Evaluating the influence of detailing on the seismic performance of diagonally reinforced coupling beams

Diagonally reinforced coupling beams (DRCBs) play a critical role in energy dissipation and ductility in reinforced concrete core walls subjected to seismic forces. This study evaluates the cyclic response of DRCBs and examines potential limitations in US and Canadian design codes. A database of 51 experimental tests is compiled to assess the influence of embedded longitudinal bars (ELB), axial restraints (AR), and confinement details on force-deformation behavior. Results indicate that specimens with AR or ELB exhibit significant overstrength, which can be estimated using sectional analysis and incorporating the flexural contribution of longitudinal bars in calculations. DRCBs without AR or ELB had a median overstrength around 1.25; however, the presence of AR or ELB can increase shear forces by a further 30 to 40 percent. Specimens with low diagonal reinforcement also demonstrated reduced rotational capacity. Based on these findings, a new force design limit is proposed, and it is recommended that seismic codes introduce lower rotational limits for low-aspect ratio coupling beams to better reflect observed performance. • Developed a database of 51 tested diagonally reinforced coupling beams. • Identified overstrength trends in embedded longitudinal bars and axially restrained specimens. • Evaluated confinement and tie spacing on rotational capacity. • Compared stiffness predictions with experimental data.