Cyclic Behavior of Retrofitted-Reinforced Concrete Coupling Beams

Coupling beams are utilized in shear walls to connect one shear wall to another. A high amount of reinforcement is required in these beams to resist the forces developed during a seismic event. Generally, the main reinforcements in a coupling beam are provided in a diagonal manner but due to the high reinforcement content, the constructability and construction time management becomes an issue. Past earthquakes and experimental studies on coupling beams have shown that these members are subjected to high shear forces and it becomes imperative that the members should have adequate shear reinforcement. To reduce the reinforcement concentration and enhance the ductility of coupling beam, an experiment was conducted on two coupling beam specimens, (a) reinforced concrete specimen with the double-beam-type reinforcement arrangement, and (b) steel fiber-reinforced concrete specimen with again the double-beam-type reinforcement arrangement. Both beams were geometrically identical and were subjected to a reversed-cyclic loading up to 6% lateral drift. The steel fiber-reinforced concrete specimen showed higher resistance than the reinforced concrete specimen. The failure patterns observed in steel fiber-reinforced specimen showed distributed microcracks, whereas the reinforced concrete specimen showed wider and fewer numbers of cracks.