Strengthening Concrete Beams with Prestressed Fiber Reinforced Polymer Sheets: Behavior at Room and Low Temperatures

When the serviceability of ultimate strength of a reinforced or prestressed concrete beam is assesses to be inadequate, fiber reinforced polymer (FRP) sheets may be suitable for strengthening these beams. FRP sheets exhibit high strength-to-weight ratios and are non-corrosive. When bonded to the tensile face of a concrete beam, FRP sheets supplement the flexural reinforcement of the beam, increasing the beam's strength. To improve the efficiency of this strengthening technique, FRP sheets may be applied with an induced prestress. This paper presents results from an on-going experimental investigation that examines the effectiveness and feasibility of using prestressed carbon fiber reinforced polymer (CFRP) sheets to increase the capacity and improve the serviceability of damaged concrete members. A practical mechanical anchorage system for prestressing the CFRP sheets against the concrete beam is presented and the results of the prestressing process are discussed. The flexural behavior of one 4.5 meter T-section prestressed concrete beam strengthened with prestressed sheets and loaded to failure at room temperature (22 degrees celsius) is presented and compared to that of an unstrengthened control beam. The paper describes the on-going investigation into the behavior of beams strengthened with prestressed CFRP sheets and testes at low temperature (-27 degrees celsius). Aspects of the research program related to the long-term behavior of beams strengthened with prestressed FRP are also discussed.