| The orthotropic steel bridge deck has been widely used in the construction of highway bridges and railway bridges at home and abroad for its various superiorities. But with soaring traffic flow, increasing vehicle load and the phenomenon of overloading, a huge amount of fatigue cracks appear on the orthotropic steel bridge deck. Therefore, regarding to fatigue cracks of the orthotropic steel bridge deck, detailed fatigue cracks classification, reasons of different cracks, life forecasting and rehabitation methods have been anaysised and discussed in this dissertation. The main contents are as follows:(1) The development of orthotropic steel bridge deck, research results of its fatigue crack problems and rehabilitation techniques are discussed and analysed. Problems need to be solved and methods are proposed.(2) Based on theories of fatigue cumulative damage and methods of fatigue life forecasting, diffenences of fatigue details and design curves among standards in each countries are compared and analysed systematically. Based on the detection of a suspension bridge using orthotropic steel deck, combining with research results, four fatigue details of orthotropic steel deck which suffer fatigue cracking are summaried. They are the connecting structure at deck and longitudinal ribs with diaphragm, the connection at deck and longitudinal ribs between diaphragms, the vertical connection welds between longitudinal ribs and diaphragm and the free edge of diaphragm. Moreover, reasons why these fatigue cracks occour and fatigue strength ratings of these fatigue details are analysed.(3) Related content about full scale test of orthotropic steel deck is introduced, including size of test model, selection of materials, test platforms, layout of test points and four types of fatigue details of orthotropic steel deck under various loading conditions. In addition, finite element model of the test was established though Abaqus, the results calculated by finite element model are compared with the experimental results, which demonstrated the rationality and validity of the finite element model.(4) The fatigue lives of four fatigue details of orthotropic steel bridge deck are calculated and compared anaysised based on different fatigue load, daily traffics and fatigue life forecasting methods in BS5400Part-10, Eurocode3and AASHTO. Furthermore, the stress history and spectrum of four fatigue details are analysed based on finite element model and rain-flow counting method. Fatigue lives of four fatigue details were calculated using S-N curves and the differences of the results calculated by three standards were discussed.(5) Solutions to solve the fatigue problems of orthotropic steel bridge deck are analysed from three aspects, which including preventive measures, crack repair and reinforcement of the deck. Reasonable values of deck thickness, diaphragm thickness and longitudinal rib thickness are discussed through parameter analysis. Regarding to existed fatigue cracking details of orthotropic steel bridge deck, corresponding repair methods are summarized. Afterwards, two kinds of reinforcement methods are introduced:improvement of pavement and sandwich plate system (SPS). Finally, reinforcement effect influenced by the thickness of pavement, elastic modulus of pavement and sandwich layer were discussed.In summary, the common four types of fatigue details in orthotropic steel bridge deck have been collected and analyzed based on the detection of a suspension bridge and the full scale test of orthotropic steel deck. And the fatigue lives of four fatigue details of orthotropic steel bridge deck are calculated using the methods described in three standards. Moreover, the common methods to solve fatigue problems of orthotropic steel bridge deck are analysed from three aspects, which including the preventive measures, the crack repair and the reinforcement of the deck. |
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