Design and Analysis of Underground Circular & Rectangular Water Tank and Intze Water Tank

GRD Journals- Global Research and Development Journal for Engineering | Volume 6 | Issue 6 | May 2021 ISSN- 2455-5703

Design and Analysis of Underground Circular & Rectangular Water Tank and Intze Water Tank Sahil Patel PG Student Department of Civil Engineering Sankalchand Patel College of Engineering, Visnagar-384315, Mehsana, Gujarat, India

Dhruvkumar H. Patel Assistant Professor Department of Civil Engineering Sankalchand Patel College of Engineering, Visnagar-384315, Mehsana, Gujarat, India

Abstract With the increase in population the requirement of water is increased. The liquid retaining structure should be crack free, leakage free. Therefore container design should be as per codal provision. water tank design as per is-3370 i.e. Code of practice for concrete structure for storage of liquid BIS implement the revise version IS-3370 part-1[general requirement] IS-3370 part- 2 [reinforcement concrete structure] after a long time from its 1965 version in year- 2009.In which most of water tank where design as per old IS code 3370-1965.The objective of research is to say light on difference in the design parameter of Codal provision IS 3370-1965 and IS 3370-2009. For the same capacity of tanks there are different geometry used because of that structural cost of water tank is varies as per geometry of container. The costal comparison as per GWSSB SoR year 2020-21 is done and the most economical container is preferred for construction.

Keywords- Water Container, Joints in Structures, Control of Cracking, Limit State Method

I. INTRODUCTION Without water survival is impossible. Water is one of the most important substances in daily life of all animals and plants because of that every water drop is important. For use of water, Liquid storage tanks are used by municipalities for storing water. For the distribution purpose elevated water tanks are used. For the storage purpose underground water tanks are used. For the design of water tanks Indian standard code is used. The tanks are made of steel structure or RCC structure but in India generally RCC water tanks are used by Indian government. For governmental project life of structure and cost of structure is important factor to be considered. In water tank design, all elements of tanks should be designed and checked as per codal provision. The cost of water tank is depend upon the geometry of water tank elements based on site condition and allowable place for construction of this structure.

Water tanks are classified into two types based on position and shape of tanks:A. – – –

Based on Location the Water Tanks are Classified into Three Ways Underground water tanks Tanks are resting on the ground Elevated or overhead water tanks

B. – – – – –

The Water Tanks are Classified based on the Shapes Circular tanks Rectangular tanks Intze tanks Circular tanks with conical bottom Square tanks

II. DESIGN REQUIREMENTS It is necessary that the reinforced concrete member for any liquid retaining structure should be impervious. For reinforced concrete to be impervious you following two condition must be satisfied:– The concrete used must be of uniform well graded mix of low water-cement ratio and it should be fully compacted and should be free from all defects such as segregation and honey-combing.

– The concrete must be free from cracks.

Reinforced concrete may developed various types of cracks. The cracks are generally of the following:– Very fine well distributed cracks in the tension zone of a concrete member.

– Excessive cracks in the tension zone of concrete member caused by overloading it.

– Crack caused by expansion and contraction of restrained members.

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Design and Analysis of Underground Circular & Rectangular Water Tank and Intze Water Tank (GRDJE/ Volume 6 / Issue 6 / 007)

– Cracks caused by differential expansion in thick member due to heat of hydration.

– Cracks caused by shrinkage of concrete.

– Cracks caused by settlement of structure.

Avoiding normal tensile cracks. The very fine cracks which occur in the tension zone of designed by the normal methods must be avoided in impervious reinforced concrete by designing it in two ways: – By designing against cracking having regard to tensile strength of concrete.

– By designing for structural strength ignoring the tensile strength of concrete.

The following points concerning this aspect of design:– The safety factor against cracking is less than the safety factor required for the structural safety.

– Since the safety factor in design against cracking is relatively small, the possibility of tensile cracks occurring must be envisaged. Hence to strict the width and the depth of such potential crack a low permissible tensile stress in steel is adopted in the structural design.

In addition to these steps taken to prevent tensile cracks to prevent creep of concrete may turn out to be a practical advantage to prevent cracking by applying the working load slowly. This is often possible in the case of a tank or reservoir by slow filling.

Avoidance of other cracks:– Cracks caused due to expansion and contraction due to shrinkage can be avoided by the proper use of movement joints in reinforced concrete. Shrinkage cracks may also be avoided by slow drying out of concrete.

– Cracks caused by deferential expansion in thick members due to the heat of hydration are not likely to occur in members less than the 450 mm thick.

– Cracks caused by settlement can be minimized or avoided by careful site selection and good foundation design and construction.

III. OBJECTIVE The main objective is design, analysis and cost comparisons of different model of underground circular & rectangular water tank and Intze water tank.

IV. COMPARISON OF VARIOUS PARAMETER A. Comparisons of Design Method 1) Working Stress Method Reinforced concrete are non-homogeneous in nature and therefore, an exact theory of bending cannot be developed. The fundamental theory used is straight line theory or the elastic theory.

1) Uncracked Section: The fig shows the beam section with steel at bottom.

Fig. 1: Equivalent area - Uncracked section

The stress diagram shows stress in the beam section consisting of an equivalent concrete section. The tensile stress in the concrete below the neutral axis is similar than the permissible, so concrete area below the neutral axis will not crack.

2) Cracked Section: it is assumed that the concrete area in tensile zone will be ineffective. In that case, the compressive stress will be taken up by the concrete above N.A. and the tensile stresses will be taken up by the steel reinforcement.

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Design and Analysis of Underground Circular & Rectangular Water Tank and Intze Water Tank (GRDJE/ Volume 6 / Issue 6 / 007)

Fig. 2: Equivalent area - Cracked section

The fig shows the equivalent concrete section and stress diagram. Since the concrete is assumed to have cracked, the equivalent area of concrete will be such that the load carried by steel is the same as the load carried by an equivalent concrete area.

The differences between the stress diagrams of fig 1 & 2 must be clear that. In fig 1 the tensile stress distribution is all over the portion of the concrete below the neutral axis. While in fig 2 the tensile stress is in the equivalent concrete area concentrated at the level of steel reinforcement.

2) Limit State Method The method is that a structure will not become unserviceable in its lifetime for the use for which it is intended, that is, it will not reach its limit state. It should withstand all the loads and also satisfy the serviceability requirement such as deflection and cracking.

The following limit states are examined in design Limit state of collapse: - which implies maximum load carrying capacity. Which corresponds to flexure, compression, shear and torsion two different safety factors, one for load and other for material strength are used. They are termed as partial safety factors.

The partial safety factors for loads as per IS: 456.

Limit state of serviceability: which implies the cracking of member with respect to deformation, which corresponds to deflection, and cracking.

Deflection: - The deflection shall generally be limited to following – The final deflection due to all loads including the effects of temperature, creep and shrinkage and measured from the as-cast level of the support of floor, roofs and all other horizontal member should not normally exceed span/250.

– The deflection including the effects of temperature, creep, and shrinkage occurring after erection of partition and the application of finishes should not normally exceed span/350 or 20mm whichever is less.

Cracking: The maximum calculated surface width of cracks for direct tension and flexure or restrained temperature and moisture effects shall not exceed 0.2 mm with specified cover.

B. Comparison of Minimum Grade of Concrete IS: 3370:1965 The minimum grade of concrete is used M35. The parts of the structure neither in contact with the liquid on any face nor enclosing the space above the liquid, concrete mix weaker than M20 shall not be used.

IS: 3370:2009 The minimum grade of concrete is used M30. For small capacity tanks, up to 50 m3 at locations where there is difficulty there in providing M30 grade concrete may be taken as M25. However, this exception shall apply in coastal area.

C. Comparisons of Serviceability Criteria IS: 3370:1965 The design of liquid retaining structure was based on elastic theory, with keeping a material stresses substantially lower than used for normal reinforced concrete structure. Such low stresses fulfilled the purposes of tanks to reduce cracking.

IS: 3370:2009 The new code introduced a limit state method of design with serviceability criteria like Crack width for water tightness.

V. DESIGN, ANALYSIS AND COSTAL COMPARISONS OF WATER TANKS –

There are total 9 containers of water tank is designed manually by working stress method. The cost of elements and component is taken from GWSSB SoR Year 2020-21. Design and check of water tank as per Codal provisions.

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Design and Analysis of Underground Circular & Rectangular Water Tank and Intze Water Tank (GRDJE/ Volume 6 / Issue 6 / 007)

1 2 3 4 5 6 7

1 2 3 4 5 6 7

1 2 3 4 5 6 7

1 2 3 4 5 6 7 8 9

1 2 3 4 5 6 7 8 9

1 2 3 4 5 6 7 8 9

Container dimension (1) [UGC] require capacity of tank 1000.00 m3 provided capacity of tank 1007.78 m3 dia of water tank (D) 21.00 m height of water tank 3.18 m rise of top dome 3.00 m size of top ring beam 880*360 mm thickness of cylindrical wall 0.150 m TOTAL COST 20,37,030.66 Container dimension (2) [UGC] require capacity of tank 1000.00 m3 provided capacity of tank 1005.39 m3 dia of water tank (D) 18.00 m height of water tank 4.23 m rise of top dome 2.60 m size of top ring beam 750*300 mm thickness of cylindrical wall 0.180 m TOTAL COST 18,29,070.96 Container dimension (3) [UGC] require capacity of tank 1000.00 m3 provided capacity of tank 1001.76 m3 dia of water tank (D) 25.00 m height of water tank 2.35 m rise of top dome 3.60 m size of top ring beam 1050*420 mm thickness of cylindrical wall 0.130 m TOTAL COST 25,80,526.37 Container dimension (4) [UGR] require capacity of tank 100.00 m3 provided capacity of tank 108.62 m3 length of water tank 5.00 M width of water tank 5.00 M height of water tank 4.75 M thickness of flat slab 0.125 M no of column 1 Nos dia of column 0.300 M thickness of wall 0.260 M TOTAL COST 6,93,219.89 Container dimension (5) [UGR] require capacity of tank 100.00 m3 provided capacity of tank 111.37 m3 length of water tank 7.00 M width of water tank 5.50 M height of water tank 3.25 M thickness of flat slab 0.125 M no of column 2 Nos dia of column 0.300 M thickness of wall 0.240 M TOTAL COST 6,07,229.32 Container dimension (6) [UGR] require capacity of tank 100.00 m3 provided capacity of tank 104.24 m3 length of water tank 6.00 M width of water tank 4.50 M height of water tank 4.25 M thickness of flat slab 0.125 M no of column 1 Nos dia of column 0.300 M thickness of wall 0.270 M TOTAL COST 6,46,055.53

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Design and Analysis of Underground Circular & Rectangular Water Tank and Intze Water Tank (GRDJE/ Volume 6 / Issue 6 / 007)

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

Container dimension (7) [INTZE] require capacity of tank 1000.00 m3 provided capacity of tank 1008.13 m3 staging height 18.00 M dia of water tank (D) 15.00 M dia of bottom D0 10.40 M height circular portion 4.40 M angle of conical wall 45.00 Degree require height of conical dome 2.30 m TOTAL COST 55,99,261.93 Container dimension (8) [INTZE] require capacity of tank 1000.00 m3 provided capacity of tank 1010.14 m3 staging height 18.00 M dia of water tank (D) 16.00 M dia of bottom D0 10.40 M height circular portion 3.40 M angle of conical wall 45.00 degree require height of conical dome 2.80 M TOTAL COST 54,62,343.51 Container dimension (9) [INTZE] require capacity of tank 1000.00 m3 provided capacity of tank 1008.36 m3 staging height 18.00 m dia of water tank (D) 17.00 m dia of bottom D0 11.90 m height circular portion 2.95 m angle of conical wall 45.00 degree require height of conical dome 2.55 m TOTAL COST 59,82,606.39

VI. CONCLUSION From the comparison of underground circular water tanks different models: – The economical design with geometry ratio of diameter of container to height of circular wall is 1:0.235.

– For the same capacity of water tank; if diameter increase and height or depth decreases then the cost is increased.

– For the economical construction design, provide height or depth is 25% of provided diameter of tank.

From the comparison of underground rectangular water tanks different models: – The economical design with geometry ratio of length of side wall to width of side wall to depth or height of tank is 1:0.79:0.46.

– For the same capacity of water tank; if the depth or height is increase then the cost is increased.

– For the economical construction design, provide width of tank is 80% of long wall and height or depth of wall is 50% of length of long wall.

From the comparison of Intze type water tanks different models: – The economical design with geometry ratio of diameter of container to height of cylindrical wall is 1:0.21.

– For the economical construction design, provide 20% to 25% of diameter of cylindrical wall.

REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9]

IS: 3370(Part-1)-1965, “Code of Practice for Concrete Structures for the Storage of Liquids – General Requirements”, Bureau of Indian Standards, New Delhi, India.

IS: 3370(Part-2)-1965, “Code of Practice for Concrete Structures for the Storage of Liquids – Reinforced Concrete Structures”, Bureau of Indian Standards, New Delhi, India.

IS: 3370(Part-4)-1965, “Code of Practice for Concrete Structures for the Storage of Liquids – Design Tables”, Bureau of Indian Standards, New Delhi, India.

IS: 3370(Part-1)-2009, “Concrete Structures for the Storage of Liquids – Code of Practice - General Requirements”, Bureau of Indian Standards, New Delhi, India.

IS: 3370(Part-2)-2009, “Concrete Structures for the Storage of Liquids - Code of Practice – Reinforced Concrete Structures”, Bureau of Indian Standards, New Delhi, India.

IS: 456-2000, “Plain and Reinforced Concrete – Code of Practice, Bureau of Indian Standards, New Delhi, India” Design of Reinforced Concrete Structures; 2013 by S Rammamurtham.

Reinforced Concrete (Volume - 2) 9th by H. J. Shah.

Sagar Mhamunkar, Mayur Satkar, Dipesh Pulaskar, Nikhil Khairnar, Reetika Sharan and Reshma Shaikh ,“Design and analysis of overhead water tank at PhuleNagar, Ambernath”, International Research Journal of Engineering and Technology (IRJET) 6.4 (2018): 3851 – 3870.

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