Combined constructions of steel tubes and sheet metal are used as retaining walls where high differences in ground levels have to be secured . Such 'Combiwalls' consist of vertically positioned steel tubes (usually spiral welded) with diameter to thickness ratios in the range d/t = 70 - 100 (d = 800 – 1200 mm) that provide the necessary bending stiffness, together with infill sheeting composed of standard sheet pile profiles (Fig. 1). The experimental and numerical investigation of these thick-walled steel tubes in bending is the main objective of the RFCS-funded Combitube research project, which aims to improve the existing design rules for buckling. The project is a partnership between the Universities of Delft (Netherlands), Thessaly (Greece), Karlsruhe (Germany) and Edinburgh (Scotland) together with the industry partners ArcelorMittal (Luxemburg) and BAM Infraconsult (Netherlands). This paper focuses on large scale bending tests of a set of spiral welded steel tubes that were conducted at the Karlsruhe Institute of Technology (KIT) which aimed to investigate the bearing behaviour of these tubes under a bending moment and axial force. ... mehrThe effect of the geometric imperfections caused by the spiral welding process is investigated and compared with the test results.