Refine
Document Type
- Conference Proceeding (2)
- Article (1)
Institute
Keywords
- Architektur <Informatik> (1)
- Bogenbrücke (1)
- Brückenbau (1)
- CAD (1)
- Computerunterstütztes Verfahren (1)
- Finite-Elemente-Methode (1)
- Lebensdauer (1)
- Materialermüdung (1)
- Optimierung (1)
- Physikalisches Verfahren (1)
Der lebensdauerorientierte Entwurf von Stabbogenbrücken, mit Zuschnitt auf die Auslegung von Hängern, die durch Ermüdung infolge wirbelinduzierter Querschwingungen gefährdet sind, wird als stochastisches semi-infinites Optimierungsproblem formuliert. Zur Lösung dieses Problems sind mehrere Modellierungsebenen erforderlich, so dass ein Mehrebenenproblem entsteht. Es wird der derzeitige Entwicklungs- und Implementierungsstand bei der Umsetzung des Mehrebenenproblems in ein Entwurfsleitsystem (Software) aufgezeigt. Außerdem werden die Konzepte der noch ausstehenden Forschungsarbeit, die bereits erfolgreich beim lebensdauerorientierten Entwurf von Industriehallen mit Rahmensystem als Haupttragwerk eingesetzt wurden, diskutiert und ihre Einbildung in die bisher umgesetzte Forschungsarbeit erläutert.
The influence of vortex-induces vibrations on vertical tie rods has been proved as a determinant load factor in the lifetime-oriented dimensioning of arched steel bridges. Particularly, the welded connection plates between the suspenders and the arches often exhibit cracks induced primarily rods. In this context, the synchronization of the vortex-shedding to the rod motion in a critical wind velocity range, the so-called lock-in effect, is of essential interest.
LIFETIME-ORIENTED OPTIMIZATION OF BRIDGE TIE RODS EXPOSED TO VORTEX-INDUCED ACROSS-WIND VIBRATIONS
(2006)
In recent years, damages in welded connections plates of vertical tie rods of several arched steel bridges have been reported. These damages are due to fatigue caused by wind-induced vibrations. In the present study, such phenomena are examined, and the corresponding lifetime of a reference bridge in Münster-Hiltrup, Germany, is estimated, based on the actual shape of the connection plate. Also, the results obtained are compared to the expected lifetime of a connection plate, whose geometry has been optimized separately. The structural optimization, focussing on the shape of the cut at the hanger ends, has been carried out using evolution strategies. The oscillation amplitudes have been computed by means of the Newmark-Wilson time-step method, using an appropriate load model, which has been validated by on-site experiments on the selected reference bridge. Corresponding stress-amplitudes are evaluated by multiplying the oscillation amplitudes with a stress concentration factor. This factor has been computed on the basis of a finite element model of the system "hanger-welding-connection plate", applying solid elements, according to the notch stress approach. The damage estimation takes into account the stochastics of the exciting wind process, as well as the stochastics of the material parameters (fatigue strength) given in terms of Woehler-curves. The shape optimization results in a substantial increase of the estimated hanger lifetime. The comparison of the lifetimes of the bulk plate and of the welding revealed that, in the optimized structure, the welding, being the most sensitive part in the original structure, shows much more resistance against potential damages than the bulk material.