DESIGN OF UNDERGROUND RECTANGULAR CONCRETE WATER TANK PROJECT REPORT Submitted by
ANIRUDHA.B
714013103004
PALANIAPPAN.RM
714013103029
REVANTH KUMAR.S
714013103037
SRIRAM.S
714013103045
in partial fulfillment for the award of the degree of
BACHELOR OF ENGINEERING in
CIVIL ENGINEERING
SRI SHAKTHI INSTITUTE OF ENGINEERING AND TECHNOLOGY COIMBATORE - 641062
ANNA UNIVERSITY: CHENNAI 600 025 OCTOBER 2016
BONAFIDE CERTIFICATE Certified that this project report “DESIGN OF UNDER GROUND RECTANGULAR CONCTERE WATER TANK” is the bonafide work of “ANIRUDHA.B, PALANIAPPAN.RM, REVANTH KUMAR.S, SRIRAM.S” who carried out the project work under my supervision.
SIGNATURE
SIGNATURE
Er. M. Ravichandran
Dr. D. Karunanidhi
HEAD OF THE DEPARTMENT
SUPERVISOR
DEPARTMENT OF CIVIL
ASSISTANT PROFESSOR
ENGINEERING,
DEPARTMENT OF CIVIL
SRI SHAKTHI INSTITUTE OF
ENGINEERING,
ENGINEERING AND TECHNOLOG,
SRI SHAKTHI INSTITUTE OF
COIMBATORE-62.
ENGINEERING AND TECHNOLOGY, COIMBATORE-62
Submitted for the design project viva voce examination held on ……….at Sri Shakthi Institute of Engineering and Technology, Coimbatore-62.
Internal Examiner
External Examine
ACKNOWLEDGEMENT First and foremost, we place this design project work on the feet of GOD ALMIGHTY who is the power of strength in each step of progress towards the successful completion of my project. We express deepest gratitude to our Chairman Dr. S. Thangavelu, for his invaluable guidance and blessings. We are very grateful to our Principal Dr. C. Natarajan, for providing us with an environment to complete this project successfully. We are very grateful to our Joint Secretary Mr. T. Sheelan and Director Dr. R. Manian, for the encouragement to complete our project successfully. We are deeply indebted to our Head of the Department Mr. S. Ravichandran, who molded us both technically and morally for achieving greater success in life. We are very grateful to our Supervisor Dr. D. Karunanithi, for being instrumental in the completion of my project with his valuable guidance. We are very thankful to our Project Coordinator Er. S. Ravichandran, who helped me in the completion of the project with his valuable guidance. We are also thankful to all the staff members of our college and technicians for their help in making this project a successful one. Finally, we take this opportunity to extend our deep appreciation to our Family and Friends, for all that meant to us during the crucial times of the completion of our project. ANIRUDHA.B PALANIAPPAN.RM REVANTH KUMAR.S SRIRAM.S
i
TABLE OF CONTANTS CHAPTER NO
1.
TITLE
PAGE NO
LIST OF TABLE
vi
LIST OF FIGURES
vii
LIST OF SYMBOLS
viii
INTRODUCTION
1
1.1 UNDERGROUND WATER TANK
1
1.2 IMPORTANCE OF UNDERGROUND
2
WATER TANK 1.3 DIFFERENT TYPES OF WATER TANKS
3
DEPENDING ON ITS LOCATION 1.4 DIFFERENCE BETWEEN CIRCULAR AND
4
RECTANGULAR WATER TANK 1.5 DIFFERENT TYPES OF WATER TANKS
5
BASED ON MATERIALS 1.5.1 PLASTIC
5
1.5.2 STEEL TANK
6
1.5.3 FIBRE GLASS
6
1.5.4 CONCRTE TANK
6
1.6 ADVANTAGES OF CONCRETE WATER TANK
ii
7
1.6.1 COST
7
1.6.2 DETERIORATION/LIFESPAN/
8
DURABILITY 1.6.3 SIZE AND SHAPE
8
1.6.4 ENVIRONMENT CREDENTIALS 8 1.6.5 MERITS OF CONCRETE WATER 9 TANK 1.6.6 DEMERITS OF CONCRETE
9
WATER TANK 1.6.7 SITE PREPARATIONS 1.7 OBJECTIVES
2.
GENERAL DESIGN REQUIREMENTS
9 9
10
2.1 DESIGN REQUIREMENT OF WATER TANK 13 2.2 JOINTS IN LIQUID RETAINING
15
STRUCTURES 2.2.1 MOVEMENT JOINTS
15
2.2.2 CONTRACTION JOINTS
17
2.2.3 TEMPORARY JOINTS
18
2.2.4 SPACING OF JOINTS
18
2.3 FLOORS
20
2.4 WALLS
22
2.5 ROOF
24
2.6 MINIMUM REINFORCEMENT
25
2.7 FLEXIBLE BASE WATER TANK
26
iii
2.8 RIGID BASE TANK
26
2.9 DESIGN REQUIREMENTS FOR UNDER
27
GROUND WATER TANK
3.
ANALYSIS AND DESIGN
31
3.1 DETERMINATION OF FIELD DENSITY OF
31
SOIL BY CORE CUTTER 3.2 FIXED FUNNEL TEST
33
3.3 DESIGN OF RECTANGULAR
35
UNDERGROUND CONCRETE TANK
4.
CONCLUSION
49
5.
REFERENCE
50
iv
ABSTRACT Water tanks and reservoirs are used to store liquids like water, petroleum or chemicals. For any domestic and commercial purposes, water tanks are very basic need to meet their day to day use. In this project an attempt is made to design the rectangular underground tank, the tank is to maintain atmospheric temperature and provided optimum height for easy pumping of water to overhead tank. Since it is underground water tank the lateral earth pressure and water pressure also considered for the design calculations, so the design is to be carried out as per IS code norms. This project deals with analysis and design of under ground water tank of 2lakh liter capacity. The design in this project comprises of side walls, base slab and roof slab. The analysis and design of underground water tank is done using AutoCad. For this design project limit state method is used.
v
LIST OF TABLES TABLE NO.
TITLE
PAGE
2.1
PERMISSIBLE CONCRETE STRESS
12
3.1
FIXED FUNNEL TEST
34
3.2
BENDING MOMENT ON WATER FACE AND EARTH FACE
3.3
38
BENDING MOMENT AT CENTER AND SUPPORT
45
vi
LIST OF FIGURES FIGURE NO.
TITLE
PAGE NO
2.1
MOVEMENT JOINT
16
2.2
EXPANSION JOINT
17
2.3
SLIDING JOINT
18
2.4
CONTRACTION JOINT
18
2.5
TEMPORARY JOINT
19
2.6
SPACING OF JOINT
19
3.1
REINFORCEMENT OF PLAN
46
3.2
REINFORCEMNT OF SHORT AND LONG WALL
47
vii
LIST OF SYMBOLS φ - Angle of repose σcbc – Permissible stress in concrete in bending σst – Permissible stress in steel in tension jd – Lever arm depth m – Modular ratio d – Overall depth de – Effective depth b – Breadth W – Load at the structure M – Bending moment Mv – Bending moment at vertical direction Mh – Bending moment at horizontal direction At – Area of tensile steel L – Length of the tank B – Width of the tank H – Overall height of the tank
viii
CHAPTER 1 INTRODUCTION 1.1 UNDERGROUND WATER TANK Underground water tanks are structures which act as a reservoir for small domestic or commercial buildings. Basic components of underground water tanks are Base slab, Side walls, And Roof slab. Tanks are very ductile, enabling to withstand seismic forces and varying water backfill. Tanks utilize material efficiently – steel in tension, concrete in compression. Underground water tanks have Low maintenance throughout the life as these are built with concrete, durable material that never corrodes and does not require coatings when in contact with water or the environment. The main advantage of underground water tank is that the temperature is lower than the overhead tanks, which will reduce evaporation inside water tank. Underground water tank faces different type of loads compared to other structures, they mainly face horizontal or lateral loads due to earth pressure and water pressure or any liquid pressure which is been stored in the tank. The side walls of the underground water tank will face greater load at the bottom and the load linearly decreases towards the top. The underground water tank not only faces loads inside the tank it also has to bear the surcharge above the ground level. So the roof slab of the underground tank should have enough strength to with stand the surcharge.
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1.2 IMPORTANCE OF UNDERGROUND WATER TANK • Seepage It is very important to store water and not to lose it. The tank should have a durable, watertight, opaque exterior and a clean, smooth interior. Below ground tanks must also be plastered well and correctly installed, otherwise they can collapse. • Evaporation All storage tanks should have a roof made from locally available materials. A tight fitting top cover prevents evaporation. • Safety We should prevent mosquito breeding and keeps insects, rodents, birds and children out of the tank. A suitable overflow outlet(s) and access for cleaning are also important. • Storage of water It is very imperative for all tanks to store water because the main process of the tank is to store water due to lack of running fresh water in all areas. • Emergency Underground tanks are used as reservoirs where water is pumped to overhead tanks. When water is not available it will help us store and use water.
2
1.3 DIFFERENT TYPES OF WATER TANKS DEPENDING ON ITS LOCATION (i)RESTING ON GROUND • Deals with normal pressure of gravity and corresponding outward pressure of water stored in water tank (Internal hydrostatic pressure) • Pipes can be attached directly for irrigation purpose. • Pumps can be attached depending on the usage. • More economical than other type of tanks. • No need for excavation. (ii)OVERHEAD • The water pressure to all the processes being supplied is held at a relatively constant level. • In power failure or pump failure pressure remains constant. • At work any pipe can be taken for maintenance. • If all the pumps are failed water pressure will be still for fire suppression and other critical needs. • Gravity plays an important role for the flow of water. • Columns are provided for the support of tank. (iii)UNDERGROUND • Used as water reservoir for irrigation purpose. • Used for rainwater harvesting. • Difficulty in installation.
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• It is protected from animals in forest areas. • Pumps are needed for supply of water. • Expensive compared to tanks resting on the ground. • In case of fire the water will be safe underground. 1.4 DIFFERENCE BETWEEN CIRCULAR AND RECTANGULAR WATER TANK. 1.4.1CIRCULAR: It is the simplest form of water tank. For the same amount of storage circular water tank requires less amount of materials compared to rectangular water tank. It has no corner and can be made water tight easily. It is economical for smaller storage of water up to 200000000 lits and with dia 5 to 8 m. Depth of the storage is between 3 to 4 m. The side walls are designed for hoop tension and bending moment. Round tanks is really a cylinder holding the water. Water exerts pressure equally in all directions. When place in cylinder round water vessels can be constructed using minimum thickness of wall. Circular water tanks can be transported and installed easily. Merits: Structural strength, Economic, Constant heat level, Clean and hygienic. 1.4.2RECTANGULAR: Rectangular tanks are modular, fit in most yards. Large tanks of high capacity can be constructed. It occupies less space compared to circular tanks. Multiple units of water storage can be constructed using rectangular type tanks. Merits: Occupy less space when multiple units used.
4
Provide longer travel distance for settling to occur. 1.5 DIFFERENT TYPES WATER TANKS BASED ON MATERIAL: 1.5.1 PLASTIC TANK: Poly (plastic) water tanks are made from polyethylene; a UV stabilized food grade plastic. The tanks are light, you only need a sand base to place them on, and they come in a wide variety of colours and have a long serviceable life. Many poly tanks carrying a 25 year warranty, although many claim 15 years is a very realistic lifespan. They are also usually the second cheapest. One of the major disadvantages of polyethylene is the material is made from petrochemicals. Even after their serviceable life has ended, there's still a great big hunk of plastic that will take generations to break down and will release toxins as it does so. However, polyethylene tanks can still be easily recycled after 15 years, so it's just a matter of breaking the tank up and then carting it away rather than trying to squeeze a few more years out of one. Some poly tanks are made with a vertical seam - this is a weak point that may cause splitting and subsequent water loss. Polyethylene water tanks and fire don't really mix either - they'll just melt. This can be a real problem if you're in a rural area and you need that water to fight a fire. The other issue is the long term effects of drinking water stored for such a long time in this material. Polyethylene tanks are relatively new on the market, it is not known if there are any credible serviceable life studies that have been done in relation to these issues. Some people do note a bit of an odd taste to the water if the tank is placed in full sun. Just on that point - before purchasing a poly tank, check the warranty for temperature stipulations as some manufacturers will void the warranty if conditions where the tank is installed can get extremely hot.
5
1.5.2 STEEL TANKS: Steel tanks Galvanized tanks have been around for over 150 years and are usually the cheapest type of tank. Hot-dip galvanizing is a process used to coat steel or iron with zinc. The Zinc helps slow down corrosion, but depending on environmental factors, a galvanized tank may last well under 5 years. This is due to electrolysis. Some metal tanks now also have polyethylene linings to further help retard corrosion - escaping plastic altogether can be a difficult thing to do these days. With a steel based tank, seriously consider the composition of the water you are storing and its potential to accelerate corrosion in any exposed metals. 1.5.3 FIBRE GLASS: Fibre glass, this is another long-lasting option that can be installed above or below ground. Fiberglass tanks resist corrosion and are not generally affected by chemicals. As fiberglass tanks tend to allow more light in than other types of tank materials, this can encourage the growth of algae, so they should be painted. Fiberglass can also tend to be brittle, leaving it prone to cracks - something you don't want, particularly in an in-ground situation. 1.5.4 CONCRETE TANK: Concrete water storage tanks can be built above grade or mostly hidden from view. They are built on site because of the material’s weight. Concrete is a porous material and needs to be sealed to prevent minerals leaching into the water. With proper sealing and construction techniques, this is can be addressed. Mining production and delivery of concrete is energy intensive. The advantage is achieved
6
by its long life and its ability to be simply recycled. Choosing a tank material Choice is wonderful, but as you can see, there are advantages and disadvantages with each type of tank, particularly when it comes to environmental impact - so it's really a matter of gagging your needs and budget and then choosing the lesser of the evils. In regards to the financial side of things, bear in mind not just the initial cost, but how many times the tank will need replacing over X years. This also plays a role in the Concrete tanks have been used in rural areas for many years but are becoming more common in the city, particularly pre-cast underground concrete tanks that can be placed under driveways or front and back yards. The advantage of underground concrete tanks is that they can collect large volumes of water in properties tight for space that could not otherwise accommodate above-ground tanks. Houses with small gardens still consume large volumes of water internally through laundries, toilets and showers and could benefit from using underground concrete tanks for 'whole of house' water supply. 1.6 ADVANTAGES OF CONCRETE WATER TANK 1.6.1 COST: The actual concrete tank itself is generally only slightly more expensive than some steel options, however it becomes more expensive per litre when placing concrete tanks underground as excavation, transport and crane hire (for larger tanks) can be quite expensive. However, with rising land and water prices it may be a wise long-term investment for inner-city and small blocks, as an underground tank does not take up any valuable space on the property. See the Price Comparison for price estimates.
7
1.6.2 DETERIORATION/LIFESPAN/DURABILITY: Concrete tanks are extremely durable and most purpose-built concrete rainwater tanks have plasticizers added for strength and are poured into a seamless mould to prevent leaks. Most manufacturers offer warranties of between 20 and 30 years, however a good quality concrete tank can last several decades. While not as easy to repair as steel or fiberglass tanks, leaking concrete tanks can be fixed with various sealants depending on the size of the crack and the position.
1.6.3 SIZE AND SHAPE: There are more and more companies producing pre-cast concrete tanks in many shapes and sizes including rectangular ones that fit neatly under driveways. Underground concrete tanks can also be cast on site (in situ). Most concrete tanks, whether pre-cast or built on site, are designed to be load bearing and are therefore ideal for placing under driveways. Water quality: Some older concrete tanks may leach lime, increasing the pH of water and affecting its taste. However, in most cases the water quality from concrete tanks is very good. Concrete tanks tend to keep the water cooler than most other tanks, reducing the likelihood of bacterial growth.
1.6.4 ENVIRONMENTAL CREDENTIALS: Concrete tanks have high embodied energy; however a good quality concrete tank will have a long life-span and can be recycled at the end of its life.
8
1.6.5 SITE PREPARATION: Concrete tanks are extremely heavy and therefore some settling tends to occur once put in place. The use of packing sand or cracker dust is recommended and it may be worth rolling or compacting the sand before installing the tank to reduce initial movement. It is advisable to allow the tank to settle for a number of weeks before connecting fixed plumbing. Of resources used.
1.6.6 MERITS OF CONCRETE WATER TANK • When rain water is stored it reduces its acidity. • Concrete water tanks can with stand bush fire. • Keeps water cool. • Free from algae up to 100 years. • Lasts longer.
1.6.7 DEMERITS OF CONCRETE WATER TANK • Leakage • Leaching • Expensive 1.7 OBJECTIVES The objective of this project is to plan and design a underground concrete water tank for 2,00,000 liter capacity for Sri Shakthi institute of engineering and technology.
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CHAPTER 2 2. GENERAL DESIGN REQUIREMENTS OF CONCRETE (I.S.I) Concrete Structures. Plain concrete member of reinforced concrete liquid retaining structure may be designed against structural failure by allowing tension in plain concrete as per the permissible limits for tension in bending. This will automatically take care of failure due to cracking. However, nominal reinforcement shall be provided, for plain concrete structural members. Permissible Stresses in Concrete. (a) For resistance to cracking. For calculations relating to the resistance of members to cracking, the permissible stresses in tension (direct and due to bending) and shear shall confirm to the values specified in Table 2.1. The permissible tensile stresses due to bending apply to the face of the member in contact with the liquid. In members less than 225mm. thick and in contact with liquid on one side these permissible stresses in bending apply also to the face remote from the liquid. (b) For strength calculations. In strength calculations the permissible concrete stresses shall be in accordance with Table 2.1. Where the calculated shear stress in concrete alone exceeds the permissible value, reinforcement acting in conjunction with diagonal compression in the concrete shall be provided to take the whole of the shear.
10
Table 2.1 Permissible concrete stresses in calculations relating to resistance to cracking Grade of concrete Permissible stress in KN/m^2 tension
M15
Direct
Bending
1.1
1.5
shear
1.5 M20
1.2
1.7
1.7
M25
1.3
1.8
1.9
M30
1.5
2.0
2.2
M35
1.6
2.2
2.5
M40
1.7
2.4
2.7
11
Permissible Stresses in Steel (a) For resistance to cracking. When steel and concrete are assumed to act together for checking the tensile stress in concrete for avoidance of crack, the tensile stress in steel will be limited by the requirement that the permissible tensile stress in the concrete is not exceeded so the tensile stress in steel shall be equal to the product of modular ratio of steel and concrete, and the corresponding allowable tensile stress in concrete. (b) For strength calculations. In strength calculations the permissible stress shall be as follows: (i) Tensile stress in member in direct tension (ii) Tensile stress in member in bending on liquid retaining face of members or face away from liquid for members less than 225mm thick (iii)On face away from liquid for members 225mm or more in thickness (iv) Tensile stress in shear reinforcement, For members less than 225mm thickness 1000 kg/cm 1250 kg/cm (v)Stresses due to drying shrinkage or temperature change may be ignored provided that ñ The permissible stresses specified above in (ii) and (iii) are not otherwise exceeded. Adequate precautions are taken to avoid cracking of concrete during the construction period and until the reservoir is put into use. Recommendation regarding joints given above and for suitable sliding layer beneath the reservoir are complied with, or the reservoir is to be used only for the storage of water or aqueous
12
liquids at or near ambient temperature and the circumstances are such that the concrete will never dry out. (ii)Shrinkage stresses may however be required to be calculated in special -6 cases, when a shrinkage co-efficient of 300 x 10 may be assumed. (iii) When the shrinkage stresses are allowed, the permissible stresses, tensile stresses to concrete (direct and bending) may be increased by 33.33 per cent. 2.1 DESIGN REQUIREMENT OF WATER TANK (I. S. I) In water retaining structure a dense impermeable concrete is required therefore, proportion of fine and course aggregates to cement should be such as to give high quality concrete. Concrete mix weaker than M20 is not used. The minimum quantity of cement in the concrete mix shall be not less than 30 kN/m . The design of the concrete mix shall be such that the resultant concrete is sufficiently impervious. Efficient compaction preferably by vibration is essential. The permeability of the thoroughly compacted concrete is dependent on water cement ratio. Increase in water cement ratio increases permeability, while concrete with low water cement ratio is difficult to compact. Other causes of leakage in concrete are defects such as segregation and honey combing. All joints should be made water-tight as these are potential sources of leakage. Design of liquid retaining structure is different from ordinary R.C.C, structures as it requires that concrete should not crack and hence tensile stresses in concrete should be within permissible limits. A reinforced concrete member of liquid retaining structure is designed on the usual principles ignoring tensile resistance of concrete in bending. Additionally, it should be ensured that tensile 13
stress on the liquid retaining face of the equivalent concrete section does not exceed the permissible tensile strength of concrete as given in table 1. For calculation purposes the cover is also taken into concrete area. Cracking may be caused due to restraint to shrinkage, expansion and contraction of concrete due to temperature or shrinkage and swelling due to moisture effects. Such restraint may be caused by ñ (i) The interaction between reinforcement and concrete during shrinkage due to drying. (ii) The boundary conditions. (iii) The differential conditions prevailing through the large thickness of massive concrete. Use of small size bars placed properly, leads to closer cracks but of smaller width. The risk of cracking due to temperature and shrinkage effects may be minimized by limiting the changes in moisture content and temperature to which the structure as a whole is subjected. The risk of cracking can also be minimized by reducing the restraint on the free expansion of the structure with long walls or slab founded at or below ground level, restraint can be minimized by the provision of a sliding layer. This can be provided by founding the structure on a flat layer of concrete with interposition of some material to break the bond and facilitate movement. In case length of structure is large it should be subdivided into suitable lengths separated by movement joints, especially where sections are changed the movement joints should be provided. Where structures have to store hot liquids, stresses caused by difference in temperature between inside and outside of the reservoir should be taken into account. 14
The coefficient of expansion due to temperature change is taken as 11 x -6 -6 10 / C and coefficient of shrinkage may be taken as 450 x 10 for initial shrinkage and 200 x 10^-6for drying shrinkage. 2.2 JOINTS IN LIQUID RETAINING STRUCTURES 2.2.1 MOVEMENT JOINTS There are three types of movement joints. (i)Contraction Joint. It is a movement joint with deliberate discontinuity without initial gap between the concrete on either side of the joint. The purpose of this joint is to accommodate contraction of the concrete. The joint is shown in Fig.1
Fig(2.1)
Figure (1) A contraction joint may be either complete contraction joint or partial
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contraction joint. A complete contraction joint is one in which both steel and concrete are interrupted and a partial contraction joint is one in which only the concrete is interrupted, the reinforcing steel running through as shown in Fig (2.1). (ii)Expansion Joint. It is a joint with complete discontinuity in both reinforcing steel and concrete and it is to accommodate either expansion or contraction of the structure. A typical expansion joint is shown in Fig (2.2)
Fig(2.2) This type of joint requires the provision of an initial gap between the adjoining parts of a structure which by closing or opening accommodates the expansion or contraction of the structure. (iii) Sliding Joint. It is a joint with complete discontinuity in both reinforcement and concrete and with special provision to facilitate movement in plane of the joint. A typical joint is shown in Fig (2.3). This type of joint is provided between wall and floor in some cylindrical tank designs.
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Fig (2.3). 2.2.2 CONTRACTION JOINTS This type of joint is provided for convenience in construction. Arrangement is made to achieve subsequent continuity without relative
Fig(2.4) movement. One application of these joints is between successive lifts in a reservoir wall. A typical joint is shown in Fig (2.4). The number of joints should be as small as possible and these joints should be kept from possibility of percolation of water.
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2.2.3 TEMPORARY JOINTS A gap is sometimes left temporarily between the concrete of adjoining parts of a structure which after a suitable interval and before the structure is put to use, is filled with mortar or concrete completely as in Fig (2.5) with suitable jointing materials. In the first case width of the gap should be sufficient to allow the sides to be prepared before filling.
Fig (2.5).
Fig (2.6).
2.2.4 SPACING OF JOINTS
Fig(7).
Fig(8)
Unless alternative effective means are taken to avoid cracks by allowing for the additional stresses that may be induced by temperature or shrinkage changes or by unequal settlement, movement joints should be provided at the following spacing: 18
(a)In reinforced concrete floors, movement joints should be spaced at not more than 7.5m apart in two directions at right angles. The wall and floor joints should be in line except where sliding joints occur at the base of the wall in which correspondence is not so important. (b)For floors with only nominal percentage of reinforcement (smaller than the minimum specified) the concrete floor should be cast in panels with sides not more than 4.5m. (c)In concrete walls, the movement joints should normally be placed at a maximum spacing of 7.5m. in reinforced walls and 6m in unreinforced walls. The maximum length desirable between vertical movement joints will depend upon the tensile strength of the walls, and may be increased by suitable reinforcement. When a sliding layer is placed at the foundation of a wall, the length of the wall that can be kept free of cracks depends on the capacity of wall section to resist the friction induced at the plane of sliding. Approximately the wall has to stand the effect of a force at the place of sliding equal to weight of half the length of wall multiplied by the co-efficient of friction. (d)Amongst the movement joints in floors and walls as mentioned above expansion joints should normally be provided at a spacing of not more than 30m between successive expansion joints or between the end of the structure and the next expansion joint; all other joints being of the construction type. (e)When, however, the temperature changes to be accommodated are abnormal or occur more frequently than usual as in the case of storage of warm liquids or in uninsulated roof slabs, a smaller spacing than 30m should be adopted that is greater proportion of movement joints should be of the expansion type). When the range of temperature is small, for example, in certain covered structures, or where restraint is small, for example, in certain elevated structures none of the movement joints
19
provided in small structures up to 45mlength need be of the expansion type. Where sliding joints are provided between the walls and either the floor or roof, the provision of movement joints in each element can be considered independently. 2.3 FLOORS (i)Provision of movement joints. Movement joints should be provided as discussed before. (ii) Floors of tanks resting on ground. If the tank is resting directly over ground, floor may be constructed of concrete with nominal percentage of reinforcement provided that it is certain that the ground will carry the load without appreciable subsidence in any part and that the concrete floor is cast in panels with sides not more than 4.5m. with contraction or expansion joints between. In such cases a screed or concrete layer less than 75mm thick shall first be placed for members 225mm or more in thickness 1250 kg/cm (v)Compressive stress in columns subjected to direct load 1250 kg/cm Stresses due to drying Shrinkage or Temperature Change. On the ground and covered with a sliding layer of bitumen paper or other suitable material to destroy the bond between the screed and floor concrete. In normal circumstances the screed layer shall be of grade not weaker than M 10, where injurious soils or aggressive water are expected, the screed layer shall be of grade not weaker than M 15 and if necessary a sulphate resisting or other special cement should be used. (iii) Floor of tanks resting on supports
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If the tank is supported on walls or other similar supports the floor slab shall be designed as floor in buildings for bending moments due to water load and self weight. When the floor is rigidly connected to the walls (as is generally the case) the bending moments at the junction between the walls and floors shall be taken into account in the design of floor together with any direct forces transferred to the floor from the walls or from the floor to the wall due to suspension of the floor from the wall. If the walls are non-monolithic with the floor slab, such as in cases, where movement joints have been provided between the floor slabs and walls, the floor shall be designed only for the vertical loads on the floor. In continuous T-beams and L-beams with ribs on the side remote from the liquid, the tension in concrete on the liquid side at the face of the supports shall not exceed the permissible stresses for controlling cracks in concrete. The width of the slab shall be determined in usual manner for calculation of the resistance to cracking of T-beam, L-beam sections at supports. The floor slab may be suitably tied to the walls by rods properly embedded in both the slab and the walls. In such cases no separate beam (curved or straight) is necessary under the wall, provided the wall of the tank itself is designed to act as a beam over the supports under it. Sometimes it may be economical to provide the floors of circular tanks, in the shape of dome. In such cases the dome shall be designed for the vertical loads of the liquid over it and the ratio of its rise to its diameter shall be so adjusted that the stresses in the dome are, as far as possible, wholly compressive. The dome shall be supported at its bottom on the ring beam which shall be designed for resultant circumferential tension in addition to vertical loads.
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2.4 WALLS (i)Provision of joints Where it is desired to allow the walls to expand or contract separately from the floor, or to prevent moments at the base of the wall owing to fixity to the floor, sliding joints may be employed.The spacing of vertical movement joints should be as discussed above while the majority of these joints may be of the partial or complete contraction type, sufficient joints of the expansion type should be provided to satisfy the requirements given in article (ii)Pressure on Walls. In liquid retaining structures with fixed or floating covers the gas pressure developed above liquid surface shall be added to the liquid pressure. When the wall of liquid retaining structure is built in ground, or has earth embanked against it, the effect of earth pressure shall be taken into account. (iii) Walls or Tanks Rectangular or Polygonal in Plan. While designing the walls of rectangular or polygonal concrete tanks, the following points should be borne in mind. In plane walls, the liquid pressure is resisted by both vertical and horizontal bending moments. An estimate should be made of the proportion of the pressure resisted by bending moments in the vertical and horizontal planes. The direct horizontal tension caused by the direct pull due to water pressure on the end walls, should be added to that resulting from horizontal bending moments. On liquid retaining faces, the tensile stresses due to the combination of direct horizontal tension and bending action shall satisfy the following condition:
22
(tí/t)+(Ûctí/Ûct )≤1 tí = calculated direct tensile stress in concrete t = permissible direct tensile stress in concrete (Table 1) Û′ct = calculated tensile stress due to bending in concrete. Ûct = permissible tensile stress due to bending in concrete. At the vertical edges where the walls of a reservoir are rigidly joined, horizontal reinforcement and haunch bars should be provided to resist the horizontal bending moments even if the walls are designed to withstand the whole load as vertical beams or cantilever without lateral supports. In the case of rectangular or polygonal tanks, the side walls act as two- way slabs, whereby the wall is continued or restrained in the horizontal direction, fixed or hinged at the bottom and hinged or free at the top. The walls thus act as thin plates subjected triangular loading and with boundary conditions varying between full restraint and free edge. The analysis of moment and forces may be made on the basis of any recognized method. (iv) Walls of Cylindrical Tanks. While designing walls of cylindrical tanks the following points should be borne in mind: Walls of cylindrical tanks are either cast monolithically with the base or are set in grooves and key ways (movement joints). In either case deformation of wall under influence of liquid pressure is restricted at and above the base. Consequently, only part of the triangular hydrostatic load will be carried by ring tension and part of the load at bottom will be supported by cantilever action. It is difficult to restrict rotation or settlement of the base slab and it is advisable to provide vertical reinforcement as if the walls were fully fixed at the base, in addition to the reinforcement required to resist horizontal ring tension for hinged at base, conditions of walls, unless the appropriate amount of fixity at the base is established by analysis with due consideration to the dimensions of the base slab the type of joint between the wall and slab, and , where applicable, the type of soil supporting the base slab. 23
2.5 ROOF (i) Provision of Movement joints. To avoid the possibility of sympathetic cracking it is important to ensure that movement joints in the roof correspond with those in the walls, if roof and walls are monolithic. However, provision is made by means of a sliding joint for movement between the roof and the wall correspondence of joints is not so important. (ii)Loading. Field covers of liquid retaining structures should be designed for gravity loads, such as the weight of roof slab, earth cover if any, live loads and mechanical equipment. They should also be designed for upward load if the liquid retaining structure is subjected to internal gas pressure. A superficial load sufficient to ensure safety with the unequal intensity of loading which occurs during the placing of the earth cover should be allowed for in designing roofs. The engineer should specify a loading under these temporary conditions which should not be exceeded. In designing the roof, allowance should be made for the temporary condition of some spans loaded and other spans unloaded, even though in the final state the load may be small and evenly distributed. (iii)Water tightness. In case of tanks intended for the storage of water for domestic purpose, the roof must be made water-tight. This may be achieved by limiting the stresses as for the rest of the tank, or by the use of the covering of the waterproof membrane or by providing slopes to ensure adequate drainage.
24
(iv) Protection against corrosion. Protection measure shall be provided to the underside of the roof to prevent it from corrosion due to condensation. 2.6 MINIMUM REINFORCEMENT The minimum reinforcement in walls, floors and roofs in each of two directions at right angles shall have an area of 0.3 per cent of the concrete section in that direction for sections up to 100mm, thickness. For sections of thickness greater than 100mm, and less than 450mm the minimum reinforcement in each of the two directions shall be linearly reduced from 0.3 percent for 100mm thick section to 0.2 percent for 450mm, thick sections. For sections of thickness greater than 450mm, minimum reinforcement in each of the two directions shall be kept at 0.2 per cent. In concrete sections of thickness 225mm or greater, two layers of reinforcement steel shall be placed one near each face of the section to make up the minimum reinforcement. In special circumstances floor slabs may be constructed with percentage of reinforcement less than specified above. In no case the percentage of reinforcement in any member be less than 0 15% of gross sectional area of the member. Minimum Cover to Reinforcement. For liquid faces of parts of members either in contact with the liquid (such as inner faces or roof slab) the minimum cover to all reinforcement should be 25mm or the diameter of the main bar whichever is grater. In the presence of the sea water and soils and water of corrosive characters the cover should be increased by 12mm but this additional cover shall not be taken into account for design calculations. For faces away from liquid and for parts of the structure neither in contact 25
with the liquid on any face, nor enclosing the space above the liquid, the cover shall be as for ordinary concrete member. 2.7 FLEXIBLE BASE WATER TANK For smaller capacities rectangular tanks are used and for bigger capacities circular tanks are used. In circular tanks with flexible joint at the base tanks walls are subjected to hydrostatic pressure .so the tank walls are designed as thin cylinder. As the hoop tension gradually reduces to zero at top, the reinforcement is gradually reduced to minimum reinforcement at top. The main reinforcement consists of circular hoops. Vertical reinforcement equal to 0.3% of concrete are is provided and hoop reinforcement is tied to this reinforcement. 2.8 RIGID BASE TANK The design of rigid base circular tank can be done by the approximate method. In this method it is assumed that some portion of the tank at base acts as cantilever and thus some load at bottom are taken by the cantilever effect. Load in the top portion is taken by the hoop tension. The cantilever effect will depend on the dimension of the tank and the 2 thickness of the wall. For H /Dt between 6 to 12, the cantilever portion 2 may be assumed at H/3 or 1m from base whichever is more. For H /Dt between 6 to 12, the cantilever portion may be assumed at H/4 or 1m from base whichever is more.
2.9 DESIGN REQUIREMENTS FOR UNDER GROUND WATER TANK The tanks like purification tanks, Imhoff tanks, septic tanks, and gas holders are built underground. The design principle of underground tank is same as for tanks 26
are subjected to internal water pressure and outside earth pressure. The base is subjected to weight of water and soil pressure. These tanks may be covered at the top. Whenever there is a possibility of water table to rise, soil becomes saturated and earth pressure exerted by saturated soil should be taken into consideration. As the ratio of the length of tank to its breadth is greater than 2, the long walls will be designed as cantilevers and the top portion of the short walls will be designed as slab supported by long walls. Bottom one meter of the short walls will be designed as cantilever slab. Comparative Study on the Design of Rectangular and Circular Concrete Water Tanks Structural Layouts: The rectangular and circular walls were considered to be propped cantilevers. Each of the propped cantilevers was made rigidly fixed to its base slab and was expected to be drawn inward at the top by the wall/top slab connecting reinforcements; in response to the outward hydrostatic loading on the wall. This was put in view based on the fact that continuity reinforcement must be provided at corners and at member-junctions to prevent cracking. The base slabs were typically a double overhanging single-spanned continuous slab, with wall point load and its applied fixed end moment at each overhang end. And the top slabs were laid out to be either two-way spanning or simply supported as stated by Anchor. The tank dimensions were deduced by the application of the related formula for solid shapes‟ volume calculations. Therefore, (L x B x H) for cuboid (or cube) was used for the rectangular tank and (π x R2 x H) for cylinder was applied for the circular tank; where L, B, H and R are Length, Breadth, Height and Radius respectively. For each tank, the preliminary member sizing was done for the walls, base slab and top slab. 27
Water free-board was also provided for the possible volume increase above the require capacity in order to limit or check the overflow of the tanks in accordance with recommendations by BS 8007 (1987), and Reynolds and Steedman (1988). This was practically allowed to ease the reinforcing and construction of joints. Wall Loading: The average water force or load, P in kN per meter width of the rectangular tank walls under flexural tension was derived as a point or concentrated load by calculating the areas of the triangular pressure diagrams of the water content on the walls, to be (ρH) x H/2, where ρ is the water density. By the centroidal consideration of loading of the pressure diagram, one-third distance from the base, up each wall, was chosen as the point of application of the concentrated load. The circular tank wall would be clearly in a state of simple hoop tension and its amount in kN per meter height of wall would be (ρH) x D/2. And it would still act at one-third distance from the base up each wall. The wall total working loads for both options were assumed purely hydrostatic. And the inclusion of wind load in the working load was purely made to be dependent on tank elevation above the ground level, but would always be applicable in the design of its support. The wind load’s application point, if considered, would be at one-half the tank’s height and acting against the lateral water force. Hence, the resultant lateral force, from the combination of the water force and wind force; if applicable, would be one-half way between the two forces, that is, five-twelfth of the tank’s height. For the purpose of this study, tanks elevated at 12 m and above were considered to be influenced by wind load. Base Slab Loading: For each of the water tank options, the base slab’s characteristic serviceability uniformly distributed load in kN/m per m run, was the sum of its dead 28
load; the concrete self weight and its finishes, and its live load; that is, the weight of water to be contained. And the serviceability point load in kN per meter run, acting on each of the base slabs, at the extremes of the overhangs was derived by adding up the wall dead load; i.e. the base projection’s weight and a calculated fraction of the top slab load. But some noticeable difference might be experienced in the calculations of the fractions of the loads from the rectangular and the circular top slabs. Top Slab Loading: The top slab uniformly distributed load, in kN/m per meter run was calculated by adding up its combined dead load; that is, concrete self weight, waterproof finish and its live load (for tank access), to derive the characteristic serviceability load. Factors of safety of 1.4 and 1.6 were applied to the combined dead and live loads respectively before their sum was made to achieve the required ultimate design load for the top slab. The ultimate requirement, that is, stability would dictate its design and serviceability requirements; basically, deflection would be checked (BS 8007, 1987) Structural Analyses: General: This entails the analyses of the loaded structural elements; walls, base and top slabs in order to determine their bending moments for the required design conditions. Serviceability loadings were considered for the general analysis to concentrate on crack width and reinforcement tensile stress limit except for top slab where this requirement would only be a check on the structural performance through measure of deflection. The maximum bending moment from the support and span for each condition was generally used and confirmed less than the moment of
29
resistance, Mu= 0.156 f bd 2 , where f is the 28-day concrete characteristic strength, b is one meter width of slab and d is the effective slab depth (BS 8110, 2007).
30
CHAPTER 3 3.ANALYSIS AND DESIGN 3.1 DETERMINATION OF FIELD DENSITY OF SOIL BY CORE CUTTER METHOD. AIM: To determine the field density of soil by core cutter method.
APPARATUS: Ø Cylindrical core cutter. Ø Steel rammer. Ø Steel dally. Ø Balance. Ø Moisture content cups. PROCEDURE: Ø Measure the height (h) and internal diameter (d) of the core cutter and apply grease to the inside of core cutter. Ø Weigh the empty core cutter (w₁). Ø Clean and level the place where density is to be determined. Ø Drive the core cutter, with steel dally on its top into the soil to its full depth with the help of a steel rammer. Ø Excavate the soil around the cutter with a crow bar and gently lift the cutter without disturbing the soil in it. 31
Ø Trim the top and bottom surface of the sample and clean the outside surface of the water. Ø Weigh the core cutter with soil (w₂). Ø Remove the soil from the core cutter, using a sample ejector and take a representative soil from it to determine the moisture content (w). OBSERVATION: Internal diameter of core cutter (D) =10cm Height of the core cutter (h) =13cm Volume of the core cutter (v) =1021.02cm² Specific gravity of the core cutter (G) =2.738 Empty weight of the cylinder (w₁) =1.004 kg Weight of the cylinder with soil (w₂) =4.570 kg CALCULATION: Field density=weight of soil Volume Volume=1021.02 cm² Field density=4.570-1.004 1021.02 =3.493 g/cc =34.93 KN/m. 32
3.2 FIXED FUNNEL TEST AIM OF THE TEST: To find the angle of repose of the soil sample.
MATERIALS REQUIRED: Ø Soil sample Ø funnel PROCEDURE: The material (sand) is poured through a funnel to form a cone .The tip of the funnel should be held close to the growing cone and slowly raised as the pile grows, to minimize the impact of falling particles. Stop pouring the material when the pile reaches a predetermined height or the base a predetermined width. Rather than attempt to measure the angle of the resulting cone directly, divide the height by half the width of the base of the cone. The inverse tangent of this ratio is the angle of repose. FORMULA USED:
Tan ø= Tan ø=
!""!#$%& #$(& )(*)+&,% #$(& (//1)
Ø=tan67 [
.
9 :
( )
]
33
CALCULATION: Table3.1 Fixed funnel test TRIAL
BASE(B)
HEIGHT(H)
ANGLE
OF
REPOSE (ø) 1
11.5
4.2
36°8ʹ50ʺ
2
11.3
4.1
35°58ʹ00ʺ
3
10.8
4.3
38°31ʹ50ʺ
Finally by taking average the angle of repose is found to be 37° for the taken soil sample. Angle of repose=37°.
34
3.3. DESIGN OF RECTANGULAR UNDERGROUND WATER TANK Capacity of water tank=200m3 Shape: Rectangular underground water tank Unit weight of soil=34.93 KN/m3 Angle of internal friction φ=37° Bearing capacity of soil = 230 KN/m2 Free board= .25 m Materials available: M20 grade of concrete, Steel- Grade 1. Characteristic Strengths σcb=7 N/mm2 σst=140N/mm2 σctb=1.7 N/mm2 m=13, j=.84 DIMENSION CALCULATIONS Required capacity= 200 m3 Assumed depth= 4 m Total height with free board= 4.25 m Area of tank in plane= 200 4= 50 m2 Use 10x5x4.25 m CONDSIONS OF LOADING L=10m, H=4.25m, B=5m ? / / -
>2 =
; A C.1A
7@ A
= 2 (Long wall)
= 1.17 < 2 (Short wall)
35
? -
=
7@ C.1A
= 2.35
Long wall span in one direction, Shot wall span in two directions. Roof slab in one direction only. ROOF SLAB ONE WAY Assuming thickness of wall = 300 mm Span of roof slab in the direction of bending =5.3 m Live load=1.5 KN/m2 Self weight(200mm) =.2x1x1x24= 4.8 KN/m2 Screeding = 1 KN/m2 Total load (w)= 7.3 KN/m2
BENDING MOMENT(BM) E
F.G
C
H
BM= xl2 =
x5.32 = 25.63 KN-m
DEPTH OF SLAB BM= 8.7bd2 d=
1A.IG∗7@@@ .HF∗7@@@
= 1.71 m
de=175mm, d=200mm
36
Amount of reinforcement At =25.63 ∗ 10^6 . 87 ∗ 140 ∗ 175 =1202 mm2 (At=
R *(S#%
)
Provide 12mm dia bars at 100 mm c/c Secondary reinforcement =
.7A 7@@
x 200 x 1000 = 300 mm2
Provide 6mm dia bars at 100 mm c/c
LONG WALL ? -
=
7@ C.1A
= 2.35 > 2
Wall spans in vertical direction only, Walls are assumed fixed at the base and supported at top. Case(i) Tank full dry earth outside Max water pressure = ww H = 10 x 4.25 =42.5 KN/m2 Max earth pressure = weH(
76TUV W 7XTUV W
)
= 34.93x4.25(
76TUV GF 7XTUV GF
)
=36.9 KN/m2 Net pressure on wall (P) = 42.5-36.9 = 5.6 KN/m2
37
Max negative BM (water face) Mw =
Y- : 7A
=
A.I∗C.1A: 7A
= 6.74 KN-m
Max positive BM (Earth face) Me =
Y- : GG.A
=
A.I∗C.1A: GG.A
= 3.01 KN-m
Case-(ii) Tank empty dry earth pressure outside Max earth pressure = weH(
76TUV W 7XTUV W
)
= 34.93x4.25(
76TUV GF 7XTUV GF
)
=36.9 KN/m2 Max negative BM (water face) Mw =
Y- : 7A
=
GI.Z∗C.1A: 7A
= 44.43 KN-m
Max positive BM (Earth face) Me =
Y- : GG.A
=
GI.Z∗C.1A: GG.A
= 19.89 KN-m
Table.3.2 BM at water face and earth face. Case
BM water face KN-m
BM earth face KN-m
1
6.74
3.01
2
19.89
44.43
38
Thickness of wall on cracking stress Consideration Resisting moment Mr =
[( : S+%[ I
7
44.43x106 = x1000xd2x1.7 I
d=395.99mm provide 400mm de=400mm d=440mm REINFORCEMENT DETAILS FOR LONG WALL Case(i) Tank full dry earth outside At required for –ve BM A t=
RE S#% *(
=
I.IF∗7@\ 7C@∗.HC∗C@@
= 141.79 mm2
Provide 12mm dia bars at 300 mm c/c At required for +ve BM A t=
R& S#% *(
=
G.@7∗7@\ 7C@∗.HC∗C@@
= 63.98 mm2
Provide 12 mm dia bars at 400 mm c/c Case (ii) Tank empty dry earth outside 39
At required for –ve BM A t=
RE S#% *(
=
CC.CG∗7@\ 7C@∗.HC∗C@@
= 944.5 mm2
Provide 12mm dia bars at 115 mm c/c At required for +ve BM A t=
R& S#% *(
=
7Z.HZ∗7@\ 7C@∗.HC∗C@@
= 422 mm2
Provide 12 mm dia bars at 250 mm c/c Provide reinforcement details of Case(ii) Secondary reinforcement At =
.G 7@@
x 440 x 1000 = 1320 mm2
Provide 10mm dia bars at 60 mm c/c SHORT WALL BM VERTICAL DIRECTION Case(i) Mv=0.083wh2(
] ]X7
)
K=0.375 from the graph Mv=0.083x5.6x4.252(
.GFA .GFAX7
)=2.28KN/m
Max –ve moment (water face)=.89x2.28=2.0292KN/m 40
Max +ve moment(earth face)=.65x2.28=1.482KN/m Case(ii) Mv=0.083x36.9x4.252(
.GFA .GFAX7
)=15.09KN/m
Max –ve moment (water face) =.89x15.09=13.43KN/m Max +ve moment (earth face) =.65x15.09=9.808KN/m BM HORIZONTAL DIRECTION Case(i) Mh= Mh=
.@IF∗E- : (^X7) .@IF∗A.I∗C.1A: (.GFAX7)
= 6.82 KN/m
-ve moment at corner (water face) =.57Mh=.57x6.82=3.88KN-m +ve moment at center (earth face)=.43Mh=.43x6.82=2.93KN-m
Case(ii) Mh= Mh=
.@IF∗E- : (^X7) .@IF∗GI.Z∗C.1A: (.GFAX7)
= 44.95KN/m
-ve moment at corner (water face) =.57Mh=.57x44.95=25.62KN-m
41
+ve moment at center (earth face)=.43Mh=.43x44.95=19.32KN-m DIRECT TENSION IN SHORT WALL p=42.5KN/m TB =
C1.A∗7 1
=21.25KN
Maximum moment in short wall occurs in Case (ii) Thickness of the side wall 7 I
∗ _` 1 abc_=25.62x106 N/mm2
d2 =
1A.I1∗7@\ ∗I 7@@@∗7.F
d=300.7 mm How ever use the same thickness as the long wall that is de=400mm d=440mm MAIN REINFORCEMENT FOR THE SHORT WALL Steel required for Max bending moment at corner (water face ) At =
1A.I1∗7@\ 7C@∗.HC∗C@@
= 544.64 mm2
Provide 12 mm dia bars at 200 mm c/c Steel required for Max bending moment at center (earth face )
42
At =
7Z.G1∗7@\ 7C@∗.HC∗C@@
= 410.7 mm2
Provide 10 mm dia bars at 160 mm c/c Secondary reinforcement A t=
@.G 7@@
x440x1000=1320mm2
Provide 10mm dia bars at 60 mm c/c BASE SLAB d 10 = = 2 e 5 Spans in one direction only Case(i)Tank full and dry soil outside In this case the water pressure on base slab will be concentrated by the soil pressure below it. Loads Weight of the roof = 24x5.88x10.88=1535.38KN Weight of side walls=2x(10.44+5.44)x4.25x24x.44=1425.38KN Total weight =1535.38+1425.38=2960.76KN Base slab dimensions =6.88x11.88 Soil reaction below base=
[email protected] I.HH∗77.HH
43
=36.33KN/m
I.HH
BM at center of the slab(water face)=36.22x
1
x(
A.CC 1
–
I.HH C
)
=124.59KN/m GI.GG∗@.F1
BM at support(earth face)=
1
=13.03KN/m
Case(i) -ve BM at base due to loads on the side wall (water face )=19.89KM-m Net max BM at center (produces tension on the water face) = 124.59+6.74 =131.33KN-m Net Max BM at support (produces tension on the water face) =13.03-6.74 =6.29KN-m Case(ii) Tank empty dry soil outside BM due to Self weight of roof and side walls and center(water face)=124.59KN-m At support=13.03KN-m BM at the base due to soil pressure (earth face) =44.43KN-m Net moment at center of the slab (Produces the tension on the outer face) =124.59-44.43=80.16KN-m Net BM at the support =44.43+13.03=57.46KN-m
44
Table 3.3 BM at center and at supports Case
BM at center
BM at support
1
131.33KN-m
6.29KN-m
2
80.16KN-m
57.46KN-m
Thickness of the slab on cracking stress consideration 7 I
xbxd2xσctb=131.33
d=
7G7.GG∗I 7@@@∗7.F
=463.51mm
de=470mm ; d=520mm Main reinforcement Case(i) A t=
7G7.GG∗7@\ 7C@∗.HC∗CF@
= 2376.06 mm2
Use 16 mm dia bars at 80 mm c/c steel at support (water face) A t=
I.1Z∗7@\ 7C@∗@.HC∗CF@
=113.8 mm2
Use 16mm dia bars at 100 mm c/c Case(ii) A t=
AF.CI∗7@\ 7C@∗.HC∗CF@
= 1039.58 mm2 45
Use 10 mm dia bars at 80 mm c/c Secondary reinforcement At=0.2% of cross sectional area (d>450mm) A t=
@.1 7@@
x520x1000 = 1040 mm2
Use 10 mm dia at 150 mm c/c.
46
Fig(3.1)Reinforcement details of plan
47
Fig(3.2)Reinforcement details of long wall and short wall 48
CHAPTER 4 4. CONCLUSION Thus rectangular underground water tank with a capacity of 2,00,000 liters is planned, designed, and manually analyzed for Sri Shakthi Institute of Engineering and technology. In this project we analyzed all materials behavior that are used for water storage and found that concrete tanks can be effectively used for water storage. The other details of reinforcement used, Concrete mixture, Symbols used, Tables, Diagrams and plan are shown in the project. This project helped us to gain sufficient knowledge about the planning, Design and analyze of rectangular underground concrete water tanks.
49
CHAPTER 5 5.REFERENCE • Dayaratnam P. Design of Reinforced Concrete Structures. New Delhi. Oxford & IBH publication.2000 • Vazirani & Ratwani. Concrete Structures. New Delhi. Khanna Publishers.1990. • Sayal & Goel. Reinforced Concrete Structures. New Delhi. S. Chand publication.2004. • D.Krishnamurthy, Structural Design and Drawing (volume 2) . • IS 456-2000 CODE FOR PLAIN AND REINFORCED CONCRETE • IS 3370-1965 CODE FOR CONCRETE STRUCTURES FOR HE STORAGE OF LIQUIDS
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