Prestress Transfer in NSM CFRP-Strengthened RC Structures Under Curing and Service Temperature Effects: Experimental Validation and Analytical Modeling

This study examines the prestress transmission behavior in near-surface-mounted (NSM) carbon fiber-reinforced polymer (CFRP)-strengthened reinforced concrete structures, with particular emphasis on the effects of temperature. Experimental tests were conducted to evaluate the tensile and shear properties of epoxy adhesives under a range of curing temperatures (20-100 °C) and ambient service temperatures (0-80 °C). The results reveal an inverse exponential relationship between curing time and temperature. Notably, adhesive strength declines significantly above 60 °C and the adhesive loses functionality at 80 °C. Building on these findings, an analytical model was developed to predict prestress transfer length, CFRP strain distribution, and interfacial shear stress. The model incorporates effective bond stiffness and a prestress reduction coefficient to account for varying prestress levels (10-50%). Parametric analyses identify the CFRP elastic modulus, cross-sectional geometry, adhesive thickness, and degree of curing as critical factors influencing prestress transmission. The model's predictions were validated against experimental data, demonstrating its reliability. Overall, this work provides a theoretical foundation for optimizing the design of NSM CFRP-strengthened structures under complex thermal conditions.