Abstract

Strings and cables are often used to support loads. Made of stiffer and stronger steel cables, the metal ropes find applications in heavy load bearing situations such as cable supported bridges, elevator, cable car transportation systems, and in overhead transmission line cables. Much more flexible and thin fibres, a key element in textile and optic fibre industry, are wound on high speed bobbins. In most of string and cable studies, very little attention has been given to the boundary condition that may affect their motion. In this thesis, two case studies are analyzed to study the effect of boundary condition on the string behaviour. In the first case, a string with a boundary condition in between fully clamped and free state is studied. The effect of such a partially clamped condition on the natural frequency has been tabulated. The second case investigates the axial-transverse coupled motion of a fixed-fixed string supported at two points. The nonlinearity of the tension during vibration is considered as well as the orbital motion of the excited string. The simulation of string motion is done using numerical finite difference method along with von Neumann and Courant stability conditions to ensure minimum iteration errors. Experiments are conducted by tracking the string's axial motion with a dynamic force sensor and lateral motion with a stroboscope to record the orbital behavior. In addition fast Fourier transform (FFT) has been performed on sound produced by the vibrating string to obtain the frequency spectrum