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314 Barry’s Advanced Construction of Buildings
Steel wedge holds the
base in the correct line
(position)
Base plate welded to column (plate
minimum 12 mm thick)
Steel packing shims fix column at
correct level
Temporary bund wall (sand)
Non-shrinkable grout fills void left
below plate (liquid grout poured into
voids)
Void formed by cardboard or
polystyrene cones, which allows
±20 mm horizontal tolerance is filled with
grout
Large washer fixed to bolt to prevent
pull out
Figure 5.39 Column base fixed to holding-down bolts.
load, and to provide a means of fixing with holding-down bolts. The bases of steel columns
are accurately machined so that they bear truly on the steel base plates to which they are
welded. The three types of steel base plate that are used are the plate base, the gusseted
plate base, and the slab or bloom base. For comparatively light loads, it is usual to use a
12 mm thick steel base plate fillet welded to the column. The thin plate is sufficient to spread
the light loads over its area without buckling. The plate, illustrated in Figure 5.39 and Figure
5.40, is of sufficient area to provide holes for holding-down bolts.
Prior to the column being positioned, the foundation base is checked for level, and steel shims
are used to ensure that the base of the column sits at the required level. The column is hoisted
into position over the concrete base so that it is plumb (vertical). The column is then lowered
over the bolts. Because the bolts are cast with a void around them, which allow a small amount
of moment (lateral tolerance), wedges are used to move the base into the correct position. The
base is checked for line and level before being grouted in. A small bund wall of sand is then
positioned around the column base and non-shrinking grout is then poured between the base
and the foundation. The grout fills all the voids, including those made by the cones, which
had allowed movement. Once the grout has set, the column is securely held in position.