UTILIZATION OF STEEL FIBRES IN DIAGONALLY REINFORCED CONCRETE COUPLING BEAMS AS ADDITIONAL TRANSVERSE REINFORCEMENTS

The purpose of this study is to investigate the effects of transverse reinforcement such as crossties or steel fibers on the cracking and hysteretic behaviors of diagonally reinforced coupling beams aligned vertically over coupled special structural walls. Four 1/3-scale short beams were made and tested under cyclic shear in a double curvature condition. All specimens have the same reinforcement configuration except for transverse reinforcing details and the clear span length-to-section depth ratio (ln/h) of 2. Control coupling beam (CCB) was designed with full confinement of diagonally reinforced concrete beam section based on the seismic design provisions of the ACI 318-14 Code. The other specimens include simplified transverse reinforcement to improve the constructability while retaining adequate strength and ductility. Test results revealed that transverse reinforcement in the diagonally reinforced coupling beams have a significant effect on the cracking and structural behaviors. For fully confined coupling beams with diagonally oriented reinforcement and without crossties and hoop legs, the addition of steel fiber at volume fraction of 0.75% to concrete provides equal cracking and structural behaviors as compared to those of diagonally reinforced coupling beam with full confinement details.