Full Session with Abstracts
The use of carbon fiber anchors has been shown to improve the performance of concrete beams strengthened in flexural with CFRP sheets. This improvement results from delaying or controlling the debonding of FRP sheets at failure. In this study, three full-scale T beams and three full scale rectangular beams are strengthened with CFRP sheets and anchored with two types of CFRP splay anchors. The first T beam was strengthened with CFRP without any anchors. The second T beam was strengthened with CFRP sheets and anchored with ¾” diameter anchors at 8” spacing along the shear span. The third T beam was strengthened with CFRP sheets and anchored with 5/8” diameter anchors at 5.5” spacing along the shear span. The three rectangular beams were strengthened in an identical manner to that of the T beams. The purpose of maintaining the same identical designs was to perform one on one comparisons between the T and rectangular beams. The anchored beams were designed using a newly developed design procedure to provide adequate anchorage. Experimental testing and nonlinear analysis showed the excellent performance of the anchored beams by attaining the full flexural sectional capacity up to FRP rupture failure mode for T beams and concrete crushing failure mode for rectangular beams. The results prove that anchors offer an effective solution against premature debonding failure. An improvement multiplier is proposed here to augment the ACI 440.2R-17 debonding strain level, which is defined as the ratio of the CFRP strain at ultimate section capacity to the debonding strain. The importance of using a bi-directional CFRP laminate as the final layer is explained.