Modeling of innovative bolted shear connectors in demountable cold-formed steel-concrete composite beams: Validation of finite element model and parametric study

Composite cold-formed steel (CFS)-concrete structures have been widely used due to their benefits such as more ultimate strength, stiffness, and postponement of lateral buckling compared to bare CFS steel. Appropriate shear connectors should be used in order to establish composite performance between the CFS section and the concrete component. Traditional welded-stud connectors cannot be used due to the low thickness of the CFS members. Therefore, in this paper, a novel composite connection consisting of bolted-shear connectors embedded in grout is proposed and its performance is investigated by numerical models of push-out tests. A three-dimensional finite element model of the composite connection considering the non-linearities of the material and geometry, interfaces, and interactions between the components and materials are developed and verified against the results of the experimental study. After that, an extensive parametric study is carried out and the effects of different parameters, such as bolt strength and diameter, CFS section thickness, concrete compressive strength, and pretension load on the structural behavior of this type of composite connection are investigated and discussed in detail. It is concluded that the behaviour of the composite connection is significantly influenced by bolt strength and diameter, CFS section thickness and strength. The available design models provided in different provisions, including AISI, EC4 and AISC that predict the shear load capacity of connections with preload bolted shear connectors are reviewed and assessed. The results show that the ultimate shear load capacity values predicted by these provisions were found to be relatively less accurate. Finally, a new and more accurate design equation based on the results of this study is then proposed.