Fatigue Life Prediction Of Cable-stayed Bridges Under Random Traffic Loading

As the hub of highway engineering,bridges are the throat of transportation,and vehicles,as one of the main loads borne by the bridge operation stage,are an important factor leading to fatigue damage of bridge structures.Based on the real bridge monitoring data,this paper studies the fatigue life of key vulnerable components of cable-stayed bridges under random traffic flow.The main contents included are as follows:(1)The research background of bridge fatigue is introduced,the development history of related research is sorted out,the research status of random traffic simulation and bridge fatigue life prediction at home and abroad is summarized and analyzed,and the research significance,research ideas and main research content of this paper are clarified.(2)Preliminary processing of the measured traffic flow data across the bridge to eliminate invalid vehicles;The distribution characteristics of the main parameters of the vehicle were calculated by statistical method,and the goodness-of-fit test of the distribution type of each parameter was tested by the T-test.The probability density distribution function is obtained by nonlinear regression,and the random traffic flow that conforms to the actual traffic characteristic distribution is output by self-programming based on Monte-Carlo method.(3)The bridge model is es Tablelished by finite element software,and the model correction is realized based on the static and dynamic response of the bridge,and the finite element model with consistent mechanical properties with the actual bridge is obtained;Bridge vulnerability analysis is carried out,and the crossing of mobile vehicles is simulated to determine the response changes of the main components of the bridge under the action of traffic load,and the bridge components that are prone to damage caused by vehicle load are determined.(4)In order to consider the influence of the interaction between loads on fatigue life,an improved Manson-Halford model is proposed for the calculation of fatigue life of vulnerable members of bridges,and the fatigue life of cable cables,junctions between transition piers and main beams,auxiliary piers and main beams,and connections between main tower and main beams are analyzed under random traffic conditions under different vehicle conditions,and the damage of overweight traffic to cables is studied.The results show that the most fatigue-damaged structure of cable-stayed bridge is cablestayed cable,and the stress amplitude of cable-stayed cable decreases with the increase of cablestayed length.When the load is in the middle of the bridge span,the cable-stayed force is maximized.The fatigue life of the cable-stayed was predicted by using the Miner model and the improved Manson-Halford model,and it was proved that the predicted values of the improved Manson-Halford model under different working conditions were slightly smaller than those of the Miner model.By predicting the fatigue life of the connection between the transition pier and the main beam,the connection between the auxiliary pier and the main beam,and the connection between the main tower and the main beam,it is found that compared with the transition pier,fatigue failure is more likely to occur at the connection between the auxiliary pier and the main beam,and fatigue failure is the least likely to occur at the connection between the tower bridge and the main beam.Overloaded traffic significantly reduces fatigue life in critical parts of the bridge.The research results in this paper have certain guiding significance for the actual bridge engineering practice.