Effect of cross-sectional corner radius on the compressive behavior of GFRP-confined concrete prisms under repetitive loading: Experimental study and ANN-RSM modeling

Enhancing strength and ductility in concrete elements through Glass Fibre Reinforced Polymer (GFRP) confinement has become a critical technique in structural retrofitting. Among the factors influencing confinement performance, the corner radius of square sections plays a significant role but remains inadequately studied, particularly under repetitive compressive loading. This study investigates the stress-strain behaviour of FRP-confined concrete prisms with varying corner radii and different lateral tie spacings subjected to monotonic and repetitive loading. An experimental investigation is conducted to assess the mechanical response of confined concrete prisms, while predictive modelling using Response Surface Methodology (RSM) and Artificial Neural Networks (ANN) is employed to simulate the behaviour and validate the experimental outcomes. Results indicate that increasing the corner radius and applying repetitive loading can improve ultimate stress and strain capacities. Specifically, the specimen WLC3, with a 25 mm corner radius and subjected to nine loading cycles, exhibited the highest ultimate stress of 47.53 MPa and the highest axial strain of 0.0420, corresponding to a 58.43 % increase over the unconfined concrete strength. Both ANN and RSM models accurately predicted the stress-strain response, with the ANN achieving a high coefficient of determination (R² = 0.9985) and RSM following closely (R² = 0.987) with a prediction error margin below 5 %. These findings underscore the critical role of cross-sectional geometry and load history in optimizing FRP confinement and contribute to more resilient design strategies for retrofitted concrete elements under repeated loading conditions. • Studied the corner radius effect on GFRP-confined concrete under cyclic loading. • Larger radii improved strength and ductility, especially with repeated cycles. • Peak stress 47.53 MPa and strain 0.0420 achieved with 25 mm radius, 9 cycles. • ANN (R²=0.9985) and RSM (R²=0.987) accurately predicted stress–strain behavior. • Findings guide FRP confinement design for resilient retrofitted concrete columns.