Strut and tie model for CFRP strengthened reinforced concrete corbels

This study aims to explore the optimal strut-and-tie-model (STM) for strengthening reinforced concrete (RC) corbels with carbon fiber-reinforced polymer (CFRP), utilizing finite element (FE) analysis. While previous studies have only examined a single type of FRP sheet arrangement, this research fills a gap by investigating the effect of four configurations with the Externally Bonded Reinforcement (EBR) installation method. Verification was conducted using a fully horizontally wrapped strengthened RC corbel. This study also evaluates other variables, such as the Near-Surface Mounted (NSM) method, concrete strength, reinforcement yield stress, and the number of CFRP layers. The results provide valuable insights into the optimal STM for strengthened RC corbels and contribute to developing effective strengthening techniques. The study suggests 12 STMs with variable main strut angles and primary tie widths lower than the proposed equations for calculating the upper limit. Results indicate that different arrangements of CFRP sheets, an increase in concrete strength, reinforcement yield stress, and the number of CFRP layers can cause up to 33%, 16%, 16%, and 7% increase in bearing capacity, respectively, with the same volume of CFRP. However, using the NSM installation method with the same arrangement and volume of FRP can decrease bearing capacity by 17%. The best proposed STM was presented for the arrangement of selected CFRP sheets based on the highest primary tie width calculated by the proposed equation of the upper limit. The total percentage difference in maximum stresses for finite elements varied by 62%.