Optimization of flexural strength for cold roll formed sections using design of experiments and response surface methodology
In this study, the buckling and ultimate strengths of cold rolled channel sections with intermediate stiffeners were studied using numerical modelling. In order to improve the section strength, various alternative sections of varying intermediate stiffeners were developed and searched for the maximum ultimate strength. The section flexural strength was optimized through a practical approach that combines finite element modelling and optimization using design of experiments (DOE) and response surface methodology. In this approach, a nonlinear finite element model was first developed for a referenced channel section subjected to four-point bending tests and this reference section was then parameterized in terms of geometric dimensions and material properties using the DOE technique. In the next step, a response surface was used to determine the influences of the stiffener’s properties on the section distortional buckling and ultimate strength including its location, shape, size and material properties by the cold work at the section corners and stiffener bends. Response surface design optimization was then used to determine the geometric dimensions and material properties of novel channel sections. The new optimized channel sections were then applied loading up to failure to obtain ultimate flexural strengths and the results were compared to those of the reference channel section. It was found that sections with maximum ultimate strength in distortional buckling could be obtained with both the stiffeners’ position, shape and size, and the cold work influence. The cold work influence was found most significant in the novel channel sections. An optimal shape for the channel section with maximum ultimate strength in distortional buckling could be obtained without increasing the amount of the material used.