Numerical study of steel-concrete composite beams strengthened by CFRP plates with prestressed unbonded reinforcement system

This work developed a three-dimension refined finite element (FE) model to study the flexural behavior of steel-concrete composite beams strengthened with CFRP plate by prestressed unbonded reinforcement (PUR) system. The numerical result has excellent agreements with the experimental results on the failure mode, overall load-deflection response and strain development at mid-span section as well as CFRP plates. The verified FE model was applied to carry out a comprehensive parametric study, evaluating the effects of sectional area, prestress level and profile of CFRP plate, to investigate the optimum parameter range of PUR system for beam reinforcement. It is found that the yielding load rises as the sectional area, prestress level, and pillar spacing of CFRP plates increase. Besides, the ultimate bearing capacity of beam can be efficiently improved by increasing the sectional area of CFRP plates, while the mid-span deflection and ductility were maintained at failure. Moreover, as the prestress level of CFFR plate increases, the bearing capacities of reinforced beams marginally rise but the ductility markedly decreases. The ideal prestress level for strengthening is considered as 10 %similar to 30 %. Furthermore, the profile of CFRP plate has significant impact on failure of reinforced beams, but has little effect on ultimate load. The results of parametric studies are of great significance for the practical reinforcement application of the PUR system with CFRP in bridge engineering.