santhi mainproject

7/29/2019 santhi mainproject

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ABSTRACT

Storage reservoirs and overhead tank are used to store water, liquid

petroleum, petroleum products and similar liquids. The force analysis of the

reservoirs or tanks is about the same irrespective of the chemical nature of the

product. All tanks are designed as crack free structures to eliminate any leakage.

This project gives in brief, the theory behind the design of liquid retaining

structure using working stress method. This report also includes computer

subroutines to analyze and design circular water tank with flexible and rigid base

and rectangular under ground water tank.


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INTRODUCTION

1.0 GENERAL

Rainwater harvesting is a technology used to collect, convey and store rain for

later use from relatively clean surfaces such as a roof, land surface or rock

catchment. The water is generally stored in a rainwater tank or directed to

recharge groundwater. The practice of collecting rainwater from rainfall events

can be classified into two broad categories:

land-based and roof-basedLand-based rainwater harvesting occurs when runoff from land surfaces is

collected in furrow dikes, ponds, tanks and reservoirs.

Roof-based rainwater harvesting refers to collecting rainwater runoff from

roof surfaces which usually provides a much cleaner source of water that can be

also used for drinking.

Rooftop rainwater harvesting at the household level is most commonly used

for domestic purposes. It is popular as a household option as the water source is

close to people and thus requires a minimum of energy to collect it. An added


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advantage is that users own maintain and control their system without the need

to rely on other community members.

1.1 NEED FOR RAIN WATER HARVESTING

In many regions of the world, clean drinking water is not always available

and this is only possible with tremendous investment costs and expenditure.

Rainwater is a free source and relatively clean and with proper treatment it can

be even used as a potable water source. Rainwater harvesting saves high-quality

drinking water sources and relieves the pressure on sewers and the environment

by mitigating floods, soil erosions and replenishing groundwater levels. In

addition, rainwater harvesting reduces the potable water consumption and

consequently, the volume of generated wastewater.

1.2 APPLICATION AREAS

Rainwater harvesting systems can be installed in both new and existing

buildings and harvested rainwater used for different applications that do not

require drinking water quality such as toilet flushing, garden watering, irrigation,

cleaning and laundry washing. Harvested rainwater is also used in many parts of

the world as a drinking water source. As rainwater is very soft there is also less

consumption of washing and cleaning powder. With rainwater harvesting, the


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savings in potable water could amount up to 50% of the total household

consumption.

1.3 CRITERIA FOR SELECTION OF RAINWATER HARVESTING

TECHNOLOGIES

Several factors should be considered when selecting rainwater harvesting

systems for domestic use:

Type and size of catchment area

Local rainfall data and weather patterns

Family size

Length of the drought period

Alternative water sources

Cost of the rainwater harvesting system.

When rainwater harvesting is mainly considered for irrigation, several factors

should be taken into consideration. These include:

Rainfall amounts, intensities, and evapo-transpiration rates


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Soil infiltration rate, water holding capacity, fertility and depth of soil

Crop characteristics such as water requirement and length of growing period

Hydrogeology of the site

Socio-economic factors such as population density, labour, costs of materials

and regulations governing water resources use.

1.4 VARIOUS METHODS OF RAINWATER HARVESTING

Rainwater can be harvested in a variety of ways:

1. Directly from roof tops and stored in tanks.

2. Monsoon run off and water in swollen streams during the Monsoon and storing

it in underground tanks.

3. Water from flooded rivers can be stored in small ponds.

There are basically two models associated with Rainwater harvesting:

Urban model

Rural model

1.5 COMPONENTS OF ROOFTOP RAINWATER HARVESTING SYSTEM

Although rainwater can be harvested from many surfaces, rooftop

harvesting systems are most commonly used as the quality of harvested


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rainwater is usually clean following proper installation and maintenance. The

effective roof area and the material used in constructing the roof largely influence

the efficiency of collection and the water quality.

Rainwater harvesting systems generally consist of four basic elements:

(1) A collection (catchment) area

(2) A conveyance system consisting of pipes and gutters

(3) A storage facility, and

(4) A delivery system consisting of a tap or pump.

Figure shows a simple schematic diagram of a rooftop rainwater harvesting

system including conveyance and storage facilities.


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Fig: A schematic diagram of a rooftop rainwater harvesting system.

(1) A collection or catchment system is generally a simple structure such as roofs

and/or gutters that direct rainwater into the storage facility. Roofs are ideal as

catchment areas as they easily collect large volumes of rainwater. The amount

and quality of rainwater collected from a catchment area depends upon the rain

intensity, roof surface area, type of roofing material and the surrounding

environment. Roofs should be constructed of chemically inert materials such as

wood, plastic, aluminum, or fiberglass. Roofing materials that are well suited


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include slates, clay tiles and concrete tiles. Galvanized corrugated iron and

thatched roofs made from palm leaves are also suitable. Generally, unpainted and

uncoated surface areas are most suitable. If paint is used, it should be non-toxic

(no lead-based paints).

(2) A conveyance system is required to transfer the rainwater from the roof

catchment area to the storage system by connecting roof drains (drain pipes) and

piping from the roof top to one or more downspouts that transport the rainwater

through a filter system to the storage tanks. Materials suitable for the pipework

include polyethylene (PE), polypropylene (PP) or stainless steel. Before water is

stored in a storage tank or cistern, and prior to use, it should be filtered to

remove particles and debris. The choice of the filtering system depends on the

construction conditions. Low-maintenance filters with a good filter output and

high water flow should be preferred. First flush systems which filter out the first

rain and diverts it away from the storage tank should be also installed. This will

remove the contaminants in rainwater which are highest in the first rain shower.

(3) Storage tank or cistern to store harvested rainwater for use when needed.

Depending on the space available these tanks can be constructed above grade,

partly underground, or below grade. They may be constructed as part of the

building, or may be built as a separate unit located some distance away from the


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building. The storage tank should be also constructed of an inert material such as

reinforced concrete, ferrocement (reinforced steel and concrete), fibreglass,

polyethylene, or stainless steel, or they could be made of wood, metal, or earth.

The choice of material depends on local availability and affordability. Various

types can be used including cylindrical ferrocement tanks, mortar jars (large jar

shaped vessels constructed from wire reinforced mortar) and single and battery

(interconnected) tanks. Polyethylene tanks are the most common and easiest to

clean and connect to the piping system. Storage tanks must be opaque to inhibit

algal growth and should be located near to the supply and demand points to

reduce the distance water is conveyed. Water flow into the storage tank or

cistern is also decisive for the quality of the cistern water. Calm rainwater inlet

will prevent the stirring up of the sediment. Upon leaving the cistern, the stored

water is extracted from the cleanest part of the tank, just below the surface of the

water, using a floating extraction filter. A sloping overflow trap is necessary to

drain away any floating matter and to protect from sewer gases. Storage tanks

should be also kept closed to prevent the entry of insects and other animals.

(4) Delivery system which delivers rainwater and it usually includes a small pump,

a pressure tank and a tap, if delivery by means of simple gravity on site is not

feasible. Disinfection of the harvested rainwater, which includes filtration and/or


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ozone or UV disinfection, is necessary if rainwater is to be used as a potable water

source.

1.6 BENEFITS OF RAINWATER HARVESTING

Rainwater harvesting in urban and rural areas offers several benefits

including provision of supplemental water, increasing soil moisture levels for

urban greenery, increasing the groundwater table via artificial recharge,

mitigating urban flooding and improving the quality of groundwater. In homes

and buildings, collected rainwater can be used for irrigation, toilet flushing and

laundry. With proper filtration and treatment, harvested rainwater can also be

used for showering, bathing, or drinking. The major benefits of rainwater

harvesting are summarized below:

Rainwater is a relatively clean and free source of water

Rainwater harvesting provides a source of water at the point where it is needed

It is owner-operated and managed

It is socially acceptable and environmentally responsible

It promotes self-sufficiency and conserves water resources


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Rainwater is friendly to landscape plants and gardens

It reduces storm water runoff and non-point source pollution

It uses simple, flexible technologies that are easy to maintain

offers potential cost savings especially with rising water costs

provides safe water for human consumption after proper treatment

Low running costs

Construction, operation and maintenance are not labour-intensive.

1.7 DISADVANTAGES

The main disadvantages of rainwater harvesting technologies are the

limited supply and uncertainty of rainfall. Rainwater is not a reliable water source

in times of dry periods or prolonged drought. Other disadvantages include:

low storage capacity which will limit rainwater harvesting, whereas, increasing

the storage capacity will add to the construction and operating costs making the

technology less economically feasible


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Possible contamination of the rainwater with animal wastes and organic matter

which may result in health risks if rainwater is not treated prior to consumption as

a drinking water source

Leakage from cisterns can cause the deterioration of load-bearing slopes

Cisterns and storage tanks can be unsafe for small children if proper access

protection is not provided.

1.8 SCOPE OF THE WORK

The scope of work includes

Chapter I Gives brief description about needs, methods, advantages and

disadvantages of rain water harvesting.

Chapter II Brief description about computation of demand and fixation of

capacity of sumps

Chapter III Gives brief description on sump design.

Chapter IV Deals with detailed and abstract estimation.

Chapter V Deals with conclusions followed by references.


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HYDROLOGICAL INVESTIGATIONS

2.0 GENERAL

Hydrological investigations constitute one of the most important aspects of

planning of roof-top water harvesting system. The fixation of capacity of water

storage tank is based on the quantity of rain water available from the roof in

different periods of a year.

2.1 COLLECTION OF RAINFALL DATA

The rainfall record for a period 30 years (1981-2010) is collected from the

M.R.O Office, Srikalahasti and is presented in Table 2.1.

2.2 ANALYSIS OF RAIN WATER

The quantity of rainwater available for storage is computed considering

50% and 75% dependable rainfalls during monsoon period from rainfall frequency

curves as shown in Figs. 2.1 to 2.7. the computations of probability of rainfall are

tabulated in tables 2.2 to 2.8.


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Table 2.1 Monthly Rainfall Data (in cm)

YEAR JANUARY FEBRUARY MARCH APRIL MAY JUNE JULY AUGUST SEPTEMBER OCTOBER NOVEMBER DECEMB

1981 4.26 - 2.10 - 6.44 3.77 17.28 9.60 20.68 21.94 6.82 22.72

1982 - - - - 0.80 6.40 8.12 3.28 1.44 23.40 30.54 -

1983 - - - - 1.60 3.44 14.81 16.39 24.35 25.37 21.02 29.04

1984 10.60 46.42 - 2.40 - 4.24 15.58 1.24 31.75 9.44 85.24 17.08

1985 4.40 - - - - 4.06 9.82 5.62 25.16 4.84 51.04 12.66

1986 37.86 2.38 - - 3.60 3.22 1.10 6.62 3.58 29.90 35.32 3.72

1987 6.72 - 3.26 - 0.92 6.34 3.42 19.01 9.38 20.35 26.70 47.99

1988 - - 0.80 7.16 11.20 3.66 11.70 12.50 13.95 5.96 27.58 12.26

1989 - - 1.86 - 3.10 4.93 18.51 3.12 8.22 1.25 21.04 43.10

1990 - 4.22 - 1.82 22.62 2.02 11.12 7.14 25.37 45.92 49.44 0.70

1991 0.60 - - - 4.56 26.09 20.55 19.27 4.12 34.61 56.00 4.56

1992 - - - - 2.76 2.86 13.77 7.06 9.07 10.56 42.69 2.36

1993 - - 0.21 - 3.94 1.81 11.26 7.98 19.66 23.51 45.08 19.52

1994 - - - - 3.11 7.06 7.12 12.39 3.66 30.26 35.82 11.16

1995 12.86 - - - 24.54 11.15 9.99 17.26 10.22 32.98 13.29 1.35

1996 - - - 2.54 1.32 32.76 8.01 12.75 18.91 65.04 14.59 57.33

1997 10.42 - - 1.80 5.04 8.48 7.08 3.20 13.89 31.99 76.68 33.91

1998 - - - - - 5.86 9.15 15.44 12.99 10.53 38.43 9.85


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1999 0.4 - - - 6.40 3.72 2.37 12.49 10.16 17.59 19.64 7.05

2000 - 3.40 - 0.75 15.15 9.52 4.77 13.14 5.67 15.94 19.66 16.80

2001 5.62 - - 4.32 3.64 7.24 6.98 3.55 12.32 57.70 17.82 16.83

2002 8.38 - - - 3.10 8.66 3.94 6.87 5.72 36.60 25.10 3.72

2003 - - 3.80 - - 7.00 42.63 8.59 16.27 15.48 2.36 5.16

2004 - - - 0.35 13.59 2.34 8.95 2.14 16.92 32.40 16.67 -2005 - 0.81 9.30 3.77 3.00 4.48 22.17 10.97 16.68 55.02 58.04 38.51

2006 - - 1.04 0.20 4.04 4.00 3.84 7.79 7.54 35.14 30.49 11.39

2007 - - - - 0.81 11.52 21.08 26.50 10.40 58.62 10.58 25.18

2008 4.55 - 3.30 - 2.26 7.40 10.68 10.11 7.94 28.07 54.44 1.10

2009 - - - - - 2.84 11.86 17.175 9.52 12.725 49.49 12.62

2010 1.62 - - 0.14 10.18 10.90 14.86 31.92 13.26 24.54 46.86 11.64


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Table 2.2 Probabilities of Rainfall for the Month of June

RAINFALL

(cm)

RANK (m) RETURN PERIOD

( )FREQUENCY (%)

32.76 1 31 3.22

26.09 2 15.5 6.45

11.52 3 10.33 9.67

11.15 4 7.75 12.90

10.90 5 6.2 16.12

9.52 6 5.16 19.35

8.66 7 4.42 22.58

8.48 8 3.87 25.80

7.40 9 3.44 29.03

7.24 10 3.1 32.25

7.06 11 2.81 35.48

7.00 12 2.58 38.70

6.40 13 2.38 41.93

6.34 14 2.21 45.16

5.86 15 2.06 48.38

4.93 16 1.93 51.61

4.48 17 1.82 54.834.24 18 1.72 58.06

4.06 19 1.63 61.29

4.00 20 1.55 64.51

3.77 21 1.47 67.74

3.72 22 1.40 70.96

3.66 23 1.34 74.19

3.44 24 1.29 77.41

3.22 25 1.24 80.64

2.86 26 1.19 83.87

2.84 27 1.14 87.09

2.34 28 1.10 90.32

2.02 29 1.06 93.54

1.81 30 1.03 96.77


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Fig.2.1 Rainfall Frequency Curve (Month : June)

0

5

10

15

20

25

30

35

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105

Rainfall(cm)

Probability (%)

2.0 cm

5.5 cm


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Table 2.3 Probabilities of Rainfall for the Month of July

RAINFALL

(cm)


( )FREQUENCY (%)

42.63 1 31 3.22

22.17 2 15.5 6.45

21.08 3 10.33 9.67

20.55 4 7.75 12.90

18.51 5 6.2 16.12

17.28 6 5.16 19.35

15.58 7 4.42 22.58

14.86 8 3.87 25.80

14.81 9 3.44 29.03

13.77 10 3.1 32.25

11.86 11 2.81 35.48

11.70 12 2.58 38.70

11.26 13 2.38 41.93

11.12 14 2.21 45.16

10.68 15 2.06 48.38

9.99 16 1.93 51.61

9.82 17 1.82 54.839.15 18 1.72 58.06

8.95 19 1.63 61.29

8.12 20 1.55 64.51

8.01 21 1.47 67.74

7.12 22 1.40 70.96

7.08 23 1.34 74.19

6.98 24 1.29 77.41

4.77 25 1.24 80.64

3.94 26 1.19 83.87

3.84 27 1.14 87.09

3.42 28 1.10 90.32

2.37 29 1.06 93.54

1.10 30 1.03 96.77


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Fig.2.2 Rainfall Frequency Curve (Month : July)

0

5

10

15

20

25

30

35

40

45

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105

Rainfall(cm)

Probability (%)

9.5 cm

5.5 cm


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Table 2.4 Probabilities of Rainfall for the Month of August

RAINFALL

(cm)


( )FREQUENCY (%)

31.92 1 31 3.22

26.50 2 15.5 6.45

19.27 3 10.33 9.67

19.01 4 7.75 12.90

17.26 5 6.2 16.12

17.175 6 5.16 19.35

16.39 7 4.42 22.58

15.44 8 3.87 25.80

13.14 9 3.44 29.03

12.75 10 3.1 32.25

12.50 11 2.81 35.48

12.49 12 2.58 38.70

12.39 13 2.38 41.93

10.97 14 2.21 45.16

10.11 15 2.06 48.38

9.60 16 1.93 51.61

8.5917 1.82 54.83

7.98 18 1.72 58.06

7.79 19 1.63 61.29

7.14 20 1.55 64.51

7.06 21 1.47 67.74

6.87 22 1.40 70.96

6.62 23 1.34 74.19

5.62 24 1.29 77.41

3.55 25 1.24 80.64

3.28 26 1.19 83.87

3.20 27 1.14 87.09

3.12 28 1.10 90.32

2.14 29 1.06 93.54

1.24 30 1.03 96.77


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Fig.2.3 Rainfall Frequency Curve (Month : August)

0

5

10

15

20

25

30

35

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105

Rainfall(cm)

Probability (%)

9.0 cm

5.5 cm


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Table 2.5 Probabilities of Rainfall for the Month of September

RAINFALL

(cm)


( )FREQUENCY (%)

31.75 1 31 3.22

25.37 2 15.5 6.45

25.16 3 10.33 9.67

24.35 4 7.75 12.90

20.68 5 6.2 16.12

19.66 6 5.16 19.35

18.91 7 4.42 22.58

16.92 8 3.87 25.80

16.68 9 3.44 29.03

16.27 10 3.1 32.25

13.95 11 2.81 35.48

13.89 12 2.58 38.70

13.26 13 2.38 41.93

12.99 14 2.21 45.16

12.32 15 2.06 48.38

10.40 16 1.93 51.61

10.22 17 1.82 54.8310.16 18 1.72 58.06

9.52 19 1.63 61.29

9.38 20 1.55 64.51

9.07 21 1.47 67.74

8.22 22 1.40 70.96

7.94 23 1.34 74.19

7.54 24 1.29 77.41

5.72 25 1.24 80.64

5.67 26 1.19 83.87

4.12 27 1.14 87.09

3.66 28 1.10 90.32

3.58 29 1.06 93.54

1.44 30 1.03 96.77


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Fig.2.4 Rainfall Frequency Curve (Month : September)

0

5

10

15

20

25

30

35

40

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 1

Rainfall(cm)

Probability (%)

7.5 cm

10.5 cm


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Table 2.6 Probabilities of Rainfall for the Month of October

RAINFALL

(cm)


( )FREQUENCY (%)

65.04 1 31 3.22

58.62 2 15.5 6.45

57.70 3 10.33 9.67

55.02 4 7.75 12.90

45.92 5 6.2 16.12

36.60 6 5.16 19.35

35.14 7 4.42 22.58

34.61 8 3.87 25.80

32.98 9 3.44 29.0332.40 10 3.1 32.25

31.99 11 2.81 35.48

30.26 12 2.58 38.70

29.90 13 2.38 41.93

28.07 14 2.21 45.16

25.37 15 2.06 48.38

24.54 16 1.93 51.61

23.51 17 1.82 54.83

23.40 18 1.72 58.06

21.94 19 1.63 61.29

20.35 20 1.55 64.51

17.59 21 1.47 67.74

15.94 22 1.40 70.96

15.48 23 1.34 74.19

12.725 24 1.29 77.41

10.56 25 1.24 80.64

10.53 26 1.19 83.87

9.44 27 1.14 87.09

5.96 28 1.10 90.32

4.84 29 1.06 93.54

1.25 30 1.03 96.77


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Fig.2.5 Rainfall Frequency Curve (Month : October)

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 1

Rainfall(cm)

Probability (%)

22.0 cm

15.0 cm


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Table 2.7 Probabilities of Rainfall for the Month of November

RAINFALL

(cm)


( )FREQUENCY (%)

85.24 1 31 3.22

76.68 2 15.5 6.45

58.04 3 10.33 9.67

56.00 4 7.75 12.90

54.44 5 6.2 16.12

51.04 6 5.16 19.35

49.49 7 4.42 22.58

49.44 8 3.87 25.80

46.86 9 3.44 29.03

45.08 10 3.1 32.25

42.69 11 2.81 35.48

38.43 12 2.58 38.70

35.82 13 2.38 41.93

35.32 14 2.21 45.16

30.54 15 2.06 48.38

30.49 16 1.93 51.61

27.58 17 1.82 54.83

26.70 18 1.72 58.06

25.10 19 1.63 61.29

21.04 20 1.55 64.51

21.02 21 1.47 67.74

19.66 22 1.40 70.96

19.64 23 1.34 74.19

17.82 24 1.29 77.41

16.67 25 1.24 80.64

14.59 26 1.19 83.87

13.29 27 1.14 87.09

10.58 28 1.10 90.32

6.82 29 1.06 93.54

2.36 30 1.03 96.77


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Fig.2.6 Rainfall Frequency Curve (Month : November)

0

5

10

15

20

25

30

35

40

45

50

55

60

6570

75

80

85

90

95

100

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 1

Rainfall(cm)

Probability (%)

28.0 cm

19.0 cm


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Table 2.8 Probabilities of Rainfall for the Month of December

RAINFALL

(cm)


( )FREQUENCY (%)

57.33 1 31 3.22

47.99 2 15.5 6.45

43.10 3 10.33 9.67

38.51 4 7.75 12.90

33.91 5 6.2 16.12

29.04 6 5.16 19.35

25.18 7 4.42 22.58

22.72 8 3.87 25.80

19.52 9 3.44 29.03

17.08 10 3.1 32.25

16.83 11 2.81 35.48

16.80 12 2.58 38.70

12.66 13 2.38 41.93

12.62 14 2.21 45.16

12.26 15 2.06 48.38

11.64 16 1.93 51.61

11.39 17 1.82 54.8311.16 18 1.72 58.06

9.85 19 1.63 61.29

7.05 20 1.55 64.51

5.16 21 1.47 67.74

4.56 22 1.40 70.96

3.72 23 1.34 74.19

3.72 24 1.29 77.41

2.3625 1.24 80.64

1.35 26 1.19 83.87

1.10 27 1.14 87.09

0.70 28 1.10 90.32

- 29 1.06 93.54

- 30 1.03 96.77


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COMPUTATION OF DEMAND

The water requirements of selected buildings of SKIT College calculated by

knowing the members working in the institutions or residents and average

percapita demand.

As per IS 1172-1993, an average demand of 20 liters/day is considered to

meet the institutional water requirements and for hostels an average water

requirement is taken as 135 lpcd. The computations of demand are shown below:

SKIT MAIN BUILDING

Total members = 1744

Working days = 220

Quantity = 1744 X 220 X20

= 7673.6 X lit

In Holidays

Total members = 40

No. of days = 145


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Quantity = 40 X 145 X 20

= 116 X lit

Total quantity required = 7789.6 X lit

SKIT MECHANICAL BLOCK

Total members = 268

Working days = 220

Quantity = 268 X 220 X20

= 1179.2 X lit

In Holidays

Total members = 16

No. of days = 145


= 46.4 X lit



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SKIT LADIES HOSTEL

Total members = 162

Average percapita demand = 135 lit

Working days = 260

Quantity = 162 X 260 X 135

= 5686.2 X lit

In Holidays

Total members = 12

Average percapita demand = 135 lit

No. of days = 105


= 170.1 X lit



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FIXATION OF CAPACITY OF SUMPS

The monthly rain water harvesting potential is computed for a given roof

area using equation

MRHP = CIA

Where MRHP = monthly rainwater harvesting potential in

C = Runoff coefficient (taken as 0.85 for tiled roofs)

I = Dependable monthly rainfall in m

A = Roof area in sqm

The 50% and 75% dependable yields are computed during the monsoon

period and the capacity of the sump is fixed as the maximum of monthly yields

during the monsoon period.

Building Roof Area ()50% dependable 75%dependable

Rainfall

(m)

Max. of

monthly

Yields (

)

Rainfall

(m)

Max. of

monthly

Yields (

)

Main building 5672.65 0.28 1350.09 0.19 916.13

Mechanical

Block

2287.97 0.28 544.54 0.19 369.51

Ladies Hostel 1517.72 0.28 361.22 0.19 245.11


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Fig.2.8 Variation of Monthly Supply/Demand during Monsoon Period (Main Building)

265.19

458.06 433.95506.28

1060.78

1350.09

289.3

96.43

265.19 265.19

361.63

723.26

916.13

192.87

0

200

400

600

800

1000

1200

1400

1600

JUNE JULY AUG SEP OCT NOV DEC

Demand/supp

lyincum

Months

For 50% probability

For 75% probability


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Fig.2.9 Variation of Monthly Supply/Demand during Monsoon Period (Mechanical Building)

106.96

184.75 175.02

204.2

427.85

544.53

116.68

38.89

106.96 106.96

147.85

291.71

369.51

77.79

0

100

200

300

400

500

600


Demand/Supply

incu.m

Months

For 50% probability

For 75% probability


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Fig.2.10 Variation of Monthly Supply/Demand during Monsoon Period (Ladies Hostel Building)

70.95

122.55 116.1

135.45

283.8

361.21

77.4

25.8

70.95 70.95

96.75

193.5

245.11

51.6

0

50

100

150

200

250

300

350

400


Demand/Supplyincu.m

Months

For 50% probability

For 75% probability


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DESIGN AND ESTIMATION OF

UNDERGROUND TANKS

3.0 SUMP DESIGN FOR SKIT MAIN BUILDING

Capacity of tank = 1350.09

DESIGN CONSTANTS

Concrete grade :

Steel grade :

Modular ratio (m) = 13

For HYSD bars

Neutral axis co-efficient (k) = 0.378

Lever arm co-efficient (j) = 0.874

Moment of resistance factor (R) = 1.156


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ASSUMED DATA

Angle of repose () =

Saturated unit weight of soil () =

Unit weight of water () =

Assumed depth of sump (H) = 3m

So each capacity of sump =

Let assume B = 5 m

L X 5 X 3 = 270.01 m

L = 18.0 m 18 m

Therefore, L = 18 m, B = 5 m

The size provided for sump = 18 m X 5 m X 3m

DESIGN OF LONG WALLS

(a)tank empty with pressure of saturated soil from outside

Here,


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Maximum Bending Moment (B.M) at the base of the wall

Therefore,

Provide total depth T = 260 mm so that d = 260-35 = 225 mm

Using 16 mm bars, spacing

However, provide 16 mm bars @ 100 c/c on the outside face, at the bottom

long wall.

Curtailment of reinforcement

Since the B.M is proportional to we have


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From which

If (i.e. half the bars being curtailed)

() ()

Therefore, Height from base = 32.38 = 0.62m. However, as per code

requirements, the bars are to be continued further for a distance of 12 (=12 X 16

= 192 mm) or d (= 225 mm), whichever is more, beyond this point. Hence curtail

half the bars at more, beyond this point. Hence curtail half the bars at 0.62 +

0.225 0.85m from base.

Similarly, depth where only th reinforcement is required

() ()





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Minimum, % reinforcement

Minimum

This is more than of at the bottom. Hence the above curtailment is

not permissible.

Hence the reinforcement will be provided as under:

(i) at base: 16 bars @ 100 c/c(ii) at 0.85 m above base, up to top: 16 bars @200 mm c/c

Distribution steel

% distribution steel

Area to be provided on each face =330.2

Therefore, spacing of 8 mm bars


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Hence provide 8 mm bars @ 150 mm c/c on each face.

Actual

Direct compression in long walls

At h = 1 m above the base of short walls,

This direct compression developed on long walls is given by

This will be taken by the distribution steel and wall section.

(b)Tank full with water, and no earth fill outside


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However, provide 16 mm bars @ 130 c/c on the outside face, at the inside

face.


( )


()

()

As decided earlier, curtail half the bars at 0.85 m from the base.

Minimum, % reinforcement @ 0.254% = 660.4. Hence furthercurtailment is not permissible.

Thus the reinforcement at the inner face will be provided as follows:

(i) at base : 16 bars @ 130 c/c


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(ii) at 0.85 m above base, up to top: 16 bars @260 mm c/cDirect tension in long walls

Where at 1 m above base

Therefore,

Required

Area of distribution steel provided in horizontal direction .

Hence distribution steel will take direct tension.

DESIGN OF SHORT WALLS

(a)tank empty with pressure of saturated soil from outside(i) Top portion : the bottom 1 m acts as cantilever, while the

remaining 2 m acts

as slab supported on long walls



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(at supports)

M (at centre)

At supports,

Using 16 bars,

Hence provide 16 mm bars @ 100 m c/c at the outer face, at 2 mm below the

top.

At mid span


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Minimum

(as found earlier)


Hence provide 12 mm bars at 170 mm c/c at the inner face

(ii) Bottom portion : the bottom 1 m will bend as cantilever.Intensity of earth pressure at bottom

Therefore,

Therefore,

Minimum steel @ 0.254% = 660.4


Hence provide 12 mm bars @ 170 mm c/c at outside face, in the vertical

direction for bottom 1 m height. The spacing can be doubled for the upper

portion.

(iii) Direct compression in short walls


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Though the long walls bend as cantilever, it is observed that end one

meter width of long wall contributes to push in short walls, due to earth pressure,

and its magnitude is given by

(b)Tank full with water, and no earth fill outside(i) Top portion : the bottom portion h = 1 m (> H/4) acts as a cantilever,

while the remaining 2 m acts slab supported on long walls.

At h = 1 m (> H/4) above base of short wall,

Direct tension in short wall, due to water pressure on the end one metre

width of long walls is


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Effective depth d, for horizontal steel = 211 mm

Therefore, distance

Therefore, Net B.M

Therefore,

Therefore,

At the inside face (end of short walls)

Therefore, Total

Using 16 mm bars,

Hence provide 16 mm bars @ 130 mm c/c at the inner surface.

At the outside face (middle of short walls)


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Therefore, Total

Minimum

Using 12 mm bars,


(ii) Bottom portion : the bottom portion 1 m will bend as cantileverp (at bottom) = 29430 N/ (step 3)

Therefore,

(With tension at inside face)

Therefore,

Minimum steel @ 0.254% = 660.4 (found earlier)


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Hence provide 12 mm bars @ 170 mm c/c at the inside face, in the

vertical direction for bottom 1 m height. The spacing can be doubled for the

upper portion.

DESIGN OF TOP SLAB

L/B =18/4 =4.5

Hence the top slab will be designed as one way slab.

Let the live load on top slab = 2000 N/

Assuming a thickness of 20 cm including finishes etc.,

Self weight

Therefore, Total

Therefore,

Provide total thickness = 150 mm. Keeping a clear of 25 mm and using 12

mm bars,


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Spacing of 16 mm bars

Hence provide 16 mm bars @ 130 mm c/c

Distribution reinforcement *+

Therefore,


Hence provide 10 mm bars @ 180 mm c/c the other direction.

DESIGN OF BOTTOM SLAB

The magnitude

(Assuming thickness of base slab to be 300 mm)

(a)Check against flotationTotal upward flotation force


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Total downward force consists of weight of the tank. Let us assume

thickness of bottom slab = 300 mm

Weight of walls

Weight of roof slab and finishes

Weight of base slab

Therefore, Total

This is much less than the flotation force. Hence provide projection of base

slab, beyond the face of vertical walls, by an amount m all-round, so that weightof soil column supported by the projections will provide additional downward

force.

Weight of soil supported by projection

Weight of roof slab

Weight of walls

Weight of base slab


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Total uplift force

Equating total upward force to the total downward forces,

We get

Or Or

Which gives

From which

Check

Width

Length

Therefore, weight of soil supported on projection

Weight of walls =897000 N


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Weight of roof slab = 450000 N

Weight of base slab

Therefore,

Total downward weight

Total upward force

Therefore, Factor of Safety against flotation

A factor of safety of about 1.0 is needed because

(i) Concrete may weigh less than (ii) Earth may weigh less than (iii) Ground water may turn saline, and may weigh more than

Hence keep

Upward water pressure


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Self weight of slab

Therefore, Net upward pressure, p

Weight of wall per m run

Weight of roof slab, transferred to each wall, per m run

Weight of earth of projection

Therefore, Net unbalanced force per m run

Therefore, reaction each wall

Acting at above the bottom of base slab.


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Bending Moment at the edge of cantilever portion

(Causing tension at the bottom face)

Bending Moment at the centre of span

(

)

( )

(Causing tension at the top face)

Keep D=300 mm so that using an effective cover of 50 mm,

d = 300 50 = 250 mm



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Provide 16 mm bars @ 90 mm at the bottom face.

For the top face,


Distribution reinforcement in longitudinal direction

[]

Therefore, Area of steel

Therefore, Area of steel on each face

Therefore, Spacing of 8 mm bars

Hence provide 8 mm @ 130 mm c/c on each face.


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3.1 SUMP DESIGN FOR SKIT MECHANICAL AND HOSTEL BUILDINGS

Capacity of tank = 544.54

DESIGN CONSTANTS

Concrete grade :

Steel grade :

Modular ratio (m) = 13

For HYSD bars

Neutral axis co-efficient (k) = 0.378

Lever arm co-efficient (j) = 0.874

Moment of resistance factor (R) = 1.156

ASSUMED DATA

Angle of repose () =

Saturated unit weight of soil () =


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63

Unit weight of water () =

Assumed depth of sump (H) = 3m

So each capacity of sump =

Let assume B = 4 m

L X 4 X 3 = 181.51 m

L = 15.1 m 15 m

Therefore, L = 15 m, B = 4 m

The size provided for sump = 15m X 4 m X 3m

DESIGN OF LONG WALLS

(c)tank empty with pressure of saturated soil from outside

Here,

Maximum Bending Moment (B.M) at the base of the wall


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Therefore,

Provide total depth T = 260 mm so that d = 260-35 = 225 mm


However, provide 16 mm bars @ 100 c/c on the outside face, at the bottom

long wall.


Since the B.M is proportional to we have

From which



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65

() ()






Similarly, depth where only th reinforcement is required

() ()






Minimum, % reinforcement

Minimum


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66

This is more than of at the bottom. Hence the above curtailment is

not permissible.

Hence the reinforcement will be provided as under:

(iii) at base: 16 bars @ 100 c/c(iv) at 0.85 m above base, up to top: 16 bars @200 mm c/c

Distribution steel

% distribution steel

Area to be provided on each face =330.2


Hence provide 8 mm bars @ 150 mm c/c on each face.

Actual Direct compression in long walls



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67

This direct compression developed on long walls is given by

This will be taken by the distribution steel and wall section.

(d)Tank full with water, and no earth fill outside


However, provide 16 mm bars @ 130 c/c on the outside face, at the inside

face.


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( )


() ()

As decided earlier, curtail half the bars at 0.85 m from the base.

Minimum, % reinforcement @ 0.254% = 660.4. Hence furthercurtailment is not permissible.

Thus the reinforcement at the inner face will be provided as follows:

(iii) at base : 16 bars @ 130 c/c(iv) at 0.85 m above base, up to top: 16 bars @260 mm c/c

Direct tension in long walls

Where at 1 m above base


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Therefore,

Required

Area of distribution steel provided in horizontal direction .

Hence distribution steel will take direct tension.

4. DESIGN OF SHORT WALLS

(c)tank empty with pressure of saturated soil from outside(iv) Top portion : the bottom 1 m acts as cantilever, while the

remaining 2 m acts

as slab supported on long walls


(at supports)


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M (at centre)

At supports,

Using 12 bars,

Hence provide 12 mm bars @ 95 m c/c at the outer face, at 2 mm below the

top.

At mid span

Minimum (as found earlier)


Hence provide 12 mm bars at 170 mm c/c at the inner face


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(v) Bottom portion : the bottom 1 m will bend as cantilever.Intensity of earth pressure at bottom

Therefore,

Therefore,

Minimum steel @ 0.254% = 660.4


Hence provide 12 mm bars @ 170 mm c/c at outside face, in the vertical

direction for bottom 1 m height. The spacing can be doubled for the upper

portion.

(vi) Direct compression in short wallsThough the long walls bend as cantilever, it is observed that end one

meter width of long wall contributes to push in short walls, due to earth pressure,

and its magnitude is given by

(d)Tank full with water, and no earth fill outside(iii) Top portion : the bottom portion h = 1 m (> H/4) acts as a cantilever,


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while the remaining 2 m acts slab supported on long walls.

At h = 1 m (> H/4) above base of short wall,

Direct tension in short wall, due to water pressure on the end one metre

width of long walls is

Effective depth d, for horizontal steel = 211 mm

Therefore, distance

Therefore, Net B.M

Therefore,


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73

Therefore,

At the inside face (end of short walls)

Therefore, Total

Using 12 mm bars,


At the outside face (middle of short walls)

Therefore, Total


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74

Minimum

Using 12 mm bars,


(iv) Bottom portion : the bottom portion 1 m will bend as cantileverp (at bottom) = 29430 N/ (step 3)

Therefore,

(With tension at inside face)

Therefore,

Minimum steel @ 0.254% = 660.4 (found earlier)


Hence provide 12 mm bars @ 170 mm c/c at the inside face, in the

vertical direction for bottom 1 m height. The spacing can be doubled for the

upper portion.

DESIGN OF TOP SLAB

L/B =15/4 =3.8


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Hence the top slab will be designed as one way slab.

Let the live load on top slab = 2000 N/

Assuming a thickness of 20 cm including finishes etc.,

Self weight

Therefore, Total

Therefore,

Provide total thickness = 150 mm. Keeping a clear of 25 mm and using 12

mm bars,


Hence provide 12 mm bars @ 110 mm c/c

Distribution reinforcement *+


76/90


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77

Therefore, Total

This is much less than the flotation force. Hence provide projection of base

slab, beyond the face of vertical walls, by an amount m all-round, so that weightof soil column supported by the projections will provide additional downward

force.

Weight of soil supported by projection

Weight of roof slab

Weight of walls

Weight of base slab

Total uplift force

Equating total upward force to the total downward forces,

We get


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78

Or

Or

Which gives

From which

Check

Width Length

Therefore, weight of soil supported on projection

Weight of walls =741000 N

Weight of roof slab = 300000 N

Weight of base slab

Therefore,

Total downward weight


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79

Total upward force

Therefore, Factor of Safety against flotation

A factor of safety of about 1.0 is needed because

(iv) Concrete may weigh less than (v) Earth may weigh less than (vi) Ground water may turn saline, and may weigh more than

Hence keep

Upward water pressure

Self weight of slab

Therefore, Net upward pressure, p

Weight of wall per m run

Weight of roof slab, transferred to each wall, per m run


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80

Weight of earth of projection

Therefore, Net unbalanced force per m run

Therefore, reaction each wall

Acting at above the bottom of base slab.

Bending Moment at the edge of cantilever portion

(Causing tension at the bottom face)Bending Moment at the centre of span


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81

(

)

(

)

(Causing tension at the top face)

Keep D=300 mm so that using an effective cover of 50 mm,

d = 300 50 = 250 mm


Provide 16 mm bars @ 90 mm at the bottom face.

For the top face,


Distribution reinforcement in longitudinal direction


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[]

Therefore, Area of steel

Therefore, Area of steel on each face

Therefore, Spacing of 8 mm bars

Hence provide 8 mm @ 130 mm c/c on each face.


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3.2 DETAILED ESTIMATES OF MAIN BUILDINGS.No. Description Numbers Length Breadth Height Quantity

(m) (m) (m) (cu.m./sq.m)

1 Earthwork in Excavation 5 X 1 19.52 6.52 3.45 2 Sand spreading including

labour charges 5 X 1 19.52 6.52 0.30 190.91

3 CC in foundation (1:5:10) 5 X 1 19.52 6.52 0.30 190.91

4 R.C.C Work 1:1:3 in slab

excluding steel and its

bending but including

(centering, shuttering and

bending steel)

Bottom slab 5 X 1 19.52 6.52 0.30 190.91

Top slab 5 X 1 18.52 5.52 0.15 76.67

Long walls 5 X 2 18.52 0.26 3.0 144.5

Short walls 5 X 2 5.0 0.26 3.0 39.0

Deductions for manhole 5 X 1 0.75 0.60 0.15 -0.34

For manhole with

bearing 15 cm 5 X 1 1.05 0.90 0.15 +0.71

5 Steel bars including in

R.C.C. work

For side walls 1.23 MT

For top slab 0.28 MT

For bottom slab 0.58 MT

2.09 MT6 Plastering

Long walls 5 X 2 18.52 - 3.0 555.6

Short walls 5 X 2 5.52 - 3.0 165.6

Bottom slab top side 5 X 1 18 5 - 450.0

Top slab

Inside 5 X 1 18 5 - 450.0

Outside 5 X 1 18.52 5.52 - 511.15

Deduction for manhole 0.75 0.6 - -2.25

7 Sand filling

Long wall side 5 X 2 19.52 0.5 3.0 292.8

Short wall side 5 X 2 5.52 0.5 3.0 82.8


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3.3 DETAILED ESTIMATES OF MECHANICAL AND HOSTEL BUILDINGS

S.No. Description Numbers Length Breadth Height Quantity

(m) (m) (m) (cu.m./sq.m)

1 Earthwork in Excavation 5 X 1 16.52 5.52 3.5

2 Sand spreading including

labour charges 5 X 1 16.52 5.52 0.30 111.7

3 CC in foundation (1:5:10) 5 X 1 16.52 5.52 0.30 111.7

4 R.C.C Work 1:1:3 in slab

excluding steel and its

bending but including

(centering, shuttering and

bending steel)

Bottom slab 5 X 1 16.52 5.52 0.30 111.7

Top slab 5 X 1 15.52 4.52 0.15 52.61

Long walls 5 X 2 15.52 0.26 3.0 121.05Short walls 5 X 2 4.0 0.26 3.0 31.2

Deductions for manhole 5 X 1 0.75 0.60 0.15 -0.315

For manhole with

bearing 15 cm 5 X 1 1.05 0.90 0.15 +0.71

5 Steel bars including in

R.C.C. work

For side walls 1.03 MT

For top slab 0.23 MT

For bottom slab 0.47 MT1.73 MT

6 Plastering

Long walls 5 X 2 15.52 - 3.0 465.6

Short walls 5 X 2 4.52 - 3.0 135.6

Bottom slab top side 5 X 1 15 4 - 300.0

Top slab

Inside 5 X 1 15 4 - 300.0

Outside 5 X 1 15.52 4.52 - 350.75

Deduction for manhole 0.75 0.6 - -2.25

7 Sand fillingLong wall side 5 X 2 16.52 0.5 3.0 247.8

Short wall side 5 X 2 4.52 0.5 3.0 67.8


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3.4 ABSTRACT ESTIMATION OF SKIT COLLEGE MAIN BUILDING SUMPS

S. Quantity Description Rate Per Amount

No. Rs.Ps. Cu.m/sq.m Rs.

1 2195.4 Earthwork excavation and 34.50 1 cum 75742

depositing as directed with an

initial load of 10m and lift 3m

in ordinary gravel

2 190.91 sand spreading at bottom 213.18 1 cum 40699

of tank

3 190.91 C.C. in foundation(1:5:10) 497.60 1 cum 94997

4 451.45 RCC (1:11/2:3) using 20mm 2839.30 1 cum 128182

HBG metal for RCC slab and

side walls

5 2.09 Steel 29500.0 1 MT 61655

6 2130.1 Plastering with cm (1:4) min 91.00 1 sqm 193840

with 200 mm thick

7 375.6 Sand fill 213.18 1 cum 80071

8 LS Provision for contingencies - - 482

Total 675668


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3.5 ABSTRACT ESTIMATION OF SKIT COLLEGE MECHANICAL AND

HOSTEL BUILDING SUMPS

S. Quantity Description Rate Per Amount

No. Rs.Ps. Cu.m/sq.m Rs.

1 1595.8 Earthwork excavation and 34.50 1 cum 55056

depositing as directed with an

initial load of 10m and lift 3m

in ordinary gravel

2 111.7 sand spreading at bottom 213.18 1 cum 23813

of tank

3 111.7 C.C. in foundation(1:5:10) 497.60 1 cum 55582

4 316.96 RCC (1:11/2:3) using 20mm 2839.30 1 cum 899945

HBG metal for RCC slab and

side walls

5 1.73 Steel 29500.0 1 MT 51035

6 1549.7 Plastering with cm (1:4) min 91.00 1 sqm 141023

with 200 mm thick

7 315.6 Sand fill 213.18 1 cum 67280

8 LS Provision for contingencies - - 482

Total 9393716


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ESTIMATED COST OF THE PROJECT

Estimated cost of the S.K.I.T college main building = Rs.675668

Estimated cost of the Mechanical and Hostel buildings = Rs.9393716

Total cost of the project = Rs.10069384


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CONCLUSIONS

Storage of water in the form of tanks leads to artificial recharge of ground

water and also for drinking and washing purposes, swimming pools for exercise

and enjoyment, and sewage sedimentation tanks are gaining increasing

importance in the present day life.

Design of water tank is a very tedious method. Particularly design of under

ground water tank involves lots of mathematical formulae and calculation. It is

also time consuming. Hence program gives a solution to the above problems.

There is a little difference between the design values of program to that of

manual calculation. The program gives the least value for the design. Hence

designer should not provide less than the values we get from the program. In case

of theoretical calculation designer initially add some extra values to the obtained

values to be in safer side.


90/90

REFERENCES

1. B.N.Dutta., Estimation and Costing, UBS publishers2. B.C.Punmia., Reinforced Concrete Structures, Laxmi Publications3. Santhosh Kumar Garg, Water Supply Engineering, (Vol 1), Khanna

Publishers

4. Manual: Rain Water Harvesting and Conservation5. Sushil kumar., Reinforced Concrete Structures6. Codes IS : 3370 (Part II) 1965

santhi mainproject

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