Dynamic behavior of R/CR/C elevated tanks with soil–structure interaction

A critical review of past earthquakes reveals damage/failure of important lifeline facilities like elevated water tanks in recurrence, leading to serious hazards even after the event. In the context of such hazards indicating deficiencies in the existing seismic design strategy of such structures, dynamic characteristics of elevated tanks supported by cylindrical shaft (shaft staging) are comprehensively studied in the first part of present investigation. The same is made through analytical formulations developed and validated by rigorous finite element analysis and small-scale experimentation. Subsequent examination on seismic response of representative tanks indicates that the columns of the frame-supported tanks (tanks with frame staging) and the wall of the shaft-staging of such reinforced concrete (R/CR/C) tanks are susceptible to tension, particularly at tank empty condition. Such possibility seems to be further aggravated if the effect of soil–structure interaction (SSI) is ignored in design. Identifying the deficiencies in current design, simple design procedure of such elevated tanks utilizing the formulations developed is proposed. Torsional vulnerability of shaft-supported elevated water tanks is also identified to be marginal as opposed to the same for frame supported ones.