Mechanical Characteristics Of Asymmetric Extradosed Cable-stayed Bridge With Single Tower And Double Spans

The extrodosed cable-stayed bridge is a kind of composite bridge.Due to the large rigidity grider and the flat cables,most of the live load is carried by grider and the rest of live load is shared by cables,so the key issure of designing a extrodosed cable-stayed bridge is how to determined the proportion of live load sharing between cables and the grider.To ensure the proportion is properly,it is necessary to coordinate the rigidity of each component and arrange the cables reasonably.However,the number of components of the extrodosed cable-stayed bridge is large,and it is a typical high-order statically indeterminate structure,which causes the design parameters to be coupled with each other and brings difficulties both for bridge design and parameters analysis At present,the design of extrodosed cable-stayed bridge mainly relies on the finite element method,and the calculation model should be adjusted many times.The main method of parameters analysis is only for the finite element analysis of a particular bridge,which is restricted in the scope of application.In this paper,the assumption of equivalent membrane tension was introduced Based on the basic theory of beam,the bending moment function of the structure was assumed first,and the undetermined coefficient of the function were obtained by the principle of minimum residual energy,then the deflection function of the structure was derived.At last,the equivalent membrane tension formula was obtained by using the deformation coordination condition of grider and cable,and the analytical solution of the bending moment of the structure was finally obtained.Besides.Taking a extrodosed cable-stayed bridge as the engineering model,the above formula and Midas/Civil finite element software were used to calculate and error analysis.The results indicates that the accuracy of the analytical solution can satisfys the conceptual design.The load-shedding coefficient of cables was defined,and design parameters were analyed for asymmetric extradosed cable-stayed bridge with single tower and double spans.With alteration of design parameters such as the long-short spans ratio,the length without cables,the stiffness of grider,tower and pile,the area and inclination of cable,their effects were analyed for the internal force of structure and the load-shedding coefficient of cables,and the reference of some design parameters were summarized.The concept of cable-grider coupling parameters was introduced,and it was proved that the parameters can directly reflect the influence of the coupling action on the structural mechanical characteristics,which caused by the stiffness of grider,the stiffness of cables and the inclination of the cables.Through the parameter analysis,the reasonable range of the coupling parameters was concluded.The conclusion of this thesis can help designer understand the mechanical characteristics of asymmetric extradosed cable-stayed bridge with single tower and double spans and control the design globally.Beside,the reference for structural parameters is a guidance for designer.