THE EFFECT OF SCREEN GEOMETRY ON THE PERFORMANCE OF A TUNED LIQUID DAMPER

Abstract

<p>In recent years, the use of tuned liquid dampers (TLD) as dynamic vibration absorbers has increased in popularity due to their low cost and ease of installation. A TLD is a partially fluid filled tank (commonly water) that has a fundamental sloshing frequency close to the natural frequency of the structure in the vibration mode to be suppressed. Typically, water alone is insufficient to achieve the required level of optimal damping. One approach that is used to increase the damping of the TLD is to install flow damping devices (screens) into the tank. In this study horizontal slat screens are selected for investigation. For a given target response acceleration an optimal level of damping can be achieved. However, as the structural response deviates from this target value the efficiency of the structure-TLD system is significantly reduced. To increase the efficiency, an investigation into the applicability of slat screens with a varying loss coefficient is undertaken in this study.</p> <p>A TLD equipped with slat screens bf different slat heights, edge geometries, and solidities is experimentally investigated. The TLD is subjected to shake-table tests under sinusoidal excitation for a range of amplitudes that correspond to a practical range of peak hourly horizontal structural accelerations. The variation in screen losses (C_L) is correlated with the Keulegan-Carpenter (<em>KC</em>) number.</p> <p>An equivalent mechanical model is utilized by analyzing the TLD as an equivalent tuned mass damper (TMD). In addition, a nonlinear numerical model based on shallow water theory is investigated. The influence of slat height on the free surface response, base shear forces, and energy dissipation is assessed.</p> <p>A TLD equipped with various screen geometries is mathematically modelled in a hypothetical structure-TLD system. This system demonstrates the ability of slat screens with a varying loss coefficient to maintain a near optimum level of damping over a wide range of structural accelerations.</p>