Shear behavior of slender concrete beams reinforced with longitudinal GFRP bars and carbon-fiber mesh stirrups: Experimental and analytical investigations

초록

This study presents experimental and analytical investigation of the one-way shear behavior of slender concrete beams reinforced with longitudinal glass fiber-reinforced polymer (GFRP) bars and carbon-fiber mesh stirrups (GFRP-CMS-RC beams), a fully corrosion-resistant reinforcement system that partly overcomes the fabrication limitations of bent FRP stirrups. Fourteen beam specimens were tested, with key parameters including concrete compressive strength, shear and longitudinal reinforcement ratio, shear span-to-effective depth (a/d) ratio, and beam effective depth. The results showed that beams reinforced with carbon-fiber mesh stirrups transitioned toward a shear-compression failure mode, accompanied by increased flexural crack multiplicity and width. Increasing the carbon-fiber mesh reinforcement ratio from 0.06% to 0.18% significantly enhanced the shear strength up to 83% compared with non-shear-reinforced counterparts, and improved the displacement capacity and strain development in both the concrete and longitudinal GFRP bars. The maximum strains in the carbonfiber mesh stirrups at shear failure ranged from 0.004 to 0.0055. Beams with higher a/d ratios and lower longitudinal reinforcement ratios exhibited reduced post-cracking stiffness and shear strength, along with larger strains in both the concrete at the extreme compression fiber and the longitudinal GFRP bars. Furthermore, the novelty contribution of this work is the development and experimental validation of an improved strain-based analytical model by incorporating the linear-elastic GFRP response and bond-slip behavior, the effective strain limit of flexible carbon-fiber mesh stirrups, and flexure-shear interaction in slender beams. The model predictions showed good agreement with the experimental results, yielding a mean shear strength ratio of 1.13 with a COV of 7%, and provided a physically consistent explanation of the influence of key design parameters on shear behavior.

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