Seismic vulnerability assessment of a RC structure before and after FRP retrofitting

In earthquake engineering, reliable vulnerability assessment tools suitable to existing reinforced concrete structures are necessary in order to mitigate the seismic risk. Furthermore, amongst the wide range of technical solutions available for structural upgrading, external reinforcement by fiber reinforced polymer (FRP) is often an interesting option. Nevertheless, the use of FRP is limited, one of the reasons being the lack of predictive numerical tools allowing for vulnerability assessment. Based on a case study, this article presents a simplified modeling strategy to assess the seismic vulnerability of an existing reinforced concrete building before and after FRP retrofitting. The structure is simulated using multifiber beam elements and constitutive laws based on damage mechanics and plasticity, while the dynamic characteristics of the numerical model are validated using in-situ ambient vibration records. Nonlinear transient dynamic analysis studies are performed using a synthetic earthquake signal compatible with the Eurocode 8 spectra. Local indicators are adopted to quantify the damage level in the structure before and after FRP retrofitting, in correspondence with the European Macroseismic Scale 98. One of the main conclusions of this study is that the use of local indicators can lead to contradictory assessment results with the evaluations based on global indicators as adopted in HAZUS or Risk-UE.