Proposed Development Length Equations for GFRP Bars in Flexural Reinforced Concrete Members

The bond at the interface between concrete and the surface of a glass fiber-reinforced polymer (GFRP) bar is the most critical parameter to ensure that the strains between the GFRP bar and the surrounding concrete are compatible. To prevent bond failure, an adequate development length should be provided. This study evaluated the current recommended equations for the development length using an approach based on the regression analysis of an experimental database of results from 431 recent tests of beam bonding reported in the literature. The main objective of this work is to optimize the development length equation through a comprehensive assessment of the influencing parameters. The parameters studied in this investigation are the concrete compressive strength, concrete cover, confinement effect, bar diameter, bar location, bar surface profile, and bar tensile stress. The proposed equations were compared with the equations in current design codes.