Seismic Behaviour of Damaged Steel Frames Retrofitted with Inerters

Seismic-control devices are a proven cost-effective solution to enhance the seismic performance of structures and ensure their survivability during earthquakes. They are also a good alternative for post-earthquake retrofitting. Among these control devices, inerters have gained momentum in the last two decades as they can generate significant restoring forces while keeping their gravitational mass at a minimum. Nonetheless, it is often unclear precisely how much such a seismic-control strategy improves structural performance. In this paper, we assess the potential of a clutched inerter system as a seismic retrofitting strategy for damaged Steel Moment Resisting Frames (SMRF). To provide an accurate benchmark of the device’s advantages, our assessment is carried out within a hazard-consistent Performance-Based Earthquake Engineering (PBEE) framework. Six SMRF frames are subjected to 596 hazard-preserving ground motions and comparisons are presented in the form of transient and residual inter-storey drift hazard curves, where the corresponding structural demand for a certain return period of interest is estimated. These curves show that clutched inerters work very well as a post-earthquake retrofitting system for damaged frames by reducing the transient and residual demand by up to 46% returning them to back to as-new performance levels.