Steel Designers Manual - TheBestFriend.org

This material is copyright - all rights reserved. Reproduced under licence from The Steel Construction Institute on 12/2/2007
To buy a hardcopy version of this document call 01344 872775 or go to http://shop.steelbiz.org/
Steel Designers' Manual - 6th Edition (2003)
120 Industrial steelwork
advice can be sought from the Building Research Establishment (BRE) Advisory
Service or other specialist advisors.
However, on partly or wholly open structures with exposed plant or equipment
great care must be exercised in dealing with wind loading.
It is frequently the case that the total wind loads are higher than on a fully clad
building of the same size, due to two causes. First, small structural elements attract
a higher force than equivalent exposed areas which form part of a large façade.
Secondly, repetitive structural elements of plant items which are nominally shielded
by any particular wind direction are not actually shielded and each element is subjected
individually to a wind load. The procedure for carrying out this assessment
is not covered in detail in BS 6399: Part 2 4 but guidance is available from the references
listed in that document.
Loading on particularly large individual pieces of plant or equipment exposed to
wind can be calculated by considering them to be small buildings and deriving
overall force coefficients that relate to their size.
For smaller or more complex shapes, such as ductwork, conveyors and individual
smaller plant items, it is sensible to take a conservative and easy to apply rule-ofthumb
and use a net pressure coefficient Cp = 2.0 applied to the projected exposed
area. The point of application of wind loadings from plant items on to the structure
may be different from the vertical loading transfer points if sliding bearings or
guides are being used.
3.3.5 Blast loadings
This section deals only with blast loadings from industrial processes and not with
any generalized design requirements to survive blast loadings from unspecified
sources or of unspecified values.
Varying requirements exist for blast loadings. Typical examples are:
(1) transformers, where the requirement is usually to deflect any blast away from
other vulnerable pieces of plant but where frequently one or more walls and
the roof are open, serving to dissipate much of the energy discharged
(2) dust or fine particle enclosures, which are often wholly inside enclosed
buildings.
The decisions to be made are as follows.
(1) Can the potential source of the blast be relocated outside the building
altogether, in a separate enclosure?
(2) If not, can it be placed against the external wall with arrangements to have a
major permanent vented area or a specially designed blow-off panel, both of
which will limit loadings on the remaining structure?
(3) Where the location cannot be controlled, it must be established which direction