A Semi-Analytical Model for Tuned Liquid Damper (TLD) with Wave Breaking

Abstract

Recently, the applicant of vibration-control devices against wind-induced vibration of structures has become an accepted technology. A Tuned Liquid Damper (TLD) is a kind of passive control device relying upon liquid sloshing to suppress structural vibration. An analytical model for a TLD using a rectangular tank filled with shallow liquid has been proposed by the authors. The model has been experimentally verified to be able to predict liquid sloshing in the TLD with satisfactory accuracy. Since it was assumed that the free surface is continuous, the model was valid as long as no breaking of waves occurs in the TLD. To account for breaking waves, in this paper, the model is modified by introducing two coefficients into the equation of motion. The first, C da , is termed the damping coefficient and represents the increase in liquid damping due to breaking waves; the other coefficient, C fr , is termed the frequency shift coefficient and is introduced to represent phase velocity shift of liquid motion due to breaking waves. They are empirically determine by shaking-table experiments using various tank sizes and liquid depths. It is found that C da is dependent upon the base amplitude of excitation, while C fr , remains almost constant for all the experiments carried out. The empirical formulate for C da and C fr to account for breaking waves are obtained based on the nondimensionalized equation of motion, and they are expected to be valid for a wide range of TLD dimensions. The modified model is employed to predict response of a structure fitted with a TLD, in which breaking waves are expected to occur. TLD-structure interaction is also experimentally investigated. It is found that the modified model can predict structural response very well, even in the presence of breaking waves in the TLD.