Research On Bending Capacity Of Prefabricated Truss-type Steel-reinforced Concrete Box Girder

Truss-type steel reinforced concrete box girder is a new type of steel-concrete composite member formed by replacing longitudinal reinforcement with lower chord angle steel and replacing stirrup with web bar.Compared with ordinary reinforced concrete box girder,the truss-type steel reinforced concrete box girder combines the advantages of the truss steel structure and the section steel concrete structure.The truss-type steel reinforced concrete box girder structure can be prefabricated in factory,then transported to the construction site and anchored by welding or bolt,and then supplemented by a small amount of wet work to form a whole.At present,the bridge structure is continuously developing towards long-span direction,and disease problems of reinforced concrete bridges are increasingly prominent.The reinforced concrete box girder in the main girder roof,flange plate and other components can easily produce transverse cracks,thus affecting the durability of the structure and increasing the difficulty of late maintenance.The application of truss-type steel reinforced concrete box girder in long-span bridge structure can effectively improve the bearing capacity and durability of the bridge,and has important significance for promoting the development of bridge structure to long-span,large bearing capacity and industrial construction direction.At present,the research of steel reinforced concrete box girder is still in its infancy in China,and the theoretical research of steel reinforced concrete box girder is not very mature.Therefore,the flexural behavior of steel reinforced concrete truss-type box girder is studied in this paper.Six truss-type steel-reinforced concrete box girders are designed and fabricated for bending tests in this paper.The load-displacement curves and angle steel load-strain curves are investigated,and the crack load,yield load and ultimate load of the specimens are obtained.The finite element software ABAQUS is used for nonlinear analysis of bending behavior,and the results are compared with the experimental results.Based on the experimental results and the finite element analysis results,a formula for calculating the bending capacity of steel reinforced concrete truss-type box girder is proposed.The main research results are as follows:(1)The lower chord of truss-type steel reinforced concrete box girder is firstly subjected to tensile yield,then the concrete in compression zone is crushed and the compression angle steel yields,and the member is in the state of suitable reinforcement failure.(2)The ultimate bearing capacity of steel reinforced concrete box girder with truss-type is larger than that of steel reinforced concrete box girder with lower chord angle steel.The influence of the distance between vertical web members in pure bending section and the presence or absence of oblique web members in pure bending section on the ultimate bearing capacity of test box girder is not obvious,and the box girder of test specimen generally accords with the plane section assumption.(3)Based on the finite element software ABAQUS analysis,the failure form,load-deflection curves and angle steel load-strain curves of the test box girder are obtained,which are in good agreement with the test results and verify the accuracy of the finite element simulation.The results show that the larger the yield strength of the lower chord angle steel is,the larger the ultimate bearing capacity of the box girder is.The increase of the concrete strength and the size of the upper chord angle steel has no obvious effect on the ultimate bearing capacity of the truss-type steel reinforced concrete box girder.(4)Based on the normal section bearing capacity formula of I-shaped reinforced concrete beams,the bending bearing capacity formula of truss-type steel reinforced concrete box girder is derived,which is in good agreement with the test results and simulation results,and can be used for calculation and analysis.