| The main towers of cable-stayed bridge is expected to maintain small displacements and be in the ideal state of axial compression as much as possible.However,in practice,the ideal state of axial compression generally does not exist in the cable-stayed bridge with asymmetric arrangement of main girders on both sides of the main towers.Taking the long-span cable-stayed bridge with double towers as an example,firstly,because the length of the main girder in the middle span is generally longer than that of the side span,the gravity of the main girder in the the middle span is generally more than the main girder in the side span.If no measures are taken,under the action of the unbalanced load,the main towers will deviate to the middle span,resulting in its inability to be in the state of axial compression.Secondly,the cable forces lead to large bending moments in the main towers,and the maximum bending moments often appear in the middle and upper parts of the main towers.The material properties of the main towers will not be brought into full play.Finally,during the construction process,the main girder gravity will be borne by tensioning the cable;Because the cable forces will be adjusted many times,it will inevitably affect the displacements of the main towers,resulting in large bending moments.In order to solve these problems in engineering,the stiffness of the main towers,the weight of girders in the side span and the cross-sectional areas of stay cables connected with these girders are often increased,resulting in a lot of waste of materials and labors,and greatly increasing the cost of cable-stayed bridge.Therefore,this thesis proposes a new cable-stayed bridge that uses intelligent ground anchor cable to adjust the bending moments and displacements of the main towers.In the side span area,the ground anchor cables are set up and connected to the jack,and the other end is connected to the main towers,and the jack is controlled by displacements of the towers which monitored by the Beidou satellite to increase or decrease the cable forces to reduce the bending moments of the main towers of the cable-stayed bridge and its bias to the displacements of the middle span.In this paper,a cable-stayed bridge in Guangxi is selected as the research object for numerical simulation analysis.Firstly,the bending moments and displacements of the main towers of the bridge in the completion stage are analyzed as a reference.Then,the effects of the working conditions of setting one,two and three ground anchor cables on the tower columns on both sides of the main tower on the bending moments and displacements of the main towers are studied respectively.Aiming at the optimization of the bending moments and displacements of the main towers,the connection positions of the ground anchor cables on the main towers,the forces of the ground anchor cables,the optimization results of the bending moments and displacements of the main towers under these three working conditions are obtained.Secondly,the influence of ground anchor cable forces on the other cable forces and the modals under different working conditions are analyzed.Finally,the optimization of the bending moments and displacements of the main towers by the ground anchor cables in each construction stage is studied and analyzed to make the main towers in a reasonable stress state in the construction process.The new cable-stayed bridge proposed in this paper can effectively optimize the bending moments and displacements of the main towers in the construction and completion stage,improve the stress rationality of the main towers,greatly reduce the cost of the main towers and the cost of the main beam,and has good economic benefits and practicability. |
