Title:
Variable Bond of GFRP Bars for RC Beams under Arch and Beam Actions (Prepublished)
Author(s):
Yail J. Kim and Ali Alatify
Publication:
Structural Journal
Volume:
Issue:
Appears on pages(s):
Keywords:
bond length; fiber reinforced polymer (FRP); partial bond; reinforcement
DOI:
10.14359/51749131
Date:
8/19/2025
Abstract:
This paper presents the implications of variable bond for the behavior of concrete beams with glass fiber-reinforced polymer (GFRP) bars alongside shear-span-dependent load-bearing mechanisms. Experimental programs are undertaken to examine element- and structural-level responses incorporating fully and partially bonded reinforcing bars, which are intended to represent sequential bond damage. Conforming to published literature, three shear-span-to-depth ratios are taken into account: arch action, beam action, and a transition from arch to beam action. When sufficient bond is provided for the element-level testing, the interfacial failure of GFRP is brittle against a concrete substrate. An increase in the shear-span-to-depth ratio from 1.5 to 3.7, aligning with a change from arch action to beam action, decreases the load-carrying capacity of the beams by up to 40.2% and the slippage of the partially bonded reinforcing bar dominates their flexural stiffness. Compared with the case of the beams under beam action, the mutual dependency of the bond length and shear span is apparent for those under arch action. As far as failure characteristics are concerned, the absence of bond in the arch-action beam prompts crack localization; by contrast, partially bonded ones demonstrate diagonal tension cracking adjacent to the compression strut that transmits applied load to the nearby support. The developmental process of reinforcing bar stress is dependent on the shear-span-to-depth ratios, and, in terms of using the strength of GFRP, beam action is favorable relative to arch action. Analytical modeling suggests design recommendations, including degradation factors for the calculation of reinforcing bar stresses with bond damage when subjected to arch and beam actions.