An experimental investigation on passive control for elevated water tanks

Elevated water tanks are vital elements of the social and economic infrastructure of a country. Besides catering to the water supply requirements of a community, their continued performance in the post-earthquake phase of earthquake-hit areas is also crucial from fire-fighting requirements. However, these structures are highly vulnerable to earthquake forces as they comprise huge water and tank masses concentrated at the top of tall supporting towers. The conventional technique of strengthening these structures involves a stiffer design which leads to increased seismic forces. It is thus pertinent to study the application of vibration control devices for the seismic protection of elevated water tanks. Amongst the various available control technologies, passive control is reliable in the post-earthquake scenario, where power outages are common, as it does not require external power and is also cost-effective. The Tuned Liquid Damper (TLD) is a viable option as it is well-established in the field of structural vibration control having several advantages. This paper investigates the passive vibration control of elevated water tank structures by the TLD through an experimental investigation employing Real-Time Hybrid Testing (RTHT) as the TLD is known to exhibit nonlinear behaviour. In this, the elevated water tank structure is numerically modelled while a full-scale TLD is considered with synchronized physical testing. The results from RTHT are compared with the established TLD model based on shallow water wave theory. Overall, the TLD is identified as an effective passive control device to mitigate the lateral vibrations of elevated water tanks.