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Steel Designers' Manual - 6th Edition (2003)
and the need to build assemblies in a jig to represent the various points at which
connection has to be made in the main framework. An additional jig for lifting can
be particularly useful if there are many similar lifts to be made. This can be made
to combine the need to stiffen with the need to connect to stiff points in the subframe,
and the need to have the sub-frame hang in the correct attitude on the crane
hook. The weight of any such stiffening and of any jig must of course be taken into
account in the choice of crane.
Some temporary stiffening may be left in position after the initial erection until
the permanent connections are made. This eventuality should also have been foreseen,
and sufficient stiffeners and lifting devices should be provided to avoid an
unnecessary bottleneck caused by a shortage of a device for erection of the next
sub-frame.
Where a particularly awkward or heavy lift has to be made, slinging and lifting
can be made both quicker and safer if cleats for the slings have been incorporated
in the fabrication. Each trial lift made after the first one wastes time until the piece
hangs true. The drawing office should determine exactly where the centre of gravity
is.
A chart giving details of standard hand signals is illustrated in Fig. 33.18. Their
use is essential when a banksman is employed to control the rear end of the transport,
thereby bringing the component to the hook as it is reversed. The banksman
is needed to relay the signal from the man directing the movements of the crane if
he is out of sight of the crane driver. A clear system of signals should be agreed for
the handover of crane control from the man on the ground to the man up on the
steel who controls the actual landing of the component. A banksman may also be
needed up on the steel if the crane driver cannot clearly see the top man who is
giving the control instructions: it is vital that there is no confusion over who is giving
instructions to the crane driver.
33.9 Safety
33.9.1 The safety of the workforce
Safety 1001
The health and safety regulations require a project safety plan to be drawn up, which
should include a detailed assessment of anticipated risks.
There are a number of standards, regulations and guidance notes for the safety
of the workforce during construction, as referenced in the further reading.
Site safety of the workforce is subject to statutory regulation and inspection
by the Health and Safety Executive. Regulations lay down minimum acceptable
standards for the width of working platforms; the height of guard-rails; the fixing
of ladders; and so on. They refer to the use of safety belts and safety nets. They lay
down the frequency with which a shackle or chain sling must be tested and the
records that must be kept to show that this was done. Reference should be made to
the appropriate regulation for the details of these requirements.