Crack control in concrete elements reinforced with pultruded bars: comparison between analytical formulations

The durability of reinforced concrete structures is critically affected by the corrosion of traditional steel reinforcement, which leads to significant maintenance costs and structural deficiencies world- wide. Fiber-Reinforced Polymer (FRP) bars have emerged as a promising non-corrosive alternative; however, their distinct material behavior such as linear elastic behavior under tension stresses and lack of ductility compared to steel introduces design challenges. As a result, numerous studies have examined the flexural behavior of FRP-reinforced concrete elements through both experimental and numerical approaches. Many have highlighted that the serviceability limit state often governs the design of fiber-reinforced concrete elements. This thesis investigates the applicability of crack control provisions for FRP-reinforced concrete beams from the Italian guidelines CNR-DT 203/2006 and its revised version CNR-DT 203/R1/2025. A com- prehensive database of 76 experimental specimens subjected to flexural bending tests from various international studies was compiled, covering different types of FRPs of varying surface treatment, re- inforcement ratios, and concrete strengths. The specimens were classified based on concrete strength and surface treatment of the FRP bars, which influence the bond slip and affect the crack width. The- oretical crack widths were calculated according to both guidelines and compared with experimental results to assess their accuracy and reliability. The results indicate that the revised guideline provides improved predictions of crack behavior under service loads, but further calibration of key parameters, such as bond-dependent coefficients, is recommended to improve the reliability of the estimation of the crack width for FRP-reinforced concrete. This work contributes to validating and refining national standards for the safe and durable application of FRP in reinforced concrete structures.