Abstract: A reinforced concrete tank to surround a steel tank for storage of liquified natural gas which includes a base plate and an upstanding cylindrical wall with the base plate having a plurality of polygonal swing plates hinged to it to move about the hinge in a radial direction but not in a tangential direction and suporting the cylindrical wall above the base plate on projections from the wall that bear on the tops of the swing plates. The tank thus supported permits radial motion of the base plate due to thermal expansion or contraction but resists tangential forces such as those caused by earthquakes or explosions.