Modelling and preliminary design of a structure-TLD system

Tuned liquid dampers are cost effective dynamic vibration absorbers that are increasingly being employed to mitigate the dynamic response of tall buildings. A significant reduction in the dynamic response of a tall building can be achieved if the TLD is properly tuned and has sufficient inherent damping. The required level of TLD inherent damping can be obtained by installing damping screens inside the TLD tank. This paper develops an equivalent linear mechanical model that accounts for the energy dissipated by the damping screens. Equivalent linear damping ratio expressions are developed for both sinusoidal and random excitation. An equivalent linear mechanical model is subsequently developed using an equivalent displacement variable and the linear damping ratio corresponding to the type of excitation being applied to the structure. Experimental tests are conducted on a scaled model structure-TLD system subjected to both sinusoidal and random excitation to validate the proposed model. Comparisons are made between predicted and measured structural response motion and TLD free surface response motion over a range of structural response amplitudes. A preliminary design procedure for initial TLD sizing and initial damping screen design for a TLD equipped with damping screens is outlined.