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.     

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.     

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.     

Stabwerke und Teilflächenbelastung nach DIN 1045‐1 und Eurocode 2 – Modelle und Anwendungen

Strut‐and‐Tie Models and Concentrated Loading according to DIN 1045‐1 and Eurocode 2 – Modelling and Application Strut‐and‐tie models are efficient tools for the demonstration of load‐bearing characteristics and for the design of reinforced and prestressed concrete structures. The illustration and determination of so called D‐regions is one of the most common areas of application. Another related problem is concentrated loading. In comparison to bending or shear design, the standards DIN 1045‐1 and Eurocode 2 (DIN EN 1992‐1‐1) provide only limited requirements and information for application of strut‐and‐tie models and concentrated loading problems. In praxis, the Engineer has to find possible solutions on basis of the principles given in the standards. The following paper compares the basic information of DIN 1045‐1 and Eurocodes 2 (DIN EN 1992‐1‐1) concerning strut‐and‐tie‐models and concentrated loading problems and gives additional proposals for certain application issues.