Parametric evaluation of lateral load capacity in precast hybrid steel/GFRP-reinforced concrete columns with grouted corrugated duct connections

Abstract

• Finite element model of hybrid steel–GFRP reinforced precast columns • Numerical results showed good agreement with experimental observations. • A comprehensive parametric study examined the influence on capacity, stiffness, and deformability. • Deformability improved with optimised hybrid reinforcement configuration. • Analytical capacity calculations confirmed numerical results at target drift levels. Recent advances introduced hybrid precast bridge columns with an external steel layer, an inner GFRP layer, and double-layer spirals. A finite element model was developed and validated against large-scale columns with grouted corrugated duct connections under combined axial and lateral loads. The model accurately captured lateral load–drift behavior and failure modes. A parametric study examined the effects of reinforcement ratio, steel-to-GFRP replacement, diameter ratio, axial load, and concrete strength on capacity, deformability, and stiffness. It was found that the column with a 1.1% reinforcement ratio failed due to GFRP rupture and achieved a maximum drift of only 77% of that attained when the ratio increased to 1.8%. Similarly, columns with an inner-to-outer bar diameter ratio of 0.68–0.84 achieved 83–92% of the capacity and 63–88% of the maximum drift of columns with equal-diameter bars in both layers, with failure controlled by brittle GFRP rupture. Increasing reinforcement ratio and GFRP bar diameter improved ductility and reduced premature rupture. While the steel RC column reached full capacity at 2.5% drift, half and full replacement of steel by GFRP achieved only 86% and 64% of the column capacity at the same drift, respectively. The analytical model predicted capacity accurately. The comparison showed that the theoretical capacity is reached at 4% drift, with lateral loads exceeding predictions by 1.27% on average and a coefficient of variation of 6.1%. Hence, a design drift of 4% for hybrid GFRP/steel RC columns is recommended, consistent with Canadian GFRP-RC provisions and above the 2.5% drift limit for steel-RC structures.