Study On Measurment Of Suspender Tension Of Bam-Arch Association Bridge Based On Vibration Method

As the main bearing members, true determination of the internal tensile force of a suspender is very critical in both construction and maintenance of beam-arch association bridge. Many methods have been proposed to measure the suspender tension, and vibration method is one of the universally used methods. At present, the theory and the method for the suspender tension estimation are mainly adopted from stay cables. However, unacceptable errors may be caused by ignoring the suspender flexural rigidity and actual boundary condition in many applications.The work presented in this thesis focuses on several following aspects.The research background and significance of this thesis are expounded. Based on the reviewing and summarizing the existing study achievements, the advantages and problems of vibration method are indicated.The principle of cable linear vibration is presented. And based on the principle, the influences of flexural rigidity and boundary condition on the natural frequencies and tension estimation are discussed. It is demonstrate that the tension force of suspender is small or the length of the cable compared to the diameter of suspender is not very long, the boundary condition and the flexural rigidity cannot be ignored.To solve the difficult in the calculation of suspender vibration, a dynamic model for inclined cables was set up by taking the flexural rigidity and general boundary condition into account. The equation was solved using the singular perturbation method, and the analytical expressions of frequency and form function were derived. The calculation accuracy and applicability of expressions of frequency is studied by using the numerical analysis method.To improve accuracy, the expression of frequency was modified by curve fitting, whenξis relatively small. Practical formulas considering flexural rigidity and actual boundary condition are deduced based on the modified expression. Case studies prove that the derived formulae to calculate suspender frequencies and suspender tension have a high accuracy.Based on the modified expression of frequency, a new method for identification of multiple parameters such as tension force, flexural rigidity and boundary condition is established. Case study is conducted to validate the method of estimating the flexural stiffness, boundary conditions and cable tensile force. As an example, tension force testing and parameter estimation on one 1-96m tied arch bridge of Beijing-Shanghai High-speed Railway were processed.