The Public Gas Corporation of Greece required seismic isolation bearings for the construction of two large liquefied natural gas (LNG) storage tanks on the island of Revithoussa, near Athens, in one of Europe's highest seismic regions. Each 226 ft dia. x 106 ft. high tank is supported on 212 Friction Pendulum bearings (Earthquake Protection Systems, Inc., San Francisco). The total capacity of the tanks is 38 million gallons, and they provide the central storage of LNG for Greece. These are the largest and heaviest tanks in the world to use seismic isolation.

The performance requirements for the isolation bearings for this project were the most stringent in the history of seismic isolation. The bearings were required to maintain their design properties while fully accommodating the effects of:

• simultaneous lateral and vertical EQ motions
• 35 years of aging in a marine environment
• temperatures from 10°F to 86°F
• unscragged virgin properties

Friction Pendulum bearings where selected over elastomeric bearings because tests of full size bearings proved that they were best able to satisfy these demanding performance requirements. The bearings reduce lateral shear loads on the tanks by 80% for the design earthquake. Each bearing has a vertical load capacity of 2 million pounds, a dynamic period of 2.75 secs., a friction of 5%, a displacement capacity of 12 inches, and weighs 4100lbs.

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