Experimental Study Of Vibration Measurement For Cable Force

Cable force is an important indicator of the cable system bridge construction monitoring during the construction phase, but also be an important indicator of the operational phase bridge health assessment.Vibration method is often used in cable force measurement.Of the cable force calculation formula in the vibration method,the tightening string formula ignores the impact of cable stiffness, and thus only maintain high accuracy to the long cable.Hinged beam formula takes into account the impact of cable stiffness, and can be explicitly derived numerical solution.As for cable with boundary conditions at both ends of the consolidation, some scholars calculate the length by introducing effective, to make it possible to simplify as the hinged beam. Other scholars tried to solve by fitting an approximation formula. Through summarizing the two ideas in literature, this paper argues that there is a linear relationship between the force and the square of the frequency. But this view fails to come to prove by mathematical deduction, this paper attempts to use experimental means and test data to test it.Specific tasks include the following:(1) Read a lot of literature about the vibration method,sort of out the research of the previous scholars, put forward the linear relationship between cable tension and the square of frequency, and proposed Equivalent hinged beam model based on the frequency step identification method.Analysis the the influence of the factors to vibration cable force measurement accuracy, designed test program on this basis to reduced the impact of these factors..(2) Established a finite element model obtained each order frequency datas by modal analysis at different cable tension levels with different lenthes and under different boundary conditions. Calculated the cable force with hinged beam formulas between the different cable lengths under different boundary conditions. It found that for long, medium and short cable, using a linear model of cable force calculation can maintain high accuracy. And the calculated results and the literature formulas commonly used cable forces were precision comparison.(3) Tested lots of tensioned cable at a constant temperature of laboratory, used the experimental data to validate the theory in this paper. Through statistical analysis of experimental data, found at a constant temperature laboratory conditions can be obtained using a linear model of high accuracy.(4) Used the Nanpanjiang Cable Force experiment data of three shorter booms to calculate tensile force, verified the accuracy of the linear model in the actual project, and gave the use of this method in practical engineering process.