High Temperature Durability of CFRP Laminated RC Beams

摘要

This paper presents experimental results on the behavior of steel reinforced concrete beams strengthened with fiber-reinforced polymer (FRP) laminates at elevated temperatures. This unique study into the high temperature durability of this retrofit option focuses on beams simultaneously loaded while being subjected to thermal environments above the CFRP resin's glass transition temperature. The study consists of 17 identical flexurally reinforced beams proof tested at 20, 40, and 60 percent of the ultimate service load while maintaining FRP temperatures constant at 25°C, 75°C, 115°C, and 150°C. A newly developed strain gauge specifically designed for integration into FRP laminates was used to measure the performance of the FRP reinforcement and the underlying concrete. During the laminate application process, strain gauges were embedded between two CFRP layers and on the concrete at the composite reinforcement interface. Rigid "pins" normal to the gauge plane, allow for simple electrical circuit completion outside of the cured composite without disturbing its mechanical properties. Strains were recorded in the composite as well as on the rebar, allowing for better characterization of the strengthened concrete beam. Strains and deflections were recorded for 4 hours allowing for comparison to standardized fire rating tests and applicable models. The results of the study suggested very good correlation between developed strains and deflections in the test beams relative to the applied loads and temperatures. The engagement of the CFRP laminates in the load carrying beams' mechanisms, their ultimate strains and changing response at elevated temperatures with respect to time were of particular interest.