Diagonally Reinforced Concrete Coupling Beams: Effects of Axial Restraint

Abstract

Diagonally reinforced concrete coupling beams are commonly used in mid- and high-rise buildings to connect adjacent structural walls separated by openings. Under lateral loading, these beams can undergo large inelastic deformations but must retain their strength for the system to behave as desired. It is not known how or whether resistance to axial elongation of the beams, provided by the floor diaphragms and stiff structural walls, affects the strength and deformation capacity of coupling beams.

The influence of axial restraint on diagonally reinforced concrete coupling beams was investigated by comparing the results of an axially-restrained coupling beam specimen with those of a nominally equivalent control specimen tested without axial restraint but using the same loading protocol. The presence of axial restraint increased the strength of the coupling beam specimen by approximately 30%, decreased the chord rotation capacity by approximately 10%, and resulted in buckling of diagonal reinforcement at smaller chord rotations.