Civil Engineering Reference
In-Depth Information
the building. Similarly, wind pressure differences between the
gables together with longitudinal frictional drag on the build‑
ing due to wind cause longitudinal actions on the building.
Single storey industrial buildings which contain an overhead
travelling crane also have to resist transverse and longitudinal
actions caused by crane surge.
The transverse actions acting on a single storey steel framed
building are usually resisted by frame action, for example, por‑
tal frames or vertical cantilever columns (
Figure 15.3
). The
frames or cantilever columns are typically at say 6-8 m centres.
In the longitudinal direction the resultant horizontal actions
are resisted by horizontal and vertical braced bays. Wind pres‑
sures and suctions on the gables are resisted by columns span‑
ning vertically. These columns are supported at eaves level by
a gable wind girder which transmits the wind actions to the
vertical bracing which in turn conveys the actions to the foun‑
dations (
Figure 15.4
). In the case of low‑pitch portal frame
buildings, the gable columns usually span to a wind girder at
rafter level (
Figure 15.5
).
Where a lattice girder or truss exists as the roof structure
(
Figure 15.3
), the eaves wind girders at each end of the build‑
ing can be connected by means of tie members to prevent
instability of the lattice girders (
Figure 15.6
). This can occur
under wind uplift conditions causing compression in the bot‑
tom chord of the lattice girders.
In single storey steel frame construction braced, bays are
typically provided in the end bays to facilitate erection. Also
for material efficiency the braced bay should be adjacent to the
Moment
Connection
Moment
Connection
Pinned
Base
Pinned
Base
Cantilever Column
Lattice Frame
(Pinned Base)
Portal Frame
(Pinned Base)
Fixed
Base
Stanchion and Truss Frame
(Fixed Base)
Figure 15.3 Types of steel frame
Gable wind girder
(at eaves level)
Side Bracing
(Cross bracing
Tension only)
Side Bracing
(Cross bracing
Tension only)
Figure 15.4 Bracing for single storey steel frame building
