Mechanical Characteristics And Construction Control Of Super-long-span Cable-stayed Bridge With Transverse Asymmetrical Dead Load

In order to save the river-crossing channel resources and improve the functionality of the bridge,it becomes an inevitable trend for the large-span bridge to integrate rail transit,highway and urban road.And sometimes the asymmetrical bridge deck layout of rail transit and carriageway is used,which is affected by the plane alignment of approach bridge at two ends of main bridge.This makes the transverse secondary dead load of main girder asymmetric and the mechanical characteristics become more complicated.In this thesis,taking the main navigational channel bridge of Changtai Changjiang River Bridge as the engineering background,the mechanical behaviors and construction control measures of the long-span cable-stayed bridge with transversely asymmetrical dead loads are studied.The following studies are carried out:(1)The ANSYS software is used to explore the reasonable finite element simplified model of the plate-truss-box structure,and the MIDAS software is used to establish the finite space beam element model of the full bridge.For long-span cable-stayed bridge with transverse asymmetrical dead load,the method of applying asymmetric cable force is proposed to control the torsional deformation of the main girder.The influence laws of asymmetric lateral force,asymmetric longitudinal force and asymmetric vertical force on the lateral deflection of the main girder are investigated.(2)Setting transversely asymmetrical cable force which is optimized by the influence matrix method,the main girder and the bridge tower have better finished alignment and finished stress under transversely asymmetrical dead loads.At the same time,the deformation of the bridge under transversely asymmetrical live loads are analyzed.(3)The unstressed state method is used to simulate the cantilever construction process,and the non-linear calculation of the bridge structure formed in stages is performed to determine the reasonable construction state of the cable-stayed bridge.The influence of the transversely asymmetricical layout of the lower bridge deck system on the deflection of the main girder is analyzed.The reasonable construction control measures are discussed to reduce the lateral deformation and the torsional deformation caused by the local asymmetry of the bridge deck system,so as to control the structure alignment during the construction process,ensure the subsequent closure and achieve reasonable state of the bridge.(4)In order to determine the key structural parameters that have a significant impact on the mechanics behaviors during construction,the influences of main girder dead weight,main girder stiffness,cable stiffness,cable manufacturing length and other structural parameters on main girder alignment,main tower deflection and cable force are analyzed.The results show that the reasonable finished state of the bridge can be achieved by setting asymmetrical cable forces.The unbalanced longitudinal and lateral components corresponding to the asymmetric cable forces lead to the main girder to deviate railway side and the highway side,respectively,and the corresponding variance value of lateral displacement is no significant,which greatly reduces the lateral displacement of main girder.The reasonable finished state and reasonable construction state are realized by the unstressed state method.The asymmetrical effect of highway side and railway side of the lower bridge deck should be considered in the construction control,including asymmetrical first stage dead load and asymmetrical stiffness.In a word,it is possible to achieve the long-span cable-stayed bridge with transverse asymmetrical dead load,which is caused by the asymmetrical bridge deck layout.