Predicting service deflection of ultra-high-performance fiber-reinforced concrete beams reinforced with GFRP bars

The flexural behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) beams reinforced with internal glass fiber-reinforced polymer (GFRP) bars was experimentally investigated. For this, large-sized beams with four different reinforcement ratios (ρ = 0.53-1.71%) were fabricated and tested. All test beams exhibited very stiff load-deflection response beyond the first cracking point and satisfied the crack width criteria of ACI 440.1R and CAN/CSA S806 at serviceability limit state and deformability requirement by CAN/CSA-S6. Higher reinforcement ratio resulted in better flexural performances such as higher post-cracking stiffness, maximum moment capacity, ductility, and deformability. The effective moment of inertia equation from the current ACI 440.1R code, which is based on Bischoff's model, significantly overestimated the service deflections of UHPFRC beams with GFRP bars because of its inappropriate first cracking prediction and moment of inertia equation at cracked section. Therefore, alternative equation for predicting first cracking moment and moment of inertia of cracked section in strain-hardening zone for UHPFRC was suggested, and it was verified through comparison with the measured service deflections.