Experimental Study On Mechanical Performance Of Steel-concrete Bonding Section Of Self-anchored Suspension Bridge With Mixed Beam

Self-anchored suspension bridge with mixed beam has developed rapidly in highway bridges because of its advantages,such as light weight and strong spanning capacity.As the key structure of self-anchored suspension bridge with mixed beam,the stress of steel-concrete bonding section is complex.In addition,the theoretical studies on the mechanical performance,force transfer mechanism and calculation theory of flexural capacity of steel-concrete bonding section is still insufficient.Through the negative moment bending test of steel-concrete bonding section,combined with finite element analysis and theoretical analysis,the negative moment bending performance and calculation theory of steel-concrete bonding section were studied and analyzed in detail in the paper.The main research contents and conclusions are as follows:(1)The stress states of the steel-concrete bonding section of self anchored suspension bridge under the combination of maximum axial force,maximum shear force and maximum bending moment load(negative bending moment)were analyzed,respectively.The results show that the most unfavorable load condition of the bonding section is maximum bending moment load combination condition,accordingly,the loading mode of model test was analyzed.(2)Based on the finite element stress analysis of the steel-concrete bonding section of the real bridge,a 1:3 scale model of the steel-concrete bonding section(long×wide×height:7 m× 1.833 m×1.2 m)was designed,and the four point bending negative moment bending test was carried out.The research shows that the residual displacement ratio is 0.7%under the design load condition.The test model is in the elastic stage.Under this condition,the structure of the steel-concrete bonding section is reasonable,safe and reliable.Under the condition of overload,the residual displacement ratio is 19%,there are some interface slip between steel and concrete are observed and micro cracks in the bonding section,and the structure has entered the elastic-plastic stage.Under this condition,the material stress of the bonding section still meets the requirements,and the stiffness degradation is not obvious.Under both design load and overload conditions,the angle effect caused by deformation of steelconcrete bonding section is small,and the stiffness transition is stable.(3)The stress of the top and bottom steel plate of the steel-concrete bonding section decreases gradually from the transition section of the steel beam to the concrete part.The web stress decreases gradually in the process of transferring from the transition section of steel beam to the bearing plate.In the process of transferring from the bearing plate to the concrete of the bonding section,the stress increases with the increase of rows of welded studs.The relative slip of steel and concrete in the bonding section is not large(not exceed 0.25 mm).The steel-concrete bonding section has reasonable force,smooth force transmission and good deformation coordination.(4)The bending moment borne by each part of the section was calculated by using the measured stress in the steel-concrete bonding section.The force transmission mechanism of the steel-concrete bonding section was analyzed.The research shows that the bearing plate accounts for about 51.24%,which is the main force transmission component of the steel-concrete bonding section and the force transmission of other components accounts for almost the same proportion.(5)Based on the assumption of plane section and the calculation principle of bearing capacity in relevant codes,the flexural bearing capacity(cracking moment and ultimate moment)of the steel-concrete composite section was calculated by using the conversion section method and load equivalent.The moment curvature analysis of the steel-concrete composite section was carried out,and the calculation method of yield moment of prestressed steel-concrete composite section is proposed.The difference between the theoretical calculation value of flexural capacity and the finite element analysis value is no more than 10%,which is in good agreement with each other and the theoretical calculation results are biased towards safety.