Experimental investigation of the behavior composite steel-concrete composite beams containing different amounts of steel fibres and conventional reinforcement

Abstract

In this paper, an innovative method to replace steel reinforcement cage by steel fiber to form a steel shape and steel fiber reinforced concrete has been proposed to solve the problems of steel reinforced concrete structure during construction, such as position conflict between shape steel and steel bars, or difficulty of concrete placement, etc. Eighteen beams were tested under a four-point bending configuration to study the effectiveness of steel fibers on shear and flexural strengths, failure mechanisms, crack control, and ductility. The major factors considered were shear span depth ratio (λ = 2.5, 3.5), with or without longitudinal reinforcement and web reinforcement (none, stirrups and/or steel fibers). The response of Steel Fiber Steel Reinforcement Concrete (SFSRC) beams were assessed depending on the results of crack patterns, load at yielding, failure and ultimate bearing capacity, failure modes, ductility and displacement increment of plastic development, The experimental results showed that the addition of steel fibers improves the mechanical response, specifically speaking, flexural and shear strengths and ductility of the tested specimens. The longitudinal reinforcement can greatly enhance the bearing capacity, and the stirrups and steel fibers can make the reinforcement effect more prominent. The stitching effect of steel fiber between cracks leads to stable bearing capacity of the specimens always stable after the peak load. Increasing the content of steel fiber contributes to delay or even avoid bond failure. Steel fibers can be an alternative to shear reinforcement. A formula was proposed to predict the bearing capacity of SFSRC specimens, and the comparison between predictions and experiment results proved the reasonable of the formula. A formula was proposed to predict the bearing capacity of SFSRC specimens, and the comparison between predictions and experiment results proved the the formula.