Seismic Behavior of Synthetic Fiber-Reinforced Circular Columns

Abstract

Ductile behavior and high energy-dissipation ability are two essential properties for a reinforced concrete column part of a structure in a moderate to high seismic region. Concrete design codes ensure ductile behavior of columns by setting a requirement for a minimum amount of transverse steel reinforcement. Studies have shown, however, that use of fiber-reinforced concrete (FRC) can enhance the post-peak behavior and hence, the ductility and energy dissipation ability of concrete columns subjected to axial force and bending moment. Therefore, the inclusion of macro fibers in the concrete mixture, combined with a reduced amount of lateral reinforcement, can be an alternative to the conventional lateral reinforcement required by the codes. Moreover, the higher resistance to crack growth and the excellent durability of FRC over nonfibrous concrete can result in a higher cost-effective value. In this regard, tests on large-scale circular synthetic fiber-reinforced concrete (SNFRC) columns subjected to a combined constant axial load and reversed cyclic flexure simulating earthquake loading were carried out. The aim of this test program was to examine the influence of adding synthetic fibers to the concrete mixture on the behavior of normal-strength concrete (NSC) columns. The results show that, in terms of ductility and energy dissipation, SNFRC columns outperformed NSC columns. The results also show that the larger the amount of lateral reinforcement the smaller the influence of the fibers on the column's behavior. Based on the test results, the amount of confinement steel required by concrete design codes could be reduced when SNFRC is used.