Comparative approach to seismic vulnerability of an elevated steel tank within a reinforced concrete chimney

This study provides a framework for investigating the seismicresponse of an elevated steel water tank within a reinforcedconcrete chimney, to assist optimal tank placement and analysedifferent tank geometries. Elevated tank design procedures indifferent guidelines and codes are adequate for specific cases,none of which meets the exact requirements of this case study,in which the supporting structure mass is large relative to thestorage tank. The tank is located at an elevation 63 m belowthe mid-height of the 200 m chimney, resulting in a differentbehavior than a simple cantilever. Furthermore, for certainH/R ratios, coupling effects may exist between the fundamentalperiod of the chimney and that of the sloshing wave. An equivalentmodel is examined that is simple enough yet able to accuratelyproduce the design acceleration, dynamic amplification,damping and torsional effects at the chosen tank location, andto capture site effects. An analysis of the tank at ground level isconducted according to AWWA D100-11. Then, the tank at elevation63 m is analysed within the framework of three existingmethods using code spectra and site-specific spectra. A novelfourth method is then proposed which, contrary to the existingmethods, can accurately capture the conditions of this casestudy by combining the benefits of all methods. The workflowdescribed here can be readily applied to other cases of elevatedtanks for which the standard procedures are inadequate.