Calibrated Equivalent FE Modeling and Parametric Behavior of GFRP-RC Isolated Footings on Winkler Foundations

Explicit bond-slip modeling for glass fiber-reinforced polymer (GFRP)-reinforced concrete (RC) members is computationally inefficient for structural-scale parametric analyses. This study develops a calibrated equivalent finite-element (FE) framework for GFRP-RC isolated footings on Winkler foundations. A GFRP-RC two-way slab test was used for calibration. After boundary correction, a tensile stress-scaling factor was introduced into the concrete tensile model to compensate for stiffness overestimation caused by the embedded-reinforcement assumption. The calibrated model was then transferred to a full-scale isolated footing, and the effects of subgrade modulus, bar diameter, reinforcement spacing, and footing thickness were examined. The results show that the footing response is governed mainly by settlement development, concrete cracking, and stiffness degradation, while the GFRP stress remains far below its tensile strength. Footing thickness is the most effective structural parameter for improving stiffness and reducing damage, whereas increasing bar diameter provides limited improvement despite higher reinforcement consumption. Reducing reinforcement spacing mainly improves tensile-demand distribution and damage control. The proposed calibrated equivalent FE framework provides an efficient numerical approach for comparative deformation- and damage-based assessment of GFRP-RC isolated footings within the investigated parameter range.