Research On Crack Behavior Of Long-span Steel Bridges Deck Epoxy Asphalt Pavement

As a secondary layer, pavement on the steel orthotropic deck should have high strength, integrity and other good properties, such as anti-crack, anti-impaction, waterproof and wearable. In China, many steel deck pavements have the experiences of cracks during using, and some of them had to be rebuilt because of severe distresses. When cracks appearing in the deck pavement, rain or other water have the entrance to the bottom of the pavement and erode the cohesion layer between the pavement and steel deck. Gradually simple cracks will evolve into crocodile cracks or other distresses in wide area of the pavement under the traffic loadings, which may lead to the erosion of steel deck. This will not only do harm to the high speed vehicles, lower the fatigue life of the steel deck, but cause abominable social influence. Therefore, it is a key to put much effort into the analysis of cracks in pavement on the orthotropic steel deck, reducing the probability of cracking, and prolonging the life time of deck pavement.The dissertation is part of the project"Research on the Fatigue Damage and Life Prediction of Epoxy Asphalt Pavement on Steel Deck"(No. 50578038) aided by NSFC (National Natural Science Foundation of China). And the main purpose of the dissertation is doing theoretical research on the cracks of epoxy asphalt pavement.The distresses in epoxy asphalt pavement of orthotropic steel deck have been investigated, and cracks in the pavement were divided into 3 categories. The mechanism of each kind of cracks was analyzed on the basis of the research on the load patterns and different mechanic responses of the pavement with FEM. And the evolution relationship among different pavement distresses was discussed here.Composite beam made with epoxy asphalt over steel deck is the object of the research. The composite beam with a notch in the epoxy asphalt was simulated with FEM, and J-integral was used to evaluate the fracture property of the composite beam after considering the merit and demerit of the fracture criterions common used. The simulation results showed that there were two inflexions on the curve of J-integral vs. crack length, and J-integral could be a fracture criterion of the composite structure.As all known, fatigue fracture is the main cause of crack in the deck pavement. And the process of fatigue crack propagation is the addition of many times crack propagation under one-time dynamic loading. Therefore, the responses of epoxy asphalt pavement on steel deck with a crack were studied considering the stress field influenced by many factors such as different roughness of pavement, different crack depths, different pavement moduli and cohesion condition between deck and pavement.After the comparison among the research results, the R-curve of the composite structure was discussed and analyzed, on the basis of which fatigue crack propagation of composite structure was analyzed using MSC. Fatigue Programme. And the relationships between fatigue crack propagation vs. time of loading were regressed. And in order to considering the effect of the micro-void in the epoxy asphalt on the fatigue crack propagation, a new concept, Equivalent Crack Length, was put forward.The last topic in the paper was how to control crack and diminish its disbennifit effect. For the purpose, a new monitoring method, Distributed Fiber Crack Sensor, and the feasibility of how to use the fiber to monitor and predict pavement crack were discussed. Consequently some techniques of preventive maintenance and BPCI (Bridge Pavement Condition Index) model were recommended.