Behaviour of cold-formed dimpled columns under lateral impact

The UltraSTEEL® forming process forms plain steel sheets into dimpled steel sheets. During the forming process both geometry and mechanical properties are considerably altered. This study aims to understand the response of the dimpled steel columns to low velocity lateral impact loads. Explicit finite element (FE) models were created and validated, including boundary conditions, element types and element sizes. Plain, dimpled columns and columns with dimpled geometry and plain material (DGPM) were analysed under lateral impact, to find out the difference between plain and dimpled columns, and the influence of the introduced dimpled geometry. Comparisons were made based mainly on the mean impact force, crush efficiency, and ability to maintain stability. A series of numerical analysis was carried out under different axial compressive loads. The dimpled columns have shown an up to 32.5% greater mean force and an up to 24.4% greater crush efficiency over the plain ones. The dimpled columns have also shown a better stability under axial compressive loads. A further investigation on the support conditions indicated that the dimpled geometry contributes to the reduction of the maximum impact force and therefore increasing the crush efficiency, where at least one end of the column is fully fixed.