An Investigation on Seismic Vulnerability of Floating Roofs

Most floating roof designers adhere to the minimum API ۶۵۰ requirements, focusing on flotation and static buoyancy analysis that accounts for roof weight, rain, or snow. However, the history of floating roof accidents during earthquakes highlights the crucial need to consider dynamic loads for roof safety. This paper examines the induced stresses in single- and double-deck floating roofs under near-source and far-field earthquakes for both small and large tanks. Results show that the stress pattern in the roof deck is primarily controlled by the deck type. For both types of decks, the location of maximum stresses is in the inner portion of the roof, where the maximum stress in the buoyancy analysis is usually located at the deck-pontoon interface. Evaluating the ratio of the code’s target spectrum to the mean spectrum of the earthquake sets leads to large scale factors. Even for unscaled records, stresses exceed the yielding stress, particularly for single-deck roofs exposed to near-source records. It is found that there is high probability of yielding or rupture in the roof deck for ground motion intensities comparable to the target spectrum.

کلیدواژه ها:

Floating roofs ، Dynamic analysis ، Seismic Safety ، Damage ، sinking