The structural core to an "A" class division should be fixed
into the restraint frame and sealed around its perimeter as shown
in Figure 3. Steel spacers,
with an approximate thickness of 5 mm, may be inserted between the
fixing cleats and the restraint frame if the laboratory finds this
necessary.
When the structural core of an "A" class division is to
be exposed to the heating conditions of the test, i.e. when the fixing
cleats are on the exposed side of the structural core, then a 100
mm wide perimeter margin adjacent to the restraint frame should be
insulated such that the fixing cleats and the edges of the structural
core are protected from direct exposure to the heating conditions.
In no other situations, irrespective of the type of test specimen,
should the perimeter edges be protected from direct exposure to the
heating conditions.