circ wtf lx base

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DESIGN OF CIRCULAR WATER TA

BASE RESTING ON G

PREPARED BY

VAIBHAV GUPTA

VINAY KUMAR YADAVVISHAL REWAPATI

VIVEK KUMAR SINGH


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K HAVING FLEXIBLE

OUND

GUIDED BY

Mr. SUNIL PATIL

READERCED,SDBCE INDORE


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Brief introductionCircular tanks are generally more economical than those having other shapes.Ho

capacity, formwork for circular tanks proves to be costly and rectangular tanks

Forces acting

The tanks are subjected to uniformly varying lateral load due to hydrostatic press

from zero at the free water surface to the maximum at the bottom.in a circular

pressure causes hoop tension in the walls. The magnitude of this hoop tension

nature of the joint between wall and bottom slab.

Requirements

Apart from strength requirement, another essential requirement in the design of

imperviousness.To make water tanks impervious , wider cracks should be avo

concrete which my be achieved by:1)Use richer concrete mix, say M25 or M30.

2)Give a minimum clear cover of 25mm.

3)Provide smaller diameter bars at closer intervals

4)Keep the tensile stresses in concrete low.

5)Follow good construction practices like thorough mixing,good compction and g

DESIGN STE

STEP 3

DESIGN OF WALL AND BA

STEP 2

PRELIMINARY DIMENSIONI

STEP 1

CALCULATION OF DESIGN CON


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ever,for small

are preferred.

ure,increasing

ank,the lateral

epends on the

water tank is

ided in the

od curing.

S

E

G

STANTS


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Design a circular water tank with flexible base having the following specifications:

Capacity=500m,

M25 ,Fe415 to be used;

Overall height=5m , freeboard=300mm;

Bearing capacity of soil=150 kN/m.

Step 1: Determination of various design constants

Permisssible tensile stress in steel(st)=150MPa

Splitting tensile strength of concrete(ct)=1.3MPa

Modular ratio,m=280/3(cbc)

Bending tensile stress in concrete(cbt)=1.80MPa

j=1-k/3

Q=0.5*cbc*j*k

cbc st

8.5 150

Step 2:Preliminary dimensions of the tank

Capacity(in m) Overall height(in m) Freeboard( in m)

500 5 0.3

Step 3: Design of tank wall

Weight density of water ,gw=10 N/m

Maximum hoop tension, T=0.5*gw*H*D

Area of hoop steel required As=T/stNumber of bars provided,n=As/area of single bar,(use 16 mm bars)Spacing,s=1000/no. of bars

T, in kN/m As, in mm

273.4460226 1822.973484

Ae =equivalent area of uncracked composite section

Ac=concrete area in the section

As=area of steel uniformly distributed in the section

T=axial tension

Ae = Ac +(m-1)As

Ae =T/ct

Ae ,in mm Ac , in mm

210343.0943 192149.104

Distributio n steel=.35%.

Use 10 mm bars for distribution steel in vertical directionAs (mm/mm) no. of bars on each face

350 4.454545455

Step 4:Design of the tank base slab

Permissible bending stress in compression in concrete(cbc)=8.5MPa


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The thickness of base slab depends on the head of water

Head of water Thickness of base slab(t)

3m 125mm

6m 150mm

10m 175mm

Unit weight of concrete=25N/mm

t wt. of the side wall of the tank,in kN150mm 892.8733148

Maximum radial and circumferential bending moments at the centre of the circula

M= 3pr/16, where r stands for the radius of tank

Effective depth, d=(M/bQ)Use 25mm bars with 25mm cover to reinforcement

M d, in mm

51.55138289 190.4204044

Adopt a convinient overall thickness . Here let it be 300mm.

cover Overall thickness bar dia.

25 300 25

Using 20mm dia. Bars for distribution steel

dia. Of bar area of each bar

20 314.2857143

Step 5: Check for bearing pressure on soil

wt. of side walls wt. of base slab

892.8733148 824.4409681

The max. pressure is less than the bearing capacity of soil. Hence , the design is saf


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ct cbt m

1.3 1.8 10.98039216

Depth of water in tank Internal diameter of the tank

4.7 11.63600096

No. of bars on each face Spacing,in mm

4.533363815 220.5867521

thickness of wall, in mm

192.149104

spacing

224.4897959


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upward soil pressure on base slab,p kN/m8.122534081

base slab with simply supported edge are,

effective depth required steel distribution steel,mm/m

262.5 1501.172157 525

no. of bars on each face spacing

1.670454545 598.6394558

wt. of water when the tank is full total load on soil max. pressure

5000 6717.314283 16.85039168


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k j Q

0.383562 0.872146 1.421718


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DESIGN SUMMA

1.Capacity of the tank 500m

2.Grade of concrete used M25

3.Type of steel Fe4154.Depth of water in the tank 4.7m

5.Thickness of the tank wall 200mm

6.Internal diameter of the tank 11.64m

7.Reinforcement details of wall

a)Main steel 16mm dia bar rings@220mm c/c o

b)Distribution steel 10mm dia vertical bars @ 220mm c/

8.The base slab

a)Overall thickness 300mm

b)Reinforcement 20mm dia. Bars @180mm c/c in bot


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Y

n both faces

c on each face

h the directions at the top and at the bottom

circ wtf lx base

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