Material Behavior Of Steel-Concrete-Steel Panels Under Biaxial Tension Compression

A Steel-Concrete-Steel(SCS)is a composite panel in which concrete is sandwiched between two steel plates.Face steel plates are connected with core concrete by headed shear studs and with each other by steel ties.These connecting elements also minimize the slip at concrete steel interface and to resist the buckling of the steel plate.Due to its robust design for seismic,blast and impact loads,SCS structures have been used for nuclear powerplants,high rise buildings,defense and off-shore structures.In SCS,lateral expansion in concrete and steel due to the applied compressive stress is different due to the difference in their Poisson ratio.As a result,a compressive stress state can develop in concrete in principle tensile direction.This compressive stress,a confinement in concrete,in tensile direction exists along with the softening effect.And,when the confinement exceeds the effect of softening,then an increase in peak compressive stress as well as compressive strain can be observed.Stressstrain relationship of concrete in compression is modified to incorporate these behaviors.The composite action of steel plate and concrete also results in an unfamiliar uniaxial behavior of concrete in tension.When the confinement provided by the steel plate,compressive loading in tensile direction,exceeds the applied tensile load,an unloading of concrete accompanied by decreasing uniaxial tensile strain can be observed.To explain this unloading behavior of concrete,a modified uniaxial strain-stress relationship of concrete in tension is proposed.Moreover,when plastic flow of steel plate under biaxial loading is taken into consideration,it can reach a higher stress than the yield strength of steel under uniaxial loading condition.These consideration with improved performances of concrete and steel plate would help to better understand the behavior of composite action in SCS panels.Thus modified stress-strain relationship of concrete is used to predict the material behavior of SCS panel using an iterative procedure.The predicted behavior of SCS compared with the experimental results which showed a good agreement with each other.