Ultimate bending capacity of spiral-welded steel tubes - Part I: Experiments

The present investigation refers to the bending capacity of spiral-welded steel tubes. The first part of this investigation presents the results of a full-scale experimental program, aiming to investigate the structural behavior of large-diameter spiral-welded steel tubes under bending. A companion paper (Part II) is also published, which further studies the behavior of these elements numerically, using finite element simulations. The testing program presented in Part I consists of thirteen 42-inch-diameter spiral-welded steel tubes with IV ranging between 65 and 120. Some of the tubular specimens contain girth welds and coil connection welds, which are shown to penalize the ultimate bending capacity of the tubes. Extensive measurements of initial imperfections and material properties are performed for each tubular specimen. The material properties of the specimens are investigated through both uniaxial tensile and compression coupon tests. A series of large-scale four-point bending tests is performed to determine the structural behavior of the tubes, resulting in local budding failure of the tubes under consideration. The bending behavior of the thirteen specimens is documented extensively. The study offers information with regard to the ultimate bending resistance of the specimens. In addition, the full moment curvature equilibrium path is presented, supplemented by measurements on the development of cross sectional ovalisation and tube wall wrinkling during the bending tests. (C) 2015 Elsevier Ltd. All rights reserved.