REINFORCEMENT AND ACCESSORIES
apparent cost of the stairs. This is a false
view, however, since the overall cost of
connectors, when labour and finishing works
are included, can be in the region of £300 per
landing compared to using angles.
Once installed, steel angles must be
concealed and fire-protected. This operation
is frequently not included in anyone’s work
package, leading to potential disputes.
Similarly, operations such as checking bolt
torques, and indeed the design of both angle
and fixings, are often not included in costs.
When erecting landings, particularly in a
high-rise structure, it is beneficial that the
stairwell is free from obstructions that would
impede the lowering in of precast elements. If
angles are used then these cause obstructions,
requiring different lifting techniques.
The alternative is to fix angles piecemeal,
working off the landing below. For telescopic
connectors, the stairwell is completely free of
any obstructions (see Figure 3), thus allowing
a free route for the crane. This is achieved
by seating the connectors into recesses in
the wall. Forming these recesses used to be
a drawback in itself, but now, preformed
recess formers make the task easy, even with
slipformed walls (see Figure 4).
Angles and their fixings are a safety-critical
element and should be designed by a
competent engineer. Too often, drawings
vaguely show an angle with the note ‘design
by others’. This design element and that
of the fixings should be clearly defined in
contract documents, spelling out who is
Figure 5: Impractical
Figure 2: Bedding between precast and angle.
Figure 3: Stairwell clear of obstructions.
Figure 4: Preformed recess.