Use of innovative shear connectors in construction and rehabilitation of steel-concrete composite beams

Composite beams are now widely used in infrastructure such as steel-framed bridges, buildings and stadiums. Most of these composite beams have been built with welded shear studs due to the availability of detailed research on their properties, and standard design methods for using them. However, as composite beams age, their ability to withstand current and future loading requirements deteriorates. On the other hand, existing composite beams incorporating welded shear studs cannot be easily retrofitted to prolong their useful service life, nor can the steel and concrete components of these beams be separated securely to be reused due to the permanent fixing mechanism of the welded studs. This thesis attempts to investigate the design and behaviour of composite beams with innovative bolted connectors. The novel fixing mechanisms of these bolted connectors may enable composite beams to be retrofitted reliably and also be disassembled without much effort. With these aims in mind, the emphasis in this thesis is primarily on the following issues: investigating the ability of bolted and welded-stud connectors to achieve composite action in normal and retrofitted composite beams investigating the effects of time-dependent creep and shrinkage of concrete on the behaviour of composite beams incorporating either bolted connectors or welded-stud connectors investigating the feasibility of dismantling composite beams subjected to serviceability loading by removing connector bolts. This thesis comprises many experimental and numerical studies, including the flexural behaviour of composite beams with bolted and welded-stud connectors as well as the load–slip behaviour of the connectors. In addition, the behaviour of the beam and push-out test specimens in their respective experiments was simulated using finite element models developed in ABAQUS software. An extensive parametric study was also carried out using these models in order to gain further insight in to the behaviour of composite beams with bolted and welded-stud connectors in composite steel–concrete beams. The outcome of the experimental and numerical analyses is satisfying and also contains design recommendations. It is strongly hoped that the findings of this study may provide an important basis and guidelines for designing and constructing more robust and sustainable composite beam systems in the future