Behaviour and detailing of coupling beams with high-strength materials

High-strength steel (HSS) has the potential to reduce reinforcement congestion and construction difficulties for coupling beams. This paper aims to investigate coupling beams using HSS diagonal bars and HSS transverse reinforcement. Four coupling beam specimens with a clear span-to-depth ratio of 2.0 were built with varying concrete materials and confinement details and tested under quasi-static reversed-cyclic shear loading. Despite using the maximum transverse reinforcement spacing that is allowed in ACI 318–19, all coupling beam specimens exhibited satisfactory seismic performance in terms of adequate deformation capacity and stable hysteretic response. Favorable performance, characterized by a greater damage control ability, larger shear strength, and deformation capacity, was achieved in specimens using high-strength concrete, especially fiber-reinforced high-strength concrete. The coupling beam specimen with confinement provided for the entire beam cross section outperformed the specimen with confinement provided for the individual diagonals. The state-of-practice design methods for coupling beams are evaluated with experimental results.