 Open Access
 Total Downloads : 42
 Authors : Harkomal Kaur, H.S Rai
 Paper ID : IJERTCONV5IS05020
 Volume & Issue : ESDST – 2017 (Volume 5 – Issue 05)
 Published (First Online): 24042018
 ISSN (Online) : 22780181
 Publisher Name : IJERT
 License: This work is licensed under a Creative Commons Attribution 4.0 International License
Effects on Intz Type Tank with Code Revision of IS:3370 (1965) to (2009)
Harkomal Kaur, Assistant Professor
Baba Banda Singh Bahadur Engineering College Fatehgarh Sahib (Punjab)
H.S Rai
Guru Nanak Dev Engineering College Gill Road, Ludhiana
AbstractWater is stored in storage tanks, reservoirs and overhead tank which can be used to store water, liquid petroleum, petroleum products and similar liquids. The load investigation of various reservoirs or tanks is near to the same regardless of the chemical temperament of the product. Tanks are generally designed as crack free structures to eradicate any sort of outflow. Comparative study needed on the theory behind the design of liquid retaining structure. A discussion on the use and change of the code IS: 3370 (part 1& 2) is given in the paper. Overhead tank are used to store water for supplying it to the consumer. BIS has revised the version of IS: 3370 (part 1&

after a elongated time from its 1965 version in year 2009. The code is drafted for the water tank. Limit state method is included in this new version. This paper gives the brief study on the design of intz water tank using working stress method and limit state method. Comparative result of IS: 3370 (1965) and IS: 3370 (2009) is specified. This study was conducted in order to compare the design provisions of IS: 3370 (1965) and IS: 3370 (2009). This edition adopts limit state method with these additions. Cracking width of limit state design is limited and second addition is it limits the stresses in steel so that concrete does not reaches in over stressed zone.
Keywords – IS: 3370 (1965) & (2009), Intz Water Tank, Working stress method, limit state method, Design, Crack width

INTRODUCTION
In every day usage water is a essential part of life. So water is stored for daily purposes in various forms to use it for daily purposes. Tanks which are constructed above ground are used for the purpose storing water. These tanks are described according to their position as underground on ground overhead tanks. Different shapes of tanks can be constructed circular and rectangular are used most commonly. The tanks can be made of RCC or even of steel. The tanks which are constructed above ground are overhead tanks and are usually elevated from the roof to through the column. As seen in most cases Ground tanks and underground are rectangular or circular in shape but the shape of the Overhead tanks are influenced by the vision of area around and also the design of the construction. Storage tanks are containers that store liquid gases or any other medium Jain, Ashok K (2002). After a long time IS: 3370 is revised from its 1965 version IS: 3370 (PartI), 1965. In this revision introduction of limit state design is the most important addition.
Limit state design method; found to be has been found to be the best for the design of reinforced concrete structures. There are further two division of limit states limit state of collapse and limit state of serviceability which involves cracking and deflection. The structure is first analysed and
designed under limit state of collapse after that checked under usefulness IS: 3370 (PartII), 2009.

LITERATURE REVIEW

An exhaustive literature review revealed that a minimum amount of research work had been done on this topic.
Tanetal (1966), presented the minimum cost design of reinforced concrete cylindrical water tanks based on the British Code for water tanks, using a direct search method and the (SUMT). The cost function included the material costs of concrete and steel only. The tank wall thickness was idealized with piecewise linear slopes with the maximum thickness at the base.
Thakkar et al. (1974), discussed cost optimization of non cylindrical composite type prestressed concrete pipes based on the Indian code.
AlBadri (2005), presented cost optimization of reinforced concrete circular grain silos based on the ACI Code (2002).
He proved that the minimum cost of the silo increases with increasing angle of internal friction between stored materials, the coefficient of friction between stored materials and concrete, and the number of columns supporting hopper.

PROBLEM FORMULATION
The main objective to study this code is to make engineers aware about the best method available to ensure the best economical and reliable method which can be used to for designing purpose. So to do the comparison study of provisions in IS:3370 (1965) and IS:3370 (2009), Intz type of water tank was chosen since it is widely used for large capacity .
An Intz type water tank of 1million litres (1000 m3 ) supported on an elevated lower comprising of 8 columns. The base of the tank is 16 m above ground level. Depth of foundation 1 m below ground level was chosen in this study. M30 grade of concrete and Fe415 grade of tor steel was used conforming to the stresses specified in IS:3370 and IS 456, 2000. Fe500 grade of steel may be taken, but it may not be more useful in liquid retaining structures since the permissible stresses in steel is independent of grade of steel as per clause 4.5.3.2 of IS: 3370 (Part 2) 2009. Grade of concrete is taken as M30, as minimum grade of concrete for RCC structures is M30 as per IS: 3370 (Part1) 2009. As per discussion above, the water tank was designed by the following four design methods.

Working stress method in accordance IS:3370 (1965)

Working stress method in accordance IS:3370 (2009)

Limit state design method with crack width calculations and check in accordance IS: 3370 (2009).

Limit state design method deemed to satisfy (limiting steel stresses in accordance IS: 3370 (2009).


DESIGN METHOD
In past times the design method usually used was working stress method. This method has large number of limitation. Sometimes the limit state method cannot be used due to some technical clinch the working stress method can be used. In liquid retaining structure Limited cracking width calculated by working stress method was prime reason why the Indian Standard IS: 3370 (1965) did not adopt the limit state design method even after adoption by IS; 4561978. But now, IS:3370 adopted limit state design method in 2009 with the following advantages – limit state design method contemplate the materials according to their properties , and it also treat load according to their load, the structures also fails mostly under limit state and not in elastic state and limit state method also checks for serviceability. There possible intuitions that working stress method will obsolete in coming time IS: 3370 (PartI), 1965 & IS: 3370 (PartII), 1965.
Type of Stress
Permissible Stresses In N/mm2 IS:3370 1965
Permissible Stresses In N/mm2 IS:3370 2009
Plain round mild steel bars
High strength deformed bars
Plain round mild steel bars
High strength deformed bars
Tensile stress in members under
direct tension
150
150
115
130
Tensile stress in members under direct tension
a) on liquid retaining face
150
150
115
130
b) on face away from liquid for members less than 225 mm
150
150
/td>
c) on face away from liquid for
members more than 225 mm
125
190
Compressive stress in columns subjected to direct load
125
175
125
140
IS:33702009 adopts limit state design method with precautions. It adopts the criteria for limiting crack width when the structures are designed by considering ultimate limit state and restricts the stresses to 130 MPa in steel so that cracking width is not exceeded this is considered to be deemed to be satisfy condition. This safety ensures that cracking width should be less than 0.2 mm which is quite applicable for the liquids. It clearly shows how the liquid structures all different from other structures IS: 3370 (PartI), 2009 & IS: 3370 (PartII), 2009.

GENERAL REQUIREMENT ACCORDING TO IS: 3370 1965 & 2009
Table I. Minimum Cement Content, Maximum water Cement Ratio and Maximum Grade of Concrete
Table II. Comparison of Minimum Reinforcement as per code provision is shown below
IS : 3370 1965
IS : 33702009
A ) The minimum reinforcement in walls, floors and roofs in each of two directions at right angles shall have an area equal to
A) The minimum reinforcement in walls, floors and roofs in each of two directions at right angles, within each surface zone shall not be less than
1. 0.3 % of cross sectional area of sections thickness < 100 mm
1. 0.35 % of surface zone as shown in for HYSD bars.
2. Linearly varying from 0.3 % to 0.2% for thickness 100 mm to 450
mm.
2. 0.64 % of surface zone for mild steel bars.
3. 0.2 % for section of thickness > 450mm
B ) The minimum reinforcement can be further reduced to
1. 0.24 % for HYSD bars.
4. In concrete sections of thickness
>225 mm, two layers of reinforcement be placed one near each face.
2. 0.40 % for mild steel bars. For tanks having any dimension not more than15 m.
B) The minimum reinforcement specified above may be decreased by 20 % in case of HYSD bars.
C) In wall slabs less than 200 mm in thickness, the reinforcement may be placed in one face.
Table III. Comparison of Provisions for Permissible Stresses in Steel
S No.
Concrete
Minimum Cement Content
Maximum Free Water Cement
Ratio
Minimum Grade of Cement
1
Plain
concrete
250
0.5
M20
2
Reinforced
cement concrete
320
0.45
M30
3
Prestresed
concrete
360
0.4
M40

DESIGNS ON BASIS OF CRACK WIDTH

Working stress method
For No Cracking Criteria,
The quantities of materials for different components of Intz type water tank for different design theories have been tabulated in Table V, Tables VI, VII, VIII, IX and X present the quantities of materials for Intz type water tank
,respectively.
A comparison of design by working stress method as per IS
T
Ac + (m 1)As
= 280
3 cbc
Where, m = Modular Ratio
As = Area of steel
t
33701965 and IS 33702009 shows that the amount of material remains unchanged. It is further observed that the steel quantity decreases significantly as per IS 33702009 in those members where the designed amount of reinforcement is less than the minimum reinforcement. This is because, in IS 33702009, the minimum reinforcement is calculated on the basis of the area of cross section of the surface zones and not on the basis of entire cross section as in IS 33701965. The steel and concrete quantities for Limit State design
t = Allowable tensile stress in concrete
cbc= Allowable tensile stress in concrete

Limit state method
The permissible limit of crack width is 0.2mm. The crack widths due to temperature and moisture effects shall be calculated as given below:
To be effective in distributing cracking, the amount of reinforcement provided needs to be at least as great as given below:
Method as per IS 33702009 decrease significantly as compared to working stress methods of IS 33701965 and IS 33702009 because higher permissible stresses are permitted and crack width is checked. The quantities of steel for intz type tank considered in this study was observed to be the maximum for design as per Limit State Method based on Deemed to Satisfy Criteria.

TOP DOME
Meridional Thrust = 22.22 kN/m Circumferential Force =10 kN/m Meridional Stress = 0.22 N/mm2 Hoop Stress = 0.10 N/mm2
crit
fct
fy
Table V. Comparative results of top dome with WSM & LSM
TOP DOME
WORKING STRESS METHOD
LIMIT STATE DESIGN METHOD
IS:3370 1965
IS3370 2009
CRACK THEORY
CRACK WIDTH
DEEMED
TO SATISFY
Thickness
100mm
100mm
100mm
100mm
% age change
—
Nil
Nil
Nil
Area of
Steel
300mm2
175mm2
120mm2
130mm2
% age
change
—
53.16
50
– 45.8
Where, crit= critical steel ratio,
fct= direct tensile strength of the immature
fy= characteristic strength of the reinforcement.
Table IV. Comparison of provisions for permissible stresses in steel
Grade of concrete
M25
M30
M35
M40
M45
M50
, N/mm2
1.15
1.3
1.45
1.6
1.7
1.8
Maximum spacing of crack
=
fct Ã— fy 2

TOP RING BEAM
Hoop Tension = 106.6 KN
Table VI. Comparative results of top ring beam with WSM & LSM
TOP RING
BEA M
WORKING STRESS METHOD
LIMIT STATE DESIGN METHOD
IS:3370 1965
IS3370 2009
CRACK THEORY
CRACK WIDTH
DEEMED TO
SATISFY
Area of cross
section
62614mm
2
62614mm2
34500mm2
34500mm2
% age
change
—
—
32.61
32.61
Area
of steel
780mm2
820mm2
443mm2
0.06mm
820mm2
% age
change
—
+9.42
42
+9.42
fct = ratio of the tensile strength of the concrete to the average
fy
bond strength between concrete and steel which can be taken as 2/3 for immature concrete.
= size of each reinforcing bar Width of Fuly Developed Crack,
Wmax
= Smax
Ã— Ã— T1
2
Where = Coefficient of thermal expansion of concrete


RESULTS & DISCUSSION
Intz water tank was designed following the provisions of IS:3370 (1965) & (2009) by working stress method and limt state desgin method. The quantities of materials were calculated and have been tabulated in the following section.

CYLINDRICAL TANK WALL
Max. hoop tension at base of wall = 480 kN/m Hoop tension at top of wall = 200 kN/m
Table VII. Comparative results of cylindrical tank wall with WSM & LSM
CYLINDRI CAL TANK
WALL
WORKING STRESS
METHOD
LIMIT STATE DESIGN METHOD
IS:337 01965
IS337 0
2009
CRACK THEOR Y
CRACK WIDTH
DEEMED TO SATISFY
Base level thickness
350m
m
350m
m
140mm
140mm
% age
change
—
—
50
50
Area of steel
at base
3200
mm2
3700
mm2
1995
mm2
3700
mm2
% age
change
—
+30.5
73.21
+30.45
Top
thickness
200m
m
200m
m
100mm
0.16mm
100mm
% age
change
—
—
45.6
45.6
Area of steel at top
800
mm2
925
mm2
500
mm2
925
mm2
% age
change
—
+36.1
8
74
+38.18

BOTTOM RING BEAM
Table VIII. Comparative results of bottom ring beam with WSM & LSM
BOTTOM RING BEAM
WORKING STRESS METHOD
LIMIT STATE DESIGN METHOD
IS:3370 1965
IS3370 2009
CRACK THEORY
CRACK WIDTH
DEEMED TO
SATISFY
Area of
cross section
720000
mm2
720000
mm2
540000
mm2
540000
mm2
% age
change
—
—
49.2
50.1
Area of
steel
5320
mm2
6140
mm2
3315
mm2
0.14
Mm
6140
mm2
% age
change
—
+28.4
31.46
+76.21

CONICAL DOME
Table IX. Comparative results conical dome with WSM & LSM

BOTTOM SPHERICAL DOME
Table X. Comparative results of bottom spherical dome with WSM & LSM
BOTTOM SPHERICAL DOME
WORKING STRESS METHOD
LIMIT STATE DESIGN METHOD
IS:3370 1965
IS3370 2009
CRACK THEORY
CRACK WIDTH
DEEMED
TO SATISFY
Thickness
300mm
300mm
200mm
200mm
% age
change
—
—
31
31
Area of steel
900
mm2
525
mm2
642
mm2
0.17
mm
1506
mm2
% age change
—
+33.09
65.03
+213.16


CONCLUSION
According to the result and discussions following conclusions are made.

Limit State Method was found to be most economical for design of Intz type water tank as the quantity of steel and concrete needed is less as compared to working stress method.

The thickness of wall and depth of base slab is comes to different for IS 3370:(1965) and IS 3370:(2009) because of the value of permissible stress in Steel (in direct tension, bending and shear) IS 3370:(1965) value of st is 150 N/mm2 and in IS 3370:(2009) st is 130 N/mm2.Water tank is the most important container to store water therefore, Crack width calculation of water tank is also necessary.

There was no change in size of members for working stress method by IS: 3370 (1965) and IS: 3370 (2009). However, steel requirement decreased in IS: 3370 (2009) for intz type water tank, as the allowable stresses in steel were lower.

It was found that the provisions of reinforcement through the surface zones in IS: 3370(2009) provides economical and more effective reinforcement by limit state method.
REFERENCES
CONICAL DOME 
WORKING STRESS METHOD 
LIMIT STATE DESIGN METHOD 

IS:3370 1965 
IS3370 2009 
CRACK THEORY 
CRACK WIDTH 
DEEMED TO SATISFY 

Thickness 
600mm 
600mm 
500mm 
500mm 

% age change 
— 
— 
61.1 
61.1 

Area of steel 
5100mm2 
5885mm2 
3180mm2 
0.19mm 
5885mm2 
% age change 
— 
+32.2 
41.2 
+32.2 

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/li>

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