Assessing the effectiveness of glass fiber reinforced polymer laminates for retrofitting plastic fibre-reinforced geopolymer concrete composite beams: a GANNcrete and NSGA-II multi-objective approach

Abstract

This study presents a laboratory investigation into the shear behaviour of geopolymer composite beams retrofitted using externally bonded Glass Fiber Reinforced Polymer (GFRP) laminates. To enhance shear resistance, spiral transverse reinforcements were incorporated in selected beam specimens. The beams were cast using sustainable cementless concrete-commonly referred to as geopolymer concrete-incorporated with plastic fibres to improve crack control and contribute to environmental sustainability in construction practices. All beam specimens were initially preloaded to induce shear cracks up to 75 % of their respective ultimate loads. Following this, retrofitting was carried out using different GFRP laminate configurations at the shear zone. Post-retrofitting, the beams were reloaded until failure, and their structural performance was evaluated and compared with beams strengthened using spiral transverse reinforcements. Key performance parameters, including load-carrying capacity, crack propagation, failure modes, load-deflection behaviour, and ductility characteristics, were examined in detail. Along with lab tests, an innovative method as a machine learning framework GANNcrete is implemented with a multi-objective optimization approach that is utilized in modeling and forecasting the behaviors of beams with various scenarios. The Non-dominated Sorting Genetic Algorithm II (NSGA-II) is used to identify optimal solutions considering multiple objective conflicts, to ensure the structural and computational outcomes are balanced. The proposed approach performance is assessed based on accuracy, precision, recall, F1-score, specificity, scalability, and response time as parameters the findings suggest that hybrid retrofitting solutions enhance the strength and functionality of geopolymer concrete beams. The mechanical performance of geopolymer concrete was improved by adding 1 % plastic-PP fibers with an aspect ratio of 30, according to testing results. The spiral transverse reinforcement improved the ultimate load capacity by 21 % as compared to the reference beam, while the use of plastic-PP fibers in conjunction with retrofitting enhanced the load capacity by up to 46 %.