Abstract: In the support arrangements for a semi-membrane tank walls described in the specification, the top and side walls of a semi-membrane tank are provided with stiffener members and a surrounding tank support structure has support members which are connected to the stiffener members through support assemblies which provide vertical support for the tank walls while permitting relative motion in the horizontal direction. Each support assembly includes a bracket affixed to one of the support members and a spool affixed to a wall stiffener along with a thermally insulating block having an end portion slidably received in the bracket and having an internal groove extending in a direction orthogonal to the sliding motion of the end portion. The enlarged head of the spool affixed to the stiffener is received in the groove, thereby permitting relative motion of the tank wall with respect to the support structure and two orthogonal directions while providing load support for the tank wall in the vertical direction.