Cyclic behavior of high-performance concrete columns reinforced with hybrid-GFRP bars

This study examines the cyclic performance of high-performance concrete (HPC) columns with hybrid steel-glass fibre-reinforced polymer (GFRP) bars, filling a gap in existing research. Six full-scale columns were tested under axial compression (60 kN) and cyclic lateral loading, divided into two groups by bar diameter (10 mm and 12 mm). Each group included one steel-reinforced control column and two hybrid-reinforced specimens. Lateral displacement increased incrementally from ± 3 mm to ± 36 mm. Results showed hybrid columns achieved 53.24% (10 mm) and 38.27% (12 mm) higher lateral strength than controls, but exhibited reduced ductility and energy dissipation, with narrower hysteresis loops and pinching effects. Finite-element (FE) models in Abaqus software employed the concrete damaged plasticity approach to simulate material non-linearity, bond-slip and cyclic degradation, demonstrating strong agreement with experimental load–displacement behaviour and failure modes. These findings indicate that the reduced ductility of hybrid-reinforced columns may impose limitations on their seismic design applicability, emphasising the need for enhanced detailing to ensure adequate deformation capacity under earthquake loading. The study provides critical experimental data and validated modelling for hybrid-reinforced HPC systems, demonstrating their structural potential while identifying key challenges for earthquake-resistant design. The FE analysis supports its use for future parametric studies of hybrid reinforcement configurations in cyclic loading conditions.