water tank

1. 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

2. GROUP NO.-22 SL NO. NAME OF THE PARTICIPANTS UNIVERSITY ROLL NO. SECTION 1. SUBHANKAR KUMAR BISWAS 120108101 CIVIL – 4B 2. SUBHASIS SINGHA 120108102 3. SUDIP DAS 120108103 4. SUDIPTO BISWAS 120108104 5. SUKANTA PAUL 120108105

3. 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.

4. 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.

5. TYPES OF WATER TANK:  1 Based on the types of material and location: 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.

6. (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.

7. 2Based upon the shapes: i Circular Tanks : They are most economical and used for large capacity in water supply, sewage treatment etc.  ii Rectangular 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.

8. INTZE TANK A 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.

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

10. DETERMINATION OF MAXIMUM DAILY DEMAND REQUIRED FOR THE POPULATION OF THE LOCALITY: Location : Kalyani Target Population : 1500 Maximum daily consumption (demand ) = 180% of average daily demand = 1.8 q [Ref: Water Supply Engineering by S.K.Garg, Page-19]

11. 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  10 3 litres/day = 540 m 3 /day

12. 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 m 3 . Let h be the height of the cylindrical tank.  Capacity of tank =  R 2  h  

13. Substituting the values, we get  6 2  h = 540 or, 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

14. DESIGN DATA:-   Proposed Foundation – Raft foundation Bearing Capacity of soil - 90 KN/m 2 Grade of Concrete – M30 Grade of steel – Fe500 Staging height – 12m up to bottom of tank Capacity – 540000 litres No. of columns – 8 Diameter of columns – 1.5m

15. DETERMINATION OF GEOMETRICAL PARAMETERS OF TOP DOME : Notations : D = Diameter of the tank = 12m r = Central rise of the dome R1= 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]

16. We take, r = 1/6 of span  r = 1/6  12 = 2 Thus, central rise of the dome is 2 m.   From  AOC, OC 2 + AC 2 = AO 2 or, (R 1 -r) 2 + (D/2) 2 = R 1 2 or, (R 1 -2) 2 + (12/2) 2 = R 1 2 or, R 1 2 – 4R 1 +4+36=R 1 2 or, 4R 1 = 40 or, R 1 = 40/4 = 10 Thus, radius of the dome is 10m.

17. 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]

18. Again,  = 36.87  < 51.8  Hence, 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 .    

19. 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/m 2 [ as per IS-875 Part-2 ] Self-weight of the dome = 0.1  25 = 2.5 KN/m 2 Finishing = 0.05  24 = 1.2 KN/m 2 ___________________________________________________  Total load = (1.5+2.5+1.2) = 5.2 KN/m 2

20. 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/mm 2  0.29 N/mm 2 (compressive )      

21. As the minimum grade of concrete is M30 , thus for M30 [as per IS-456:2000, Table-21, page-81] σ cc = 8N/mm 2 Thus, 0.29 < 8 N/mm 2 . Hence, OK.

22. 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/mm 2  0.13 N/mm 2 (compressive)  Thus, 0.13 < 8 N/mm 2 . Hence OK. Hence, the stresses are within the safe limit.

23. 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] = 0.3 or, A st =  1000  100 or, A st = 300 mm 2 Thus, area of steel reinforcement is 300 mm 2 .

24. 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/c Thus, we provide 6 – 8mm @180mm c/c both ways. Actual Percentage of steel required (P t ) = = = 0.30%  

25. 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 .    

26. DESIGN SUMMARY OF TOP DOME:   Thickness = 100mm Clear cover = 45mm Grade of concrete = M30 Grade of steel = Fe500 Reinforcement = 8 mm # @180 c/c – Meridional Direction 8 mm # @180 c/c – Circumferential Direction

27. 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) IS-456:2000 IS: 3370:2009 [Part-2] Wikipedia (vii) Softwares – AutoCAD & STAAD.Pro