Considering The Boundary Conditions Of The Hanging Cable Tension Estimation And Testing

With the merits of high strength and light weight, suspenders have been commonly used in tension structures such as half through or through arch bridges and cable-supported bridges. As the main bearing members, the suspender tension is a key indicator of the health condition assessment and long-term monitoring for such structures. At present, the theory and the method for the suspender tension estimation are mainly adopted from stay cables. In the vibration-based methods to determine cable tension, a simply supported or fixed supported cable at both ends is commonly used in both string or beam theory. However, the suspenders are somewhat different from stay cables, especially in the boundary conditions and bending stiffness. This thesis is focused on the theoretical and experimental studies on the effect of boundary conditions and bending stiffness on suspender vibration frequencies and tension estimation. In details, the following aspects are investigated:1. The vibration-based methods to determine cable tension are reviewed. With the special properties of suspenders. The string model and beam model with general boundary conditions for the estimation of suspender tension are presented.2. The influence of the boundary condition on the natural frequencies and tension estimation of suspenders is investigated in details with proposed string and beam models. It is demonstrated that the influence of boundary conditions cannot be ignored and therefore the actual boundary conditions of suspenders need to be considered necessarily in the tension estimation.3. The properties of the characteristic frequency equation solutions of proposed string and beam models are studied by using the numerical analysis method. The suspender tension estimation formulae of two models are proposed and corresponding applicable conditions are investigated. It is indicated that the derived formulae have a comparable accuracy with that obtained from finite element method. 4. The laboratory test setup equipping up with the rotation restraints of a suspender is conceived. Some critical issues in obtaining suspender frequency response function are also addressed. The experimental results verify again that the derived formulae to calculate suspender frequencies and suspender tension have a high accuracy. As a result, the proposed formulae can be used to calculate the natural frequencies and tension of suspenders with the general boundary conditions.