Study On The Mechanical Behavior Of Steel-Concrete Composite Beam During The Normal Use Stage

In this paper,the shear connector of composite beam bonding layer is analyzed theoretically,by means of beam test and finite element simulation,the mechanical behavior of steel-concrete composite beam in normal use is studied,the variation of steel box girder roof strain,steel box girder web strain,stud strain,concrete slab strain,joint surface strainand vertical displacement at different positions of beam body under symmetrical loading and partial load loading are studied.The conclusions are drawn by beam test and finite element software analysis:(1)In the course of loading grade,the steel beam,concrete and bolt in the composite beam are in the elastic stage,the strain gradually increases with the increase of load grade,after unloading is completed,the strain value is basically restored to the initial state,the strain of steel box girder roof and concrete are under compression,under the same load,the mid-span section strain is the largest and the fulcrum section is the smallest;(2)The bolt mainly bears the tensile stress in the bearing process of the steel-concrete composite beam,but the compression strain is small after unloading;at the midspan position,the bolt strain is the maximum and the fulcrum section is the minimum.In the limit state of normal use,there exists deformation difference between steel beam and concrete slab,but the difference is small;(3)As the load grade of composite beam increases,the vertical displacement ofsteel-concrete composite beamincreases linearly.The vertical displacement is the largest at the midspan section and the smallest at the fulcrum section;in the process of loading,the steel-concrete composite beam has a certain deflection deformation,but after unloading,it is basically restored to the original position.(4)In the loading process of steel-concrete composite beam,the roof strain of the steel box girder with the same horizontal plane presents the rule that the deformation on the outside of the roof of the steel box girder is greater than that on the inside,maximum strain difference of mid-span section,in other words,the shear lag effect is most obvious at the midspan;(5)In the finite element analysis,the stress of steel beam roof are dominated by compression,at the fulcrum position,the tensile property is smaller,and the stress and strain decrease gradually from the mid-span to the fulcrum position.The stress and strain of steel girder underside show tensile behavior,the tensile stress at the mid-span section is the maximum,it can be used as the value of whether the steel beam reaches the yield state,the tensile stress at the fulcrum position is almost zero,Under the action of mid-span load,the vertical displacement value of mid-span is the maximum,which is zero at the fulcrum,both ends of the composite beam warp upward,but its value is small.Comprehensive analysis of stress and strain of steel girder roof and floor with load,when the load of a single loading point is 200 k N,steel-concrete composite beams are under elastic stress and do not yield.