Design Considerations of Carbon Fiber Anchors

Carbon fiber-reinforced polymer (CFRP) sheets can be used to strengthen existing reinforced concrete members. However, debonding (separation of the CFRP sheet from the concrete surface) may occur at less than 50% of CFRP sheet's tensile capacity, implying that half of the CFRP material is ineffective in increasing the strength of a concrete member. The use of carbon fiber anchors can increase the amount of tension carried in the CFRP sheets. Forty specimens were tested to develop initial design parameters of carbon fiber anchors. Tests showed that by providing anchors with a total cross-sectional area at least two times greater than that of the longitudinal sheet, it was possible to fracture the CFRP sheets. The best results were obtained using a greater number of smaller anchors. Further, surface preparation is unimportant when the CFRP sheets were well anchored and a 1:4 transition slope can manage any offsets in surface level. The general anchor design was then implemented on a series of long beams and demonstrated that the full CFRP sheet tensile capacity can be realized without incurring limitations due to debonding.