Shear performance of glass fiber reinforced concrete beams with diverse embedded GFRP trusses

This paper investigated the shear performance of internal embedded glass fiber reinforced polymer (GFRP) trusses as a novel shear reinforcement instead of conventional steel stirrups for concrete beams reinforced with top and bottom GFRP bars, and for this goal, different proposed patterns of embedded GFRP trusses were offered. In addition, the effect of GFRP stirrup spacing and the comparison with steel stirrups are also studied. For this purpose, an experimental program consisting of nine specimens was utilized that tested under one concentrated load with an unequal span-to-depth ratio up to failure. The program included one specimen with no stirrups in the studied shear zone as a control beam. The GFRP stirrups or proposed trusses were cut as single straight legs without bends or hooks, and they were then linked together with plastic ties to create the necessary shape. Besides, numerical analysis using the finite element program ANSYS V-19.2 was utilized for computational modelling as a 3-D model to examine the capability of the model to capture the observed shear behaviour and to obtain extra results in order to better comprehend the shear behaviour. Cracking patterns, ultimate loads, failure mechanisms, load-deflection relationships, load versus strain in GFRP bars, and strain distribution along the height of the GFRP truss member were evaluated. The shear capacity was enhanced via the use of internal GFRP embedded trusses by about 56–80 % compared to the control beam (BC) without stirrups, while these forms improved the capacity by about 29–50 % compared to the specimen that had only vertical stirrups. In addition, the normal strain distribution along the GFRP truss member height was non-uniform and significantly affected by the member location. The shear capacity was also increased by decreasing the GFRP stirrups' spacing, while the use of GFRP stirrups instead of steel stirrups decreased the ultimate load by about 3–10 %, according to stirrup spacing. Finally, the comparison between the results obtained from the numerical model and the experimental work showed a good agreement.