Inelastic Test and Design Method of Cold-formed Steel Lipped Channel Members in Bending

The aim of this paper is to investigate the inelastic bending capacity and design method of cold-formed steel lipped channel bending members. The bending tests were conducted on 30 cold-formed steel lipped channel members. The nominal yield stress and the nominal thickness of the bending members were 235 MPa and 2mm. The theoretical global buckling stress was higher three times than the yield stress which can make sure the failure of members were in inelastic stage. For each specimen, an analytical analysis using Finite Element Method (FEM) was also conducted considering the influence of the boundary, the ultimate bending capacity, and the failure mode could also be captured. The test results show that the Chinese cold-formed steel specificationTechnical code of cold-formed thin-walled steel structures(GB50018-2002) is conservative for lipped channel bending sections in inelastic stage. The test results are used to put forward to a revised design method based on effective width method for the current Chinese cold-formed steel specification. The comparison on the bending capacity between the test results and the calculated results by using the proposed method, effective width method and direct strength method in North American cold-formed steel specification (AISI-S120-2016(draft)) shows that the proposed method can consider the inelastic reserve capacity of bending members well. The failure modes and bending capacity of bending members obtained using the idealized shell finite element model, which are close to the experimental results, shows that the idealized model is very well to model the buckling behavior and calculate capacity of bending members.