Impact of Unbonded CFRP Strengthening on the Bending Performance of Steel I-Beams: A Numerical Study

The performance of steel structures can decrease over time due to several factors and therefore requires serious consideration to avoid any risks to users. Currently, strengthening of structures using fiber-reinforced polymer (FRP) materials is gaining in popularity. This paper presents a finite element (FE) analysis to investigate the flexural performance of steel I-beams strengthened with unbonded carbon FRP (CFRP). A total of 38 beam models is developed with four influential parameters considered, namely CFRP thickness, CFRP elastic modulus, type of steel beam cross-section, and strengthening length. The results of the investigation confirm that unbonded CFRP strengthening improves the performance of steel I-beams. Initial stiffness and moment capacity of the beams increase as the thickness of CFRP, CFRP elastic modulus, and strengthening length increase. The increase in the initial stiffness of beams tends to be linear as the length of strengthening increases. Meanwhile, the linear trend occurs only up to CFRP lengths of 700 mm or 800 mm for the increase in beam moment capacity. Unbonded CFRP strengthening contributes higher to steel beams with a lower moment of inertia.