Effects of geometric and material parameters on failure modes of SC elements

A steel-concrete-steel composite (SC) element resembles double skin sandwich composite structure in which the concrete core is in-filled between steel skins. Mechanical shear connectors connect the skins and they are embedded in concrete. These connectors transfer shear forces and have an important role in performance of composite element. SC element is prone to different failure modes such as flexural failure, de-bonding between steel plate and concrete, and shear failure. There are 3 aims of the thesis to study the effects of geometric and material parameters on the failure modes of SC elements via finite element (FE) method. Six SC beam specimens are used to examine failure modes in this research. The first two specimens are configured to a four-point bending test with the intention of obtaining flexural failure. The remaining specimens are configured to a three-point bending test with the intention to obtain a shear failure. Based on characteristics of the specimens, models are created and analysed with the aid of commercial Abaqus/Explicit FE software. A quasi-static analysis is accomplished to replicate the experimental behaviour of the specimens. The results of experiments and simulations are compared to validate the models. Failure modes in experiments and simulations are similar. Specimen may fail due to yielding of the tensile steel plate followed by buckling of the compression steel plate or due to vertical shear cracks in the concrete followed by yielding of the shear connectors. According to the parametric study, the failure of SC beam in bending is affected by thickness of tensile steel plate as well as stud geometry. Failure of SC beam in shear is affected by stud geometric parameters. With increasing tensile plate thickness in bending, the beam fails only because of yielding of tensile steel plate. Geometric parameters and position of studs significantly affect the end slip between concrete and steel plate in both bending and shear failures. Although magnitude of ultimate load is different, the failure modes of SC beams considered in this study are not affected by material properties of steel plates in bending and material properties of tie bars in shear