Study On Related Problems Of Excavation Trestle Bridge Design

With the promotion of urbanization,urban buildings are becoming more and more dense and the demand for high rise buildings are increasing,which has led to more and more deep foundation pits and the narrowing of the construction site.Trestle bridge of foundation pit can relieve the tense situation of construction site,and can improve the excavation efficiency of the earthwork,so it has been used more and more widely.In order to realize the unification of the economy and safety of the project,this paper has studied some of the problems that are often encountered in the design of trestle bridge of foundation pit to provide the basis for the rational design of trestle bridge.In this paper,the structural form of common trestle bridge of foundation pit is summarized,and the equivalent load of vehicle,lateral stiffness and stability bearing capacity of the trestle bridge of foundation pit are studied.(1)Using the general finite element analysis software ABAQUS to simulate the effect of the load of earthwork vehicle on concrete beam and plate of trestle bridge,analyzing the most unfavorable distribution of wheels of earthwork vehicle,the equivalent uniformly distributed load value of the earthwork vehicle is calculated and some suggestions on the equivalent load value of the earthwork vehicle of the beam and the plate are given.It can be seen from the analysis that,with the change of thickness,the equivalent uniformly distributed load of earthwork vehicles on panel of trestle bridge of foundation pit changes with the thickness,but the variation range is not large.With the increase of plate span,the equivalent uniformly distributed load of earthwork vehicles on the trestle panel gradually decreases.(2)The finite element model of trestle bridge of foundation pit is established by means of the finite element software ANSYS.On this basis,the influence of the column bracing system on the lateral stiffness of the trestle bridge is analyzed.According to the change of the lateral stiffness of trestle bridge with the change of the position of the longitudinal cross-bridging,the rational arrangement of the longitudinal cross-bridging is analyzed based on the actual situation.In addition,the influence of transverse cross-bridging in different positions on the lateral stiffness of trestle bridge is analyzed,and the suggestions for the arrangement of the column bracing between the columns of trestle bridge are given.According to the analysis,the longitudinal and transverse lateral stiffness of the trestle is improved obviously with the increase of the amount of column bracing.(3)The buckling load of trestle bridge with different amount of column bracing is calculated and the influence of the column bracing system on the stability bearing capacity of trestle bridge is studied through the buckling analysis of the trestle bridge of foundation pit.The analysis shows that the horizontal link can obviously improve the stability of the trestle bridge,and the stability of the trestle bridge can be greatly improved by placing a certain amount of Cross-bridging.The results may be the references to the designers of the trestle bridge.