Research On Defects Of Rail-road Cable-stayed Bridge And Analysis Method Of Cable Fatigue Performance

As one of the main types of long-span bridges,the rail-road cable-stayed bridge can make full use of bridge site resources and save project investment.However,the impact of harsh environment and traffic loads during the operation period will cause different kinds of bridge diseases and reduce the safety and service life of the bridge.Therefore,in order to ensure the safe operation of the long-span rail-road cable-stayed bridge,the possible diseases should be summarized and analyzed.On the other hand,the fatigue performance of the cable stayed as a key component of the long-span cable-stayed bridge has always been the focus in the engineering field.For the special bridge of the long-span rail-road cable-stayed bridge,the analysis of the fatigue performance of stay cables under the combined action of highway and railway loads is of great significance to the maintenance and management.According to the structural characteristics of the long-span rail-road cable-stayed bridge,this bridge is divided into five main components: stayed cable,steel truss,concrete cable tower,pier and infrastructure,and auxiliary structure.The characteristics and causes of the diseases of different components are investigated,analyzed and summarized.Secondly,in view of the characteristics of rail-road bridges that simultaneously undertake vehicle loads and train loads,the random vehicle load model is established based on the measured vehicle data of the Third Nanjing Yangtze Bridge.And the train load model is established based on the common train types of Shanghai-Nantong Railway and the monitoring data of Shanghai-Nantong Yangtze River Bridge.Then,combining the bridge finite element models and the measured cable force data,the validity of the random vehicle load model and the train load model are verified.Finally,according to the vehicle(train)load model of the rail-road bridge,considering the influence of corrosion on the fatigue performance of stayed cables,the fatigue life of the cables of Hutong Yangtze River Bridge is analyzed and predicted by using the constant amplitude fatigue design criterion and the fatigue linear cumulative damage theory based on S-N curve.