Enhancing the Seismic Performance of Moment Frames Using a Dumbbell-Shaped Rocking Shear Wall with Energy-Dissipating Devices

Abstract

Studies have shown that repairing damaged structures and rebuilding them after an earthquake, especially in densely populated cities, can impose severe financial and economic pressures on countries. To address this, rocking systems have been developed to improve the seismic performance of structures, which allow the rocking wall to engage in rocking motion while elastic devices provide self-centering and dissipate seismic energy, resulting in less structural damage and reduced repair costs. However, there are limitations concerning common rectangular-shaped rocking walls, including high use of materials and difficulty in controlling large displacements. This study investigated the use of modified rocking shear walls attached to 3- and 9-story moment-resisting frames by reducing the thickness of the wall, adding border elements in the form of dumbbells, and modifying the prestressing ratios of the posttensioning cables. The models were designed according to seismic codes and analyzed through nonlinear time-history analysis when subjected to 14 sets of modified near-field ground motions. It was concluded that the modified system reduced the amount of concrete used by 36% and 20%, increased the fundamental period by 19.3% and 26.6%, and increased the base shear by 8% and 20% in 3- and 9-story models, respectively. Moreover, the proposed method effectively reduced the overall interstory displacements in the midrise model by 11%, whereas the low-rise model had 8% higher interstory displacements. This indicates that the proposed method can be effective for deployment in mid- to high-rise buildings because it can control the upper floors’ displacements.