Influence of UHPFRC jacketing on the static, blast and post-blast behaviour of doubly-reinforced concrete beams

This paper investigates the effects of ultra-high performance fiber-reinforced concrete (UHPFRC) jacketing on the static and blast behavior of reinforced beams. The test program included a total of six beams with dimensions of 150 mm x 200 mm x 2440 mm, including three replicate control beams, and three replicate beams retrofitted with a 20 mm UHPFRC jacket. The beams were doubly-reinforced, with provision of compression bars and ties spaced at 75 mm throughout the beam span. Each beam type included specimens tested under quasi-static fourpoint bending, and repeated or singly-applied blast loads applied using a shock-tube. Under static loading the UHPFRC is shown to increase beam stiffness and capacity, however the high bond capacity of the UHPFRC, crack localization effect, and relatively low steel ratio resulted in bar rupture, thereby reducing ductility. Under repeated blast loading the UHPFRC effectively reduced maximum and residual displacements at equivalent blasts, but the crack localization which initiated at the earlier blasts eventually led to bar rupture. Under the singly-applied blast, the UHPFRC was found to reduce displacements, and better control damage when compared to the companion RC beam, without bar rupture. As part of the numerical study, finite element (FE) modelling was used to predict the blast response and damage in the test beams. A parametric study is also used to examine the effects of steel ratio, jacket thickness and jacket interface location on blast behavior.