Construction-friendly ductile shear joints for precast concrete panels

The scope of this paper is the shear capacity of in-situ cast joints between precast concrete panels. Current practice with vertical lowering of the wall panels experiences difficulties in the assembly phase, since the traditional U-bar connection requires an overlap in a horizontal plane to allow for the mounting of a vertical locking bar. Where limited space is available bending and subsequent straightening of the U-bars are required to assemble the adjacent panels, a procedure which imposes substantial ductility requirements on the reinforcement as well as some manual workload. This paper introduces a construction-friendly design with U-bars overlapping in the same plane as the panel itself. The design allows for a trouble-free vertical lowering of the panels without pre or post processing of the preinstalled reinforcement loops. Furthermore, an overall more ductile behavior of the joint is obtained. The solution is tested in a push-off experimental setup and the influence of important geometric parameters of the keyed shear joint is investigated. The first peak load carrying capacity is assessed using plasticity models, and the failure modes are identified by the use of digital image correlation. The upper bound models produce satisfactory results capturing the experimental tendencies and predicting the mode of shear failure in the shear keys.