Stress Concentration Around Cutouts in Spirally Welded Steel Columns

Abstract

Spirally welded (SW) columns have found widespread application in diverse structures, including pipeline constructions, wind turbine towers, foundation piles, and high-rise buildings. While prior research has examined cutouts in flat plates, there is a noticeable gap in the investigation of circular columns with similar cutouts. Given the critical role these structures play, it is increasingly imperative to direct research endeavours toward comprehending the behaviour of stress concentration in curved plates featuring cutouts. Specifically, the presence of circular cutouts in a column is shown to induce a diminished stress concentration, owing to the even distribution of stresses. This research delves into a comprehensive study of SW steel columns of different length-to-diameter ratios (L/D) that incorporate circular cutouts of varying sizes and subjected to axial compression. Experiments were conducted on 18 specimens, with results scrutinized and benchmarked against analytical outcomes obtained through Abaqus software. For a comprehensive analysis, 990 finite element (FE) models were created, and non-linear analysis was carried out. Subsequently, a comparative examination was undertaken between longitudinally welded (LW) and SW columns, incorporating varying cutout sizes and positions. The results of both analytical investigations and experimental tests exhibited a remarkably strong correlation. One intriguing and paradoxical observation emerged: an increase in the size of the cutout within an SW column simultaneously enhanced buckling loads while reducing the structural mass. SW columns achieve a more uniform stress distribution along their length due to the presence of a continuous helical weld seam. This helical seam enables the column to efficiently distribute applied loads, minimizing localized stress concentrations. In contrast, LW columns feature weld seams that run parallel to the column's length, potentially creating stress concentrations and vulnerable areas within the structure. Consequently, the continuous nature of the helical weld seam in SW columns enhances load distribution and reduces the likelihood of stress concentration induced weaknesses compared to the linear weld seams in LW columns. This phenomenon underscores the superior load-bearing capacity conferred by the spiral welding technique, positioning SW columns as the preferred choice for applications where strength and efficiency are of paramount importance. Additionally, the data derived from both experimental tests and analytical investigations have been used to propose an equation for the calculation of stress concentration factor around cutouts in SW columns.