Behaviour of Self Consolidating Steel Fiber Reinforced Concrete Beams Under Reversed Cyclic Loading

Abstract

Concrete is a very weak and brittle material in tension. It has been shown in previous researches that the addition of steel fibers to a concrete matrix can improve this behavior. The ability of fibers to control and redistribute stresses after cracking results in a number of improvements in the structural behaviour of concrete. A review of existing literature shows that the addition of steel fibers enhances concrete’s tensile resistance, crack control properties, ductility and damage tolerance. In beams, fibers can transform brittle shear response into a flexural response and promote ductility, thereby allowing for a full or partial replacement of traditional shear reinforcement. The enhanced shear capacity, ductility and damage tolerance of Steel Fiber Reinforced Concrete (SFRC) can also potentially be used to relax seismic detailing requirements in frames by partially replacing the required transverse reinforcement in the plastic hinge regions of RC beams.

One of the drawbacks associated with SFRC is that the addition of steel fibers to a traditional concrete mix at high fiber contents can result in workability problems. The combined use of Self-Consolidating Concrete (SCC) and fibers can solve this problem and facilitate placement for a wider range of structural applications.

Although several studies have been conducted on the behaviour of SFRC beams subjected to monotonic loading, there is limited research on the behaviour of SFRC beams under cyclic or reverse-cyclic loading. This thesis presents the results of an experimental and analytical study conducted on nine SFRC beam specimens tested under load reversals. The main objective of this research program was to investigate the effect of fibers on structural behaviour and to examine the ability of steel fibers to replace transverse reinforcement. The experimental and analytical results show that use of fibers results in several improvements in behaviour, including enhanced damage tolerance and post-peak ductility. The results also show that steel fibers can potentially be used to allow for a reduction of transverse reinforcement in beams, however further research is required.