Static And Integral Stability Analysis Of Double Towers Cable-stayed Bridge Without Backstays

The cable-stayed bridge without backstays has the characteristics of novel exterior and aesthetic shape.However,the no-back cable-stayed bridge is a special structural form,which leads to its spatial force state that is very different from that of the conventional cable-stayed bridge.The requirement stability of no-back cable-stayed bridges becomes much higher.Taking the Shouchunxilu bridge in Lu'an city,Anhui Province,as an example,the finite element model of the bridge is built in this paper.The loading behavior,stability and ultimate bearing capacity of cable-stayed bridge without backstays are investigated to understand the ultimate strength and instability behavior of the bridge.The outcomes can provide the reference for the design and construction of the same type bridge.The main contents and conclusions of this study include:1.The beam type finite element model of the Shouchunxilu bridge is established to analyze static performance and the parametric studies are carried out accordingly.The results show that the mid span deflection of the main girder is small under the design cable tension forces because the bending stiffness of the main girder is quite large.The displacement of the tower is more obvious than the displacement of the girder,which is because the pylon of the no-back cable-stayed bridge is inclined,and if the cable tension is not large enough,there will be a large displacement under the action of gravity.Therefore,to meet the requirements of design strength of cables and towers,it should be as much as possible to increase the cable tension for the completed bridge stages.2.The solid and shell system finite element model of the no-backstays bridge is established and the calculated results are then compared with those of the beam element model.It is demonstrated that the solid finite element modeling is very complex and time consumed.The results are conservative,but it can better simulate the local loading behavior of the key parts.So for the large-scale bridge structure,the global finite element model can be established by the beam element,but it is necessary to establish a solid and shell finite element model for the local analysis in order to consider the failure behavior of the local area more accurately.3.The elastic instability under the action of self-weight is studied based on the beam type finite element model of the no-backstays bridge.It is found that the firstbuckling is lateral bending of the main tower and the buckling coefficient is 6.79,which indicates that the overall elastic stability of the Shouchunxilu bridge is sound.If only consider the first-order elastic instability,the two columns of the main tower and the vice tower need not to be consolidated,and the structural stability of the bridge still meets the requirements in the case of hinge.4.The nonlinear stability and the nonlinear influence factors are investigated based on the beam type finite element model of the no-backstays bridge.The results show that the geometrical nonlinearity has a little effect on the ultimate bearing capacity of the bridge,but the material nonlinearity is the key factor to control the ultimate bearing capacity of the bridge.Under the initial cable tension,the ultimate failure path of Shouchunxilu bridge is the yield of steel box girder,while the cable force has not reached the ultimate state in the time.