Structural behavior of ultra-high performance fiber reinforced concrete-normal strength concrete or high strength concrete composite members

The primary objective of this research was to develop composite members of ultra-high performance fiber-reinforced concrete (UHPFRC) and normal strength or high strength concrete (NSC/HSC). 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 parameters such as fiber volume content and shear connectors were investigated. The test results revealed that the performance of the proposed composite system, in terms of flexural and shear capacity, was successfully enhanced. All of the composite beams failed in shear at a force that is 1.6-2.0 times higher than that of the resistance of the NSC/HSC beams. The results also revealed that the effect of using high strength concrete versus normal strength concrete in the composite beam was negligible. The test results also revealed that the bond strength between the two concrete material layers (UHPFRC and NSC/HSC) was significantly high, rendering the addition of shear connectors unnecessary. An analytical model was proposed to predict the ultimate shear capacity of UHPFRC composite beams and validated using the experimental results. (C) 2015 Elsevier Ltd. All rights reserved.