MITIGATION OF 3-DIMENSIONAL VIBRATION OF INCLINED SAG CABLE USING DISCRETE OIL DAMPERS - I - FORMULATION

Three-dimensional small-amplitude free and forced vibration problems o f an inclined sag cable equipped with discrete oil dampers are formula ted in this paper using a hybrid method. The hybrid method can readily consider cable sag, cable inclination, cable internal damping, damper direction, damper stiffness and others. Multi-pairs of oil dampers wi th either symmetric or unsymmetric arrangement can also be dealt with. From complex vibration analyses, the damping ratios of a cable, attri buted to the installed oil dampers, in both in-plane and out-of-plane modes of vibration can be estimated. The dynamic in-plane and out-of-p lane responses of the cable under harmonic excitation can also be dete rmined in the frequency domain. The application of the derived formula e to sag cables in a real cable-stayed bridge is presented in part II of this paper with extensive parametric studies. (C) 1998 Academic Pre ss.