Flexural strengthening of ductile high-performance concrete beam with low reinforcement ratio using glass fibre-reinforced polymer sheets

No specific work concentrates on the structural performance of ductile high-performance concrete (DHPC) beams with a very low reinforcement ratio of As<As,.min=max{[0.25fcbd/fy] and 1.4bd/fy}. Accordingly, a comprehensive investigation was conducted using the glass fibre-reinforced polymer (GFRP) strengthening technique to enhance the flexural performance of a DHPC beam. Initially, various types of fibres within DHPC mixtures were evaluated through micro-scale experiments to achieve a practical mix design. Following this, a large-scale DHPC beam was created utilising the optimal mix design and subjected to a flexural test. The tested beam was also validated in a numerical model using Abaqus software. The GFRP strengthening technique was incorporated into the numerical model, exploring multiple scenarios with varying lengths of single GFRP sheets, U-shaped GFRP sheets, U-GFRP strips and hybrid GFRP sheets. The findings revealed that the application of the GFRP strengthening technique significantly enhanced the flexural capacity and altered the cracking pattern of the DHPC beam. Nevertheless, it is essential to regulate the lengths and types of GFRP strengthening methods to prevent unexpected shear failures. In addition, some inefficient hybrid GFRP strengthening methods not only fail to enhance the flexural strength but can negatively affect the beam’s failure pattern.