Improvement of the seismic response of frame structures through the coupling with an external structure equipped with inerter

This paper analyses the effectiveness of connecting the first storey of a frame structure to an external structure shorter than the frame structure by a visco-elastic device. Additionally, an inerter device is applied to the external structure to modify its inertial force and increase the effectiveness of the coupling. The coupled structure is modeled as a three-degree-of-freedom mechanical system, and its equations of motion are obtained by a direct approach. The coupling with the external structure is considered beneficial for the frame structure if the absolute displacements of the coupling level or the inter-storey drifts reduce compared to those of the stand-alone frame structure. A preliminary modal analysis shows that the coupling with the external structure equipped with the inerter device improves the dynamic and seismic performances of the system. A further analysis is performed by considering some ground motion records. The results, organized in performance maps, confirm that the coupling with the external structure reduces the displacements and drifts of the frame structure in large ranges of values of the parameters that characterize the external structure and connection device.