File - Mechatronics 2k14
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Roofing
1
ROOFS
It is constructed to protect the building
from weather (rain, wind, heat, snow, etc)
Roof is the uppermost part of the building
REQUIREMENTS OF A ROOF
Durable against various natural agencies
Adequate thermal insulation
Water proof
Fire resistant
Sound insulation
Good drainage arrangement
CLASSIFICATION OF ROOFS
1. Pitched or sloping
Single roof,
2. Double roof,
3. Trussed roof.
2. Flat or terraced
1. R.C.C roof,
2. Madras terrace roof.
3. Curved
1. Shell roof,
2. Dome roof.
1.
PITCHED ROOFS
These roofs have sloping top surface
Suitable in those areas where rainfall/snowfall is very heavy
Span: clear distance between the supports of beams,
roofs or truss
Rise: vertical distance between the top of the ridge
and the wall plate
Pitch: inclination of sides of a roof to the horizontal
Ridge: an apex line of a sloping roof
PITCHED ROOFS
TERMS - ROOF
Gable: triangular upper part of a wall formed at the
end of a pitched roof
Purlin: horizontal member placed over the principal
rafters to support the roof membrane.
TERMS - ROOF
TYPES OF PITCHED ROOFS
Single roofs
Double or purlin roofs
Trussed roof
King post truss
Queen post truss
Mansard truss
Bel fast truss
Steel truss
Composite truss
SINGLE ROOF: 1.LEAN TO-ROOFS
Rafters slope to one side only.
Upper ends- rafters are fixed by
nails to the wooden plates.
Lower ends- rafters are
notched & nailed to the
wooden post plate.
Battens are placed and fixed
over rafters.
Roof covering materials.
Spans upto 2.5 m.
2.COUPLE ROOF
Pair of rafters
Slopes to both sides
Upper ends- nailed to
common ridge piece
Lower ends- notched &
nailed to wooden wall
plates.
Battens are fixed
Roof covering materials
Span upto 3.60 m.
3.COUPLE CLOSE ROOF
Tie beam
Prevent from
spreading
Spans upto
4.20 m.
COLLAR BEAM ROOF
Span increase or heavy
load- leads to bend
Prevent by raising the tie
beam
1/3rd to ½ of the vertical
ht. from wall plate to the
ridge.
Spans upto 5m
DOUBLE OR PURLIN ROOFS
Rafters- rest at the ends
on wall
Purlins- intermediate
supports
Spans upto 5.5 m.
TRUSSED ROOF
A
number
of
straight members
connected in the
shape of triangle
and forming a frame
is known as truss.
Truss are provided
at regular interval of
about 3m along the
length.
Used for the span
more than 5m.
KING-POST TRUSS
King post- central
post
Struts- inclined
members
Principal rafterssupport the purlins
Spans- 5 to 8 m.
QUEEN-POST TRUSS
2 vertical posts
Straining beam
2 struts
Straining sill
Spans- 8 to 12 m.
MANSARD TRUSS
Combination of king
& queen post trusses.
Upper portion- king
post truss
Lower portionqueen post truss.
Upper pitch- 30 to 40
degree
Lower pitch- 60 to 70
degree.
BELFAST TRUSS/ BOW STRING
TRUSS
Thin sections of timber
Top chord – curved
30 m span – if roof
covering is light
Rise not more than 1/8th
of the span
STEEL
TRUSSES
KING-POST STEEL TRUSS
COMPOUND FINK & COMPOUND HOWE’S
STEEL TRUSS
ADVANTAGE:
stronger than wooden truss
Very large span (5m to 30m)
Easy to construct
Fire-proof
More rigid
Permanent
More economical
STEEL TRUSSES…..Cont 1
DISADVANTAGE:
Likely to get rusted
Need anti corrosive paints.
Periodical maintenance
required.
USES:
Building with large span
Building with no intermediate
columns.
Place of heavy rainfall of snow
fall.
COMPOSITE TRUSS
Timber and steel
Tension
members – steel
Compression
members –
timber
Light and
economical
FLAT ROOFS
It is one which is either horizontal or horizontal with
slope less than 10°.
TYPES OF FLAT ROOFS:
Madras terrace roofs
Reinforced cement concrete slab roof
MADRAS TERRACE ROOF
MADRAS TERRACE ROOF
REINFORCED CEMENT CONCRETE
ROOF
Easy to cast
Very smooth surface
Length / width > 2 – one way
Length / width < 2 – two way
CURVED ROOFS
Modification of pitched roof and are frequently
employed in modern age to cover large areas.
Useful for assembly halls, recreation centres, factories,
monumental works
Pleasing appearance
Types
Shell roofs
Domes
NORTH LIGHT SHELL ROOF
Mostly used in
Factories
Work shops
Where good day light id
desired
BARREL VAULT SHELL ROOF
Long multiple cylindrical shell
Feather edge beams
Where day-lighting is not must
DOMES
Semi-elliptical or semi-
spherical
Uniform or varying thickness
Brick, stone, steel, wood,
concrete or tile