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.