A fragility-oriented approach for seismic retrofit design

This study proposes a practical fragility-oriented approach for the seismic retrofit design of case-study structures. This approach relies on mapping the increase of the global displacement-based ratio of capacity to life-safety demand ( CDRLS) to the building-level fragility reduction. Specifically, the increase of CDRLS due to retrofitting is correlated with the corresponding shift in the fragility median values of multiple structure-specific damage states, observing that a pseudo-linear trend is appropriate under certain conditions. Accordingly, a practical approach is proposed to fit such a (structure-specific) linear trend and then use it by first specifying the desired fragility median and subsequently finding the corresponding target value of CDRLS that must be achieved through retrofit design. The validity of the proposed approach is illustrated for an archetype reinforced concrete (RC) structure not conforming to modern seismic design requirements, which has been retrofitted using various techniques, namely, fiber-reinforced polymers wrapping of columns and joints, RC jacketing, and steel jacketing