Author(s)

M. J. Smith, J. J. Kobine & F. A. Davidson

Abstract

An investigation is made into controlling the natural frequency of tuned liquid column dampers (TLCDs) as a function of the geometry of the tank. A model is derived for free oscillations and the natural frequency is given as a function of the ratio of the vertical columns and the dimensions of the horizontal chamber. Asymmetric TLCDs are modelled in a structure-damper system. A numerical example demonstrates how the asymmetry of a TLCD affects beat phenomena exhibited in the decay of the structure. Keywords: tuned liquid column dampers, structural vibration, beat phenomena, optimisation. 1 Introduction Wind-induced vibrations of tall buildings can be a source of occupant discomfort and structural damage unless they are sufficiently suppressed. Auxiliary damping devices are a successful solution to the problem. TLCD are passive vibration absorbers comprised of vertical and horizontal liquid columns forming the shape of a U-tube. They have proved effective in reducing structural vibration and are also advantageous due to low cost andmaintenance. In this system, the momentum of the fluid is used to counteract the motion of the building. Energy is lost by generating friction in the horizontal chamber. Previous studies on TLCD have focused on U-tubes with a constant crosssectional area [1], [2] and, more recently, on symmetric U-tubes with a variable height of horizontal chamber [3], [4]. The latter allows greater versatility as the natural frequency can be controlled as a function of the geometry of the tank rather than the volume of fluid alone. In this paper we complete a study of free

Keywords

tuned liquid column dampers, structural vibration, beat phenomena, optimisation.