Seismic behaviour of R/C elevated water tanks with shaft stagings: Effectof biaxial interaction and ground motion characteristics

Abstract

An important lifeline facility such as elevated water tanks with R/C shaft staging has been observed to be potentially damaged during earthquakes in the past. Seismic demand of lateral load-resisting members are seldom evaluated accounting bi-directional interaction. Existing guideline to estimate total response combining 100 % of the maximum response for excitation in one direction and 30 % of the maximum responses for excitation in the other horizontal direction (as per ‘30 % rule’) is evidently deficient at least for systems excited well into inelastic range.Present investigation aims to explore the response of shaft-supported reinforced concrete elevated water tank under bi-directional near-fault records with forwarddirective signature. Following detailed review, shaft staging of elevated tank is modelled through distributed plasticity element. Hydrodynamic action is also adequately modeled following established standards. Bi-directional interaction may considerably amplify global response particularly at tank-empty condition. Complex combination of bi-directional load-path may lead to adverse system response. Increase of ground motion characteristics such as mean period, significant duration relative to the impulsive period of the tank, with some scatter, leads to increase interaction effect.