Seismic performance of special RC coupling beams with modified diagonally oriented reinforcement

Abstract

In the Asian region, high-rising apartment buildings constructed in areas with high risk of earthquake and utilized coupledshear wall system as a major lateral force resistance system are required recently to apply special detail to the walls andcoupling beams. Coupling beams with a small span-to-depth ratio and high shear stress, in particular, are required to reinforcewith two intersecting group of bars symmetrical about the mid-span. In South Korea, however, apartment buildings areconstructed using coupling beams with about 200 mm thickness, the same as the wall thickness. In this case, the couplingbeams have already complicated bar arrangement and are hardly workable in the field. When applied in connection with wallswith special detail, bar arrangement is too complicated especially in the joint between the coupling beams and walls to beconstructed in the field. To solve such a problem, this study reports the seismic performance evaluation results of a new typeof reinforcement detail (DSB detail) that replaces the reinforcement with two intersecting groups of diagonally placed barssymmetrical about the mid-span with single diagonally oriented reinforcement and substitutes tie force for some part of theforce upon the diagonally oriented bundle-formed reinforcements. As a test result, the specimens with DSB details were foundto 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 alternativeto replace the hoop of diagonally bundle-formed reinforcement, which is to constraint concrete in coupling beams.