Behavior of externally bonded fiber reinforced polymer systems for strengthening concrete girders in shear

"Deficiencies in shear resistance are a primary concern in concrete members due to the sudden and unpredictable nature of shear failures. Shear deficiencies in concrete structures can arise due to improper design, long-term deterioration, man-made damages, increases in loads, or as a result of over strengthening in flexure. A number of shear strengthening techniques offer a cost effective means for restoring or enhancing the shear capacity of a concrete member. The use of externally bonded fiber reinforced polymers (FRP) is one such technique that has gained recent recognition for its high strength-to-weight ratio and simplicity of application. The development of this technique relies on experimental testing to better understand the behavior and failure mechanisms. Previous experimental investigations and analytical models/design guidelines were studied to identify and understand the parameters influencing the shear strengthening effect of externally bonded fiber reinforced polymers (FRP). The knowledge acquired from the literature was used to design and carryout a full-scale experimental investigation for further evaluating the effectiveness of externally bonded FRP for shear strengthening. Test specimens consisted of reinforced concrete (RC) and prestressed concrete (PC) girders. Parameters of interest included the effects of: pre-existing damage (cracks), transverse steel (stirrup) reinforcement ratio, FRP strengthening scheme, and methods of FRP anchorage. The experimental results were compared with predictions from existing analytical models and design guidelines. Lastly, an alternative analytical approach was developed which takes into consideration multiple parameters shown to have influence on the FRP shear strengthening effectiveness, but which have not been collectively incorporated in previous models"--Abstract, page iii.