Strengthening and retrofitting techniques to mitigate progressive collapse: A critical review and future research agenda

Abnormal events, that are unforeseeable low-probability and high-impact events, cause local failure(s) to structures that can lead to the collapse of other members and, eventually, to a disproportionate progressive collapse. Ordinary design procedures, which are usually limited to gravity and seismic/wind loads, are inadequate for preventing the progressive collapse. Therefore, a focus on strengthening and retrofitting techniques to mitigate progressive collapse is necessary. Parameters such as topology of the structure, nature of the triggering event, size of the initial failure, typology of the collapse and seismic design requirements affect the strengthening and retrofitting strategy. A discussion on the impact of these parameters on strengthening strategy is first presented. Then, a comprehensive review on strengthening and retrofitting techniques to mitigate progressive collapse is provided. The paper concludes with an ambitious comprehensive list of issues covering different aspects of future research agenda.