Reinforced concrete pedestal (circular, hollow shaft type supports) are popular choice for elevated tanks for the ease of construction and the more solid form it provides compared to framed construction. In the recent past Indian earthquakes, Gujrat (2001) and Jabalpur (1997), thin shells (~ 150 to 200 mm) of concrete pedestals have performed unsatisfactorily when great many developed circumferential tension-flexural cracks in the pedestal near the base and a few collapsed. These observations partially fill the void that exists about the actual performance of such structures in earthquakes of significant magnitude.

The shaft support of elevated tanks should have adequate strength to resist axial loads, and moment and shear forces due to lateral loads. The observed damage pattern shows that, for tanks of large aspect ratio and falling in long time period range, flexural behaviour is more critical than shear under seismic loads.