Nonlinear Behavior of the Concrete Core of the Diagonally Reinforced Coupling Beams

Abstract

Coupled shear walls with coupling beams are constructed because of openings such as doors, windows, or other installations that are left behind due to functional reasons in shear walls. In coupling beams having a ratio of span-to-depth less than two, shear fracture occurs rather than flexural fracture. In order to meet the shear force and the bending moment formed by the coupling beams, diagonal bundles are used in the coupling beams. Diagonal reinforced coupling beams are generally preferred because diagonal reinforced coupling beams exhibit better behaviour than conventional reinforced coupling beams. The diagonal reinforcement bundles have to be confined by transverse reinforcements prescribed in the codes. Confined concrete in the diagonal reinforcement bundles has stress-strain characteristics that are distinctly different from those of plain concrete. The effects of longitudinal and transverse reinforcement ratios on the stress-strain behaviour of confined concrete inside the diagonal reinforcement bundles were investigated. Fifty-four reinforced concrete coupling beams with different confining parameters of the diagonal reinforcement bundles and different variables were analysed using the program. It was demonstrated that the strength and the maximum strain of the concrete inside the diagonal reinforcement bundles increase with the reinforcement ratio of the confinement reinforcement. The increase in the diameter of the transverse reinforcement and the decrease in the spacing of the transverse reinforcement diagonal bundles, increase the confining effect, strength, and ductility in the concrete sections. The increase in the ratio of transverse and diagonal reinforcement significantly affects the seismic behaviour of the coupling beams.