VULNERABILITY ASSESSMENT OF SEISMIC RETROFIT MEASURES FOR FRAME AND WALL PRE-CODE BUILDINGS

The number of existing buildings that may be at risk because of insufficient seismic design provisions cannot be underestimated. Recent studies have confirmed the pressing need for the seismic retrofit of pre-code structures to reduce their probability of collapse. A number of retrofit approaches are therefore assessed in this study, namely reinforced concrete jacketing, fiber reinforced polymers wrapping, and installing externally unbonded steel plates. Detailed structural design and fiber-based modeling are carried out for five reference structures representing frame and shear wall multi-story buildings before and after retrofit. Forty earthquake records are selected to represent potential earthquake scenarios in a region of medium seismicity that was selected as a reference study area. A large number of inelastic pushover and dynamic analyses are performed to assess the lateral capacity and to derive a wide range of fragility relationships for the reference structures. The highest positive impact of retrofit is observed on the pre-code flat slab-column systems. The reductions in the vulnerability of the retrofitted structures confirmed the effectiveness of the selected techniques for mitigating the earthquake losses of pre-code building inventory.