An-Najah Staff

Waste water treatment plants tanks are invariably built below grade and are constructed of a series of adjacent smaller tanks properly linked to suit the water purification process. Design of such structures under static loadings poses little or no challenge. However, in seismic prone zones the structural design is rather involved since it involves the prediction of all seismic forces induced by the liquid on the walls of the tank comprised of a number of cells in addition to considering the various construction stages. This is a code obligation in order to guarantee that the treatment plant remains watertight under all projected loads and load combinations. It is prudent to mention that such considerations are overlooked at times under the pretense that seismic actions are of minor importance for structures built below grade. ACI 350.3 and ACI 350.06 outline the general requirements of the design of regular water tanks. The following is a detailed numerical account of the design undertaking of an actual project. The structural analysis procedure that follows is brief yet it addresses adequately the fundamental principles involved. Sectional slab or wall reinforced concrete design poses a trivial exercise hence it is not dealt with. The following discourse is limited to vernacular upright rectangular water treatment tank. The Tank’s dimensions are relatively small leading to modest magnitude of forces; yet it is the procedure that forms the present focus.