Shear performance of FRP Reinforced Deep Beams Made of Ultra High Performance Concrete (UHPC)

A Master of Science thesis in Civil Engineering by Omar Salman entitled, “Shear performance of FRP Reinforced Deep Beams Made of Ultra High Performance Concrete (UHPC)”, submitted in December 2023. Thesis advisor is Dr. Farid Abed. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).

Abstract

This thesis studied the shear performance of ultra high performance concrete (UHPC) deep beams reinforced longitudinally with glass fiber reinforced polymer (GFRP) bars without web reinforcements. Eight beams were longitudinally reinforced with GFRP bars, while the remaining were reinforced with steel bars for comparison. All beams had similar lengths and widths of 2000 mm and 150 mm, respectively, while the depths varied. The parameters investigated were the effective depth (d), shear span-to-depth ratio (a/d), number of longitudinal bars, and longitudinal reinforcement ratio (ρ). The shear performance of the beams was reported in terms of load deflection response, strains in the concrete and reinforcement, failure modes, and ultimate capacity. All the GFRP reinforced beams had higher shear capacities and lower post cracking stiffness than their steel counterparts. The test results show that decreasing the a/d ratio for the GFRP reinforced beams from 1.8 to 1.5 and from 1.8 to 1.1 increased the peak load by 33% and 95%, respectively. Moreover, the GFRP reinforced beam with 1.1 a/d ratio had 13% higher peak load than its steal counterpart. Also, increasing the depth of the GFRP reinforced beams, from 260 to 310 mm and from 260 to 360 mm, increased the peak load by 23% and 34%, respectively. However, the steel reinforced beams only saw an increase of 26% when the depth was increased from 260 to 360 mm. The increase in depth in the GFRP reinforced beam may have allowed the GFRP bars to deform more, which increased the tensile strength of the tie, thus providing a higher increase in the peak load. The experimental results for the shear capacity were compared against the predictions obtained using the strut and tie method as per the ACI-318-19 and CSA-S806-12 codes. The failure load predictions by the ACI and CSA code showed the same trends as those shown in the experimental results. Moreover, both codes were conservative in predicting the shear capacities.