Effect of epoxy repairing on girders shear strengthened with external post tensioning

Abstract

Every year numerous concrete girder bridges are damaged by overweight vehicles. When this happens, bridge engineers are faced with numerous questions relative to the behavior and strength of the bridge. These questions must be answered, so decision can be made concerning traffic restrictions and future maintenance of the actions. External post-tensioning is an effective technology to upgrade and strengthen existing structures whereas epoxy resins usually are used as a treatment in a cracked structure. The focus of this work is on the behavior and effectiveness of external post-tensioning for shear strengthening of bridge girders with epoxy repairing. This study examines four-point loading in four rectangular beams; one control beam and the others are constructed to simulate the effect of external post-tensioning repaired with epoxy resins on girders. Four beams are 2500 mm in length with supports of 2000 mm apart. Experimental studies are performed on four beams to develop basic understanding of the shear behavior. Tests are then extended on four girders and experimental results for the failure loads show different features. This study first reviews failure mode including delamination with the use of external post-tensioning to rehabilitate various concrete structures and discusses methodologies used to characterize the failure processes of the system. Physical models of reinforced concrete beams are precracked, then retrofitted with epoxy and post tensioned and tested in an experimental program. Strengths are shown to increase with the strengthening technique of external post-tensioning and the addition of epoxy resin, the specimens are observed to fail through a similar type of mechanism. Parameters affecting these failure modes are discussed, and techniques used in the analysis of these modes are reviewed. Results of this review are used to make recommendations for future work in the understanding of shear strengthening by external post-tensioning with epoxy repairing of concrete structures.