Short-Term Tensile Strength of Carbon Fiber-Reinforced Polymer Laminates for Flexural Strengthening of Concrete Girders

Externally bonded carbon fiber-reinforced polymer (CFRP) laminates are a feasible and economical alternative to traditional methods for strengthening and stiffening deficient reinforced concrete (RC) and prestressed concrete (PC) girders. There is, however, a general lack of established techniques for estimating a reliable value for the short-term tensile strength of CFRP laminates. Manufacturers typically list the strength of an individual fiber or dry strand, and not that of the laminate, in the product data sheet, leaving engineers no choice but to resort to coupon tests. This paper presents an analytical technique based on the Weibull theory for brittle materials that can be used to estimate the strength of unidirectional CFRP laminates from fiber properties reported by the manufacturer. Good agreement is found between theory and experimental results of concrete T-beams strengthened with a varying amounts of CFRP laminates. The design implications of the developed methodology are discussed, and a chart is provided for calculating CFRP laminate strength from fiber data reported by the manufacturer.