Effective width equations accounting for element interaction for cold-formed stainless steel square and rectangular hollow sections

Rectangular hollow sections featuring high height-to-width (aspect) ratios have shown to offer improved ultimate capacity due to the effects of the interaction between the elements within the cross-section which are particularly significant for slender cross-sections (class 4) undergoing local buckling. The European design rules dealing with stainless steel, EN 1993- 1-4 [1], utilises the concept of cross-section classification and the effective width method for the design of slender cross-sections susceptible to local buckling neglecting such interaction effects, hence resulting in conservative predictions. This paper examines the benefits of element interaction effects on cold-formed ferritic stainless steel compressed sections on the basis of carefully validated finite element models. Following parametric studies, the applicability of various alternative design approaches accounting for element interaction to ferritic stainless steel is assessed and effective width curves, as well as a Class 3 limiting slenderness equation, are derived herein as an explicit function of the aspect ratio. Comparisons with the loads achieved in the FE models have shown that the proposed effective width equations allowing for the benefits of element interaction improve capacity predictions making design more cost-effective.Ministerio de Ciencia e Innovació

Flexural behaviour of hot-finished high strength steel square and rectangular hollow sections

High strength steels, considered in the context of the structural Eurocodes, as steels with a yield strength over 460 MPa, are gaining increasing attention from structural engineers and researchers owing to their potential to enable lighter and more economic structures. This paper focuses on the bending strength of hot-finished high strength steel (HSS) square and rectangular hollow sections; the results of detailed experimental and numerical studies are presented and structural design rules for HSS cross-sections are proposed. A total of 22 in-plane bending tests, in three-point bending and four-point bending configurations, on HSS sections in grades S460 and S690 were conducted. The experimental results were replicated by means of non-linear finite element modelling. Upon validation of the finite element models, parametric studies were performed to assess the structural response of HSS sections over a wider range of cross-section slenderness, cross-section aspect ratio and moment gradient. The experimental results combined with the obtained numerical results were used to assess the suitability of the current European (EN 1993-1-1 and EN 1993-1-12) cross-section classification limits for HSS structural components. The reliability of the proposed cross-section classification limits was verified by means of the EN 1990 - Annex D method.The Research Fund for Coal and Steel (RFCS) under grant agreement No. RFSR CT 2012-00028. V&M DEUTSCHLAND GMBH, Mr. Gordon Herbert, Mr. Fillip Kirazov and Mr. Isaak Vryzidi

Geschweißte Verbindungen höherfester Stähle

Im Beitrag werden nach einer kurzen Einführung zu hochfesten Stählen und dem Schweißen von hochfesten Stählen die gültigen und zukünftigen Bemessungsregeln von Schweißverbindungen mit hochfesten Stählen behandelt und an Beispielen erläutert. Es werden die für den Schweißprozess wichtigen Material‐ und Gefügeeingeschaften und Herstellungsverfahren von höherfesten Stählen beschrieben und die sich daraus einstellenden Anforderungen während des Schweißvorgangs dargelegt. Anhand von Beispielen werden die derzeit gültigen Bemessungsregeln für Schweißverbindungen mit höherfesten Stählen erläutert und ein neues durch Versuche abgesichertes Bemessungsmodell für Kehlnähte vorgestellt, das es erlaubt, gezielt den wichtigen Einfluss des Schweißzusatzwerkstoffs zu erfassen. Abschließend werden die aus numerischen Schweißsimulationen gewonnenen Erkentnisse hinsichtlich Temperatur, Gefüge, Eigenspannungszustand und auch Tragverhalten einer Schweißnaht beschrieben und durch Beispiele veranschaulicht