Research On Influence Of Temperature And Vehicle Load On Cable Forces Of Cable-Stayed Bridge

With the development of society and bridge engineering,cable-stayed bridge structure has increasingly become the most mainstream bridge type in long-span bridges.As the main force component of cable-stayed bridge,the stay cable bears the weight of almost the entire bridge under dead load and live load.For a bridge in operation,not only the vehicle driving will cause the change of cable force,but also the change of environmental temperature will affect the force of each component of the bridge,which will cause the change of cable force.This change often masks the change caused by cable damage and brings great trouble to bridge health monitoring and evaluation.Therefore,it is particularly important to study and analyze the influence of temperature and vehicle load on cable force.Based on the finite element simulation analysis and a large number of measured data analysis,the correlation between temperature load,vehicle load and cable force is studied in this paper.The main research contents and conclusions are as follows:(1)The finite element simulation analysis of Hedong Bridge.The finite element model of Hedong Bridge is established by Midas finite element analysis software,and the sensitivity of cable force to system temperature,construction temperature gradient and vehicle load is studied respectively.It is found that the temperature of the system can comprehensively reflect the influence of the temperature gradient of each component,and the temperature and vehicle load effects of cables at different positions are different.For cable-stayed bridges with similar structures,attention should be paid to the cables at the end of the side span without auxiliary piers and the middle long cables at the middle span.(2)The relationship between temperature load and cable force.Based on the monitoring data of the past ten months,the correlation between the ambient temperature and the cable force was analyzed.The representative values of each time interval were calculated according to the four analysis time intervals of 10 min,20min,30 min and 1h.FFT and PSD frequency identification methods are used to identify the cable frequency at the same time,and the peak extraction method is used to identify the cable frequency in the measured data.The second-order frequency of each cable is converted into cable force through the cable force conversion formula.Calculate the average temperature measured by the temperature sensor within ten months according to the different time interval as the representative value of the temperature in each time interval.The root mean square of acceleration(ARMS)is calculated according to different time intervals as the representative value of vehicle load in each time interval.Under the same time interval,the same number of samples were obtained from the data of temperature,cable force and ARMS,and corresponding to the time axis,the number of samples obtained at each time interval was 27504,13752,9168 and 4584 respectively.In order to eliminate the influence of vehicle load,the cable force and temperature samples corresponding to arms values in the range of [0.001,0.0012] were selected for correlation analysis.The results show that there is different correlation between cable force and temperature of different cables:the cable forces of Y4,Y6 and Z3 have significant positive correlation with temperature,and Y6 cable has the largest correlation coefficient which is about 0.82;Z6 showed significant negative correlation,and the correlation coefficient of Z6 was 0.18 to 0.22;the correlation between the cable forces of Z9,Z18 and temperature is negligible;the appropriate time interval should be selected for the correlation analysis between the cable force and the temperature load.(3)The correlation between vehicle load and cable force.Using the same method as above,the correlation analysis between ARMS and cable force under different time interval is analyzed by using arms value instead of vehicle load.The correlation analysis between the cable force and ARMS with temperature value of [21,22] can eliminate the influence of temperature to the greatest extent.It is found that the cable forces of different cables have different correlations with ARMS:the cable forces of Y4,Y6,Z3 and Z18 are positively correlated with ARMS,Y6 cable has the highest correlation coefficient which is about0.48;Z6 showed significant negative correlation,and the correlation coefficient varied from0.013 to 0.023;the correlation between Z9 cable force and arms is negligible;the appropriate time interval should be selected for the correlation analysis between the cable force and ARMS.