Seismic Torsion Control in Concrete Buildings Using Repairable Rocking Shear Walls

Examination of the behavior of structures in past earthquakes shows that the asymmetric torsion has been one of the causes of severe vulnerabilities. Considering the advantages of modern seismic design methods in which energy dissipation additives such as dampers are used to control the responses in an earthquake, it is possible to control the seismic torsion in the structure. However, recent earthquakes have shown that concrete structures are damaged by earthquakes, making them very difficult and even impossible to repair. For this reason, after relatively severe earthquakes, these buildings have been damaged and destroyed, and in order to reuse the structure, it is necessary to spend a lot of time and money due to the extent of damage to the structure, and this issue creates a new idea to limit damage. In this way, buildings can be exploited more quickly by replacing damaged elements. One of the new methods to improve the seismic performance of concrete buildings is the use of systems that limit damage to the structure. Among these methods, we can mention systems with rocking motion, in which the main building behaves elastically so that the energy absorption and nonlinear performance occur only in certain parts of the building that have been predicted. Therefore, in this study, a new system has been introduced using the mechanism of cradle movement in the shear walls of the structure, transmits damage to the structural fuses and makes the concrete structure safe in earthquake and after, and very repairable. Precise details of connections, design and nonlinear analysis of this system have been done in ABAQUS and SAP2000. The solid element was used to model the rocking system in ABAQUS and concrete damage palsticity model was used to modeling the concrete, which is used to model the nonlinear behavior of concrete. The contact between the steel bolts and the concrete shear wall is simulated using the contact element.The concrete shear wall in this method remains in the elastic range, but the dampers connected to the shear wall due to the elevation of the shear wall absorb most of the seismic force. It should be noted that the system reversibility is provided by post-tensioned cables. The torsion in the structure is of the concentrated mass type and the exit from the 5%, 10% and 20% axes is applied in the concrete structure. The results show that the use of this new system in comparison with concrete structures without it effectively reduces the damage to the structure and the concrete structure remains intact and by changing the retraction force of retracted cables seismic torsion control is performed. Also, the functional levels of the structure remain in the IO area. The use of a controlled rocking motion system significantly reduces axial force in structural members by about 30%. Post-tensioned cables in the cradle drive system have a more than 70% effect on reducing the deformation of the structure and then the flow damper is placed. According to the written DEMATEL code, the tensile strength and stiffness of the structure and the stiffness of the Gap element are the most effective; besides, the vibration mode and displacement of the structure are the most effective factors in controlled rocking motion. The use of a new repairable shear wall with rocking motion has caused the vibration mode to dominate the structure of the first vibration mode and the distance between the torsion mode, and the first and the second modes are very large.