Mechanical Analysis Of Cable-stayed System During The Cable-stayed Suspension Installation In Large-span Arch Bridge

The cable-stayed suspension method is one of the common methods in the construction of long-span arch bridge.In the construction process of steel arch rib with cable-stayed suspension method,the forces on cable-stayed tower are complicated.The mechanical property of cable-stayed tower plays an important role for construction safety and construction quality.Taking the MXH double-line railway arch bridge project as an engineering background,the study on the cable-stayed suspension system is done in this thesis.Based on the mechanical modeling of the system,the 3D overall analysis model is established using the Midas/Civil finite element software,and then,the influences on three kinds of cable-stayed tower are discussed when temperatures change.According to the principle of one-time tension and the control conditions of construction precision,the reasonable and effective cable forces are calculated.Under the whole construction process and the most dangerous working conditions,the mechanical behaviors of the cable-stayed tower structure are analyzed.The main works of this thesis are summarized as follows.(1)The cable-stayed tower stands at the top of the pier at the connecting position of main bridge and approach bridge.Between the approach bridge,the main bridge and the cable-stayed tower,the interactions are complicated.When temperature changes,the influence on the stiffness and strength of cable-stayed tower structure is studied with different structural connections between approach bridge,pier and tower.Then by comparison,the appropriate system structure is selected.One hand,the appropriate structure guarantees the rigidity and strength of the system,on the other hand,it can reduce the adverse effect of temperature change.(2)Based on the one-time tension principle,the cable forces are obtained by using the unknown load coefficient method.The calculated cable forces can meet the control conditions of construction precision and the safety requirements of the cable-stayed system.(3)During the construction of arch bridge cable-stayed suspension,the incomplete structure system has been changed many times.In this thesis,by the simulation analysis of the whole construction process,the mechanical properties of the cable-stayed tower are discussed in different construction stages.The areas with large displacements or large stresses in the tower and the corresponding construction stages are also ascertained,which provides the monitoring basis for the actual construction.(4)In the construction process of arch bridge,there is the worst stress situation of cable-stayed tower.Considering the combined effect of temperature change and wind load,there are 12 possible dangerous working conditions provided in this thesis,under which the stiffness,strength and stability of the structure is analyzed.This work can furtherly guarantee the construction safety and construction quality.(5)In the process of construction,real-time monitoring of the cable-stayed suspension system is carried out.Then the displacements and stresses monitoring datum are compared with the finite element calculation results.By analyzing the monitoring data,the FEM model is checked.Meanwhile,the safety and reliability of the cable-stayed tower are ensured.The results and conclusions given in this thesis,obtained by analyzing the cable-stayed system of MXH double-line railway bridge,not only provide technical supports and safety guarantees for practical construction,but also provide references for the design and engineering application of cable-stayed system in the construction of same type bridge.