Enhancing the performance of moment frames using a dumbbell-shaped rocking shear wall with additional devices

Abstract

Studies have shown that the high cost of repairing damaged structures and the time it takes to rebuild them after an earthquake, especially in densely populated cities, impose severe financial and economic pressures on countries. To solve this problem, rocking systems were introduced as new systems to improve the seismic performance of structures. In these systems, the rocking wall is allowed to rock and elastic devices are used to provide self-centering and dissipate the seismic energy. The advantages of this system include low structural damages, ease in performing structural repairs as well as reducing the costs regarding them. In the current study, the geometry of an existing rocking shear wall attached to three- and nine-story moment-resisting frames was investigated by reducing the rocking wall’s thickness in height and also by adding border elements to the wall as dumbbells. The models were designed according to common seismic codes and then were analyzed through nonlinear time-history analysis when subjected to a series of modified near-field ground motions. According to the results, it was observed that besides exhibiting desired behavior through the combination of prestressed cables and energy dissipating elements, the modified rocking shear wall improved the performance level of the structures and reduced the amount of concrete used by 36 and 20% in 3- and 9-story models. The new system with a modified rocking wall had on average a higher fundamental period, higher base shear, and more properly distributed plastic hinges. This was because of less concrete usage, as well as deploying less prestressed cables compared to the conventional model.