Structural behaviour of ultra high performance fibre reinforced concrete composite members
thesisposted on 08.06.2021, 10:32 by Luaay Hussein
The aging and deterioration of reinforced concrete infrastructures in North America present major technical and economical challenges to infrastructure owners. To effectively address some of the challenges, there is a need to develop innovative and cost-effective systems. The main objective of this research was to develop composite members of ultra-high performance fibre reinforced concrete and normal strength concrete or high strength concrete (UHPFRC-NSC/HSC). In order to achieve this objective, the first phase of this research investigates the structural behaviour of UHPFRC with varying fibre content beams without web reinforcement. Test results indicated that the addition of 1% of steel fibres effectively improves the shear strength of UHPC beams by 77% due to the crack-bridging stress that develops across the crack surface. In the second phase, experimental studies were carried out on UHPFRC-NSC/HSC prisms and beams without stirrups to investigate the flexural and shear capacity of those composite members. Each beam specimen was designed to have the UHPFRC layer in tension and the NSC/HSC layer in compression. Additional varied parameters included fibre volume content, and shear connectors were investigated. Test results showed that the performance of the proposed composite system in terms of the flexural and shear capacity was successfully enhanced. All composite beams failed in shear at a force that is 1.6 to 2.0 times higher than that of the NSC/HSC beam's resistance. Test results showed that the effect of using HSC versus NSC in the composite beam was negligible, and the bond strength between the two concrete material layers (UHPFRC and NSC/HSC) was significantly high that the addition of shear connectors was unnecessary. In the third phase, an analytical and finite element models to predict the ultimate shear capacity of UHPFRC composite beams were proposed and validated with the experimental results. The results of the finite element analysis showed that the size effect in structures made of UHPFRC material has little influence on the shear capacity. Finally a comparison between the finite element model and the analytical model indicated that both models developed in this research are capable of predicting the shear behaviour of UHPFRC and UHPFRC-NSC/HSC beams.