Research On Membrane Model Of Steel-concrete-steel Sandwich Composite Panel For Nuclear Power Plants

Steel-concrete-steel(SCS)sandwich composite structure is formed by the outer steel plates and the inner concrete,and the combination of the steel plates and concrete is realized by tie bars and shear studs.SCS composite structure has been widely used in nuclear facilities,offshore platforms and core tubes of high-rise buildings in recent years due to its high bearing capacity,good ductility,impact resistance and modular construction.The above structures are composed of many SCS panels.This paper will study on the in-plane mechanical performance of SCS panel.In-plane biaxial compression-tension loading tests on nine SCS panels were carried out in this paper.The load-strain relationship and the failure mode of the specimens,and the constraints of concrete were analyzed.All the specimens showed excellent bearing capacity and ductility.Baesd on the smeared Poisson's effect of materials and test results,the composite effect of the steel plates and concrete in SCS panels was analyzed.Three types of stress state changes of steel plates and concrete under different compression-tension loading mode were summarized.The analysis shows that compression softening effect and confinement strengthening effect coexist in the concrete in SCS panels.The compressive stress-strain relationship of concrete considering both compression softening effect and confinement strengthening effect is established in this paper.A method for determining the elastic modulus of concrete in the tensile direction of SCS panel and the mathematical formulas of the biaxial smeared Poisson's ratios of cracked concrete are also proposed.By using the ideal elastoplastic constitutive relation of the Prandtl-Reuss model in steel plate,a membrane model suitable for proportional loading calculation of SCS panel is established and a numerical calculation program is compiled.The numerical model calculation results are in good agreement with the existing experimental results,and also,the rationality and accuracy of the membrane model are verified.Based on the numerical model,a finite element calculation model suitable for ABAQUS software is established by adjusting the stiffness matrix of concrete.This model shows good applicability for predicting the ultimate bearing capacity of SCS panles and the stress-strain relationship of both concrete and steel plates in large compression-tesion loading mode.