Repair of damaged end regions of prestressed concrete girders using fiber reinforced polymer composite materials
Over the past couple decades, fiber reinforced polymer (FRP) composites have emerged as a lightweight and efficient repair and retrofit material for many concrete infrastructure applications. FRP can be applied to concrete using many techniques, but primarily as either externally bonded laminates or near-surface mounted (NSM) bars or plates. These repair methods have been shown to be effective when used to provide supplemental flexural and shear reinforcement for reinforced concrete and prestressed concrete beams. One problem afflicting bridge girders in cold climates is the deterioration of the girder ends due to deicing salt exposure, thus reducing their shear strength. This thesis presents the results of the beginning stages of an Illinois Department of Transportation (IDOT) sponsored study to use FRP materials to repair and retrofit the damaged ends of prestressed concrete beams. In the first phase of the study, direct shear pull-out tests on glass-FRP (GFRP) and carbon-FRP (CFRP) externally bonded laminate and NSM bar concrete specimens are performed. An accelerated aging scheme consisting of freeze/thaw cycling in the presence of a deicing salt solution is implemented to determine the effect of long-term environmental exposure on the FRP/concrete interface. In the next phase, three-point bending tests are performed on small scale prestressed concrete beams. End region deterioration is simulated by imposing damage to the cover concrete, and mortar and FRP repairs are applied to test their effectiveness. Finally, a 3D finite element (FE) model of a full scale prestressed concrete (PC) I-girder is used to investigate the effect of damage to the cover concrete and stirrups in the end region of the girder. Parametric studies are performed using externally bonded CFRP shear laminates to determine the most effective repair schemes for the damaged end region. The results of the shear pull-out tests of CFRP laminates that have undergone accelerated aging are used to calibrate a bond stress-slip model for the interface between the FRP and concrete substrate and approximate the reduced bond stress-slip properties associated with exposure to the environment that causes this type of end region damage. The results of this study indicate the potential for FRP repairs to be an effective means of recovering the original strength of PC bridge girders with damaged end regions, even after environmental aging.
Fiber reinforced polymer (FRP), End region, Prestressed concrete, Damage, Accelerated aging
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign