Keyed shear connections with looped U‐bars subjected to normal and shear forces Part I: Experimental investigation

Shear connections in prefabricated concrete buildings are important for the structural performance in both the serviceability and the ultimate limit state. A normal force has a large impact on the shear strength and deformation capacity, however, no experimental record includes compression–shear and tension–shear interaction. This article presents an experimental investigation of keyed shear connections with looped U‐bars subjected to combinations of shear and normal forces. The tests were performed in a custom‐built double frame, where forces could be applied in two perpendicular directions, which was utilized to introduce normal and shear forces. The load combinations ranged from pure tension, over shear–tension and pure shear to shear–compression. The results include load–displacement relationships supplemented by digital image correlation (DIC) results to exemplify the experimental findings and underline the influence of a normal force on the behavior. It was found that a compressive normal force has a positive influence on the shear capacity in the entire displacement domain tested. A tensile normal force reduces not only the shear capacity but also the deformation capacity of the connection. The ultimate shear load was associated with failure in the joint mortar, which in all cases took place as a local key corner shearing. This article constitutes Part I of the investigation, while Part II introduces rigid‐plastic modeling of the ultimate load carrying capacity.