Large deflection analysis of floating roofs subjected to earthquake ground motions

Storage tanks with floating roofs have suffered severe damages during past earthquakes. To evaluate the seismic response of the cylindrical liquid storage tanks with floating roofs Hamilton’s variational principle is used. This study investigates the seismic response of the tanks accounting for nonlinearity due to large deflection of the deck plate. The ground motions include the long-period far-field record of Tokachi-oki, the near-source record of Kobe and far-field record of El Centro. It is found that accounting for large deflections in some cases could slightly magnify the roof deflection. However, usually the suppressing effect of the large deflection is more pronounced. Moreover, the frequency range in which large deflections have a suppressing effect is where ground motions are rich in the frequency content. These results are applicable for all of the ground motions considered in the analysis.