Notes on building
1) Horizontal formwork is called centering and
vertical is called shuttering.
2)
In slabs bars parallel to the shorter span are
main bars. They are laid below distribution bars.
3)
In slabs bars parallel to longer span are called
distribution bars. They are laid above main bars.
4)
In the slabs bar is cranked at one side then the bar is straight at the other side in slabs.
5)
At the corner of each slab what happens is that
the crank and the straight bars from both the sides merge at the point and make
a mesh like formation of rebars.
6) The thumb rule is rebar size in slab should not
be greater than 1/8 th of the depth of slab and the minimum diameter for slab
rebar is 8mm.
7)
In discontinuous end bars are bent U-turn after
providing upto end of slab and extended upto (L/4) length from the face of the
beam where L is the span of the slab on the direction of the rebar. For
continuous end the rebar is extended to adjacent slab up to length (L/4) where
L is the length of adjacent slab in direction of rebar.
8)
The rebar of slab is cranked at the length (L/4)
at 45 degrees where L is the span of slab on the direction of rebar.
9)
The minimum size of rebar used in column is 12mm
and minimum area of steel is 0.8% and maximum is 6% but practically 4%.
10)
The minimum size of longitudinal rebars used in
beams is 10 mm and normally 10-16mm size are used.
11)
The minimum stirrups size to be used is 8mm and
maximum of 10mm.
12)
The main bars in slabs shall not be less then
8mm (HYSD) or 10mm plain bars and distribution bars shall not be less then 8mm.
13)
Maximum spacing of main bar is restricted to 3
times effective depth or 300 mm whichever is less.
14)
Maximum spacing of distribution bar is
restricted to 5 times effective depth or 450 mm whichever is less.
15) For a UDL applied in beam the total point load will be Load(KN/m) * Length of UDL which will act at the centroid of the beam.
16) Minimum thickness of slab is 125mm
17)
Lap slices shall not be used for bars larger
than 36mm.
18)
In steel reinforcement binding wire required is
8kg per MT.
19)
Free fall of concrete is allowed to maximum of
1.5m to prevent from segregation.
20)
Maximum spacing of chairs is 1m or 1nos. per
sq.m.
21)
Ph value of water used in concrete and curing
shall not be less than 6.
22)
Compressive strength of bricks should be 3.5N/mm2.
23)
Cuing time for Ordinary Portland Cement is 10
days.
24) Slumps according to IS 456.
·
Lightly reinforced = 25-75 mm.
·
Heavily reinforced = 75-100 mm.
·
Trench fill = 100-150 mm.
25)
Tolerance in: -
·
Formwork: - (according
to IS 14687)
In C/S of beams and column deviation = +12mm more size and -6mm less size
In footing plan = +50mm more size and -12mm less size
In footing depth = +- 0.05D (Specified thickness)
·
Reinforcement: -
For effective depth <=200mm = +-10 mm
For effective depth >200mm = +-15 mm
For cover to reinforcement = +10mm
26)
Cover to main reinforcement: -
Column = 40 mm
Beam = 25 mm
Slab = 15 mm or not less that dia. of bar.
Footing = 50 mm
Sunshade = 25 mm
Comments
Post a Comment