Study On Fatigue Reliability Of Long-Span Cable-Stayed Bridge Under Combined Action Of Random Flow And Wind Load

With the increase of bridge span,the fatigue of long-span cable-stayed bridge under the action of wind load and vehicle load has become the focus of attention in the engineering community.As the main force transmission component of long-span cable-stayed bridge,the cable is easily damaged by cyclic stress due to its large flexibility,small mass,high stress and so on.Therefore,it is necessary to study it.In this paper,by considering the joint distribution of wind speed and wind direction at the bridge site and the situation of random flow,the fatigue reliability of cable is studied by using multi segment bar to study the cable fatigue reliability.The main contents are as follows:1.The wind speed and wind direction joint distribution of bridge site is sampled and processed,and the transverse wind speed and its probability are obtained,which is the basis for analyzing fatigue reliability of cables under wind load.2.The finite element model is established by simulating the stay cables with multi bar and single pole.The natural vibration characteristics of the two models are compared and analyzed,and the feasibility of the multi section bar simulating the stay cables is verified.In order to facilitate the application of the wind load on the later cable,the model of multi rod simulated cable-stayed cable is selected.3.Based on the harmonic synthesis method,the fluctuating wind field is simulated for main girder,main tower and cable joints.The stress time history and displacement response of cables under different wind speeds and different wind angles are analyzed.4.The comparison and analysis of various working conditions such as different cables,different wind speeds and different wind angles of attack are carried out,and the most unfavorable cable position and the most unfavorable angle of attack are obtained,and the most unfavorable tension time history under different wind speeds is analyzed.The stress amplitude and the number of cycles were obtained by the rain flow counting method.Based on the Miner linear cumulative damage theory,the corresponding equivalent stress is obtained.The distribution of equivalent stress is obtained by analysis and statistics.The fatigue reliability of cable under wind load is analyzed by using the established fatigue limit state equation of cable.5.A vehicle model is established to simulate random vehicle loads in different periods of the day.Using the influence line loading to find the most disadvantageous tension position of stress,the stress influence surface of the most unfavorable cable is fitted by fitting the stress influence line,and the stress time history of the cable is obtained by loading random traffic on the stress surface,and the stress situation of the cable under the different cross flow is obtained by simulation of several typical time blocks.6.Considering the joint action of wind load and vehicle load on the stress of the cable,the stress time history of the joint under the combined action of the windmill is obtained by the random combination of the stress time history of the cables under different wind speeds and different traffic flows,and the fatigue reliability of the cable under the combined action of the windmill is analyzed.