Assessing the net section resistance and ductility requirements of EN 1993‐1‐1 and EN 1993‐1‐12

Abstract

In Eurocode 3 the strength functions are derived from simple engineering models, which always require a certain degree of material ductility. With regard to high-strength steels and the accuracy of the design models themselves, several problems are involved due to a lack of sound consideration of the plastification and damage process. Additionally, the current ductility requirements of EC3 obstruct the use of high-strength steels with f y ≥ 500 MPa. Within the current revision of EC3, comprehensive investigations have been conducted to overcome these obstacles. To complement extensive experimental tests, improved numerical methods considering damage mechanics have been used to predict the real plastification and damage process for relevant details. The numerical models were validated by comparing them with experimental results. Subsequently, a parametric study was conducted to investigate the influence of strength and toughness properties separately. It could be shown that the reduction factor of 0.9 to account for the net section resistance can be omitted if cracks can be excluded. Furthermore, it became clear that a strain requirement based on the uniform elongation e u is not appropriate. Moreover, it was revealed that the yield ratio f u /f y has a significant impact on the toughness requirements necessary to reach the full net section resistance. Owing to a lack of minimum upper-shelf toughness requirements in delivery standards, which would secure an appropriate inner damage resistance of the material, a substitution criterion is proposed.

AUBI‐äquivalente Anforderungen an die Zähigkeitshochlage aus Versuchen und Schädigungssimulationen

“…Der AUBI ist somit nicht als freies Kriterium zur Beurteilung der Materialzähigkeit, sondern eher der Rotationsfähigkeit von Blechen mit Anriss anzusehen. Deutliche Parallelen lassen sich zu den Hochlagenzähigkeitsanforderungen für angerissene Nettoquerschnitte unter Zug gemäß DIN EN 1993‐1‐1, 6.2.3 feststellen. Auch hier stellt sich für den Bereich um S460 ein Minimum an Hochlagenanforderung heraus, während sie für S355 und S690 in etwa gleich deutlich höher ausfällt [2–4]. …”

“…B. bei ermüdungsbeanspruchten Konstruktionen rechnen muss, treten deutlich höhere plastische Dehnungen auf, um den angezielten ULS zu erreichen. Dies erfordert eine erhöhte lokale Duktilität, die weniger durch die Kennwerte des Zugversuchs, wie das Streckgrenzenverhältnis f u / f y , die Gleichmaßdehnung ε u oder die Bruchdehnung A , sondern eher durch die Materialzähigkeit der Hochlage sichergestellt wird [1–5]. Obwohl davon für die meisten Feinkornbaustähle ausgegangen werden kann, dass ausreichende Hochlagenzähigkeit vorhanden ist, ist dies für die Güte S355 zu hinterfragen.…”

Application of damage theory to structures made from high‐strength steels

“…A general description of the use of an appropriate damage model suitable for structural steel components was already presented by the authors in [5] and [6], where, using damage theory, primarily plated net sections up to S700 were treated and it was shown how ductility requirements for steel structures can be derived. The aim of this paper is, firstly, to have a closer look at what happens with notched net sections other than plates under tension across the whole range of steel grades and, secondly, to investigate details other than holed or notched plated net sections such as tubes and components joined to gusset plates.…”

“…Part 12 of EN 1993-1 is being revised. One aspect of this work is challenging and modifying the ductility requirements by means of damage theories [5], [6] for steel grades up to S700. The net section resistance as given by the following equations:…”

Damage Model Calibration for S275 and S690 Steels

“…It has become daily practise to incorporate damage models in steel structural Finite Element Analysis (FEA) for exploring the effects of steel damage and fracture properties on the structural resistance and deformability [1][2][3]. Both micromechanical damage models and phenomenological damage models can be used to simulate the structural failure process [2][3][4][5]. The micromechanics-based GTN damage model requires at least five calibrated parameters while few parameters are needed for phenomenological damage models.…”