Behavior of Ultrahigh-Performance Concrete Confined by Fiber-Reinforced Polymers

Abstract

Over a decade of studies have demonstrated the benefits of ultra high performance concrete (UHPC) in terms of damage tolerance, energy absorption, crack distribution, and deformation capacity. However, little information is available on the confinement behavior of UHPC, especially when confined with fiber-reinforced polymers (FRP). Sixteen UHPC-filled FRP tubes with different fiber type and tube thickness were tested under monotonic uniaxial compression. All specimens failed by rupture of the tube at or near the midheight. Similar to conventional concrete, test results showed significant enhancements in the ultimate strength and strain of UHPC—up to 98% and 195%, respectively, compared with its unconfined counterpart. The experimental results were compared with a number of available confinement models. Although one of the models provided a reasonable fit for the stress-strain response in most cases, all models generally underestimated the effectiveness of FRP confinement at higher confinement ratios. The study demonstrated the need for confinement models that could accurately predict the behavior of FRP-confined UHPC in terms of the stress-strain relationship and the respective ultimate strengths and strains.