Evaluation of Storage Tank Floating Roofs for Stress and Stability Due to Earthquake Induced Liquid Sloshing

Abstract

Considerable interest has developed in the engineering community concerning the damage to the floating roof of oil storage tanks due to liquid sloshing from earthquake loading. Engineering groups in countries bordering the circum-Pacific seismic belt in particular are devoting extensive efforts to obtaining solutions capable of identifying vulnerable roof designs and developing modifications to improve strength. The recent efforts of the Japanese Fire Disaster and Management Authority (FDMA) as a result of 1995 Kobe and the 2003 Tokachi-Oki earthquakes are examples of recent work in this area. This paper focuses on efforts to analyze floating roof structures for stress and stability under typical earthquake velocity spectrums using advanced finite element methods. It employs ideas included in the Japanese FDMA studies, work done as part of the ASCE Committee on Gas and Liquid Fuel Lifelines, and some original methods developed at ExxonMobil. It has been applied to several tank designs and been submitted as a suitable advance analysis method to the Japanese FDMA. The paper provides both the theoretical foundation as well as an example covering typical tank geometry.

Sloshing Characteristics of Single-Deck Floating Roofs in Cylindrical Storage Tanks

“…However, the theoretical background of the fluid motion were not described in these papers. Experimental (12)- (14) and design criteria (15) studies for the sloshing response of the floating roofs have also been reported. In addition, one of the authors reported the elastic buckling strength of the floating roof pontoon (16)- (18) .…”

Axisymmetric Finite Element Analysis for Sloshing Response of Floating Roofs in Cylindrical Storage Tanks

“…Furthermore, such analyses are very expensive, and is not suitable for analysis by parametric survey. Experimental (11) and design criteria (12) studies for the sloshing response of the floating roofs have also been reported. The basic vibration characteristics of the floating roof during sloshing, such as the natural periods and vibration modes, can be obtained by linear analysis.…”