Vollständige äquivalente Imperfektionsmethode für biege‐ und druckbeanspruchte Stahlträger

Overall imperfection method for flexure and compression steel beam‐columns. The principles and applications of the overall (global) imperfection method (OIM) for beam‐columns are presented in this paper. The buckling resistance of a beam‐column member is determined by the resistance of its critical cross‐section taking into account second‐order effect of the eigenform equivalent initial imperfection. The maximum amplitude of this initial imperfection, in the shape of elastic buckling mode, is determined from fundamental cases, which are simply fork supported members with uniform cross‐section under uniformly distributed normal force or bending moment. The standardized buckling resistance of the fundamental cases is based on theoretical and empirical background. The proposed global imperfection method is adequate for computer‐aided design method using advanced elastic beam‐column finite element method including the warping behavior of the cross section. The accuracy of the presented method is illustrated step‐by‐step with numerical examples.     

Einfluss der Zugspannungen auf das Beulverhalten eines Beulfeldes unter mehraxialer Beanspruchung – Nachweis nach DIN EN 1993‐1‐5, Abschnitt 10

Influence of tension stresses on the buckling behaviour of slender panels subjected to multiaxial stress – Verification according to DIN EN 1993‐1‐5, chapter 10. In DIN EN 1993‐1‐5 according to the reduced stress method multiaxial stress states are already considered in the determination of the single plate slenderness. The interaction curves according to DIN EN 1993‐1‐5 [1] therefore allow for a systematic utilisation of the favourable effect of tensile stresses on the buckling behaviour. However, studies to justify this beneficial effect are missing. Therefore, experimental and numerical investigations have been conducted to give an insight in the buckling behaviour of multiaxially loaded plates. Six tests on isolated steel plates were realized and are presented giving an insight into the buckling behaviour of multiaxially loaded panels. The recalculations of the above mentioned experimental investigations were performed showing an appropriate agreement between the experimental and the numerical results, so that numerical recalculations of the tests confirmed the experimental observations and the applied procedure for conducting the numerical investigations can be regarded as validated. For the realization of the parametric studies, simplified models are generated considering several kinds of boundary conditions. Based on the presented parametric study a new design proposal has been developed and compared to the numerical results showing good agreements for the investigated load cases justifying the utilisation of positive effects from tensile stresses.     

Schnelle Berechnung von Änderungen und Varianten bei komplexen Tragsystemen (3D‐Modellen)

Rapid assessment of modifications and variations in complex structural systems (3D models) – New technique in structural engineering based on influence functions. The use of building information models in the planning phase allows for a convenient and simple way to create three‐dimensional models (3D) for structural analysis from the geometric data. A negative side‐effect of 3D analysis though is that the number of time‐consuming calculations increases with the complexity of a structure. In the different stages of the design process various modifications must be tested to find the optimal structural system. This requires numerous recalculations and thus leads to a significant increase in computational time. In this paper an approximate method of analysis based on a novel use of influence functions is presented, which allows to predict the effects of design modifications with significantly less computational effort. In addition it is shown, that influence functions can be used very advantageously in computer‐oriented structural analysis in order to optimize 3D models and to identify load paths.     

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.