design and drawing of water tank

7/30/2019 Design and Drawing of Water Tank

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Design and drawing of wate

r tank

PREPARED BY:

TUSHAR GAUR

SAUGAT DUTTA

PRIYA KUMARI

SHABNAM DHULL


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LEARNINGOUT COME

INTRODUCTION

TYPES OF TANKS

DESIGN OF CIRCULAR TANK

RESTING ON GROUND WITHRIGID BASE


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INTRODUCTION


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INTRODUCTION:

Use of high strength deformed bars of grade Fe415 arerecommended for the construction of liquid retaining structures

Correct placing of reinforcement, use of small sized and use

of deformed bars lead to a diffused distribution of cracks

A crack width of 0.1mm has been accepted as permissible

value in liquid retaining structures

Code of Practice for the storage of Liquids- IS3370 (Part I toIV)


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INTRODUCTION:

Fractured strength of concrete is computed using the formula

given in clause 6.2.2 of IS 456 -2000 ie., fcr=0.7fckMpaAllowable stresses in reinforcing steel as per IS 3370 are

st= 115 MPa for Mild steel (Fe250) andst= 150 MPa for HYSD bars(Fe415)


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INTRODUCTION:

In order to minimize cracking due to shrinkage andtemperature, minimum reinforcement is recommended as:

For thickness 100 mm = 0.3 % For thickness 450 mm = 0.2% For thickness between 100 mm to 450 mm = varies

linearly from 0.3% to 0.2%

For concrete thickness 225 mm, two layers ofreinforcement be placed, one near water face and other away

from water face.


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INTRODUCTION:

Cover to reinforcement is greater of

i) 25 mm, ii) Diameter of main bar

For tension on outer face:st=140 MPa for Mild steel andst=230 MPa for HYSD bars

For concrete thickness 225 mm, two layers ofreinforcement be placed, one near water face and

other away from water face.


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TYPES OF WATER TANKS


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RESTING ON GROUND


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UNDERGROUND


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ELEVATED


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CIRCULAR


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RECTANGULAR


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SPHERICAL


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INTZ


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CONICAL BOTTOM


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DESIGN OF CIRCULAR TANKS

RESTING ON GROUND WITH RIGIDBASE


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When the joints at base are flexible, hydrostaticpressure induces maximum increase in diameter at base

and no increase in diameter at top

When the joint at base is rigid, the base does not move


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Due to fixity at base of wall, the upper part of the wall

will have hoop tension and lower part bend likecantilever.

For shallow tanks with large diameter, hoop stresses are

very small and the wall act more like cantilever

For deep tanks of small diameter the cantilever action

due to fixity at the base is small and the hoop action is

predominant


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The exact analysis of the tank to determine the portionof wall in which hoop tension is predominant and the

other portion in which cantilever action is predominant,is difficult

Simplified methods of analysis are

1. Reissners method2. Carpenters simplified method

3. Approximate method

4. IS code method


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IS code method

Tables 9,10 and 11 of IS 3370 part IV gives coefficients forcomputing hoop tension, moment and shear for variousvalues of H2/Dt

Hoop tension, moment and shear is computed asT= coefficient ( wHD/2)

M= coefficient (wH3)

V= coefficient (wH2)


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Thickness of wall required is computed from BM

consideration

Qb

Md

where,

Q= cbcjk

j=1-(k/3)

stcbc

cbc

m

mk

b = 1000mm


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Over all thickness is then computed as

t = d+cover.

Area of reinforcement in the form of vertical bars on water

face is computed as

Area of hoop steel in the form of rings is computed as

jd

MA

stst

st

1st

TA


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Distribution steel and vertical steel for outer face of wall

is computed from minimum steel consideration

Tensile stress computed from the following equation

should be less than the permissible stress for safe design

st

cA)1m(t1000

T

the permissible stress is 0.27 fck

Base slab thickness generally varies from 150mm to 250

mm and minimum steel is distributed to top and

bottom of slab.


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Design Problem No.1 on Circular Tanks

resting on ground with Rigid base


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A cylindrical tank of capacity 7,00,000 liters is resting on

good unyielding ground. The depth of tank is limited to 5m.A free board of 300 mm may be provided. The wall and the

base slab are cast integrally. Design the tank using M20

concrete and Fe415 grade steel .

Draw the following

Plan at base

Cross section through centre of tank.


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Step 1: Dimension of tank

H= 5-0.3 = 4.7 and volume V = 700 m3

A=700/4.7 = 148.94 m2

D= (4 x 148.94/) = 13.77 14 m


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Step 2: Analysis for hoop tension and bending

moment

One meter width of the wall is considered and thethickness of the wall is estimated as t=30H+50 = 191 mm.

The thickness of wall is assumedas 200 mm.

Referring to table 9 of IS3370 (part IV), the maximum

coefficient for hooptension = 0.575


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Tmax=0.575 x 10 x 4.7 x 7 =189.175 kN

Referring to table 10 of IS3370 (part IV), the maximum

coefficient for

bending moment = -0.0146 (produces tension on water side)

Mmax= 0.0146 x 10 x 4.73=15.15 kN-m


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Step 3: Design of section:

For M20 concrete cbc=7For Fe415 steel st=150 MpaFor M20 concrete and Fe415 steel m=13.33

The design constants are:

j=1-(k/3)=0.87

Q= cbcjk = 1.19Effective depth is calculated as:

39.0m

mk

stcbc

cbc

mm94.1121000x19.1

10x15.15

Qb

Md

6


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Let over all thickness be 200 mm with effective cover 33 mm

dprovided=167 mm

26

st

st mm16.695167x87.0x150

10x15.15

jd

MA

Spacing of 16 mm diameter bar = c/mmc23.28916.6951000x201

(Max spacing 3d=501mm)

Provide #16@275 c/c as vertical reinforcement on water face


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Hoop steel:

Spacing of 12 mm diameter bar =

Provide #12@80 c/c as hoop reinforcement on water face

Actual area of steel provided

23

st

1st mm1261

150

10x275.189TA

c/mmc.891261

1000x113

2

st mm5.141280

1000x113A


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Step 4: Check for tensile stress:

Permissible stress = 0.27fck=1.2 N/mm2 > c Safe

23

st

c mm/N87.05.1412x)133.13(200x1000

10x275.189

A)1m(t1000

T


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Step 5: Distribution Steel:

Minimum area of steel is 0.24% of concrete area

Ast=(0.24/100) x1000 x 200 = 480 mm2


Provide #8 @ 100 c/c as vertical and horizontal distribution

on the outer face.

c/mmc.7.104

480

1000x24.50


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Step 6: Base slab:

The thickness of base slab shall be 150 mm. The baseslab rests on firm ground, hence only minimumreinforcement is provided.

Ast=(0.24/100) x1000 x 150 = 360 mm2

Reinforcement for each face = 180 mm2


Provide #8 @ 250 c/c as vertical and horizontaldistribution on the outer face.

c/mmc.279180

1000x24.50


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design and drawing of water tank

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