Retrofitting of Irregular Structures for Seismic Loads Using Rocking Walls

Self-centring rocking walls are expected to regulate the inter-story drifts (ISDs) of vertically irregular moment resisting frame structures and to prevent soft story mechanisms. Usually, these walls include a rocking section located at their base. Large bending moments are expected throughout the height of these walls due to the higher vibration modes effect. Recently, the multiple rocking mechanism was proposed, using additional rocking sections designed at higher floor levels. Previous studies have shown that this mechanism can reduce a large portion of these forces. However, it has not been implemented for vertically irregular buildings. In this work, the behaviour of irregular plane setback buildings with multiple rocking wall systems is studied. A post-tensioned concrete rocking wall is added to a vertically irregular moment resisting frame with a setback. The results show that this design regulates the ISDs of the frame and significantly reduces them. However, large moment demands are observed at the setback level. Thus, an additional rocking section is added at different levels with different designs and its effect on the behaviour of the structure was examined. The results give insights regarding the location of the top rocking section and its effect on the behaviour of these systems.