Dieser Aufsatz befasst sich mit dem Beulnachweis nach DIN EN 1993‐1‐5 Abschnitt 10. Es wird detailliert das Vorgehen und die Nachweisführung erläutert. Hierbei wird ein Flussdiagramm zur Anwendung der Methode der reduzierten Spannungen vorgestellt. Anschließend werden offene Fragen zum Beulnachweis aufgelistet und hierzu Empfehlungen und Klarstellungen gegeben. Für ein Beulfeld unter mehraxialer Beanspruchung wird ein Beispiel vorgestellt, um die Nachweisführung und die Anwendung der Empfehlungen aufzuzeigen.
Verbunddübel stellen eine sehr tragfähige und robuste Verbindung zwischen Stahlbauteilen und Betonquerschnitten dar. Mittels Verbunddübelleisten lassen sich neue Querschnitte für den konstruktiven Ingenieurbau entwickeln. Der erste Teil der Veröffentlichung befasste sich mit der Technologie der Verbunddübel, deren Tragverhalten und der Bemessung der Verbindung unter ruhender Belastung. Für den Einsatz in Brücken ist das Verhalten unter dynamischen Lasten von Bedeutung und Schwerpunkt dieses Beitrages. Das Ermüdungsverhalten der neuartigen Verbindung wird anhand von zyklisch belasteten Biegeträgern untersucht, mit numerischen Simulationen verglichen und ein Bemessungsvorschlag auf Grundlage des Strukturspannungskonzeptes vorgestellt. Dabei wird sich auf die Betrachtung von Dübelleisten mit modifizierter Klothoidenform (MCL) beschränkt. Load bearing behaviour of composite dowels — Fatigue behaviour (part II). Composite dowels realise a high load bearing capacity and ductile connection between steel members and concrete parts. Using these composite dowels for shear transmission new systems of composite construction can be designed. The first part deals with the technology of composite dowels, it’s bearing behaviour and the design of the connection under static loads. For the use in bridges the cyclic load bearing behaviour becomes more important and on this is the focus of this paper. The behaviour of the new connection under fatigue loads is investigated by cyclic loaded simple supported beam tests compared to numerical simulations and a design concept is established on the basis of a hot spot model. The investigations are restricted to composite dowels implementing the modified clothoidal shape (MCL).
<p>During <i>incremental launching </i>(a known manufacturing method in bridge construction) of steel and composite bridges, biaxial stresses occur in webs and bottom plates of box girders, which mostly dominates their design. An eccentric loading from the launching bearings into the webs is practically unavoidable due to mounting tolerances, variations in plate thicknesses and tolerance requirements of the lateral restraint. The buckling verification of longitudinally stiffened plates under biaxial compression is defined in EN 1993-1-5:2019section 10 [1] through the <i>reduced stress method</i>. While the geometric and structural imperfections are considered using the coefficient α or an equivalent geometric imperfection (term from Eurocode, including geometric and structural imperfections) according to Annex C of this code, the influence of eccentricity has not been considered by this code. In order to investigate the impact of the load eccentricity on the buckling behaviour of longitudinally stiffened plates, large-scale buckling tests were carried out under biaxial compression at the Technical University of Munich. Based on the test results, a numerical model was validated and an extensive parametric study was carried out. It was observed that the direction of the equivalent geometric imperfection of the longitudinally stiffened plates is significant for the load capacity of the plates. With a centric load application, the minimum load capacity is always found when the equivalent geometric imperfection is located on the opposite side of the stiffeners. In the case of eccentric loading, the load capacity is further influenced by the combination of the directions from the eccentric load application and the equivalent geometric imperfection. As a result, an eccentric loading leads to an increased buckling resistance compared to a centric loading when the equivalent geometric imperfection is on the same side of eccentric loading.</p>
Mit Hilfe eines Ritzschen Näherungsansatzes wird das Problem des Gesamtfeldbeulens unter biaxialem Druck diskutiert. Es zeigt sich, dass bei einer Begrenzung der Durchbiegung der Längssteifen, wie sie in Abschnitt 9.2. der DIN EN 1993-1-5:2010 für Quersteifen gefordert wird, der Nachweis des Gesamtfeldbeulens nach Gl. 10.5 der Norm durch den Nachweis des maßgebenden Einzelfelds und den Stabilitätsnachweis der Längssteifen unter Berücksichtigung der zusätzlichen Abtriebskräfte aus Querdruck ersetzt werden kann. Umgekehrt kann, wie am Beispiel des Beulfelds einer Bodenplatte beim Taktschieben gezeigt wird, der Gesamtfeldbeulnachweis nach Gl. 10.5 der DIN EN 1993-1-5:2010 den Stabilitätsnachweis der Längssteifen nicht ersetzen. Am Beispiel des Gesamtfeldbeulens eines Stegblechs einer Brücke wird gezeigt, dass der Nachweis nach Gl. 10.5 in manchen Fällen auch zu unwirtschaftlichen Ergebnissen führen kann.Remarks on the stability verification of longitudinal stiffened plates under biaxial compression. By using the Ritz method, the buckling of plates with longitudinal stiffeners exposed to biaxial compression is discussed. When limiting the deflection of the longitudinal stiffeners analogously to clause 9.2 of DIN EN 1993-1-5:2010 for transverse stiffeners, the buckling verification of the stiffened plate according to Eq. 10.5 of the code can be replaced by the verification of the relevant subpanel and the stability verification of the longitudinal stiffeners taking the additional stresses and deformation due to the compression in transverse direction into account. The example of the stability analysis of bottom chord of a box girder bridge during incremental launching shows that the verification against buckling according to Eq.10.5 of DIN EN 1993-1-5:2010 cannot replace the mentioned stability analysis of the longitudinal stiffeners. Using the example of the web of the box girder, it is shown that a design according to Eq. 10.5 may in some cases also lead to inefficient results.
In general, two types of launching bearings are used for launching: sliding rockers and systems with hydraulic bearings. During incremental launching, the centre of the webs of the superstructure is not perfectly in line with the centre of the launching bearings due to unavoidable tolerances. These eccentricities are not considered in the current design against plate buckling according to EN 1993‐1‐5 [2]. Furthermore, there is a significant difference between the different types of launching bearings due to their boundary conditions. At the Technical University of Munich, large‐scale buckling tests of longitudinally stiffened plates under biaxial stresses with different types of launching bearings and eccentric load introduction were carried out. The results from the validated numerical model and parameter study of the influence due to different types of launching bearings on the buckling behaviour are shown. The results are compared with the buckling verification according to the reduced stress method proposed in EN 1993‐1‐5:2019 [2]. A proposal is given that makes it possible to consider an eccentric load in the buckling verification while keeping the economical aspects in mind.
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