Preliminary Study On Influence Factors Of Cable Force Measurement Uncertainty Of Cable-stayed Bridge

There are many methods for cable tension testing of cable-stayed bridges.The frequency method is widely used because of its simple test principle and convenient operation.The accuracy of the frequency method test results depends on the reliability of the calculation model and the accuracy of the parameter values.The existing cable force calculation models are mostly based on certain assumptions,while the cable in the real state is difficult to meet the assumptions.The value of the parameter is also affected by various factors.In this paper,the factors affecting the cable force test results are studied.In order to better describe the quality of the cable force test results,the test uncertainty results are used to evaluate the test results.Through the investigation of the two aspects of the cable test technique and the frequency method test,the vibration characteristics and calculation theory of the cable are clarified,and the main factors affecting the cable force test results are analyzed.On this basis,the analysis clarifies the applicable range of various cable force dynamic measurement models,and proposes the uncertainty evaluation method of cable force test results.The numerical simulation of common specifications cable is given and the conditions under laboratory conditions are given.Example of uncertainty assessment of force test results.The main research contents are as follows:(1)According to the free vibration differential equation of cable,the vibration characteristics of cable string vibration and the self-vibration characteristics of beam theory are analyzed.The cable-frequency relationship of cable under different boundary conditions is derived.Formula,simply supported beam formula and fixed beam formula.Taking 10 cable as an example,the finite element analysis model is used to compare the cable force calculated by the string vibration theory and the beam theory with the finite element results.It is verified that the two calculation theories have higher calculated cable forces under their respective applicable conditions.Precision.(2)Based on the dynamics,metrology and cable force test requirements,the cable is classified,and the classification requirements and parameter determination criteria of short cable,medium cable and long cable are given.For the 10 cables exemplified in Chapter 2,the effects of bending stiffness,effective length and sag on the cable force test results are analyzed respectively.The calculation formulas of the cable forces under the influence factors are discussed in numerical simulation.Scope of application.(3)Based on the theory of error and uncertainty theory,the relationship and difference between the two theories in evaluating the cable force test results are analyzed.Taking the cable test of the cable in the reference as a case,the cable force test results were evaluated according to the error theory and the uncertainty theory.The measurement uncertainty assessment of the cable force test is analyzed with reference to the measurement uncertainty evaluation process.(4)According to the uncertainty theory,the uncertainty evaluation method of cable force test results is given from numerical calculation and field test.The numerical simulation of the cable type recommended in the specification is carried out,and the uncertainty of the cable with different lengths and specifications is calculated under the string vibration formula and the simply supported beam formula,and the string vibration formula and the simply supported beam formula are given.Scope of application.Taking the steel stranded tensioning tension test as an example,the actual cable tension test is simulated,and the uncertainty evaluation method of the cable's measurement results under different tension is given.