Simplified Analysis Method For Shape Of Long-span Suspension Bridge Considering Variable Stiffness Of Main Cable During Construction Period

The construction of long-span suspension Bridges will become more and more common due to the needs of infrastructure development in various countries.Main cable,as an important bearing component of suspension bridges,plays a huge role in the design and construction of long-span suspension bridge,and the current research on main cable for the most part are based on the main cable is an ideal flexible cable,not bending,nor compression on this assumption,but in actual construction process,the main cable not only has a certain bending stiffness,but also has a complicated bending resistance mechanism.This paper presents an equivalent truss cable element method to calculate the shape and internal force of the main cable by considering the variable stiffness characteristics of the main cable in the construction process.Firstly,the paper summarizes several types of element and relevant analytical and numerical methods of finite element simulation of main cable of suspension bridge in domestic and foreign literature.Then a new numerical method for calculating the shape and internal force of the main cable considering the variable stiffness of the main cable is presented.The method in each meet small deformation assumption of incremental load steps considering the cable clip within the scope of cable clip hanging point change due to the bending Angle and the rigidity of the incremental,combined with the flexural stiffness of cable and its average tensile stress of the existing theory and experimental study,the approximate fitting the flexural stiffness of main cables and the relation between the tension,and reference to the UL(Update-Lagrange)processing method considering bending incremental geometric stiffness of column type,In combination with the nonlinear coordinate iterative method(similar to the TL(Total-Lagrange)),a hybrid incremental iterative numerical calculation method for the main cable shape and internal force in the construction process is established.Based on engineering examples,this paper compares this method with the traditional methods of cable,rod and beam used in the design and calculation of the main cable shape,analyzes the influence of the bending rigidity of the main cable on the line shape and internal force in different construction stages,and quantifies the influence of the bending effect of the parallel wire main cable on the main cable during the construction period.Through the above studies,it can be concluded that there is a certain difference between the calculation results of the main cable shape and internal force considering the bending stiffness of the main cable in the construction process of long-span suspension bridge and the calculation results without considering the bending stiffness of the main cable.In the future construction design of long-span suspension bridge,if the characteristics of the bending stiffness of the main cable can be truly considered,the whole construction process will be more accurate and safe.