Strength and Ductility of Hollow Circular Steel Columns Filled with Fibre Reinforced Concrete

Abstract

This chapter investigates the behavior of hollow circular steel cross-sections filled with Fiber Reinforced Concrete (FRC), subjected to monotonic loads. The casting of different types of composite members—steel columns, steel columns filled with Normal Strength Concrete (NSC), and steel columns filled with Fiber Reinforced Concrete (FRC) was employed. The columns were tested in uniaxial compression utilizing a universal testing machine operating in displacement control. The maximum strength of composite members filled with FRC was 20% higher than that recorded for steel pipes filled with FRC. After the peak load was reached, failure was due to the crushing of concrete and due to local and global buckling of the steel pipes. The vertical loads of the composite members were obtained by considering of the steel pipes and concrete core to strength, without any reduction in the transverse cross-section of the concrete core, because of the effective confinement reached in concrete inside steel pipes. In the case of FRC, the buckling effects were reduced by the presence of fibers and failure was due to essentially plasticization of materials ensuring a good prevision of experimental results with the analytical model based on these concepts. In the case of steel pipes filled with plain concrete, the buckling effects reduced the bearing capacity of the columns in the softening branch.