Investigation on the behaviour of CFRP strengthened CHS members under monotonic loading through finite element modelling

During the past several years, civil infrastructure has made extensive use of tubular hollow steel members as structural elements. However, the rehabilitation and strengthening of tubular hollow steel members is a major concern due to design errors, environmental effects, reduction in material properties over time caused by corrosion and the need to withstand increased loads. A comprehensive investigation on the strengthening of tubular hollow steel members is therefore required. Although carbon fibre reinforced polymer (CFRP) strengthening technique has shown its effectiveness to improve the structural response of different steel members, studies on the structural response of circular hollow section (CHS) steel members strengthened with CFRP is limited. In the present study, an effective finite element (FE) model is first developed by comparing the FE model simulated results with the authors' experimental results. This is followed by a parametric study on the effect of the bond length of CFRP, number of CFRP layers, ratio of CFRP thickness to CHS wall thickness, diameter to thickness ratio of CHS and steel grade of CHS on the structural behaviour of the strengthened member subjected to monotonic loading. These parameters had noteworthy effects on the behaviour of the CFRP strengthened CHS steel members under monotonic loading. The CFRP strengthened CHS steel members showed an improvement in the moment capacity, secant stiffness, energy dissipation capacity and ductility compared to their bare CHS steel members. It can be concluded that the effectiveness of the CFRP strengthening technique is enhanced with the increase in the ratio of CFRP thickness to CHS wall thickness and/or increasing the diameter to thickness ratio of CHS. In contrast, the effectiveness of the CFRP strengthening technique is decreasing with the increasing of the steel grade.