Invesigation On The Influence Of Transverse Strengthening Of Composite Truss On The Mechanical Properties Of Beam Bridges

In the early construction of the T-beam bridge and the small box girder bridge,the midspan diaphragm was not provided due to the small design load.With the increase of the service life and the problems of vehicle overload,the horizontal connection of the bridge has damage or even failure.The weakened working capacity is not suitable for the normal use of the bridge.In order to solve the problem of insufficient horizontal connection of bridges,this paper puts forward a new reinforcing method with two composite truss symmetrically arranged in the middle of the span.After the impact on the mechanical properties of the bridge,the comprehensive evaluation of the reinforcing effect was carried out.The main research contents and conclusions of the paper are as follows:(1)Designed a scale test of a concrete T-beam bridge with three main beams.The ultimate load,deflection,concrete strain in tension area of T-beam web,concrete strain in tension at the bottom of bridge deck slab,concrete strain in tension at the bottom of each main beam,strain of tensile reinforcement,crack width and support slip are compared under four loading conditions.The results show that the composite truss can improve the comprehensive mechanical properties of the bridge.The composite truss can improve the bearing capacity and stiffness of the bridge structure,in which the ultimate bearing capacity is increased by 11.0%and the deflection of the main girder is reduced by 39.7%.It has a good restraining effect on the crack development,which can significantly reduce the bearing slip of the specimen and improve the overall mechanical performance among the main beams.(2)Combining the reality of a small box girder bridge,through the analysis of the bottom strain and the maximum dynamic displacement of each main girder before and after the composite truss reinforcement in bridge operation.The results show that the composite truss can significantly reduce the strain variation of the main girder near the heavy roadway and the wet joints,significantly reduce the maximum dynamic displacement of the main girder bottom,and improve the transverse stiffness of the box girder bridge.(3)The ANSYS finite element software was used to establish the finite element model of the 30m-span concrete small box girder bridge,the deflection and lateral distribution coefficient of each main beam before and after the composite truss reinforcement were analyzed.The results show that the composite truss can significantly reduce the deflection of the main girder near the loading point,and the maximum reduction of deflection is 10%.After reinforcement,the transverse distribution coefficient distribution of the main girder is more uniform.The composite truss can improve the transverse stiffness of the small box girder bridge,and enhance the ability of the main girder to bear the force together.