Abstract

Purpose: This study quantitatively investigates the synergistic effects of deterioration depth and temperature changes on the durability and structural behavior of reinforced concrete (RC) structures strengthened with Carbon Fiber Reinforced Polymer (CFRP) sheets. It provides empirical evidence to address the limitations of current design standards that primarily focus on newly constructed structures. Research design, data and methodology: Experimental data from global literature were systematically reinterpreted to analyze correlations between deterioration depth, load-carrying capacity, temperature-dependent epoxy adhesion, and CFRP-concrete interfacial behavior. Regression analysis was employed to derive prediction models for strength reduction rates and to review failure mode transitions at various deterioration stages. Results: Structural performance decreased nonlinearly as deterioration depth increased; yield strength dropped by up to 35% in the 10–30 mm range. A quadratic regression model (R²=0.997) demonstrated higher explanatory power than a linear model (R²=0.989), confirming accelerated degradation. Beyond 30 mm of deterioration, interfacial debonding became the dominant failure mode. Furthermore, epoxy adhesion weakened sharply between 80–100°C, effectively nullifying the CFRP strengthening effect. In combined environments, performance degradation appeared as a synergistic rather than a simple additive effect. Conclusions: CFRP strengthening design must quantitatively incorporate deterioration depth, thermal impacts, and interface-oriented approaches. This study establishes a quantitative evaluation framework to improve durability assessment and design standards for aging structures.