| The precast simply supported prestressed concrete T-girders are widely used in highway bridges in China.With the increase of vehicle load and traffic volumes and the effect of external environment,fatigue damage may aggravate on the prestressed concrete bridges at service.In order to study the fatigue performance and time-dependent reliability of prestressed concrete bridges,the main work has been done in this paper:(1)Considering the characteristics of the prestressed concrete girder bridge,the fatigue reliability analysis models and the calculation methods are discussed.The fatigue reliability analysis framework of prestressed concrete bridge is put forward.(2)The applicability of the vehicle fatigue load model of highway bridges from all around the world is discussed.A forecast model of growth of traffic volume based on gray GM(1,1)forecasting method is given.Taking the recorded traffic datas from the Second Nanjing Yangtze River Bridge as an example,the PDF of total weight and axle load of several typical models and future traffic volumes are given.(3)The mechanism and mathematical models of concrete carbonation and chlorination are discussed.Based on the area reduction process of materials in the section,the time-dependent performance of prestressed concrete bridge is studied.Fatigue damage analysis process of concrete bridge considering environment is put forward.(4)A precast simply supported prestressed concrete T-girders is selected.When the structural,load and environmental parameters are given,critical moment of degradation under the environment can be calculated.Considering the process of section reduction of each material,the fatigue performance under repeated loading is developed.On the basis of this,the fatigue reliability of the bridge is analyzed by Monte Carlo method considering the dispersion of structural parameters and environmental parameters,and the actual PDF of fatigue load,which can be a reference as fatigue reliability assessment of prestressed concrete bridges. |
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