Building the code for design and optimization of members and joints of steel lattice structures composed of cold-formed circular hollow sections, along with a comparison between the old and the new version of the standard EN 1993-1-8

Abstract

Alongside the typical joint models: pinned and continuous joints, the European Standard EN 1993-1-8 (Eurocode 3: Design of steel structures – Part 1-8: Design of joints) also considers the design of semi-continuous joints, which represents the basis for designing economically viable structures. The first part of this paper deals with the alterations made in the first eight clauses and annexes of the draft of the new version of this standard (prEN 1993-1-8: 2021) in comparison with the old version (EN 1993-1-8: 2005). The second part of this paper concentrates on the making of a code for the design and optimisation of lattice girder joints (and their members). From that arose the need to go through the available literature concerning these types of joints and also to determine the alterations made in the ninth chapter of prEN 1993-1-8:2021. The paper focuses particularly on K gap joint configurations made of cold formed circular hollow sections. In order to have an overview of the alterations made in the draft of the second generation of this standard, a comparison between the old and the new version of EN 1993-1-8 has been made. The differences between the old and the new resistance formulas for K joints made of hollow sections have been considered in order to determine in which cases the design resistance was overestimated, and in which underestimated. Different add-ins have been considered in order to find the most simple way to make an Excel file for the design and optimisation of the subject joint. Alterations made to prEN 1993-1-8: 2021 were listed in accordance with the structure of the new standard. Generally speaking, prEN 1993-1-8: 2021 is more organized, more extensive and clearer than EN 1993-1-8: 2005. This primarily reflects in the part of the Standard that deals with joints between open sections. Alterations made in the ninth clause of the Standard are only given for the provisions that encompass all types of lattice girder joints. Relevant analytical models of failure, as well as comparisons between the old and the now resistance formulas are shown only for the K gap joint made of circular hollow sections. In accordance with the new resistance formulas, the code for the design and optimization of this joint type and its members was successfully made. This paper allows the users of the old version of EN 1993-1-8 an insight into the new generation of the Standard. Code for the design and optimisation of K gap joint made of circular hollow sections represents only the start of an application that could find its place in the everyday practice. If this application could be expanded to any members and joints, this could reduce the complete calculation of any steel structure (i.e., the calculation of both its members and its joints) only to the input of the general geometry of the structure and its loads.