Mechanical properties and constitutive model of steel fiber reinforced manufactured sand concrete columns: Experimental, theoretical and numerical investigation

The intensive extraction of natural sand (NS) has created significant challenges related to resource depletion and ecological consequences, driving the need for manufactured sand (MS) as an eco-friendly substitute in construction applications. This research systematically examines the structural performance and deformation characteristics of steel fiber-reinforced manufactured sand concrete (FRMSC) columns subjected to eccentric loading, with particular focus on MS replacement percentage (0%, 50%, 100%), load eccentricity (20 mm, 40 mm, 60 mm), and steel fiber dosage (0%, 1%, 2%). Testing outcomes reveal that whereas variations in MS replacement ratio and reinforcement ratio showed minimal effect on concrete strain, decreasing the slenderness ratio and elevating fiber content substantially improved deformation capability. Steel fiber integration enhanced the mechanical performance of MS concrete, successfully mitigated surface spalling, and promoted both load-bearing capacity and deformability. While the failure mechanism of MS concrete columns remained fundamentally unchanged, fibers optimized stress redistribution through improved shear-friction capacity, consequently prolonging the failure progression and augmenting energy absorption. Additionally, a constitutive framework for MS concrete was established using experimental data, with its reliability confirmed via finite element modeling of the loading sequence. The computational outcomes correlated well with empirical observations, demonstrating minor deviations of 4.84% in maximum displacement and 1.40% in ultimate load.