Effects of coupling ratios on the behavior of coupled walls

Coupled walls are often used in mid-rise and high-rise structural systems to provide adequate lateral stiffness and strength to resist earthquakes. A coupled wall is composed by two or more structural walls connected by coupling beams. Under severe earthquakes, coupling beams are expected to undergo large deformation reversals. Therefore, they have to possess sufficient strength and ductility capacity. The paper presented herein investigates the influence of coupling ratio on the seismic behavior of coupled walls using nine coupled walls with different designs; coupling ratio is defined as the proportion of the moment resistance generated by coupling actions to the overall overturning moment. The behavior of the various coupled walls is investigated using nonlinear pushover analysis. It is found that for coupled walls with small coupling ratios, the resulting coupling action might not be sufficient to connect individual structural wall, thus causing excessive seismic response. On the other hand, although the coupled walls that are designed to have a large coupling ratio can reduce the base moment demand, the resulting system behavior might not satisfy the preferred yield mechanism. Based on the analysis results, the paper suggests appropriate ranges of coupling ratios for coupled walls with different heights.