Strengthening of web perforated CFS lipped channel columns with CFRP: a numerical study

In this study, the influence of Carbon Fiber Reinforced Polymer (CFRP) wrapping on the axial capacity of web perforated Cold-Formed Steel (CFS) lipped channel columns is investigated numerically. Circular perforations are provided at the center of the web, at mid-height of the columns. The dimensions of the lipped channel section are assumed such that local and distortional interactive buckling governs the failure mode. The numerical analysis is carried out by developing finite element models with the help of ABAQUS. Initially, the developed numerical models are validated against the relevant results reported in the literature. Then, various strengthening/wrapping configurations are adopted on the calibrated numerical model, and their influence on the structural response of the columns is investigated. A 'composite layer/ply' modeling technique is adopted for simulating the CFRP wrapping. The various strengthening configurations analyzed in the current investigation include uni-directional (UD) CFRP of 0 & DEG; and 90 & DEG; (CF_UD-0 & DEG; and CF_UD-90 & DEG; respectively) fiber orientations and bi-directional (CF_BD) CFRP. Apart from orientation of CFRP fibers, the influence of the CFRP type, number of CFRP layers, yield strength of steel, and the size of the perforation on the axial capacity of web-perforated CFS lipped channel columns is discussed. All the column specimens were of constant height and are short columns based on the slenderness. The results revealed a significant improvement in ultimate strength by adopting CF_UD-0 & DEG; in the case of a single layer of CFRP and either CF_UD-0 & DEG; + CF_BD or CF_BD + CF_UD-0 & DEG; in the case of two layers of CFRP, irrespective of the yield strength of steel.