Behavior of Short-Span Concrete Members Internally Reinforced with Glass Fiber–Reinforced Polymer Bars

This paper aims to investigate the behavior of short-span concrete members with a shear span–to–effective depth ratio ($a/d$) less than 2, internally reinforced with glass fiber–reinforced polymer (GFRP) bars. The study comprised testing of 12 specimens. Test parameters included the $a/d$ ratio, GFRP reinforcement ratio, and concrete grade. The study was supplemented by an analytical investigation to predict the strength of the tested specimens. The experimental study highlighted that increasing the longitudinal GFRP reinforcement ratio together with the concrete strength in the absence of web reinforcement might be detrimental to the strength of GFRP-reinforced short-span concrete members due to a shift in the mode of failure from crushing of a diagonal strut to diagonal splitting. Experimental results indicate also that increasing the $a/d$ does not necessarily reduce the strength of short-span GFRP-reinforced concrete specimens with a low concrete strength due to a greater angle of inclination of the critical shear crack developed during testing relative to that considered in the analysis. The strut-and-tie modeling (STM) provided conservative predictions for the nominal strength of the tested specimens except for those failed by diagonal splitting where it overestimated the strength by a maximum of 12%. The accuracy and validity of two published analytical approaches were examined. These approaches tended to provide less conservative, yet reasonable, nominal strength predictions but overestimated the strength of the specimens with the diagonal splitting mode of failure.