Different CFRP strengthening techniques for prestressed hollow core concrete slabs: Experimental study and analytical investigation

This study presents an experimental-analytical investigation on the structural behavior of precast prestressed hollow core RC slabs strengthened in flexure by CFRP laminates. Externally bonded and near surface mounted (NSM) laminates were used. The CFRP area and using transverse anchorage were also investigated. Results demonstrated that NSM technique resulted in optimum strengthening efficiency. The increased bond strength also resulted in full activation of the NSM laminates at failure. However, the NSM flexural strengthening level should be carefully designed to avoid unfavorable shear-tension failure mode. Moderate efficiency was associated with the externally bonded technique due to the premature de-bonding. However, this efficiency was optimized by using transverse CFRP laminates as anchorage, which re-directed de-bonding further away from the laminates' ends and delayed failure, but at much lower deformations than those of the control slab. A rational analytical study was conducted. Comparisons between the experimental and analytical results demonstrated satisfactory agreements.