[FAST TRACK] Stage-wise analytical modeling and full-scale validation of TRC-strengthened RC beams under sustained loading: application to 30-year-old bridge members

Analytical modeling and experimental validation of TRC-strengthened RC beams under sustained loading

Abstract

This study presents a closed-form, stage-wise sectional analytical model for reinforced concrete (RC) beams strengthened with carbon textile-reinforced concrete (TRC) under sustained service loading. The formulation explicitly incorporates pre-cracking, partial unloading, residual curvature, and activation of the TRC layer under non-zero initial strain. The TRC layer is modeled as a composite material with bilinear tensile behavior, while tension stiffening of the cracked concrete substrate and residual tensile mechanisms are consistently included. The model is validated against full-scale bridge slab beams after approximately 30 years of service, tested under realistic loading and strengthening conditions. The strengthened beam exhibited an increase in ultimate load of approximately 25% compared to the control specimen, and significantly improved crack control, with crack widths and spacing reduced to approximately one-third to one-half. Strain measurements indicate effective stress redistribution, with steel strains reaching about 16‰ and high utilization of the textile reinforcement. Analytical predictions agree well with experimental results, with discrepancies generally within 5–10%. Comparison with design guidelines shows that Z-31.10-182 provides the closest prediction, while ACI 549.4R-20 and CNR-DT 215/2018 overestimate flexural capacity by 6–12%. The results demonstrate that the proposed model provides a more accurate and mechanically consistent framework for evaluating TRC-strengthened RC members under realistic in-service conditions.