Civil Engineering Reference
In-Depth Information
For areas with crowd loading consider carefully whether vibration
supported and in the case of a tall building which has a tower
crane climbing within the core during construction it is one of
the factors to consider in the design of the core geometry.
The type of crane which is probably most often encountered
by building structural engineers is a runway girder supported
workshop crane; these vary in size from effectively simple man-
ual hoists to very significant cranes in steel fabrication yards
for example. Typically, the structural designer will design the
runway beam and then the primary structure to which the run-
way beam attaches. It is important to understand that the crane
will impose not only vertical loads but also transverse and lon-
gitudinal loads (due to dynamic effects, braking, etc.)
Rules of thumb:
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will be an issue.
10.5.2 Plant and equipment loads - typical values
(and why)
In order for buildings to operate they require sometimes sig-
nificant amounts of building services plant; there are also struc-
tures which support plant and equipment involved in servicing
another building structure, or which are related to industrial
processes.
Generally the code recommends a loading minimum of
7.5 kN/m
2
, which is supposed to be checked against 'actual'
loads. Obviously at the early stages of a design process it is
unlikely that the 'approximate' weights of plant will be avail-
able and it is generally the case that even at the point of 'com-
pletion' of the design the actual final equipment load will be
known.
Using 7.5 kN/m
2
for a typical building (office, residential,
etc.) for any plant areas is generally conservative and appropri-
ate; however, for tall buildings and areas with large plant areas
a value of 10, 12.5 or 15 kN/m
2
may be more appropriate.
It should be recognised that a lot of equipment supported
by structures will contain oscillating parts which will impose
dynamic loads greater than the 'at rest' weight of the equip-
ment. It is also important to not use 'shipping weights' but
actual 'operating weights' particularly for items of plant con-
taining liquids of various sorts (principally water in the context
of buildings).
Rules of thumb:
Use a dynamic amplification factor of 100% over the rated 'lifting
■
capacity'.
If you are not sure on the capacity assume 10 metric tonnes and
■
look at a crane manufacturer's literature and clearly state your
assumptions.
Allow a 10% lateral load at each wheel location of a runway crane.
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10.5.4 Vehicle loads - highway, fire truck, garbage
truck, cars, impact loads
For general building structures the ramps and loading bays
contained within need to be designed for the largest wheel
loads likely to occur in service.
For car parking structures the recommendations of the ICE/
IStructE guide to the design of parking structures can be fol-
lowed as a starting point.
One significant loading effect is vehicle impact. To assess
what sort of loading is suitable it is necessary to understand
the type of vehicles which will be used and also to consider the
type of protection (kerbs, bollards, etc.) which are provided to
the structure.
Rules of thumb:
Allow 20% above 'operating weight' for typical elements of plant.
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Anything which involves hoists or winches (lift machinery) should
be designed for 100% of the 'dead weight' of the load - including
weight of cables, tackles, etc.
For tall buildings and for 'energy centres' allow a minimum of
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10 kN/m
2
and consider water tanks and cooling towers in detail
for their weights.
2
UDL and
For a 'car parking' area only - allow for 2.5 kN/m
■
10 kN point load.
For a 'general commercial vehicles area' - allow for 5 kN/m
2
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10.5.3 Crane loads - tower cranes (foundations),
workshop cranes, etc.
Cranes are divided between those (typically) larger cranes used
during construction (tower cranes and 'crawling' or mobile
cranes) and workshop or building integrated cranes.
The design of tower cranes and mobile cranes for use in con-
struction is done to particular codes of practice and standards
applicable to the location. In general, the structural designer will
be provided with reactions from the crane manufacturer which
will provide 'service' level loads for the crane for use. It is not
general practice to allow for construction loads on the perman-
ent structure as a building designer - typically the contractor
will check and strengthen the structure if required. It is often
more important to understand the way in which cranes will be
UDL and 35 kN point load.
2
UDL and
For a 'heavy highway vehicle' - allow for 10 kN/m
■
50 kN point loads - at 1.2 m × 1.8 m pitch.
Braking forces - allow 10% of the vehicle mass in any horizontal
■
direction (i.e. in worst case direction).
Vehicle impact loads:
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For columns/walls near a driveway, without massive bollards
■
or rails - allow 200 kN at 1 m above kerb.
On columns/walls protected by a robust structure - allow
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100 kN at 1 m above kerb.
On rails, etc. designed to protect the structure or prevent fall of
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the vehicle - allow 100 kN at 0.5 m above kerb.
