Rebar indentation on performance of CFS columns strengthened by rebar at flange-lip

Abstract

To facilitate easier construction when longitudinally reinforcing cold-formed thin-walled lipped channel steel columns with steel bars, here, both ends of the steel bars used for reinforcement were cut, and the impact on the reinforcement effect was studied through experimental and numerical simulation methods. Seven groups of reinforced column specimens with different indentation lengths and one group of unreinforced specimens were designed, and axial compression tests were conducted. Parametric analyses were performed using the numerical models calibrated by tests. These numerical models included three types of specimens with typical sections and several series of specimens with different steel plate thicknesses. Using these models, the effects of the steel bar indentation length Li, steel bar diameter D, and other factors on the ultimate bearing capacity and deformation of the reinforced specimens were studied. The experimental results indicated that when the steel bar is the same length as the specimen, the compressive bearing capacity of the cold-formed thin-walled lipped channel column can be significantly improved by bonding the steel bar. Additionally, the numerical analysis results indicated that the influence of changing the steel bar diameter D on the bearing capacity of the specimens is not significant when the steel bars are indented within a certain range. As the length of the steel bar indentation increases to a certain extent, the stress concentration at the end of the steel bar becomes more significant, causing local buckling of the specimen and ultimately leading to a sharp decrease in the bearing capacity of the specimen. To achieve reinforcement, facilitate construction, and ensure structural safety, the total indentation length Li of the steel bars should not be >2 cm in practical engineering projects. Considering the economy of reinforcement engineering, it is suggested that steel bars with smaller diameters, i.e., 6 mm, should be selected. Through a comparison between the FEA and the experimental process, it was confirmed that the failure model of the numerical model is basically consistent with the experimental phenomenon, and the bearing capacity deviation was <3.3%. This indicates that the FEM established in this study was reliable.