A numerical study on the elastic buckling behaviour of simply supported cylindrically curved panels, with longitudinal edges unconstrained and loaded edges constrained, including the influence of ...curvature, aspect ratio and loading type (from pure compression to full in-plane bending) is presented in this paper. Subsequently, an extension of rules for internal plated members’ critical stress calculation from EN 1993-1-5 is proposed that takes into account the effect of curvature. The proposed approach, based on the numerical results, gives a safe but accurate estimate (lower bound) for the elastic critical stress.
•Past and current approaches for the elastic buckling coefficient of curved panels under compressive stresses (from pure compression to pure in-plane bending) are discussed.•An extensive parametric study is performed and the critical behaviour of curved panels is fully described identifying relevant characteristics.•Relevant parameters are identified and calibrated against numerical simulations.•A proposal for computing the buckling coefficient of curved panels is developed maintaining the format of EN1993-1-5.
In this paper we present a comparative analysis regarding the shear web resistance between five types of steel plate girders and a girder with corrugated webs.
In the case of girders with corrugated ...webs, the design is conducted according to SR EN 1993-1-5:2008.
The use of girders with corrugated webs is at its beginnings in Romania, due to the manufacturing technology that require automation, therefore the design is as well new to most of the engineers. Through the paper, we want to underline the improved behavior that girders with corrugated webs have upon their competitors, steel plate girders, and to give an example for the design of such girders.
The phenomenon of shear lag refers to the increases of the bending stresses near the flange-to-web junctions, and the corresponding decreases in the flange stresses away from these junctions.
In the ...plated structures with wide flanges, such as in the orthotropic deck of the steel road bridges, shear lag caused by shear strains, may be taken into account by a reduced flange width concentrated along the webs of the steel plate girders.
In the norm EN 1993-1-5, the concept of taking shear lag into account is based on effective
width of the flange which is defined in order to have the same total normal force in the gross flange subjected to the real transverse stress distribution as the effective flange subjected to a uniform stress equal to the maximum stress of the real transverse distribution.
This paper presents some aspects concerning the shear lag phenomenon and a design analysis taking into account the geometrical parameters such as the stiffeners thickness, flange width and the girder span for a steel deck of a road bridge.
Results of four full-scale tests on plate girders stiffened with transverse and longitudinal stiffeners subjected to interaction of high bending moment and shear force are presented and discussed. In ...longitudinal direction the web was stiffened with open or closed stiffeners positioned in the compression zone. Detailed information on initial geometric imperfection and residual stresses is given. The experimental results were used to verify numerical model. The resistance is compared against reduced stress method and effective width method given in EN 1993-1-5.
•Experimental tests on plated girders subjected to bending moment and shear force•Development and verification of numerical model•Comparison of eurocode design resistance to experimentally obtained ones
The term of shear lag is related to the discrepancies between the approximate theory of the bending of beams and their real behaviour. It refers to the increases of the bending stresses near the ...flange-to-web junctions and the corresponding decreases in the flange stresses away from these junctions. In the case of wide flanges of plated structures, shear lag caused by shear strains, which are neglected in the conventional theory, may be taken into account by a reduced flange width concentrated along the webs of the steel girders. In EN 1993-1-5, the concept of taking shear lag into account is based on effective width of the flange which is defined in order to have the same total normal force in the gross flange subjected to the real transverse stress distribution as the effective flange subjected to a uniform stress equal to the maximum stress of the real transverse distribution. Some aspects concerning the shear lag phenomenon and a working example for a box girder of a heavy crane runway to illustrate the determination of the shear lag effect are also presented.
Abstract
Bei der Montage von Stahl‐ und Stahlverbundbrücken im Taktschiebeverfahren sind die schlanken Stegbleche des Überbaus temporär einer biaxialen Druckbeanspruchung ausgesetzt. Neben den ...Längsspannungen infolge des Biegemoments tritt am Verschublager gleichzeitig eine einseitige Querdruckbelastung auf, sodass der Bauzustand oft bemessungsrelevant wird. Für längsversteifte Stegbleche ist in Deutschland für eine analytisch gestützte Bemessung die Methode der reduzierten Spannungen nach DIN EN 1993‐1‐5 zu verwenden. Jüngere Untersuchungen hatten für den Fall einachsiger Druckbeanspruchungen festgestellt, dass das Nachweisformat für längsausgesteifte Beulfelder unter Berücksichtigung der Torsionssteifigkeit geschlossener Steifen bei der Bestimmung der kritischen Beulspannung zu unsicheren Ergebnissen führt. Deswegen wurde im November 2018 in den Nationalen Anhang zu DIN EN 1993‐1‐5 aufgenommen, dass die Torsionssteifigkeit in diesen Fällen zu vernachlässigen ist. Im Oktober 2019 wurde auch die Hauptnorm DIN EN 1993‐1‐5 entsprechend ergänzt. Im Rahmen einer Masterarbeit wurde in einer numerischen Parameterstudie untersucht, inwiefern sich die hohe Torsionssteifigkeit geschlossener Steifen gegenüber offenen Querschnitten auf die Versagenslast und ‐form eines Stegblechs unter mehrachsiger Druckbeanspruchung auswirkt. Die Traglasten aus der Parameterstudie werden herangezogen, um sie den Ergebnissen nach dem Verfahren aus DIN EN 1993‐1‐5 gegenüberzustellen und Empfehlungen für die Bemessung zu entwickeln.
Abstract
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.
This paper presents a new resistance model for steel plate girders subjected to patch loading. The model aims to correct the EN 1993‐1‐5 formulation concerning the resistance to transverse forces ...with the help of findings presented in several doctoral studies on this topic. In addition, a statistical calibration of the new model is addressed. This calibration includes a new proposal for the resistance function χ‐λ. The proposal is conceived for fulfilling safety levels of the partial safety factor that match the current values included in EN 1993 for instability‐related problems. These new proposals are in accordance with the design philosophy found in EN 1993‐1‐5 for the design of plated structures.
The design of longitudinally stiffened plates under direct stresses according to Eurocode 3 Part 1.5 implies the calculation of the global critical buckling stress
σ
c
r
,
p
, a specific stress, ...which is difficult to define and assess. After analysing and clarifying this concept, and on the assumption that the global mode corresponding to this stress is associated with the buckling of the stiffeners in the elastic continuum of the plate, this article proposes a general method for assessment of
σ
c
r
,
p
based on the use of a software which calculates the critical buckling stress of plates. This software,
EBPlate, has been developed by the authors, is free of charge and can be downloaded from the internet.
Numerous experimental and numerical studies on prismatic plate girders subjected to shear can be found in the literature. However, the real structures are frequently designed as non-uniform ...structural elements. The main objective of the research is the development of a new proposal for the calculation of the ultimate shear resistance of tapered steel plate girders taking into account the specific behaviour of such members. A new mechanical model is presented in the paper and it is used to show the differences between the behaviour of uniform and tapered web panels subjected to shear. EN 1993-1-5 design specifications for the determination of the shear strength for rectangular plates are improved in order to assess the shear strength of tapered elements. Numerical studies carried out on tapered steel plate girders subjected to shear lead to confirm the suitability of the mechanical model and the proposed design expression.
Längsausgesteifte Stege von Biegeträgern oder längsausgesteifte Querschnittsteile von Kastenquerschnitten weisen in der Regel ausreichend steife Quersteifen auf, so dass hinsichtlich der ...Beultragfähigkeit jeweils jedes Teilfeld zwischen zwei Quersteifen isoliert betrachtet werden kann. Infolge unterschiedlicher Beanspruchungen innerhalb der Bauteile ändert sich oft auch die Anordnung der Längsaussteifung in Längsrichtung. Damit weisen einzelne Teilfelder endende Längssteifen auf. In den alten nationalen und aktuellen Normenwerken (DIN, Eurocode) wird auf diesen Sachverhalt nur sehr pauschal am Rande eingegangen. Eine Quantifizierung der Traglastreduktion, gegenüber dem Standardfall durchlaufender Längssteifen, ist jedoch nicht möglich. Dieses Informationsdefizit war Anlass für eine vergleichende numerische Studie zum Beultragverhalten von längsausgesteiften Teilfeldern mit und ohne endenden Längssteifen. Dabei wurden für die materiell und geometrisch nichtlinearen Traglastberechnungen mit geometrischen Ersatzimperfektionen bereits die im Eurocode EN 1993-1-5 vorgeschlagenen Berechnungshinweise angewendet. Nach einem Vergleich der Traglasten für ausgewählte repräsentative Beispiele, erfolgt auch ein Vorschlag für die Modifikation des Berechnungsmodells im Eurocode zur Ermittlung der Beultragfähigkeit rc nach dem Konzept der reduzierten Spannungen, um den Effekt endender Längssteifen mit zu erfassen. Plate buckling capacity of longitudinally stiffened panels with ending stiffeners under normal stresses. Longitudinally stiffened panels of plated or boxed girders generally have transverse stiffeners with sufficient stiffness out of plane, so that for plate buckling each panel can be treated independently. Due to varying stresses along the member also the position of longitudinal stiffeners changes. Therefore several panels have ending longitudinal stiffeners. In the old national and actual codes (DIN and Eurocode) this effect is only mentioned by the way, but the reduction of load bearing capacity due to ending longitudinal stiffeners is not quantified. Therefore a numerical study was made dealing with the buckling capacity of longitudinally stiffened panels with and without ending stiffeners. The geometric and material nonlinear calculations with equivalent geometric imperfections were based on the new recommendations in the Eurocode EN 1993-1-5. After the presentation of the results of this study for representative panels, also a suggestion for the modification of the design model in the Eurocode for the buckling capacity rc of a panel is made, considering the effect of ending stiffeners. PUBLICATION ABSTRACT
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