Most tower cranes have to be assembled
and erected on site prior to use and can be equipped with a horizontal or
luffing jib. The wide range of models available often make it difficult to
choose a crane suitable for any particular site but most tower cranes can be
classified into one of four basic groups thus:
1. Self Supporting Static Tower
Cranes † high lifting capacity with the mast or tower fixed to a foundation
base - they are suitable for confined and open sites.
2. Supported Static Tower Cranes
† similar in concept to self supporting cranes and are used where high lifts
are required, the mast or tower being tied at suitable intervals to the
structure to give extra stability.
3. Travelling Tower Cranes †
these are tower cranes mounted on power bogies running on a wide gauge railway
track to give greater site coverage - only slight gradients can be accommodated
therefore a reasonably level site or specially constructed railway support
trestle is required.
4. Climbing Cranes † these are used
in conjunction with tall buildings and structures. The climbing mast or tower
is housed within the structure and raised as the height of the structure is
increased. Upon completion the crane is dismantled into small sections and
lowered down the face of the building.
All tower cranes should be left
in an `out of service' condition when unattended and in high wind conditions,
the latter varying with different models but generally wind speeds in excess of
60 km p.h. would require the crane to be placed in an out of service.
buildersengineer.info
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