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Single-Storey Frames, Shells and Lightweight Coverings 183
Patent glazing on both
faces of monitor
Roof sheeting on over
purlin lining
Zinc gutter
Zinc capping
Angle
sheeting
rail
Sidewall
sheeting
Beam section
post of portal
frame
Roof sheeting
Weld
Plate welded to
rafter and bolted
to post on site
Portal rafter
Portal rafter
Cranked welded
purlins bolted to
portal rafter
Weld
Portal frame
Pitch
1:10 or
2:10
Ridge plates
welded to
rafters and
bolted together
on site
Cranked welded
purlins as framing
for monitor rooflights
Weld
Portal
rafter
bolted
to post
Beam section
portal rafter
Purlin
Beam section posts
of portal frame at
4.5 centres
Baseplate welded to post and
bolted to pad foundation
Rafters bolted
at ridge
Portal rafter
Figure 4.27 Solid web steel portal frame with monitor rooflights.
lights finish short of the eaves to avoid any unnecessary complications, and can be constructed
to provide natural and controlled ventilation to the interior.
Wind bracing
The side wall columns (stanchions) and their fixed bases that support the roof frames are
designed to act as vertical cantilevers to carry the loads in bending and shear that act on
them from horizontal wind pressure on the roofing and cladding. The rigid knee joint
between rafter and post will carry the loads from horizontal wind pressure on roof and
side wall cladding. Where internal columns are comparatively widely spaced, it is usually