Behaviour of innovative demountable shear connectors subjected to combined shear and axial tension

Composite steel-concrete beams are being used increasingly in construction due to its benefits over beams consisting of the steel component alone. Composite steel-concrete beams comprise of a steel component which is under tension and a concrete component which is under compression. Shear connectors at the steel-concrete interface connect the two components together as well as resist shear forces. However, in some applications such as in composite coupling beams and infill walls, these shear connectors have to resist uplift forces in addition to shear forces. Therefore, there is a need to carry out experimental testing to investigate the performance of shear connectors under combined loading. Furthermore, the steel and concrete components of a composite beam cannot be separated without destroying the components since the shear connectors are welded to the steel beam and embedded in concrete. If the steel is to be reused, it has to be remelted which requires energy that usually comes from unsustainable sources. Hence research has been carried out on demountable shear connectors as they allow demounting and easy separation of the steel and concrete components. The performance of three types of innovative shear connectors subjected to combined shear and tensile loading was investigated experimentally. A pull-out test was first being carried out with each type of shear connector to determine the tensile capacity of each type of shear connector. This was then followed by a series of modified push tests that were carried out to determine the interaction between shear and tension loading on each type of shear connector. Tensile capacity which had been determined from pull-out tests was applied in increments of 25 % to each group followed by shear loading until failure of the shear connector was observed. A comparison of the results was carried out with shear-tension relationships for traditional headed studs proposed by other researchers. Based on the experiment investigation carried out, significant reduction in shear strength was observed when tensile force was applied. Demountable headed studs had a much higher ductility than AJAX Oneside and Hollo bolts