Experimental study and model of steel plate concrete composite members under tension

Steel-concrete composite tension is a widely observed mechanical behavior in both reinforced concrete (RC) members and steel plate concrete (SC) composite members. Because the structures utilize both steel and concrete materials, and more importantly, the tension, flexure, shear and torsion loads can always be decoupled into a steel-concrete composite tension issue on the principle tensile direction and compression issue in the principle compression direction. However, the steel-concrete composite tension issue has not been thoroughly studied because of the complex fracture mechanism of concrete and the behavior of the steel-concrete interface. Thus, in this study, the tensile force transfer mechanism of the SC panel is investigated theoretically, experimentally, and numerically. Six SC specimens are tested. The tension-stiffening, confining-stiffening, and tension-stiffening degradation are investigated. Equivalent constitutive laws are developed. Based on experimental test results, the SC panel under uniaxial tension exhibit notable tension softening of concrete and tension stiffening of steel plate, which were observed in RC members. In addition, a significant confinement effect was observed due to the difference in Poisson's ratio between steel plate (0.3) and cracked concrete (close to 0). Therefore, the steel plate is under a biaxial tension and the cracked concrete is under compression in the transverse direction due to composite action. Due to tension stiffening, the ultimate tensile capacity and effective stiffness of SC panels are significantly increased compared to that of the steel section. The uniaxial constitutive models of steel and concrete are proposed based on calibration of test results, which include the test observations of tension confinement and stiffness degradation simultaneously.