On the behaviour of thin-walled steel regular polygonal tubular members

This paper presents an investigation concerning the mechanics of deformation of thin-walled steel tubular members with single-cell regular polygonal cross-sections, such as those employed to build transmission line structures, towers, antennas and masts. This type of cross-sections exhibit rotational symmetry of order equal to the number of walls, which leads to remarkable peculiarities concerning the cross-section in-plane and out-of-plane (warping) deformation. The investigation is based on a specialization of Generalised Beam Theory (GBT), aiming at fully uncoupling the main cross-section deformation mode sets, which makes it possible to obtain analytical results and thus extract in-depth information concerning the structural behaviour of this type of members. Several illustrative examples, employing both analytical and numerical (using GBT-based beam finite elements) strategies, are presented throughout the text. For validation and comparison purposes, results obtained with standard shell finite element models are also provided.