Seismic Performance of Diagonally Reinforced Concrete Coupling Beams with Penetrations

An efficient structural system for tall buildings to resist earthquake and wind loads consists of reinforced concrete structural walls linked by coupling beams, where the coupling beams act as the primary fuses to limit force demands on capacity-protected elements and actions and provide reliable energy dissipation mechanisms. Penetrations (openings) horizontally through coupling beams are often needed to accommodate piping and cables-for example, into a concrete elevator core, which could potentially have adverse impacts on coupling beam performance. ACI 318-19 is silent on whether penetrations are permitted or not, and if penetrations are needed, there are no provisions on the size and location of penetrations and the additional detailing needed at the penetration regions, primarily due to the lack of experimental data. To address this issue for diagonally reinforced concrete coupling beams, this study reviews data from six Japanese experimental programs that include results on 18 coupling beams with diagonal reinforcement and penetrations. The findings indicate that the penetration size and the detailing in the penetration region play an important role in the seismic performance of the beams. Recommendations are proposed on the location and size of penetrations and the additional detailing of the penetration region such that they do not adversely impact the seismic performance of the coupling beam.