Theory And Test Research On Cable Tension Estimation Method Of Cable-Stayed Bridge With Shock Absorber

Cable is one of the most important bearing configurations of the cable stayed-bridge. After installing the shock absorbers to the cable, the vibration frequency of the cable will be increase, if we want to calculate the tension exactly, we should consider the influence of the shock absorbers and modify the old tension calculation formula. The shock absorbers are equal to the function of symmetrical or single side elastic supports. For educing the direct relations between frequency and tension, conservation of energy theorem can be used to establish the relation equation between the angular frequency and tension.Measuring the cable tension by vibration frequency method has the characteristic of nicety, convenience and speediness, but its precision also can be influenced by some factors. Some scholars have carried on the discussion about the factors, but still have not find a good way to reduce the influence of the shock absorber. There was a scholar who inferred the cable tension formula with shock absorber, but its reasoning process is imperfect. The article mainly embarked on the cable shock absorber, studied the transformation of the vibration shape of the cable after installing the shock absorber, and established the equation according to the conservation of energy theorem, the article also inferred the tension formula of cable with single side and double sides of cable absorb system. For further understood the cable vibration shape and examined the accuracy of the tension formulas, the article has also carried on the experiment to test the Tension, using the INV1601 vibration test system to measure the vibration frequencies of cables. In the experiment, single steel wire or steel strand was used to replace the cable vibration. Different specification springs were used to replace the function of shock absorber. One end of the cable was fixed, and another end of the cable hung weights to provide tension. Then power the cable to make it vibrate. The first, second and third frequencies of the cable were measured in different situation, such as different stiffness of the springs, different place of the springs, different materials of the cables, different length of cables and different cable tension, etc. Because the test condition was limited, the paper used ANSYS software to simulate the work condition of the test to educe the theoretic vibration frequency and vibration shapes, also compared the data with the test data. And confirmed the accuracy of the formula in the article by the test data, theoretic data and the actual data of some bridge. Finally, the article summarized the cable calculation methods, which considered the influence of the shock absorbers, compared their tension results with the formula calculation result. The article also analyzed the merit and shortage of each method.