STAY-CABLE VIBRATION MITIGATION USING NONLINEAR TARGETED-ENERGY- TRANSFER DEVICES: A PARAMETRIC STUDY

Large-amplitude oscillation of inclined stays are often associated with rain-wind induced phenomena, vortex shedding and parametric excitation. To suppress the problematic vibrations and to minimize the potential high cost of maintenance or repair, passive damping system have been widely employed. In most investigations the damper was modelled as a pure linear viscous device or as a linear viscous damper with internal stiffness perfectly anchored to the deck. Other authors evaluated the effectiveness of the damping system introducing the effects of the flexibility in the damper support. The aim of this paper is to investigate the use of Targeted-Energy-Transfer (TET) devices for cable vibration suppression; a new family of devices is proposed in which a nonlinear elastic stiffness force mechanism and device, modelled as a power-law elastic spring element, is placed in parallel with a linear viscous damper. The imperfect anchorage to the deck is also taken into account by an elastic support. The free vibration of a taut-cable with an attached passive TET device is investigated using an analytical formulation of the complex generalized eigenvalue problem in the presence of two cable segments. The concept of “universal design curve” was examined. A parametric study was performed on a reference cable to verify the adequacy of the “universal design curve” and to evaluate the effectiveness of TET device; the study was subsequently extended to two real stays, taken from the Fred Hartman Bridge (Houston, Texas, USA) and from the Stonecutters Bridge (Hong Kong, China). In all the investigations, theoretical and numerical results were obtained and compared.