Fatigue Reliability Analysis Of Prestressed Concrete Beam-Bridge

With the vigorous development of our country's highway transportation construction and the increasment of infrastructure investment, the increasing traffic, automobile weight and spreed of the vehicle that follow results in our country's transportation showing the characteristics of "large traffic volume, heavy load and channel traffic". The bridges srtructures and members including concrete, reinforced and pretessed steel strand, which endure the long-term and frequent altering-load, occur fatigue damage easily. The bridges in service have been heavily destroyed and saftety hidden trouble is existed. Analyzing the degree of fatigue reliability of the bridges becomes an urgent problem, on the base of evaluating of bear the bridge security performance.The basic concepts of structural reliability is described in this paper firstly. And then the idears and steps to calculate and analyse the pretressed concrete beam bridges' fatigue is obtained through analysing the basic concepts of fatigue and fatigue of reliability theory. Taking 20m prestressed concrete box girder bridge in FuDian First-Class Highway as an example, nine fatigue load model vehicles which are the fatigue checking load of the pretress concrete beam bridge is formulated in this paper through carrying investigate status of FuDian First-Class Highway.In the paper , the time-history charts of the mid-span moment of the nine fatigued vehicle loading models is obtained using the MIDAS/Civil, the time-history charts of the mid-span moment based on rainfall method is statisticed and the stress of concretes,common reinforced and prestressed steel strand is gotten. At the same time, the fatigue reliability analysis of the concretes, common reinforced and Prestressed Steel Strand of corresponding prestressed girder bridge is carried out substituting the obtained fatigue load effect and fatigue resistance into the formula derived based on Reliability Theory using First Order Second Moment calculated method. Considering the traffic conditions without loading limit and the practical working condition of the prestressing concrete plate bridges, after the correction of traffic volume and axle weight, the paper calculates the fatigue reliability index of the twenty metres-span prestressed-girder based on the Fatigue Reliability theory and estimates fatigue lifetime of it based on Cumulative Fatigue Damage Miner.