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Utmattningshållfasthet hos svetsade detaljer i stålbroar med ortotropa plattor

Mustafa Aygül
Göteborg : Chalmers tekniska högskola, 2004. 225 s. Master's thesis - Department of Structural Engineering and Mechanics, Chalmers University of Technology, ISSN 9322128; 126, 2004.
[Examensarbete på avancerad nivå]

The fatigue life of steel bridge structures is often governed by their fatigue performance. In many fatigue design standards, welded joints are divided into a number of different classes, each class having its own S-N curves for use in design calculations. In the fatigue design of bridges, the choice of suitable fatigue detail category is important to determine the life of the bridges. The fatigue design rules in current standards, at least most of them, are not really relevant to the design of orthotropic decks because they are generally meant for simple structures. For the choice of the detail category in the orthotropic bridge deck design there are certain difficulties and unsafeness for the designers because in such decks the stress analysis and classification of details are complex and beyond the scope of the standards. The aim of this master thesis is to theoretically analyze the fatigue strengths of the various joints, which typically occur in orthotropic steel plate deck bridges and box girder bridges, to be used in the design of these kinds of bridges by collecting fatigue tests that have been carried out by the researchers. Afterwards the results of the tests are evaluated and a summary of joint classifications emanating from these test results is set out in the tables. The orthotropic steel plate deck bridges are complex and sensitive to fatigue damage. Analysis of these constructions showed that the trough to cross-beam connection is the most sensitive link in an orthotropic bridge deck. Trough to deck plate connection is another sensitive welded joint, which is prone to fatigue cracking through the weld root as well as the weld toe. This joint is classified as C71 with butt weld and C50 with fillet weld by EC 3 (Eurocode 3). The results from the fatigue tests coincide with these classifications. The longitudinal trough stiffeners are usually fitted by positional site welding, for instance overhead welding, and their adequacy is therefore of great importance. The results from the site simulated tests showed that the butt-welded splice with a baking strip has the most sufficient fatigue strength. The steel box girder bridges are often chosen of their great torsional rigidity. Even though the steel box girder bridges are often stiffened by longitudinal welded stiffeners these construction are not sensitive to the fatigue as much as orthotropic steel bridge decks. If the crack propagation rate can be estimated reasonably well, this knowledge can give more efficient scheduling of repairs before the construction collapses totally. The test results showed that the box special girders that tested and analyzed have good resistance to long fatigue cracks, which can grow up to 1.5 m.

Nyckelord: Fatigue life, Fatigue test, orthotropic bridge decks, box girder, crack growth, fatigue crack, joint category



Publikationen registrerades 2010-12-08. Den ändrades senast 2013-04-04

CPL ID: 130409

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