water tank design calc

7/28/2019 Water Tank Design Calc

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Sheet1

Tank Piping Data :

Inside Dia = 2.3 m

EL of 50 NB overflow pipe = (+) 2.4 mMax water level considered as = (+) 2.4 m

Free board upto bottom of roof assumed = 0.4 m

RCC roof thickness = 0.15 m

i.e. (+) 2.95 m

EL of Top of Roof considered = (+) 3.10 m

Level of float pipe (BOP) (INLET) = (+) 2.20 m

Min. clearance reqd. from roof bottom = 0.4 m

Roof thickness = 0.15 m

i.e. (+) 2.75 m

Thus, Roof Top EL taken at (+) 3.10 m is OK

Capacity:

Finished bottom of tank EL = (+) 0.500 m

Max water level EL = (+) 2.40 m

Max water height (2.40 0.500) = 1.9 m

Gross capacity = 3.14/4 x (2.3)2x 1.9 = 7.9 m

2

Roof Slab: (150 mm thick)

Loading:-

DL Self wt of slab:(0.150X2.5) = 0.375 T/m2

50 thk. avg. screed conc.

(0.05X2.5) = 0.125 T/m2

0.500 T/m2

LL LL = 0.15 T/m2

Dust Load = 0.1 T/m2

0.25 T/m2

Total Load (0.50 + 0.25) = 0.75 T/m2

Circular Slab simply supported

Span (d) = (2.5 + 0.200) = 2.700 m

Moment at span / m =( wd2 /16) = 0.75X(2.7)2 = 0.34 T-m

16

Designing by Working Stress method, with M25 & Fe500

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Sheet1

Steel stress allowed = 1900 Kg/cm2

d reqd. = 0.34 X 105

= 5.22cm = 52.2 mm

12.44 X 100

Provide overall depth = 150 mm OK

Def= (150 25 4) = 121 mm = 12.1 cm

Ast Reqd = Moment = 0.34X105

= 1.66 cm2per meter

( stX j X d) 1900X0.89X12.1

Provide 8 Y @ 200mm c/c (2.51 cm2) at top bottom (bothways)

Shear:

= 0.506 T/m

X 2.7

100As = 100X2.51 = 0.20%

bd 100X12.1

Allowable Shear Stress Tc = 3.3 KN/mm2

Allowable Shear Force / m 3.3 X 100 X 12.1 = 3.9 T > 0.51 T OK

1000

2900 RL TOC 366.95 M

2300

2.325

RL (+) 364.475 M

FGL RL (+) 364.0 M

4000

Design of Wall: (200 Thk)

H2

= 2.3252

= 11.75

Dt 2.3 X .200

Fixed base, Free Top

Referring Table 9 of IS 3370 (part IV)

Taking value of H2/ Dt as 16 to be on the conservative side, co-efficients comes to be +0.641

Max Tension / m = (+) 0.641 X 1 X 2.325 X 2.3/2 = 1.64 T at 0.6H from top

(Horizontally)

Shear / m = /4 X (2.7)2

X 0.75

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Sheet1

Alternative Max hoop stress = pr / t = 2.325 X 1.15 = 13.36 T/m2

0.2

Max hoop tension / m = (13.36 X 0.200 X 1.00) = 2.67 T

From Table 10 of IS 3370 (Part IV)

Vertical Bm / m = (+) 0.0019 X 1.0 X (2.325)3

= 0.02 T-m

(Tension outside at 0.8H from top)

Vertical Bm / m = (-) 0.0079 X 1.0 X (2.325)3

= 0.09 T-m

(Tension Inside)

Now,

m = 280 = 11

3 X 8.50

For st = 1900 Kg/cm2

Value of k = 0.38

J = 0.87

Vertical reinforcement

d = (200 25 - 6) = 169 mm

Ast Reqd = 0.14X105

= 0.5 cm2

per meter

0.87X16.9X1900

Provide 12 Y @ 200mm c/c (5.65 cm2) on each face.

Check for Cracking:

For M25 RCC grade, R = M/bd2

= 3.11

With d1 / d = 169/200 = 0.845

Therefore, d reqd. = 0.14X105

= 6.70 cm = 67.0 mm

3.11X100

Thus provided overall depth considered as 200 mm is OK

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Sheet1

Horizontal Reinforcement:

Providing 10 Y @ 200 c/c on both face

Total reinforcement / m = 2 r = 2 X 3.14 X 1.25 = 7.86

Tensile stress in concrete due to hoop stress = Max Hoop Tension per meter X 103

Provided overall depth(cm) X 100 + (m -1) X Total Hori. reinfr / meter(cm2)

= = 1.38 kg / cm2

20.0 X 100 + (11 1) X 7.86 < 13.0 kg / cm2

Hence OK.

Tensile stress in steel = 2.86 X 103

= 363.86 kg / cm2 < 1500 kg / cm2

Hence OK.

7.86

200 mm thk

10 @ 200 c/c

12 mm @ 200c/c

12 mm @ 200 c/c

Extended some thickness & reinforcement upto the Base raft of foundation.

Tank Bottom Slab (200 mm thck)

Load on slab:

Max water load = 2.325 T / m2

s/w of slab (200Thk) = 0.200X2.5 = 0.5 T / m2

25thk finish = 0.025 X 2.4 = 0.06 T / m2

W = 2.885 T / m2

Circular Slab:

Circle dia (h) = 2.500 m

M = wh (1 + v) (3+ v) =dist of point considered from slab center

64 radius of slab

= wh2

(1.2) (3.2) X 12

= 1.250 / 1.250 = 1.00

64

= - wh2

2 v = poison's ratio = 0.20

64

= ( - ) wh2

32

M = 2.89 X 2.502

= 0.56 T-m

32 D = (200 25 10 5) = 160 mm

Ast Reqd = 0.56 X 105

= 2.12 cm2

0.87 X 16.0 X 1900

Provide 12 Y @ 200mm c/c (5.65 cm2) top & bottom bothways.

2.86 X 103

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Sheet1

Check for Cracking:

I = 100 X 203

+ (11 - 1 ) 5.65 X 2 X (2.68)^2

12

= 67478.3 cm4

Z = 67478.3 = 7711.80 cm3

8.75

Max tensile stress in concrete = 0.56 X 105

= 7.26 Kg/m2

< 18.0 kg / m2

Hence OK.

7711.8

Foundation Raft: (250 thk)

Wt of water: X 2.32

X 1.925 X 1 = 8 T

Wt of roof: X 2.72

X 0.75 = 4.29 T

Wt of tank bottom slab: X 2.32

X 0.5 = 2.07 T

Circular wall: X 2.5X 3.675 X .200 X 2.5 = 14.43 T

Wt of PCC below tank: X 2.32X 0.075 X 2.4 = 0.75 T

Wt of sand fill : X 2.32X 1.025 X 2.0 = 8.51 T

Wt of backfill in tank portion: X (4.002 2.7

2) X (0.75) X 1.8 = 9.23 T

Wt of raft : X 4.002X 0.250 X 2.5 = 7.85 T

Total 55.13 T

Gross Base Pressure = 55.13 = 4.38 T / m2

X 4.002

Provided 12 Y @ 200 c/c top & bottom bothways.

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water tank design calc

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