Study On Mechanical Behavior Of Main Girder Of Steel-Concrete Composite Girder Cable-Stayed Bridge Considering Interface Slip Effect

The steel-concrete composite girder bridge is a kind of bridge structure which connects the steel beam and the concrete bridge deck as a whole by the shear connector and receives the force together,which gives full play to the high compressive strength of the concrete bridge deck material and the high tensile and compressive strength of the steel beam material.As for steel-concrete composite girder bridge,the connection between steel beam and concrete bridge deck determines the overall mechanical performance of steel-concrete composite beam,and the interfacial slip effect at the interface of steel-concrete composite beam will affect the overall mechanical behavior of composite beam deck and steel beam.As a kind of steel-concrete composite structure bridge,the steel-concrete composite girder cable-stayed bridge has the characteristics of composite girder bridge and also has the characteristics of large span and complex force of cable-stayed bridge.In this paper,the mechanical performance of the steel-concrete composite girder cable-stayed bridge considering the interface slip effect is mainly studied.The work and results are as follows:(1)Analysis on the mechanical performance and bearing capacity of shear studs for the specimens of expansive concrete.Through 6 groups of push-out tests,the shear bearing capacity,load-slip law and mechanical failure characteristics of the push-out test specimen of expansive concrete were analyzed,and the influences of shear stud diameter,shear stud length and concrete expansive agent on the shear strength of the shear stud were also analyzed.Through test and analysis,it can be concluded that the expansive concrete material has a small impact on shear behavior of shear stud,and the shear stud load-slip rule and mechanical failure characteristics of the expansive concrete material specimen are similar to those of the ordinary concrete material.The diameter of shear stud is the most important factor affecting the shear performance of the shear stud for the specimens of expansive concrete,while the length of shear stud has little influence on the shear strength of shear stud.(2)Numerical simulation study on push-out test of expansive concrete specimens.The finite element model was established to verify with the experimental results,and the influence law of concrete strength,shear stud size and other factors on shear bearing capacity and shear stiffness of shear stud was further analyzed,and the stress and strain variation rules of shear stud and concrete were analyzed.It is concluded that the shear bearing capacity of expansive concrete specimens is directly proportional to the cross-sectional area of the shear stud,and the shear stud length has little influence on the bearing capacity and load-slip curve of the shear stud.The maximum axial stress is distributed within about 4 cm of the root of the shear stud,and the maximum shear stress is within 0.5 cm of the root of the shear stud.The closer the distance from the root of the shear stud,the faster the stress increases and the earlier the yield stress is reached.(3)Numerical simulation study on the influence of interface slip effect on mechanical behavior of main girder of steel-concrete composite girder cable-stayed bridge.Based on the project of the Yellow River highway bridge on the Qingdao-Lanzhou line,the finite element model of steel-concrete composite girder cable-stayed bridge is established.According to the actual bridge conditions,two representative construction stages and two representative load conditions of the bridge are selected to analyze the influence of the interface slip distribution of composite girder and the interface slip effect on the mechanical performance of the main girder.It is concluded that the maximum value of interfacial slip of composite gieder is distributed in the middle span.The interface slip of composite girder will increase the deflection of the main girder cable-stayed bridge and adversely affect the force on the concrete slab and steel box girder of composite beam.(4)Practical bridge test study on the main girder of steel-composite cable-stayed bridge during the construction stage.Based on the project of the Yellow River highway bridge on the Qingdao-Lanzhou line,the strain and temperature data of the wet joints of the bridge deck and the steel box girder at the construction stage of the bridge were collected by embedding strain meters in the key sections of the bridge for analysis and comparison.It is concluded that the strain change of the measuring point inside the wet joint is inversely proportional to the temperature change of the measuring point approximately after 7 days of concrete pouring.The strain of wet joints at different positions is also different,and there are relatively weak positions.The construction condition also affects the stress and strain of wet joints.Temperature variation is an important factor affecting the strain and stress of steel box girder.There is a relative strain difference between the bottom surface of the wet joint and the corresponding steel box girder roof in the bridge direction and thechange of the relative strain difference is roughly proportional to the temperature.