Component-based Probabilistic Methodology for the Vulnerability Assessment of RC Frames Retrofitted with Dissipative Braces

The paper illustrates a probabilistic methodology for assessing the vulnerability of low-ductility reinforced concrete (RC) buildings retrofitted by dissipative braces. The aim is to highlight the most important parameters controlling the capacity of these systems and specific aspects concerning the response uncertainties. The proposed methodology is based on local engineering demand parameters (EDPs) for monitoring the seismic response and on the development of component and system fragility curves before and after the retrofit. Its capability is tested considering a RC frame designed for gravity-loads only retrofitted by elasto-plastic dissipative braces. The results show the effectiveness of the methodology in describing the changes in the response and in the failure modalities due to the retrofit. Moreover, the retrofit effectiveness is evaluated by introducing proper synthetic parameters describing the fragility curves and highlighting the importance of employing local rather than global EDPs in the seismic risk evaluation of low-ductility frames.