Multi-level seismic rehabilitation of existing frame systems and subassemblies using FRP composites

The feasibility and efficiency of a retrofit intervention on gravity load-designed frame systems using externally bonded FRP composites is herein presented, through both analytical and experimental investigations. A multi-level retrofit strategy is proposed to achieve the desired performance, based on hierarchy of strength considerations. The expected sequence of events can be visualized through demand-capacity curves within M-N Performance-Domains. An analytical procedure able to predict the enhanced non-linear behaviour of the panel zone region, due to the application of CFRP laminates, in terms of shear strength (principal stresses) vs. shear deformation, is developed and proposed as a fundamental step for the definition of a proper retrofit strategy. The experimental results from quasi-static tests on 2/3 scaled beam-column subassemblies (either interior and exterior) in as-built and retrofitted configuration, provided very satisfactory confirmations of the viability and reliability of the retrofit solution adopted as well as of the proposed analytical procedure