Reinforced Concrete Water Tank Design

 The requirements of Reinforced concrete water tank design

Table of Content:

1. To design a reinforced concrete water tank, what are the requirements?

2. What are the Types of reinforced concrete water tanks

3. Basis of concrete water tank design

4.  Permissible pressure on the concrete of a concrete water tank

     a- Permissible pressure to resist cracking

     b- Permissible pressure to calculate the force

c- Permissible pressure in steel for concrete water tank

5. Stress due to temperature or humidity changes of concrete water tank

6.  Reinforced concrete water tank floors

     a- Movement joints for reinforced concrete water tank floors

     b- The floor of the concrete water tank that rests on the ground

     c- The floor of the concrete tanks that rest on the support

7. Concrete water tank walls

     a- Providing joints for the walls of concrete water tanks

     b- Pressure on the wall of the concrete water tank

8. Reinforced concrete water tank roof

9. Minimum reinforcement for reinforced concrete water tank.

 The requirements of Reinforced concrete water tank design

1. To design a reinforced concrete water tank, what are the requirements?

The results & outcomes showed that the tank capacity consumed the least total cost & expense for the rectangular tank and was taken for the circular or round tank. The thickness of the tank floor slab takes the minimum  & basic  total cost & expense of two kinds of tanks, so that weight of a unit of water in the tank takes the minimum & basic cost of the circular or round tank and is brought down to the rectangular tank.  Cabinets can likewise be made in various & different shapes and for the most part circular or round and rectangular shapes are used & utilized. Tanks can be made of built up reinforced concrete or even reinforced iron and steel.

Normally upper cabinets (raised cabinets) are raised from the rooftop through the shaft. Also, underground tanks are put on the foundation. In this article, the design & plan prerequisites & requirements of R.C.C water tanks will be discussed & examined. R.C.C overhead water tanks are generally used to provide & give safe drinking water. In developing countries, such as India, the water supply systems are increasing day by day. Urbanization is also dependent on overhead storage tanks, thus there is a need to build & fabricate more water tanks. 

2. Types of R.C Water tanks: 

Based on the location of the water tank and its shapes, they are classified as in table-1

Based on the location of the water	Based on the shape of the water tank
Underground tanks	rectangular tank
tank resting on the floor	circular tank
Top cabinets spherical tank	Top tanks Round tank with conical bottom

3. Basis of concrete water tank design:

The design of the reinforced concrete water tank shall be based on adequate cracking resistance to avoid leakage and sufficient strength. To realize these following assumptions:

1. The normal & ordinary section prior to bending remains flat after bending. 

1. Both concrete and steel are completely & fully resilient & strong, and the standard ratio value has a worth given in the Code of Practice for Plain and Reinforced Concrete. 
2. In computing the stresses,, for both flexural and direct elastic or a  combination of both regarding breaking strength, the whole section of concrete including covering with reinforcement might be considered given that it is limited & restricted to the tensile stress in concrete. 
3. Neglecting the tensile strength of concrete while calculating & working out the strength.

The requirements of Reinforced concrete water tank design

4. Permissible pressure on Concrete of Concrete water tank: 

a- Permissible pressure for cracking resistance:

The concrete of the water tank will be free & liberated from leakage & seepage. This can be accomplished & achieved by selecting & choosing concrete with fracture strength of M 20 or more, and concrete close to the water surface requires to not have any cracking  & breaking. Hence, to make the concrete free & liberated from cracks & breaks at the water surface, the wall thickness of the water tank should be planned & designed with the goal that the tension on the concrete is not exactly the qualities given in Table 2. In members less than 225 mm thick, and in touch with the liquid & fluid on one side, these passable pressures & tensions apply in Bend likewise on the face farthest from the fluid & liquid.

Table 2: Permissible Stresses in Concrete (For Calculations Regarding Concrete Strength):

Concrete breaking strength	Direct tension (N/mm2)	`Tensile due to bending (N/mm2)
M15	1.1	1.5
M20	1.2	1.7
M25	1.3	1.8
M30	1.5	2.0
M35	1.6	2.2
M40	1.7	2.4

Table-2 of permissible stresses in concrete (for calculations related to the strength of concrete).

b- Permissible pressure for calculating the force:

In calculating the strength, the permissible concrete stresses should correspond to the values ​​given in Table 3.

Concrete breaking	Strength Allowable pressure in direct pressure (N/mm2)	Allowable bending stress (N/mm2)	Allowable average bond stress for ordinary bars in tensile (N/mm2)
M25	6	8.5	0.9
M30	8	10	1
M35	9	11.5	1.1
M40	10	13	1.2
M45	11	14.5	1.3

Table 3

c- Permissible pressure in steel for concrete water tank:
The stress in the steel should not be allowed to exceed the following values ​​at different positions to prevent cracking of the concrete.

1. •  While putting the steel near the essence of the member in touch with the liquid 115 N / mm 2 for soft & delicate iron bars and 150 Newton / mm 2 for high strength disfigured & deformed bars.
   
2. • On the off chance that the iron is set face-down away from the liquid for members with a thickness of 225 mm or more, the reasonable & allowable pressure in the steel ought to be 125 N /mm 2 for mild steel bars and 190 N /mm 2 for high-strength deformed&  disfigured bars.
   
3. • While applying steel face away from fluid for parts less than 225 mm thick as before.

5. Stress Due to Temperature or Humidity Changes of Concrete Water Tank:

A different & separate calculation of pressure is not required & needed because of the difference in humidity and temperature in concrete given that the following circumstances & conditions are met:

1. The reinforcement offered is something like the base reinforcement depicted & described in the section below.
2. Recommendations & Suggestions in regards to the tightness of the movement & development joints and a reasonable sliding layer under the water tank are implemented & carried out accurately.
3. The tank is utilized & used to store water or aqueous liquids & fluids at or near ambient or close to surrounding temperature.
4. Concrete ought to never dry out.
5. Appropriate & Suitable measures are taken to forestall & to prevent cracking & breaking of the concrete during the development & construction period frame and until the activity & operation of the tank.

In any case, a different & a separate calculation & estimation of humidity and temperature change ought to be made if:

1. The expected shrinkage factor is, a porous & permeable liner utilized for a water tank. For this situation, the possible & conceivable drying out of the tank should be considered.
   
2. A cement content ranging from 330 kg /m3 to 550 kg /m3 ought to be utilized to limit & minimize shrinkage. 

6. Reinforced concrete water tank floors:

a- Movement joints for reinforced concrete water tank floors: Movement joints must be provided in accordance with the relevant Standard Codes for this field.

b- The floor of the concrete water tank that rests on the ground:

1. Lay a layer of lean concrete on the surface of the ground with a thickness of at least 75 mm.
2. In general, the use of concrete with breaking strength M15 for fat-free concrete.
3. Use of concrete with breaking strength M20 for lean concrete in the presence of aggressive soil or harmful water.
4. Consideration should be given to sulfate resistance if necessary.
5. A layer of polyethylene is installed between the fat-free concrete and the floor.
6. Pour the earth in one layer.

c- The floor of the concrete tanks that rest on the support:

1. Bending moments should be designed due to dead load and water load.
2. Special attention should be given while designing & planning the floor of the multicellular water tank.
3. Finally, when the walls and the floor are rigidly connected, the moment at the intersection with other transmitted loads must be taken into consideration in the design of the floor.

7. Concrete water tank walls:

a- Providing joints for the walls of concrete water tanks: 

Sliding joints can be used if:

1. It is desirable to allow the walls to expand or contract separately from the floor.
2. To prevent moments at the base of the wall due to stability on the floor.

b- Pressure on the walls of Concrete water tank:

1. Gas pressure, which arises due to the presence of a fixed or floating tank cover, is added to the pressure of the fluid & liquid.
2. When the water tank is constructed & built on the ground, the ground pressure must be estimated & calculated in the wall design.

 The requirements of Reinforced concrete water tank design

8. Reinforced concrete water tank roof: 

To keep away from the possibility of sympathetic cracking, it's essential to make sure that the movement joints within the ceiling correspond to those in the walls, if the ceiling and walls are monolithic. However, that is provided through a sliding joint for movement between the ceiling and the wall, and the correspondence of the joints isn't so important. Moreover, in the case of tanks supposed for storing water for domestic purposes, the roof has to be watertight. This may be achieved by reducing pressures as for the rest of the tank, by using a water-proof membrane covering or by providing ramps to ensure right drainage.

9. Minimum reinforcement for reinforced concrete water tank:

The minimum reinforcement required for sections with a thickness of 199 mm is 0.3% of the concrete section region, which is linearly reduced to 0.2% for sections with a thickness of 450 mm. Furthermore, in the case of a floor slab of a tank resting on the ground, the minimum reinforcement of practical concerns shall not be much less than 0.3% of the entire cross-sectional area of the floor slab. Finally, if the thickness of the section (wall, floor or roof slab of tank) is 225 mm and above layers of steel reinforcement, one layer have to be placed near each section to make up for the minimum reinforcement requirement.