Steel Designers Manual - TheBestFriend.org

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Steel Designers' Manual - 6th Edition (2003)
—(a) castellated beam (b) cellular beam
(
C
(c) beam with web openings
Fig. 2.19 Beams with web openings for service penetrations
Fabricated plate girders
Conventional universal beams span a maximum of about 15 m. Recent advances in
automatic and semi-automatic fabrication techniques have allowed the economic
production of plate girders for longer span floors. Particularly if a non-symmetric
plate girder is used, it is possible to achieve economic construction well in excess of
15 m (Fig. 2.20). Such plate girders can readily accommodate large openings for
major services. If these are in regions of high stress, single-sided web stiffening may
be used. Away from regions of high stress, stiffening is usually not required.
The use of intumescent paints, applied offsite, is becoming increasingly popular.
One major fabricator is now offering an integrated design and fabrication service
for customized plate girders which can achieve a fire resistance of 2 hours when
applied as a single layer in an off-site, factory-controlled process.
Taper beams
Anatomy of structure 63
Taper beams (Fig. 2.20) are similar to fabricated plate girders except that their depth
varies from a maximum in mid-span to a minimum at supports, thus achieving a
highly efficient structural configuration. For simply-supported composite taper
beams in buildings the integration of the services can be accommodated by locating
the main ducts close to the columns. Alternative taper beam configurations can
be used to optimize the integration of the building services.