Buckling Analysis, Structural Behavior and Strength of Distortional-Global Interaction in Cold-Formed Steel Lipped Channel Columns

Abstract

Cold-formed steel members are composed of thin-walled sections, forming very slender structural systems easily susceptible to buckling. This unique characteristic obligates designers to deal with the complexity of the phenomenon and requires research development to allow structural solution with simple equations. In terms of design procedures, these structural design equations are still under constant adjustments. The goal of the present research is the distortional-global (DG) buckling interaction of cold-formed steel lipped channel columns, in its buckling structural behavior and strength nature. Recent studies on this topic have been presented in the literature, however, the DG interaction still needs investigation in order to accomplish the definition of safe design procedures. For the buckling analysis, the Finite Strip Method-based software FStr Computer Application is developed, in order to perform the elastic buckling analysis, mainly focused in a simple and accessible graphical user interface. The FStr computational program generates the modal shapes which are inserted as the initial geometric imperfections in the finite element software ANSYS, in order to perform geometric and material nonlinear analysis. The buckling modes combination as initial imperfection helps to understand the DG buckling interaction, which is not feasible to predict with the first order elastic buckling analysis. It was observed that the global buckling strength equations from the Direct Strength Method (the most widely applied design method for cold-formed steel structures included in recognized design standards, attributable to its simplicity and accuracy in identifying the ultimate load of cold-formed steel members), have shown good agreement with the geometric and material nonlinear analysis results of columns of the present research, indicating a plausible design solution for the case of DG buckling interaction of cold-formed steel lipped channel columns. As suggestions for future work, the authors recommend a more robust parametric study, including: (i) new types of cross-sections geometries, (ii) other type of parametric analysis, and (iii) experimental tests results. Additionally, the authors are also planning several updates for the FStr Computer Application.