Influence of synthetic fibers on the seismic behavior of reinforced-concrete circular columns

The addition of discrete fibers to the concrete mixture to enhance its toughness and tensile strength is well acknowledged. Studies have also shown that fiber-reinforced concrete (FRC) can be favorable for its enhanced behavior in compression. This behavior, which is attributed to the confinement action of the fibers, is, in general, superior in terms of strength and ductility, compared to plain concrete. Reversed cyclic loading in flexure under constant axial load of large scale synthetic fiber-reinforced concrete columns is scarce as opposed to steel fiber-reinforced concrete columns. This paper presents an experimental study on the behavior of large-scale synthetic fiber-reinforced concrete columns with hoops transverse steel reinforcement under constant axial load and reversed flexure simulating seismic loading. The results from this study show slightly improved cyclic behavior compared to results obtained on similar columns reinforced with spiral transverse reinforcement. Enhanced behavior of synthetic fiber-reinforced concrete is achieved for practical transverse steel reinforcement spacings (>= 75 mm). In this case, similar ductile behavior of a reinforced-concrete column can be reached with a reduced amount of transverse steel reinforcement and the inclusion of synthetic fibers with an aspect ratio of 50-100 to the concrete mixture. Difficulty in placing synthetic fiber-reinforced concrete in very congested columns precludes its use in columns with hoops or spiral spacing less than 75 mm until self leveling concrete with large amount of synthetic fibers is developed.

Automated summary

The study examined the behavior of large-scale synthetic fiber-reinforced concrete columns under constant axial load and reversed flexure, showing slightly improved cyclic behavior compared to columns with spiral transverse reinforcement. The enhanced performance of synthetic fiber-reinforced concrete can be achieved with practical transverse steel reinforcement spacings, providing similar ductile behavior with reduced reinforcement and the addition of synthetic fibers. Difficulty in placing synthetic fiber-reinforced concrete in congested columns limits its use in columns with spacing less than 75mm until self-leveling concrete with a large amount of synthetic fibers is developed.