Tensile capacity of loop connections grouted with concrete or mortar

This paper presents a study of grout failure in symmetric U-bar loop connections loaded in tension, with focus on the performance of two grouting materials – concrete and mortar. The study contains an experimental investigation as well as a rigid-plastic modelling of the tensile capacity. The test specimens consisted of symmetric ‘2-on-2’ loop connections transversely reinforced with a double T-headed rebar. The amount of transverse reinforcement was varied, including the limiting cases of specimens with no transverse reinforcement, as well as connections with sufficient transverse reinforcement to allow yielding of the U-bars. The experimental work showed that connections grouted with concrete performed better than the connections grouted with mortar. In the theoretical models, the difference in tested capacity is explained by the difference in the internal angle of friction and in the softening behaviour of concrete as compared with mortar.