Effects of plastic hinges on partial interaction behaviour of bolted side-plated beams

Slips of mechanical connectors in steel plate reinforced concrete (RC) structures can significantly affect the load-carrying capacity of the structures. The difference in deformation between the steel plate and the reinforced concrete counterpart is known as partial interaction. In this study, the flexural behaviour of bolted side-plated (BSP) reinforced concrete beams was investigated experimentally. Two new deformation-based parameters, namely the strain factor and curvature factor, were introduced to quantify the degree of partial interaction between the RC beam and the steel plates. The experimental results revealed that the degree of partial interaction between RC beams and steel plates could be reduced by as much as 50% when the BSP beam proceeded from a linear to a non-linear stage in which plastic hinges have formed in critical sections. Consequently, the load-carrying capacity was reduced by up to 30% of the theoretical additional strength provided by the bolt–plate system, which is more than double the allowance proposed previously in the literature. The under-estimation of the effect of partial interaction in composite structures can result in unsafe design.