The Research On Main Beam Construction Method Of Long-span Steel Truss Suspension Bridge

Steel truss girder is more and more widely used in large span suspension bridges in recent years.Steel truss girder suspension bridges are more flexible in construction scheme compared with steel box girder suspension bridges,and at the same time,the force situation during construction is more complicated.Therefore,it is necessary to study the construction scheme of steel truss suspension bridge main girders and determine the construction scheme suitable for the main girders of large span steel truss suspension bridge.This paper takes Baiyang Yangtze River Highway Bridge as the engineering background,and the main research contents and results are as follows:(1)The calculation method of the main cable analysis of suspension bridges is introduced,and the tangential stiffness matrix of beam,rod and cable units commonly used in geometric nonlinear finite elements is derived,the common calculation method of geometric nonlinearity and the solution method of nonlinear equations are described,the simulation analysis algorithm used in this paper is explained.(2)The finite element model of Baiyang Yangtze River Highway Bridge was established using BDCMS calculation program,and the rationality of the bridge state was analyzed.The construction process calculation models were established by using three different connection methods,namely,section-by-section hinged connection,section-by-section rigid connection and hybrid rigid-hinged method.The internal forces of the stiffened girders,the internal forces of the boom,the vertical displacement of the main cable and the stiffened girder alignment during the construction process were compared,and it was concluded that the hybrid rigid-hinged method was a reasonable construction method for this bridge.The rigid joint timing of rigid hinge hybrid method is studied,and the reasonable rigid joint timing is obtained through simulation calculation.(3)Combined with the forward iterative algorithm of BDCMS calculation program,a new method of temporary connection setting is proposed based on the traditional method of temporary connection setting,and a reasonable method of temporary connection setting is obtained by taking the chord stress as the control factor of temporary connection setting and using Baiyang Yangtze River Highway Bridge as the verification project.(4)The effects of the erection sequence and length of stiffened beams on the construction process were studied.Different erection sequences and erection lengths were used to establish the corresponding calculation models for the construction process,and the optimal erection sequence for the construction of large span steel truss suspension bridge was determined from the aspects of internal force of stiffened girder bars,internal force of sling,cable curve and stiffened girder alignment,etc.The influence of erection length of stiffened girder on the internal force of stiffened girder and cable curve during the construction process was discussed.(5)Based on the above reasonable stiffening beam connection mode and stiffening beam erection sequence,the influence of bridge deck erection sequence and transverse erection quantity on the internal force and alignment of stiffening beam in the construction process is studied.Through the comparison of four schemes,a better bridge deck erection scheme is obtained.