Effect of CFRP Bar Diameter and Concrete Strength on Shear Performance of ETS-Strengthened RC Beams with Recycled Plastic Aggregate: Validation and Parametric Study Using Abaqus

Abstract This study investigates the shear performance of sustainable reinforced concrete (RC) beams incorporating recycled plastic aggregate (RPA) and strengthened using the Embedded Through-Section (ETS) technique with carbon fiber-reinforced polymer (CFRP) bars. The experimental program involved twelve beams divided into two groups based on RPA replacement levels (25% and 50%), with variations in CFRP bar orientation (45° and 90°) and placement (edge or centre). All beams were tested under four-point loading with configurations that promote shear-dominated failure modes. To extend the experimental findings and evaluate broader parametric influences, a comprehensive finite element modelling campaign was conducted using ABAQUS. A total of 54 RC beam models were developed, including 36 models for analysing the effect of CFRP bar diameter and 18 for assessing the impact of concrete compressive strength. The numerical models were calibrated against the experimental data to ensure reliability in simulating shear behaviour, crack development, and load-deflection response.The results demonstrated that increasing the CFRP bar diameter led to a noticeable enhancement in shear capacity, with up to a 28% increase observed in some configurations. However, this improvement was accompanied by a slight reduction in bond efficiency, particularly in beams with lower concrete compressive strength. Increasing concrete strength from 30 MPa to 50 MPa resulted in a stiffness improvement of approximately 22%. Still, it also reduced the effectiveness of aggregate interlock, especially in specimens with 50% recycled plastic aggregate (RPA), where shear strength dropped by up to 15% compared to 25% RPA beams. Among all configurations, the ETS technique was most effective when CFRP bars were installed at a 45° angle and positioned near the beam edges, producing the highest shear resistance and improved crack control. The validated ABAQUS models strongly agreed with experimental results (within 5–8% deviation), confirming their reliability in predicting load-deflection response and failure modes. This integrated experimental-numerical approach offers practical insights for optimizing ETS shear reinforcement strategies in recycled aggregate concrete. It supports the development of sustainable design guidelines for shear-critical RC members.