Design of Overhead Water Tank with Floating Base for Utilization as Tuned Liquid Damper Against Lateral Excitation

Abstract

It would be economical if the overhead water tank (OWT), a common component of any conventional building structure, is designed to act as a passive tuned liquid damper (TLD) for vibration control of the primary structure under lateral excitations. However, the fluctuation in water height due to functional requirements in conventional rectangular or circular shaped OWT alters the liquid sloshing frequency, thereby causing mistuning between the frequency of the TLD and the structural frequency. Again, to ensure maximum energy dissipation in a conventional TLD, the ratio of the liquid height to the largest lateral dimension of the damper along the expected excitation is kept to about 0.1, which is practically impossible to maintain in conventional OWTs. To address these issues, a novel design of OWT with floating base (OWT-FB) is adopted. The floating base is a movable partition provided horizontally in the OWT in such a way so that the desired height of water, determined from the tuning requirement, is always maintained above the floating base. The design ensures that the water above the floating base functions as in a conventional TLD, maintaining proper tuning, even though the water level in the OWT fluctuates. The design of the OWT-FB system for an example building structure is illustrated. The effectiveness of the proposed design is demonstrated by subjecting the structure–damper system to seismic base excitation.