Research On Fatigue Property Of Integral Joint Of Steel Truss Bridge Based On Strain Monitoring Data

At this stage,steel truss girder bridges adopt integral joints instead of traditional riveted and bolted joints.Integral joints,as the members connecting chords,webs and lower beams of bridge decks in the bridge,are required to have high safety and durability.There are many welds in the integral joint,and the stress form of the integral joint is complicated,so it is easy to occur the fatigue damage.Therefore,it is necessary to adopt an effective method to analyze the fatigue property of the integral joint.Based on the measured strain monitoring data,this paper proposed a method for automatically identifying and extracting passing incidents and their characteristic information.Combining the statistical analysis results of the characteristic parameters of passing events and the finite element model of the bridge,the most unfavorable integral joint of the bridge was determined.The most unfavorable integral joint was analyzed,and the fatigue property of the most unfavorable integral joint was finally determined.The research content of this article is carried out according to the following points:(1)The original strain monitoring data was preprocessed,and the threshold filtering method was used to automatically identify and extract passing events.The stress extremes of the data from different sensors were compared to determine the direction of travel,and the peak frequency of the data spectrum was used to calculate the speed of the trains.An adaptive Butterworth low-pass filter was constructed to process the data,and the rain flow counting method was used to determine the number of the train cars.The passing incidents of different working conditions were analyzed to determine the traffic volume characteristics.(2)Cluster graph analysis and statistical analysis of the maximum stress influence line and the maximum stress cycle of the passing event data were carried out to initially determine the position of the most unfavorable integral joint.The finite element model of the bridge was established and revised,and the moving loads were applied to determine the position of the most unfavorable integral joint of the bridge.(3)The finite element model of the most unfavorable integral joint was established to determine the key connection parts.The internal force time history curve was determined based on the influence line loading method.The time history internal forces were applied on the finite element model,and the hot spot stresses of the key connection parts were obtained based on the hot spot stress method.The fatigue life was calculated by referring to the traffic volume characteristics to determine the hot spot daily stress spectrum of the key connection parts.Based on the S-N curve method of the Miner linear cumulative damage criterion,the fatigue life of the key connection parts was calculated under the condition of the increase of traffic volume,and the fatigue property of the integral joint was finally obtained.