Tuned Liquid Dampers to Mitigate Wind-Induced Motions of Buildings

Passive auxiliary dynamic vibration absorbers (DVA), in particular the tuned mass damper (TMD) and tuned liquid damper (TLD), have become accepted devices for reducing the resonant motions of lively tall structures. A TLD is comprised of a rigid tank partially filled with liquid (usually water) and fitted with energy dissipating mechanisms such as screens. Despite the simplicity of a TLD's physical components, its nonlinear dynamic characteristics complicate the prediction of its performance as a DVA. This paper focuses on the application side of tuned liquid dampers fitted with internal damping screens. Experimental data are presented from a research program conducted to provide insight into the performance of a TLD in terms of its efficiency and robustness. The efficiency of a TLD is measured by comparing the effectiveness of a particular TLD to that of an equivalent optimal linear TMD with the same mass ratio. The entire water mass often does not participate in the sloshing motion resulting in an efficiency level that is less than that of an equivalent optimal linear TMD. Robustness of a damper is the measure of insensitivity of its performance to changes in the parameters of the damper and the main structure from their proposed values. In this study, robustness is determined by examining the effectiveness of a TLD under various response amplitudes, the limiting of the sloshing motion by restricting the available freeboard, and varying the natural frequency of the structure itself. Two directional TLDs, which operate simultaneously in two orthogonal directions, are also briefly discussed.