Role of hoops on seismic performance of reinforced concrete joints

Abstract

Four exterior reinforced concrete beam–column joint specimens with varying amounts of joint hoop reinforcement are constructed and tested under reverse cyclic loading to assess their performance during earthquakes. Headed bars are used in all the specimens. Various parameters such as crack pattern, hysteresis behaviour, modes of failure, energy dissipation, displacement ductility, stiffness degradation and maximum shear strength are studied. The effectiveness of headed bars with short embedded length terminating in the exterior beam–column joint is assessed. As headed bars have the advantage of transferring a more uniform distribution of compressive stress to the concrete at the headed end, they enable the development of a wider compressive strut in the joint, which enhances the joint shear strength under seismic loading. This makes it possible to reduce transverse reinforcement in joints when using headed bars as longitudinal beam reinforcement.