Hinweise für den Ansatz der Betonzugfestigkeit beim Nachweis der Mindestbewehrung für frühen Zwang gemäß Eurocode 2‐2 (DIN EN 1992‐2/NA)

Guideline for the assumption of the effective concrete tensile strength within the minimum reinforcement check due to early cracking according to Eurocode 2‐2 (DIN EN 1992‐2/NA) In December 2015, the A1‐amendment [1] for the German National Annex [2] of DIN EN 1992‐1‐1 was published. The amendment affects among others the assumption of the effective concrete tensile strength within the minimum reinforcement check due to early cracking. The following contribution elucidates the background, why a respective A1‐amendment for DIN EN 1992‐2/NA has not been provided. Furthermore, the main differences between building‐ and bridge constructions are outlined in order to constitute the different approach.     

Zum Durchstanzen von Flachdecken nach Eurocode 2

Die Regelungen zur Durchstanzbemessung im Eurocode 2 basieren im Wesentlichen auf den Modellvorstellungen in Model Code 90, der die Durchstanztragfähigkeit auf die Querkrafttragfähigkeit zurückführt. Nach Versuchsauswertungen ist diese Analogie für punktgestützte Platten jedoch nicht in jedem Fall zutreffend. Insbesondere für bügelbewehrte Platten ist bei der Bemessung nach Eurocode 2 ein Sicherheitsdefizit möglich, und es erscheint eine Anpassung der Bemessungsgleichungen zwingend erforderlich. Dieser Beitrag erläutert die Sicherheitsdefizite und schlägt verbesserte Bemessungsgleichungen vor. Punching of Flat Slabs according to Eurocode 2 The punching shear provisions according to Eurocode 2 are based on the design recommendations in Model Code 90 where no differentiation between shear and punching shear design is made. This approach is not fully confirmed by test results for flat slabs. In particular for flat slabs with stirrups as shear reinforcement some design provisions according to Eurocode 2 do not achieve the required safety level. Therefore adjustments to the design equations seem to be necessary. In this paper the Eurocode 2 provisions are critically reviewed and improved design regulations are proposed.     

Aktualisierte Diagramme zur Bemessung von Stahlkonstruktionen für den Brandfall nach Eurocode 3

Updated diagrams for fire design of steel structures based on Eurocode 3. The forthcoming design methods for steel structures subjected to fire in Eurocode 3 [1] differ considerably from the methods in the current German standard DIN 4102. The required fire protection material cannot be specified by simplified tables any longer. The structure will now be designed for the case of fire like it is done for ambient temperature. With this method the cost‐intensive structural fire protection can be optimized or even be avoided. However, the more realistic design comes along with a higher effort of calculation. To minimize this effort, in [3] a design tool was developed and published in [4]. In this tool the design methods of the Eurocode have been diagrammed for simple use. However, it is based on the prestandard and cannot be used any longer due to some changes in the current Eurocode. Therefore updated diagrams are presented and further diagrams are added to reduce the calculation effort for the design of steel structures in fire as much as possible.     

Gemeinsame Grundlagen von Methode 1 (wirksame Breiten) und Methode 2 (Beulspannungsbegrenzung) beim Plattenbeulnachweis nach Eurocode 3 – Teil 1‐5

Demonstration of the common basis of method1 (effective width approach) and method2 (stress limit approach) for the plate‐buckling assessment of built‐up steel components according to Eurocode 3 – Part 1‐5. Eurocode 3 – Part 1‐5 gives two methods for the plate buckling verification of built up members: method 1 with an effective width approach and method 2 with a stress limit approach. These methods have a common basis in the form of a bilinear stress‐strain diagram with a “plastic plateau”, the level of which is determined by the buckling strength of the plate element considered. The integration of the plate buckling strengths of all its plated elements give the resistance of the full cross‐section in analogy to plastic design of cross‐sections. The mobilization of the strength reserves of plated elements stronger than others by this integration effects a modification of the stress fields initially determined by elastic design in the weaker plate elements. This modification leads to an increase of shear stresses and a decrease of longitudinal stresses following the interaction curve for plate buckling strengths. This modification is also the cause for the shape of the interaction formula for the cross‐sectional resistances for plate buckling. Method 2 therefore provides two levels of resistance, one without the mobilisation of strength reserves suitable for serviceability limit checks, the other with mobilisation of strength reserves applicable to ultimate limit state verifications. Method 2 with mobilizing strength reserves can be also expanded to cover the plate‐buckling of stiffened plates. Though so far no design code with an explicite rule for this case exists, the reassessment of various plated bridge structures using different criteria for the size of admissible yield zones demonstrates that such an expansion of the method would be consistent with the results of the traditional plate buckling design according to DASt‐Ri 012.     

Der Eurocode 2 für Deutschland – Erläuterungen und Hintergründe

Der neue Eurocode 2: “Bemessung und Konstruktion von Stahlbeton‐ und Spannbetontragwerken – Teil 1‐1: Allgemeine Bemessungsregeln und Regeln für den Hochbau” (EC2‐1‐1) mit seinem Nationalen Anhang ist nach einer ausführlichen Erprobungsphase bereit zur bauaufsichtlichen Einführung in Deutschland. In mehreren Beiträgen sollen Erläuterungen und Hintergründe zu einigen Regelungen im Eurocode 2 und zu den Entscheidungen für Regeln im Nationalen Anhang vorgestellt werden, die entweder zu Änderungen gegenüber DIN 1045‐1 oder zu Abweichungen vom Eurocode 2 führten. Der Teil 3 enthält Erläuterungen zur Begrenzung der Spannungen, Rissbreiten und Verformungen. The Eurocode 2 for Germany – Explanations and Backgrounds Part 3: Limitation of Stresses, Cracks and Deformations The new Eurocode 2 “Design of concrete structures – Part 1‐1: General rules and rules for buildings” (EC2‐1‐1) and its National Annex has undergone a phase of detailed testing and is now ready for the implementation in Germany. In some articles should be given explanations and backgrounds of some rules in Eurocode 2 and of decisions for rules in the National Annex, which have been taken either to changes compared with DIN 1045‐1 or to differences to Eurocode 2. Article 3 contains explanations for the limitation of stresses, cracks and deformations.