This two‐part article gives an overview of the developments of the structural member verification in prEN 1993‐1‐1:2020 ”Eurocode 3: Design of steel structures – part 1‐1: General rules and rules for buildings“, one of the second generation of Eurocodes. These developments were undertaken by Working Group 1 (WG1) of Subcommittee CEN/TC250/SC3 and by Project Team 1 (SC3.PT1) responsible for drafting the new version of EN 1993‐1‐1. In the past, WG1 collected many topics needing improvement, and the systematic review conducted every five years also yielded topics needing further development. Based on this, the current version of EN 1993‐1‐1 has been developed into a new draft version prEN 1993‐1‐1:2020 enhancing ”ease of use“. The technical content of this new draft was laid down at the end of 2019. Many improvements to design rules have been established with respect to structural analysis, resistance of cross‐sections and stability of members. This two‐part article focuses on member stability design rules and deals with the basis for the calibration of partial factors, the introduction of more economic design rules for semi‐compact sections, methods for structural analysis in relation to the appropriate member stability design rules, new design rules for lateral torsional buckling plus other developments and innovations. This second part of the article is dedicated to illustrating the most relevant changes to member buckling design rules.
The residual stress distribution influences substantially the stability behavior of steel members. Its shape, directly impacted by the fabrication process, is very different in hot‐rolled and welded members. Among welded members, flame‐cut flanges and hot‐rolled flanges are commonly employed in practice. However, buckling curves of Eurocode 3 are based on experimental tests and numerical simulations performed on welded members having hot‐rolled flanges only and lead to conservative results comparatively to the previous French design standards but also to hot‐rolled members. Investigations are strongly needed to adapt the existing buckling curves to welded members using flame‐cut flanges and a first step is to estimate the residual stress distribution in such members.
The results available in the literature dealing with residual stresses measurements in welded members with flame‐cut flanges investigate stocky profiles that can be far from common practice, welded members being preferably slender sections. This paper presents the results of an experimental campaign on residual stresses performed on eight slender welded members varying the flange width and thickness as well as the flange type : hot‐rolled or flame‐cut. The measurements were performed using the sectioning method. A new model for residual stress distribution in welded I‐section members with flame‐cut flanges is then proposed based on these tests results and existing data from the literature.
Lattice towers are extensively built in Europe and worldwide to serve telecommunication or power transmission purposes. The structural members of such towers are frequently made of equal leg angle sections that are often preferred to tubular sections due to their easy connection that results in a simple erection, a requirement set by most telecommunication or power providers. Angle sizes range from light to heavy sections with leg lengths up to 300 mm for towers with significant height. Towers, especially telecommunication ones, may need to be strengthened due to the fact that, during the design life, heavier or larger antennas resulting in a heavier wind loading may be installed. As an alternative to conventional methods, hybrid strengthening of tower angle members with carbon fiber reinforced polymers (CFRP) strips may be employed.
The present paper provides an overview of ANGELHY, an RFCS‐funded research project that comes toward its end. The scope of the project is the establishment of analysis methods for lattice towers and the development of design rules for steel and hybrid angle sections, as well as built‐up members composed of angles.
This paper focusses on the buckling resistance of compression members made of back-to-back connected angle sections. The studied built-up members are connected through bolted packing plates. Due to the flexibility of this connection, these members generally do not fully work as a single member but the connection stiffness has to be accounted for. In Eurocode 3 Part 1-1 it is currently admitted to neglect the effect of the connection stiffness if the packing plates possess a maximum distance of 15 imin (imin is the minimum radius of gyration of one individual angle section, also called "chord"). Elsewise the influence of the packing plates on the member resistance should be accounted for. The limit distance of 15imin appears to be much lower than the past practice, consequently leading to a more conservative design and a complexification of the fabrication. This paper therefore presents a sensitivity analysis focusing on the influence of several parameters as: the distance of packing plates, the presence of clearance in bolt holes and the influence of preloaded bolts. These parameters are studied with a numerical model based on solid finite elements. Owing to the use of solid elements, it is possible to model explicitly the bolts, the packing plates and all contact regions.
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