circ wtf lx base
TRANSCRIPT
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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