Evaluation of FRP-based strengthening design criteria for concrete structures

This paper looks at the influence of various parameters in flexural strengthening design specifications, as prescribed by three major international design guidelines namely, ACI440, TR55 and FIB14. A four-level conservativeness frame-work has been highlighted using which flexural conservativeness flowchart is developed to demonstrate how conservativeness is integrated within strengthening design processes at various levels. Various generalised mathematical relationships for flexural strengthening design are also described. Based on these relationships the evaluation of flexural design criteria and their influence on strengthening design, with particular emphasis on residual conservativeness in the design solutions, are presented. The results show that there is significant variation in residual conservativeness of the resultant design solutions obtained using different strengthening design guidelines. Further, it has been shown how the possibility of debonding or rupture failure of the FRP results into different residual conservativeness. A clear mathematical basis for segregating debonding and rupture failure modes as a remedy is also presented.