Research On The Fatigue Performance Of The Composite Deck System Composed Of Orthotropic Steel Deck And Ultra-thin RPC Layer

With the rapid development of national economy, many long-span bridges have been built. Orthotropic steel plates are widely used in long-span steel bridges because of their outstanding advantages, such as lighter self-weight and convenience for erection. However, a lot of engineering experiences indicate that there are two major technical challenges existing in orthotropic steel plates:fatigue cracking and conventional asphalt pavement failure. Domestic and overseas researchers have tried a lot during the past decades, but the above-mentionded problems still remain unsolvable fundamentally. Our research team proposes an innovative composite bridge deck system, which consists of an orthotropic steel deck stiffened with a compact-reinforced-reactive-powder-concrete(CRRPC) layer through stud shear connectors and is supposed to resolve those two technical problems in steel plates. The innovative bridge deck can be called for short "The Composite Deck System Composed of Orthotropic Steel Deck and Ultra-thin RPC Layer". Because of the particularity of the orthotropic steel deck and the complexity of its service environment, the research on the fatigue performance of the innovative composite bridge deck system is significantly essential for its engineering application. Based on the renovation of bridge decks in Humen suspension bridge, this paper has conducted a pilot investigation on the fatigue performance of this innovative composite deck system with the method of numerical analysis and fatigue tests. The following specific works are carried out:Firstly, the three-dimensional full-bridge global and local FE analysis models are established using FE software Midas Civil and ANSYS respectively. Taking into consideration of two parts of calculation results, stresses of the critical control points of stiffening girder in Humen suspension bridge are compared. According to relevant specifications in AASHTO design code, fatigue lives of the orthotropic steel deck are evaluated. Analysis results indicate that using "The Composite Deck System Composed of Orthotropic Steel Deck and Ultra-thin RPC Layer" can not only ensure the structural safety of the cable system, but also considerably reduce the risk of causing fatigue cracks in steel bridge decks.Secondly, completely on the basis of the cross-section of the orthotropic steel deck in Humen suspension bridge, a full-scale test model is established. The stress amplitude is determined by the maximum longitudinal stress of RPC layer in Humen suspension bridge after using the innovative composite bridge deck system. Results of flexure fatigue tests of "The Composite Deck System Composed of Orthotropic Steel Deck and Ultra-thin RPC Layer" indicate that, the RPC layer of the innovative composite bridge deck system won’t cause fatigue cracks after bearing2×106cycles of design stess amplitude. So it could be said that the innovative composite bridge deck system can be used in Humen suspension bridge technically.Thirdly, completely according to the cross-section of the orthotropic steel deck in Humen suspension bridge, a fatigue numerical analysis model is established, adopting the structure type of2×5m two-span continuous composite beam. A nonlinear analysis is conducted using FE software ANSYS. Through introducing the FE analysis results, specialized fatigue numerical analysis software MSC.Fatigue can calculate the fatigue life of the above-mentioned model. By means of fatigue numerical analysis, the failure model of the composite beam bearing static and fatigue loads can be obtained. Beyond that, the fatigue load-life curves(P-N curves) in various specified survival rate can also be obtained.