and then adopts structural optimization based on sub-contribution to topologically optimize the design of the hanger layouts.The main contents are as follows:(1)After the initial scheme of the 230-m-span basket-tied arch bridge is determined,genetic algorithm is used to carry out parametric optimization of the whole bridge,which is based on the optimization module of SiPESC.OPT on the SiPESC integration platform independently developed by Dalian University of Technology.The optimal cost of the superstructure of the whole bridge is obtained,and the total cost after optimization is reduced by 40%.(2)A structural optimization method based on sub-contribution is proposed,and the concepts of sub-structure and sub-contribution in bridge design optimization are defined.This method takes the contribution of single and combined substructures to the objective function as the index of optimizing substructure group,which reduces the calculation of the samplespace,retaining the better individual substructure contribution's advantage,as well as n-order sub-contribution to effectively avoid ignoring the advantage of combination of sub-structures.Taking a simple cantilever truss beam as an example,the objective function of the optimized scheme is reduced by about 90%,and a set of feasible solutions is obtained,which verifies the innovation and feasibility of the method.(3)Taking the maximum displacement of tie beam as the objective function,the structural optimization method based on substructure contribution is applied to the topological optimization of the suspender layout of tie arch bridge.Compared with the optimization using genetic algorithm,the maximum displacement of tie beam is reduced by 60%.By comparing the internal forces,it can be known that the optimized thin cable boom takes full advantage of the oblique boom,and improves the stiffness of the bridge as well as reduces the stress in the span of the tie beam.Meanwhile,a large number of excellent thin cable systems are available for designers to consider the displacement,internal force,cost and aesthetic requirements for the program selection.