Spiral Welded Steel Tubes

Description of impact

Spiral-welded tubes (SWTs) which are fabricated by helically bending a steel plate and welding the resulting helical seam joint, enable larger diameters, longer joint-less lengths and cost-effective construction compared to other tube types. SWTs fabricated using typical structural steel (mild-steel) as well as stainless-steel are available with the latter offering enhanced durability and deformability. Hollow SWTs have been widely used for foundations and soil retaining structures, though the use of SWTs in circular concrete filled steel tube (CCFT) columns has been limited, even though they are potentially well suited for this widely used application. CCFTs have greater strengths and enable speedier construction compared to typical hollow steel tube or concrete columns. Unlike for other types of tube, experimental verifications of the predicted behaviour as per the standardised guidelines have been limited for spiral-welded CCFT (SW-CCFT) columns. Only SW-CCFT columns under concentric axial loading, where the line of action of the load is in-line with the tube axis, has been investigated, though for most columns the line of action of the load is eccentric to the axis. Furthermore, SW-CCFTs under loadings transverse to the tube axis (beam loading) have not been effectively investigated contrary to other tube types.