Behavior of FRP Repair/Strengthening Systems for Prestressed Concrete

Abstract

This research study examines the behavior of prestressed concrete beams retrofitted with Fiber Reinforced Polymer (FRP) materials. Due to deficiencies in the built environment, engineers may be asked to retrofit or upgrade the capacity of an existing concrete structural member. This could be a result of new demands on the structure, or a repair of damage from an unforeseen event. Retrofits are possible using the traditional building materials of concrete and steel. The cross-section of the structural element can be increased, or steel plates can be bolted or adhesively affixed to the structure to increase capacity. Many of these techniques are costly, and some perform poorly under service conditions. The main benefit for using FRP materials for the strengthening of existing structures is the lightweight nature of the composite material, which makes the use of extensive scaffolding (required in the installation of steel plates) obsolete. The objectives of this research are twofold. First, the overall structural behavior of an FRP strengthened or repaired concrete beam is studied. Two different loading conditions are examined: extreme loading simulated by a monotonic load to failure, and fatigue loading designed to simulate service loads. The structural behavior of the system is evaluated under these different conditions, and an analytical model is presented which predicts the flexural behavior of the system assuming certain failure modes. The second objective of this research is to evaluate the bond behavior of an FRP strengthened reinforced or prestressed concrete flexural member. A database of experimental failures was constructed, and an analytical model is proposed which predicts the bond failure of the FRP strengthening system.