| At present,due to the effects of aging bridges,a significant increase in traffic flow,and the general overloading of operating freight vehicles,the bridge’s bearing members are subjected to longer-term and higher-amplitude stresses,resulting in more and more fatigue damage to the bridge than before.It is of practical engineering significance to evaluate the remaining fatigue life of in-service bridges and select reasonable load-limiting values to achieve the expected fatigue life of the bridges.This paper builds a typical vehicle load model based on the traffic flow survey data of Zhejiang-Shanghai-Hangzhou-Ningbo Expressway over the years and the measured vehicle load data of 23 provinces in China;using the Monte Carlo method,MATLAB is used to generate non-superior areas,weight-bearing areas,and ultra-highway areas.Random traffic flow,and proposed a traffic volume prediction method based on the ARIMA(p,d,q)time series model;based on the predicted traffic flow and the random traffic flow generated by the simulation,the residual fatigue of typical PC beam bridges in different types of super governance Life analysis;Finally,according to the remaining fatigue life and expected fatigue life of the bridge under different load limiting conditions,determine the fatigue limit load value of the bridge.The main research contents are:(1)According to the Monte Carlo method of generating pseudo-random numbers,combined with the statistical parameters of typical vehicle load models,using MATLAB software to generate random traffic flow of each lane in different super-type areas,combined with the lateral distribution coefficient of the bridge,the random traffic flow of each lane Convert to the axle load sequence,and gradually load the most unfavorable component of the bridge according to the step length,and calculate the bending moment history of the most unfavorable section of the component under the combined action of the axle load sequence of each lane;(2)According to relevant experimental verification,some prestressed concrete beams are due to the brittle fracture of non-prestressed steel bars,resulting in fatigue damage to the structure.Therefore,non-prestressed steel bars are used as the research object of stress history.The stress history at the cross section;based on the equivalent stress amplitude theory,the rain cycle counting method is used to count the stress cycles and stress amplitudes on the stress history,and the analysis shows that the most unfavorable hollow slab beams in different types of super governance are at the most unfavorable cross section.The equivalent stress amplitude and the number of cycles of non-prestressed steel bars;(3)Based on the traffic volume of Shanghai-Hangzhou-Ningbo Expressway from 1998 to 2019 and the GDP of Zhejiang Province in the corresponding year,the regression equation of both traffic volume and GDP can be obtained through mathematical regression analysis;based on the data of GDP of Zhejiang Province from 1978 to 2019,Use the ARIMA(1,2,1)time series model to predict the future GDP growth,and finally predict the future traffic volume of Shanghai-Hangzhou-Ningbo Expressway based on the mathematical regression model;(4)Based on the Palmmgren-Miner linear fatigue cumulative damage criterion and the SN curve,combining the equivalent stress amplitude of non-prestressed steel and the total number of vehicles passing random bridges during the predicted time period,the remaining fatigue life of the bridge in different time periods is analyzed And damage degree,and predict the time of fatigue failure of the bridge based on the remaining fatigue life;(5)Under various load-limiting conditions(unlimited load,30t,35t,40t,45t,50t),the residual fatigue life and fatigue damage degree of the most unfavorable hollow slab beams in various time periods are predicted,and PC beams in different super-type areas are predicted The fatigue failure time of the bridge,combined with the expected fatigue life,reasonably determines the fatigue load limit of the bridge. |
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