JIS COLLEGE OF ENGINEERING

DEPARTMENT OF CIVIL ENGINEERING SUBJECT NAME- CIVIL ENGINEERING

PROJECT SUBJECT CODE: CE- 783 (PART – 1)

GUIDE-ASST. PROF. SOURAV CHANDRA

NAME OF THE PROJECT-DESIGN OF R.C.C OVERHEAD WATER

TANK

GROUP NO.-22SL NO.

NAME OF THE PARTICIPANTS UNIVERSITY ROLL NO.

SECTION

1. SUBHANKAR KUMAR BISWAS 120108101

CIVIL – 4B2. SUBHASIS SINGHA 120108102

3. SUDIP DAS 120108103

4. SUDIPTO BISWAS 120108104

5. SUKANTA PAUL 120108105

INTRODUCTION: Storage Reservoir:

A reservoir (etymology: from French reservoir a “storehouse”) is an enlarged natural or artificial lake, storage pond or impoundment created using a dam or lock to store water.Tank reservoirs store liquids or gases in storage tanks that may be elevated, at grade level, or buried. Tank reservoirs for water are also called cisterns.Underground reservoirs store almost exclusively water and petroleum below ground.

Water Tank:In simple words a water tank is a container for storing liquid.

Use of storage reservoirs and overhead

water tank: Storage reservoirs and overhead tank are

used for the following purposes: (i) store water and liquid(ii) petroleum, petroleum products and similar liquids.

Water tank is also needed for the following purposes:

(i) drinking water, (ii) irrigation agriculture, (iii) fire suppression,(iv) agricultural farming, both for plants and livestock, (v) Chemical manufacturing, (vi) food preparation as well as many other uses.

TYPES OF WATER TANK: 1 Based on the types of material and location:(i)Chemical contact tank: This type of water tank

is made of polyethylene construction, allows for retention time for chemical treatment.

(ii) Ground water tank: This type of water tank is made of lined carbon steel, it may receive water from a water well or from surface water allowing a large volume of water to be placed in inventory and used during peak demand cycles.(iii)Elevated Water Tank: This type of water tank is also known as a water tower, an elevated water tower will create pressure at the ground-level outlet of 1 psi per 2.31 feet of elevation, thus a tank elevated to 70 feet creates about 30 psi of discharge pressure. 30 psi is sufficient for most domestic and industrial requirements.

(iv) Vertical cylindrical dome top : This type of tanks may hold from fifty gallons to several million gallons. Horizontal cylindrical tanks are typically used for transport because their low-profile creates a low center of gravity helping to maintain equilibrium for the transport vehicle, trailer or truck.

(v) A Hydro-pneumatic Tank: This type of tank is typically a horizontal pressurized storage tank. Pressurizing this reservoir of water creates a surge free delivery of stored water into the distribution system.

2 Based upon the shapes:

i Circular Tanks: They are most economical and used

for large capacity in water supply, sewage treatment etc.

iiRectangular Tanks: They are used for small storage capacity and their framework is costly.

iii Spherical Tanks: They are used for the economy

and aesthetic view point.

iv Intze Tanks: They are used for large storage capacity. In such tanks, domes are used in place of level slabs.

INTZE TANKA typical Intze tank consists of :

1) Top dome.

2) Top ring beam.

3) Side walls.

4) Bottom ring beam.

5) Conical dome.

6)Bottom spherical dome.

7) Bottom circular ring beam.

8)Staging – Columns & bracings.

9)Foundation.

DESIGN A R.C.C OVERHEAD WATER TANK LOCATED AT KALYANI FOR A TARGET POPULATION OF 1500

DETERMINATION OF MAXIMUM DAILY DEMAND REQUIRED FOR THE POPULATION

OF THE LOCALITY:

Location: KalyaniTarget Population: 1500

Maximum daily consumption (demand) =180% of average daily demand = 1.8q

[Ref: Water Supply Engineering by S.K.Garg, Page-19]

Domestic water demand = 200 lit/capita/day

Average daily demand (q) = per demand Population

= 200 1500 = 3, 00,000 lit/day

 Hence, maximum daily demand = 1.8 q litres/day

= 1.8 300000 litres/day

= 540 103 litres/day

= 540 m3/day

DETERMINATION OF OVERALL HEIGHT OF THE TANK:-

Let us assume, diameter of tank (D) = 12m (< 30m)[as per Clause 7.2.1.1 of IS:2210-1988, page 8]

Hence, radius of tank (R) = 12/2 = 6m.

Now, volume of tank = 540 m3.

Let h be the height of the cylindrical tank.Capacity of tank = R2 h

 

Substituting the values, we get

62 h = 540or, h = 540/( 36)or, h = 4.77

Thus, height of the cylindrical tank = 4.77 m.

Assuming, free board = 0.25 m.Hence, total height of the tank = (4.77+0.25) = 5.02 m 5 m

DESIGN DATA:- Proposed Foundation – Raft foundationBearing Capacity of soil - 90 KN/m2

Grade of Concrete – M30Grade of steel – Fe500Staging height – 12m up to bottom of tankCapacity – 540000 litresNo. of columns – 8Diameter of columns – 1.5m

DETERMINATION OF GEOMETRICAL PARAMETERS OF TOP DOME:

D r A C B R1 R1 O

Notations:D = Diameter of the tank = 12mr = Central rise of the domeR1= Radius of the dome= Semi-central angle of the

dome

From the geometry of the figure, AOC & BOC are right-angled triangles.Central rise, r = 1/8 to 1/6 of span [Ref: Advanced Reinforced Concrete by H.J.Shah, page-406]

We take, r = 1/6 of spanr = 1/6 12 = 2Thus, central rise of the dome is 2 m. From AOC, OC2 + AC2 = AO2

or, (R1-r)2 + (D/2)2 = R12

or, (R1-2)2 + (12/2)2 = R12

or, R12 – 4R1+4+36=R1

2

or, 4R1 = 40or, R1 = 40/4 = 10Thus, radius of the dome is 10m.

Again, cos = = = = 0.8

or, = cos-1(0.8)

or, = 36.87

Thus, semi-central angle of the dome is 36.87

30<< 40. Hence, OK.

[as per IS:2210-1988, page-8]

Again, = 36.87< 51.8Hence, tensile stress is not developed. [Ref: Advanced Reinforced Concrete by H.J Shah, page 64] Now, r/D = 2/12 = 1/6 (< 1/5) [as per IS: 2210-1988, page-10]

So, it is a deep doubly curved shell and membrane analysis is required.  

DESIGN OF TOP DOME: Load calculation:We assume, thickness of top dome = 100 mm ( 40 mm)[as per Clause 7.1.1 of IS:2210-1988, page-8]Minimum imposed load for accessible roof = 1.5KN/m2

[as per IS-875 Part-2]Self-weight of the dome = 0.1 25 = 2.5 KN/m2

Finishing = 0.05 24 = 1.2 KN/m2

___________________________________________________Total load = (1.5+2.5+1.2) = 5.2 KN/m2

Calculation of Meridional stress and Hoop stress:Meridional force: Due to UDL =

[Ref: Advanced Reinforced Concrete by H.J Shah, page-64]

Meridional force = 5.2 10 = 28.89 KN.

Meridional stress for per meter span = = 0.2889 N/mm2

0.29 N/mm2 (compressive) 

  

As the minimum grade of concrete is M30, thus for M30[as per IS-456:2000, Table-21, page-81]

σcc = 8N/mm2

Thus, 0.29 < 8 N/mm2. Hence, OK.

Hoop force:Due to UDL = [Ref: Advanced Reinforced Concrete by H.J Shah, page-64] Hoop force = 5.2 10 = 12.71KN. Hoop stress for per meter span =

= 0.1271 N/mm2

0.13 N/mm2 (compressive) Thus, 0.13 < 8 N/mm2. Hence OK. Hence, the stresses are within the safe limit.

Since the stresses are very small, we provide nominal tensile reinforcement of 0.3%  [as per IS: 3370 (Part-2:2009) page-3, Table-3 the nominal percentage of nominal tensile reinforcement shall not be less than 0.15% in any case]

= 0.3or, Ast = 1000 100or, Ast = 300 mm2

Thus, area of steel reinforcement is 300 mm2.

We provide 6 - 8mm # bars, [as per clause 12.3.1 of IS: 2210-1988]

Spacing of 8mm # bars = = 167.53 mm 180 mm c/cThus, we provide 6 – 8mm @180mm c/c both ways.

Actual Percentage of steel required (Pt) = = = 0.30%

 

CLEAR COVER:

Clear cover [as per clause 7.1.1.1 of IS: 2210-1988]:- (i) 15mm. (ii) Nominal size whichever is greater.  Now, for severe exposure, nominal cover = 45 mm [as per Table 16 of IS: 456-2000] As, 45 > 15mm, so we provide clear cover = 45mm. 

 

DESIGN SUMMARY OF TOP DOME: Thickness =100mmClear cover =45mmGrade of concrete =M30Grade of steel =Fe500Reinforcement=8 mm # @180 c/c – Meridional Direction 8 mm # @180 c/c – Circumferential Direction

REFERENCES:(i) Water Supply Engineering by S.K.Garg (ii) IS 2210-1988(iii) Advanced Reinforced Concrete by H.J.Shah (iv) IS 875 (Part 1 & 2)(iv) IS-456:2000(v) IS: 3370:2009 [Part-2](vi) Wikipedia(vii) Softwares – AutoCAD & STAAD.Pro