Experimental Seismic Study of Cylindrical Tanks

Earthquake response behavior of ground-supported, thin-shell, cylindrical liquid storage tanks was studied experimentally by means of the University of California at Berkeley shaking table. 12-ft x 6-ft and 7-¾-ft x 15-ft models, fabricated from sheet aluminum to represent steel tanks three times larger, were subjected to simulated earthquake accelerations with intensities up to 0.5 g. Principal test parameters included base fixity (fixed or free to uplift) and top condition (open, fixed, or floating roof). The most significant observation was that out-of-round distortions were induced in both fixed and free-base tanks in addition to the expected lateral deflection. Stresses and deflections associated with the out-of-round response were not negligible. Also, the uplift behavior of unanchored tanks differed greatly from design prediction, with observed stresses several times larger than expected. The models performed satisfactorily despite the unexpected behavior characteristics.