Axial–Flexural Performance of Steel Fiber-Reinforced Concrete Columns: Effects of Axial Load Ratio and Steel Fiber Volume Fraction

TL;DR

This study examines how steel fibers affect the strength and durability of concrete columns under combined loads, finding that steel fibers improve ductility and energy absorption.

Contribution

The novel contribution is quantifying how steel fiber volume and axial load ratio influence the axial-flexural performance of SFRC columns.

Findings

Steel fibers enhance ductility and energy absorption in concrete columns under moderate axial loads.

Higher axial load ratios increase peak load capacity but reduce ductility, leading to brittle failures.

Optimal performance occurs at an axial load ratio of 0.10 with steel fiber reinforcement.

Abstract

This study investigates the axial–flexural behavior of steel fiber–reinforced concrete (SFRC) columns under combined constant axial load and monotonic lateral loading. Nine column specimens with different axial load ratios (0.0, 0.10, and 0.20) and steel fiber contents (0.0%, 0.5%, and 1.0%) were tested under monotonic loading to evaluate their failure modes, load–deflection behavior, ductility, and energy absorption capacity. In addition, a sectional P–M interaction analysis was performed to examine the influence of steel fiber inclusion on flexural strength under different axial compression levels. The interaction diagrams indicated that steel fibers expanded the flexural strength envelope, with a more pronounced enhancement in the low-axial-load region. The test results revealed that increasing the axial load ratio enhanced the specimens’ peak load capacity but reduced their ductility, leading to a brittle failure mode. Conversely, the incorporation of steel fiber improved the crack distribution, delayed crack propagation, and enhanced both ductility and energy absorption, particularly under moderate axial load conditions. The failure modes were characterized generally by flexural cracking and localized crushing in the compression zone, with the specimens that contained steel fiber exhibiting a more gradual post-peak load response than the specimens without steel fiber. The energy absorption capacity, quantified as the area under the load–deflection curve, was maximized when the axial load ratio of 0.10 was used in tandem with steel fiber reinforcement, indicating an optimal balance between strength and ductility. Overall, steel fiber inclusion improved deformation capacity and energy absorption under monotonic loading, particularly at low-to-moderate axial load ratios.

Figures