Über den Einfluss der Torsionssteifigkeit von Längssteifen bei Beulfeldern unter biaxialen Druckspannungen

Abstract

Stichworte Beulnachweis; Methode der reduzierten Spannungen; Torsionssteifigkeit; Längssteifen; mehrachsige Druckbeanspruchung; Stahlund Stahlverbundbrücken; Taktschiebeverfahren;DIN EN 1993-1-5 on the influence of the torsional stiffness of longitudinal stiffeners with panels under biaxial compression stresses During the incremental launching of steel and composite bridges, the superstructure's slender web plates are temporarily exposed to multiaxial compressive stresses. Along with longitudinal stresses due to the bending moment, there are transversal compressive stresses acting on the web at the launch bearings. Often, this construction stage is governing for the structure's design. In Germany, an analytical design approach for longitudinally stiffened webs requires the application of the reduced stress method of DIN EN 1993-1-5. Current investigations showed that if longitudinally stiffened plates with closed section stiffeners are exposed to uniaxial compression and the critical buckling stresses are calculated under consideration of the torsional stiffness of the longitudinal stiffeners, the method may lead to unsafe design results. Since November 2018, the rule to neglect the torsional stiffness in these cases has been introduced into the German National Annex to DIN EN 1993-1-5 and since October 2019 it is also part of DIN EN 1993-1-5. In a recent master thesis the effects of closed-section stiffeners with a high torsional stiffness on the structure's failure load and mode under multiaxial compression have been investigated. This was done by a numerical parametric study, where the findings have been compared to the design results of the reduced stress method of DIN EN 1993-1-5. Recommendations on design approaches have been developed.

Buckling resistance of stiffened panels subjected to constant transverse compression stresses

“…This paper reflects results of the corresponding author's dissertation [8], where more in-depth investigations are given and which will be published in near future.…”

“…The numerical model was developed and validated with the tests based on panels under biaxial compression as extensively reported in [6], [8], [9] and [10]. In this paper, differently from [6], the plate is loaded in the transverse direction, however the assumptions for material and imperfections are the same as in [6].…”

Buckling resistance of longitudinally stiffened panels with closed stiffeners under direct longitudinal stresses

“…Design approach X 3 corresponds to design approach X 2, but the reduction factor of the plate-like behaviour was determined according to curve of Müller in Annex B of EN 1993-1-5 or prEN 1993-1-5 para. 12.4 (5). It should be noted that this design approach corresponds to the procedure according to prEN 1993-1-5 in case of considering the torsional stiffness of stiffeners.…”

“…As the design approach X 3, considering the torsional stiffness of the longitudinal stiffeners and using the more conservative plate buckling reduction curve of Müller still show unsafe results, a new interpolation function bet ween plate-and column-like behaviour has been developed [5].…”

“…The actual behaviour of panels usually is in between plate-and column-like behaviour. [1] and [2] therefore results of the corresponding author's dissertation [5],…”