Steel Designers Manual - TheBestFriend.org

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Steel Designers' Manual - 6th Edition (2003)
Example coating specifications for a range of environments are given, together
with an indication of relative costs.
Trusses and lattice girders
• Lattice girders and trusses are effective for medium to long spans where deflection
is a major criterion and are able to accommodate services within their depth,
but always consider the use of a plain rolled section beam first.
• Most lattice frames are joint critical. Never select a section for the chords or internals
without first checking whether it can be effectively joined – preferably
without recourse to stiffening.
• Always check the limits on transport before starting the design.
• Be aware that SHS are only available in limited standard lengths, normally from
stockists. Long lengths may therefore need additional butt welding.
• For internal members try to detail single bevel end cuts; for angles square-cut
ends are better to allow use of an automatic cropping process.
• In tubular construction use of RHS chords leads to simpler end preparation for
internals than that required if CHS chords are used.
• Think about access provisions for welding of internals to chords.
• Access for painting is difficult for double angle or double channel members; use
of SHS reduces paint area and provides fewer locations for corrosion traps to be
formed.
Transportation
• Police notification with associated programme and cost penalties will occur for
road transport loads greater than 18.3 m long, or 2.9 m wide or 3.175 m high.
32.3 Welding
Fusion welding processes are used to join structural steel components together.
These processes can be carried out either in the workshop or on site, though it is
generally accepted that site welding should not be used as a primary source of
fabrication. Welding should be undertaken only by welders who are certificated to
the appropriate level required by British Standards or other recognized authority.
Welding is covered in detail in Chapter 24.
32.4 Bolting
Bolting 955
Shop bolting may form part of the fabrication process.There are implications arising
from the use of shop bolting which need to be appreciated by the designer in order
to ensure that a cost penalty does not occur.