2. 2
ROOFS SUPPORTED WITH
VERTICAL ELEMENTS
SUBJECTS OF COMPRESSION:
POST AND BEAM
STRUCTURES:
- LOAD BEARING WALLS
- SKELETON FRAME
ROOFS SUPPORTED WITH
VERTICAL ELEMENTS
SUBJECTS OF TENSION:
MASTED STRUCTURES
- ARCHES, VAULTED HALLS, AND DOMES
- PORTAL FRAMES
- TRUSSES
- SPACE FRAMES
- FOLDED ROOFS
- SHELLS
- MEMBRANES AND TENTS
ROOF
STRUCTURES
16. PORTAL FRAME ROOF
• Portal frames are generally low-rise structures, comprising columns and horizontal or pitched rafters,
connected by moment-resisting connections.
• Resistance to lateral and vertical actions is provided by the rigidity of the connections and the bending
stiffness of the members, which is increased by a suitable haunch or deepening of the rafter sections.
• This form of continuous frame structure is stable in its plane and provides a clear span that is unobstructed
by bracing.
• Portal frames are very common, in fact 50% of constructional steel used in the UK is in portal frame
construction.
• They are very efficient for enclosing large volumes, therefore they are often used for industrial, storage,
retail and commercial applications as well as for agricultural purposes.
• This article describes the anatomy and various types of portal frame and key design considerations.
18. ANATOMY OF A TYPICAL PORTAL FRAME
• A portal frame building comprises a series of transverse frames braced longitudinally. The primary
steelwork consists of columns and rafters, which form portal frames, and bracing. The end frame (gable
frame) can be either a portal frame or a braced arrangement of columns and rafters.
• The light gauge secondary steelwork consists of side rails for walls and purlins for the roof. The
secondary steelwork supports the building envelope, but also plays an important role in restraining the
primary steelwork.
• The roof and wall cladding separate the enclosed space from the external environment as well as
providing thermal and acoustic insulation. The structural role of the cladding is to transfer loads to
secondary steelwork and also to restrain the flange of the purlin or rail to which it is attached.
31. SKETCH THE CONSTRUCTION OF:
lattice roof
portal frame roof
shell roof
Due date 14 AUGUST 2016
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32. LONG SPAN ROOF FINISHES
1) METAL DECKING
2) POLYCARBONATE
3) GLASS
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33. INSTALLATION METHOD OF METAL DECKING ON LONG SPAN
ROOF
A. Install decking as indicated and in accordance
with the approved submittals and the decking
manufacturer's installation instructions.
Provide decking complete, including shaping,
cutting, fitting, drilling, welding, flashings,
closure strips, closure plates, fasteners, and
accessories necessary for a complete and
finished installation.
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34. INSTALLATION METHOD OF METAL DECKING ON LONG SPAN
ROOF
B. Install decking in straight and continuous rows
as far as practicable, with ribs at right angles
to structural supporting members. End laps
shall occur over bearings only, and where
sheets are lapped, end laps shall be not less
than 2 inches. Where ends of decking sheets
abut without overlapping at supports, each
end of decking shall have a minimum bearing
of 1 inch on supports.
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35. INSTALLATION METHOD OF METAL DECKING ON LONG SPAN
ROOF
C. Stud shear connectors to be installed on
metal decking shall be installed directly over
webs of beams for single row installations.
D. Type of welding, number of welds, size of
welds, and locations of welds shall be in
accordance with the approved Shop Drawings
and the decking manufacturer's installation
instructions. Welding shall conform with the
requirements of Section 05 05 22 - Metal
Welding.
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36. INSTALLATION METHOD OF METAL DECKING ON LONG SPAN
ROOF
E. Welds shall be cleaned immediately by wire-
brushing, and shall be coated with galvanizing
repair material before being covered by the
succeeding sheet.
F. Decking shall be weighted at the point of
welding with sand bags or other approved
method to hold them in firm contact with each
other and structural supports.
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37. INSTALLATION METHOD OF METAL DECKING ON LONG SPAN
ROOF
G. Secure solid welds where sheets are warped
or bent to certain radii and where decking is
placed on a slope while supporting members
are framed in a straight position.
H. Holes and openings for services and other
projections through decking shall be cut and
fitted neatly and accurately and shall be
reinforced as necessary for rigidity and load-
carrying capacity.
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