In the Asian region, high-rising apartment buildings constructed in areas with high risk of earthquake and utilized coupled shear wall system as a major lateral force resistance system are required recently to apply special detail to the walls and coupling beams. Coupling beams with a small span-to-depth ratio and high shear stress, in particular, are required to reinforce with two intersecting group of bars symmetrical about the mid-span. In South Korea, however, apartment buildings are constructed using coupling beams with about 200 mm thickness, the same as the wall thickness. In this case, the coupling beams have already complicated bar arrangement and are hardly workable in the field. When applied in connection with walls with special detail, bar arrangement is too complicated especially in the joint between the coupling beams and walls to be constructed in the field. To solve such a problem, this study reports the seismic performance evaluation results of a new type of reinforcement detail (DSB detail) that replaces the reinforcement with two intersecting groups of diagonally placed bars symmetrical about the mid-span with single diagonally oriented reinforcement and substitutes tie force for some part of the force upon the diagonally oriented bundle-formed reinforcements. As a test result, the specimens with DSB details were found to have a similar deformation capacity, energy dissipation capacity and low strength reduction and stiffness reduction, compared with the diagonally bundle-formed reinforcement. DSB stirrups and ties are deemed to be a practical alternative to replace the hoop of diagonally bundle-formed reinforcement, which is to constraint concrete in coupling beams.

Keywords: Coupling beams, Seismic resistance, Modified diagonally Oriented reinforcement