Design Purposed of Rain Water Harvesting System at Roof Level
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Transcript of Design Purposed of Rain Water Harvesting System at Roof Level
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8/3/2019 Design Purposed of Rain Water Harvesting System at Roof Level
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DESIGN PURPOSED OF RAIN WATER HARVESTING SYSTEM AT ROOF
LEVEL
CALCULATION OF BEAM
CALCULATED BY: AYUB SAIDI
DATA:
Slab thickness: 200mm
Finishes: 1.0 Kn/m2
Live load (qk): 7.5 KN/ m2 (Base on table 8, BS 6399: pt1:
1984)
Exposure Condt. Mild
Fcu: 30 N/mm2
Fy: 460 N/ mm2
Self weight of slab
0.2m X 24 KN/m3 = 4.8 KN/ m2
Load due to finishes
10 KN/ m2
Load due to imposed load
7.5 KN/ m2
Ultimate Design Load
1.4 gk + 1.6 qk = (1.4(5.8) + 1.6(7.5)) = 20.12 KN/ m2
For beam C.A/1-2 = Beam C.A/2-3
Load from slab, 2 way slab action base on calculation ly/lx;
Ly/lx = 5.2/4.6 =1.13 < 2.0 ( 2 way slab)
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At beam C.A / 1-2
Each trapezium area;
5.182+0.582X 2.3 X 20.12 KN/ m2 = 133. 32 KN
2 X 133.32 KN = 266.64 KN
At end of beam, point load equal to 133.32KN each
At beam 2/C-D
Each triangle acting on it equal to
4.62 X 2.3 X 20.12 KN/ m2= 106.43 KN
4 X 106.43 KN = 425.72KN/ 9.2 m = 46.27 KN/m
Primary Beam size (600 X 225)
Self weight of beam = (0.6 X 0.23 X 24) = 3.312 KN/m
Design load = 1.4 X 3.312 KN/m = 4.64 KN/m
Add to existing load; 46.27 + 4.64 = 50.91kn/m
Hence for beam 2/C-D, all load acting on it is
Design on beam 2/C-D
Maximum bending moment
WL82 +
PL4 = 538.63 + 306.64 = 845.27 KN.M
K = M/ fcubd2
Assume main bar and cover = 25 mm, d = 600 - 25 - (25/2) =
562.5 mm
845.27 X 106 / 30 X 225 X 562.52 = 0.396 > 0.156 (doubly
reinforcement)
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Z = d ( 0.5 + 0.25-k/0.9 ) = 562.5 ( 0.5 + 0.25-0.396/0.9 )
= 528.75
Area of compression reinforcement (As)
As = (k-k) fcubd2 / 0.95 fy (d-d)
Assume diameter of compression bar = 25 mm
d = cover + diam eter of bar/2 = 37.5mm
As = (0.396-0.156) 30X225X562.52 / 0.95X460X(562.5-37.5)
= 2234.6 mm2, provide 5T25 (2450 mm2)
Area of tension reinforcement (As)
As = M/ 0.95fyz = 845.27 X 106 / 0.95X460X528.75
= 3658.17 mm2, provide 8T25 (3930 mm2)
Since the new load to resist is massive in number, we have to
check if this new load can be resist by the existing beam
structure in this area.
Deflection check
Actual, span/d = 9200/ 562.5 = 16.36
Permissible;
Fs = 2/3 X fy X (As req/ As Prov)
= 2/3 X 460 X (3658.17 / 3930 ) = 285.45
Modification factor;
= 0.55 + [(477 Fs)/ 120 (0.9 + m/bd2 )], m/bd2 = 11.87
0.55 + [0.125] = 0.675
Thus, L/d basic(simply supported) = 20
l/d allow = 0.675 X 20 = 13.5 < 16.36
(The deflection is unacceptable)
Further calculation cant be made because the deflection
criteria is not acceptable. To counter this measure, we can
suggest that we have to provide deeper concrete section for
this beam. Further calculation was made for beam 1 / C-D and
still the result is just the same. Since the existing structure
cant be alter and resist the load, we decide not to design the
rainwater harvesting system in this building.
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