Flexural Behavior of Precast Concrete Slab Connections using Loop Steel Bars and Mortar

Loop reinforcements are commonly used to connect precast concrete elements. However, the strength of the connection in the case of short overlapping lengths and mortar joints has not been discussed extensively in previous studies. Moreover, proposed equations tend to overestimate the flexural capacity of the connection. In this study, six specimens with vertical loop steel bars and mortar joints were tested. The variables were the overlapping length, bending diameter, and distance between the loop bars in a pair. The findings indicated that reducing the overlapping length and bending diameter decreased the flexural strength of the loop joint. Further, the distance between the loop bars had a negligible effect on the bearing capacity but a significant impact on the ductile performance. Three-dimensional finite element analyses were conducted to predict the mechanical behaviors of the loop connection. The numerical simulation corroborated the experiment results in terms of the load-deflection behavior and reinforcing bar strains. Finally, empirical equations were proposed to predict the flexural strength of multiple vertical loop connections.