Study On The Uncertainty Of Frequency Method Test For Cable Force

The accuracy of the cable force test is one of the research hotspots of the bridge engineering.The calibration method of the cable force tester is studied under the uncertainty framework,making it a cable force gauge under specific field conditions.It is an important part of the development of the measurement system for cable force measurement technology.This article studies the "on-site calibration" sub-item of the "Research on Measurement Standard for Cable Force Measurement Instrument" of Sichuan Provincial Transportation Science and Technology Project.Based on the theory of uncertainty,the Monte Carlo method is used to calculate the cable force measurement model.The influence of the probabilistic characteristics and non-linearity of the parameters on the accuracy of the measurement results.On this basis,the method of calibration of the cable force tester under specific field conditions was studied,and the correction value of the indication value and the standard combined uncertainty of the measurement result were determined.The main work is as follows:(1)Cable force measurement technology and accuracy of measurement results are investigated of the literature.The scope of application of various cable force measurement models was investigated and summarized,and the main influencing factors of the cable force measurement results were clarified.Based on this,the field calibration method of the meter was investigated and analyzed,and a technical solution for on-site calibration of the cable force tester using the cable force loop was proposed.(2)The influence of probabilistic characteristics and nonlinearity of the model parameters on the uncertainty of the cable force test results.Analyze and determine the probability density model of the cable.The probability distribution of cable length and frequenc are measured.Perform the MCM random numerical simulation on the most widely used string theory cable force measurement model(F_m=4mL~2f~2).The probabilistic characteristics of three parameters such as lenth,frequenc,and density,and the influence of the nonlinearity of l and f parameters on the probability distribution of cable force test results were analyzed.The MCM and GUM(Guide to the expression of uncertainty in measurement)were compared.Differences in methods,the specific conditions for the MCM simplified to GUM standard method were analyzed.(3)The calibration method of cable force tester is studying under specific field conditions.Using the measurement conditions during cable production,under the tension conditions of 70% and 100% of the design cable force,the natural frequency of the cable was tested several times with a dynamic tester,and the cable force was calculated using the string theory dynamic test model.The force-measuring device indication of the cable force is calibrated to the specific indication value by an upper-level standard device(cable force loop),and the inaccuracy of the dynamic measurement model itself and the deviation(system error)caused by other factors are corrected,and the upper-level standard device itself is taken into consideration.For all independent factors including uncertainty,the composite standard uncertainty of the measurement results of the cable force tester was calculated.