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Steel Designers' Manual - 6th Edition (2003)
work is relatively economic in relation to the equipment costs. It is normal therefore
to design the steelwork in a layout exactly suited to the plant and equipment
without regard for a uniform structural grid. Benefits can still be gained from standardization
of sizes or members and from maintaining an orthogonal grid to avoid
connection problems. The access floors and interconnecting walkways and stairways
must be carefully designed for all-weather access; use of grid flooring is almost universal.
Protection systems for the steelwork should acknowledge both the threat
from the potentially corrosive local environment due to liquid or gaseous emissions
and the requirements to prevent closing down the facility for routine maintenance
of the selected protection system.
Careful account needs to be taken of wind loading in terms of the loads that occur
on an open structure and the lack of well-defined horizontal diaphragms from conventional
floors. These two points are discussed further in sections 3.3.4 and 3.2.2.
3.1.4 Conveyors, handling and stacking plants
Range of structures and scale of construction 99
Many industrial processes need bulk or continuous handling of materials with a
typical sequence as follows:
(1) loading from bulk delivery or direct from mining or quarrying work
(2) transportation from bulk loading area to short-term storage (stacking or
holding areas)
(3) reclaim from short-term storage and transport to process plant.
Structural steelwork for the industrial plant which is utilized in these operations is
effectively part of a piece of working machinery (Fig. 3.3). Design and construction
standards must recognize the dynamic nature of the loadings and particularly must
cater for out-of-balance running, overload conditions and plant fault or machinery
failure conditions, any of which can cause stresses and deflections significantly
higher than those resulting from normal operation. Most designers would adopt
slightly lower factors of safety on loading for these conditions, but decisions need
to be based on engineering judgement as to the relative frequency and duration of
these types of loadings. The plant designer may well be unaware that such design
decisions can be made for the steelwork and frequently will provide single
maximum loading parameters that could incorporate a combination of all such possible
events rather than a separate tabulation; the structural steelwork designer who
takes the trouble to understand the operation of the plant can therefore ask for the
appropriate information and use it to the best advantage.
A further feature of this type of steelwork is the requirement for frequent
relocation of the loading area and hence the transportation equipment. Practical
experience suggests that precise advance planning for specific future relocation is
rarely feasible, so attention should be directed to both design and detailing so that
future moves can cause the least disruption.