Economics of R.C.C. Water tank Resting over Firm Ground vis-a-vis Pre-stressed Concrete Water Tank Resting over Firm Ground

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ByMS. SNEHAL R. METKAR(P.G. STUDENT)DEPARTMENT OF CIVIL ENGINEERING(STRUCTURAL ENGINEERING IIND YEAR)P.R.M.T OF TECH. & RESEARCH, BADNERA-AMRAVATISANT. GADGE BABA (AMARAVATI) UNIVERSITY (MAHARASHTRA)COUNTRY INDIA – 444701

GUIDED BYProf A. R. Mundhada(PROFESSOR)DEPARTMENT OF CIVIL ENGINEERING,P.R M.I.T.R., BADNERA, AMRAVATI.MAHARASHTRA, INDIA-4444701,

AbstractWater tanks are used to store water and are designed as crack free structures, to eliminate any leakage. In thispaper design of two types of circular water tank resting on ground is presented. Both reinforced concrete (RC) andprestressed concrete (PSC) alternatives are considered in the design and are compared considering the total cost ofthe tank. These water tank are subjected to the same type of capacity and dimensions. As an objective function withthe properties of tank that are tank capacity, width &length etc.

A computer program has been developed for solving numerical examples using the Indian std. Indian StandardCode 456-2000, IS-3370-I,II,III,IV & IS 1343-1980. The paper gives idea for safe design with minimum cost of thetank and give the designer the relationship curve between design variable thus design of tank can be moreeconomical ,reliable and simple. The paper helps in understanding the design philosophy for the safe andeconomical design of water tank.

KeywordsRigid based water tank, RCC water tank, Prestressed Concrete, design, details, minimum total cost, tank capacity

I. INTRODUCTIONStorage reservoirs and over head tanks are used to store water, liquid petroleum, petroleum products and similarliquids. The force analysis of the reservoirs or tanks is about the same irrespective of the chemical nature of theproduct. In general there are three kinds of water tanks-tanks resting on ground Underground tanks and elevatedtanks. Here we are studying only the tanks resting on ground like clear water reservoirs, settling tanks, aerationtanks etc. are supported on ground directly. The wall of these tanks are subjected to pressure and the base issubjected to weight of Water.

In this paper, both types of reinforced concrete and prestesses concrete water tanks resting on ground monolithicwith the base Are design and their results compared. These tanks are subjected to Same capacity and dimensions.Also a computer program has been developed for solving numerical examples using IS Code 456-200IS-1343-1984,IS 3370-Part I,II,III,IV 1965 & IS Code 1343-1980. From the analysis it is conclude that for tank having largercapacity (greater than 10 lakh liter) prestesses concrete water tank is economical.

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Objective• To make the study about the analysis and design of water tank.• To make the guidelines for the design of liquid retaining structure According to IS code.• To know about design philosophy for safe design of water tank.• To develop program for water tank to avoid tedious calculations.• To know economical design of water• This report is to provide guidance in the design and construction of circular priestesses concrete using tendons

Previous ResearchFrom the review of earlier investigations it is found that considerable work has been done on the method of analysisand design of water tanks.

Tanetal. [1]:- (1993) presented the minimum cost design of reinforced concrete cylindrical water tanks based on theBritish Code for water tanks, using a direct search method and the (SUMT). The cost function included the materialcosts of concrete and steel only. The tank wall thickness was idealized with piecewise linear slopes with themaximum thickness at the base.

Thakkar and Sridhar Rao [2] (1974), discussed cost optimization of non cylindrical composite type prestressedconcrete pipes based on the Indian code.

Al-Badri [3] (2005) presented cost optimization of reinforced concrete circular grain silo based on the ACI Code(2002). He proved that the minimum cost of the silo increases with increasing of the angle of internal frictionbetween stored materials, the coefficient of friction between stored materials and concrete, and the number ofcolumns supporting hopper . Al-Badri (2006) presented the minimum cost design of reinforced concrete corbelsbased on AC I Code (2002). The cost function included the material costs of concrete, formwork and steelreinforcement. He proved that the minimum total cost of the corbel increases with the increase of the shear span,and decreases with the increase of the friction factor for monolithic construction.

Hassan Jasim Mohammed [4] studied the economical design of concrete water Tanks by optimization method. Heapplied the optimization technique to the structural design of concrete rectangular and circular water tank,considering the total cost of the tank as an objective function with the properties of the tank viz. tank capacity, widthand length of the tank, unit weight of water and tank floor slab thickness as design variables. From the study heconcluded that an increased tank capacity leads to increased minimum total cost of the rectangular tank butdecreased minimum total cost for the circular tank. The tank floor slab thickness constitutes the minimum total costfor two types of tanks. The minimum cost is more sensitive to changes in tank capacity and floor slab thickness ofrectangular tank but in circular type is more sensitive to change in all variables. Increased tank capacity leads toincrease in minimum total cost. Increase in water depth in circular tank leads to increase in minimum total cost.

Abdul-Aziz & A. Rashed [5] rationalized the design procedure for reinforced and prestressed concrete tanks so thatan applicable Canadian design standard could be developed. The study investigates the concept of partialprestressing in liquid containing structures. The paper also includes experimental and analytical phases of total ofeight full scale specimens, representing segments from typical tank walls, subjected to load and leakage tests. Inanalytical study a computer model that can predict the response of tank wall segments is described and calibratedagainst the test results. The proposed design procedure addresses the leakage limit state directly. It is applicable forfully prestressed, fully reinforced and partially prestressed concrete water tanks. The conclusions that are drawn areas follows:-

• A design method based on limiting the steel stress, does not produce consistent crack or compression zone depthsunder the application of prestressing nor under a combination of axial load and moment.

• A design method based on providing a residual compressive stress in concrete dose not utilizes non-prestressedreinforcement effectively.

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• Relaxing the residual compressive stress requirement permits a more efficient design. The stresses in non-prestresssed steel are higher, but remain below yield under service load. Therefore, less reinforcement is required.

• Load eccentricity significantly affects the behavior of the prestressed concrete sections. The behavior with a smallload eccentricity, less than about half the thickness, the section may be treated as a flexure member.

• The ratio of non prestressed steel to prestressed steel in partially prestressed concrete section has a significanteffect on the member serviceability and strength. Choosing the ratio such that both non-prestress and prestressedsteel reach their strength simultaneously utilizes both types of steel at the ultimate limit state effectively.

• Increasing the wall thickness is very effective in increasing the capacity of the section and improving itsserviceability by increasing the compression zone depth and reducing the deformations.

Chetan Kumar Gautam [6] Highlights the point named “Comparison of Circular Reinforced Concrete andPrestressed Concrete Underground Shelter”. In his paper, design of two types of large circular underground sheltersis presented. The shelters are made of precast concrete sections. Both RC and PSC alternatives are considered inthe design and compared. The shelters are subjected to same type of external loadings and support conditions. Thestudy conclude that the feasibility of using the vertical casting process of making the modules of shelters as it issuitable for manufacturing of large diameter pipes. He also suggested that the incorporation of fibers, specially steelfibers improves a host of properties of concrete, including its crack resistance, flexural strength, ductility, etc. Thus,the possibility of incorporating fibers in concrete shelter may be explored.

II DESIGN PHILOSOPHYFor R.C.C. water tankFor Prestresed Concrete water tankFor R.C.C StructurePermissible stresses in concrete• For resistance to cracking:-Design of liquid retaining structure is different from R.C.C. structures. As it requires that concrete should not crackand hence tensile stresses in concrete should be within permissible limit.(i.e. TYPE-I structure).A reinforcedconcrete member of liquid retaining structure is design on the usual principle ignoring tensile resistance of concretein bending. accordingly it should be ensure that tensile stresses on the liquid retaining face of the equivalentconcrete section dose not exceed the permissible tensile strength of concrete as given in table1.

Grade ofconcrete

Permissible stress Shear=(Q/bjd)(N/mm^2)

Direct Tension(?ct)(N/mm^2)

Tension due to Bending(?cbt)(N/mm^2)

M15 1.1 1.5 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

Table 1(Permissible Compressive Stresses In Calculations Relating To Resistance To Cracking)

• For strength calculation

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In strength calculations the permissible Concrete stresses shall be in accordance with Table1. Where the calculatedshear stress in concrete a lone exceeds the permissible value, reinforcement acting in conjunction with diagonalcompression in the concrete shall be provided to take the whole of the shear.

Permissible Stresses In Steel• For resistance to cracking.When steel and concrete are assumed to act together for checking the tensile stress in concrete for avoidance ofcrack, the tensile stress in steel as in table 2will be limited by the requirement that the permissible tensile stress inthe concrete is not exceeded so the tensile stress in steel shall be equal to the product of modular ratio of steel andconcrete, and the corresponding allowable tensile stress in concrete.

• For strength calculationsIn strength calculations the permissible stress shall be as given in table 2.

TYPE OF STRESS IN STEEL REINFORCE MENT PERMISSIBLE STRESSES IN N/mm2

Plain round mildsteel bars

High yield strength deformedbars(HYSD)

1)Tensile stresses in the members under directtension(?s)

115 150

2) Tensile stress in members in bending(?st)

On liquid retaining face of members 115 150

On face of away from liquid for members less than225mm

115 150

On face away from liquid for members 225mm ormore in thickness

125 190

3) Tensile stresses in shear reinforcement(?sv)

For members less than225mm in thicknessFor members 225mm or more in thickness

115 150

125 175

Table 2 (Permissible Stresses In Steel Reinforcement For Strength Calculation)

Design RequirementGenerally M30 grade of concrete should be used Design Mix (1:1*1/2:3)Steel reinforcement should not lessthan0.3% of the gross section shall be provided in each direction Floors:-floor may be constructed of concrete withnominal % of reinforcement smaller than provided in table 1.they are cast in panels with sides not more than 45mand with contraction or expansion joints in between..In such cases a screed or concrete layer(M10) not less than75mm thick shall placed first on the ground and covered with a sliding layer of bitumen paper to destroy the bondbetween the screed and the floor.

Minimum Cover:- 35mm(both the faces).Minimum Reinforcement:-Overall .24% of total cross section should be provided.Walls:-1) provision of joints

( a ) Where it is desired to allow the walls to expand or contract separately from the floor , or to prevent moments atthe base of the wall owing to fixity to the floor sliding joints may be employed.

( b) The spacing of vertical movement joints should be as discussed. while the majority of these joints may be of the4/15

partial or complete contraction type , sufficient joints of the expansion type should be provided to satisfy therequirements given in article.

2)Pressure on wall(a) In liquid retaining structures with fixed or floating covers the gas pressure developed above liquid surface shall beadded to the liquid pressure .

(b)When the wall of liquid retaining structure is built in ground, or has earth embanked against it ,the effect of earthpressure shall be taken in to account .

III Design stepes:• Calculate diameter and height of water tank• Assumed suitable thickness• Calculate designed constants• Calculate hoop tension, maximum bending moment by using IS 1370 part IV.• Calculate hoop steel(provide in the form of rings per meter height)• Check the assume thickness with given permissible values of tensile stresses of concrete in direct tension for thegiven grade of concrete.• Check of thickness for bending• Provide vertical steel• Design base slab• Draw details

detail

IV PRESTRESSING DEFINITIONIntroduction of compressive stresses to a structural member with high-strength steel that counteract the tensilestresses resulting from applied loads

Prestressed ConcretePre-Tensioned (cast off-site in beds- precast members)Post-Tensioned (cast on-site in place)

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All types of structure can be built with reinforced and pre-stressed concrete: columns, piers, walls, slabs, beams,arches, frames, even suspended structures and of course shells and folded plates.• Tanks• Foundation panels• Poles• Modular block retaining wall system• Wall panels• Concrete units• Slabs• Roofing and flooring• Lintel and sunshade• Beams• Columns girders

Tanks:-In the construction of concrete structures for the storage of liquids, the imperviousness of concrete is an importantbasic requirement. Hence, the design of such construction is based on avoidance of cracking in the concrete. Thestructures are prestressed to avoid tension in the concrete. In addition, prestressed concrete tanks require lowmaintenance. The resistance to seismic forces is also satisfactory. Prestressed concrete tanks are used in watertreatment and distribution systems, waste water collection and treatment system and storm water management.Other applications are liquefied natural gas (LNG) containment structures, large industrial process tanks and bulkstorage tanks. Strand Wrapped circular pre-stressed concrete tanks are long life liquid storage structure withvirtually no maintenance. Concrete construction makes for a substantial, sturdy tank structure that easily contain theinternal liquid pressure while comfortably resisting external forces such as earthquake, wind.

Pre-stressed concrete is the most efficient material for water tanks and coupled with the circular shape, eliminatesall stress conditions. By placing the steel of the pre-stressed strands in tension and the concrete in compression,both materials are in an ideal states and the loads are uniformly distributed around the tank circumference.

Properties1) Low maintenance can be enjoyed throughout the life as these are built with concrete, durable material that nevercorrodes and does not require coatings when in contact with water or the environment.

2) Pre-stressing counteracts the differential temperature and dryness loads that a tank core wall experience. Thetank walls are wet on the inside and dry on outside and the temperature varies between the two sides. If not properlyaccounted for, these moisture and temperature differential will cause a tank wall to bend and crack. Counteractthese force in both the vertical and horizontal direction and diminish subsequently the cracking and leaking

3) Tanks are very ductile, enabling to withstand seismic forces and varying water backfill.

4) Tanks utilize material efficiently – steel in tension, concrete in compression

5) Pre-cast tanks can store or treat anything from potable water to hazardous waste to solid storage bins.

6)Storage capacities can range from 0.4 to 120 mega liters7) Diameters of the tank can vary up to 90 m

V Design philosophyA. Loads: Circumferential prestressing also typically causes vertical bending moment from other loading condition.B. Freeboard: freeboard should be provided in the tank wals to minimize earthquake- induced hydrodynamic effectson a flat roof.C. Wall: The design of the wall should be based on elastic cylindrical shell analysis, considering the effects of

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prestressing, internal loads and other external loads.cast in place concrete walls is usually priestessescircumferentially with high-strength strand tendons placed in ducts in the wall .the wall may be priestesses withbonded and unbounded tendons. Vertical prestessed reinforcement near the center of the wall thickness, or verticalnon prestessed reinforcement near each face, may be used. Non priestesses reinforcement may be providedvertically in conjunction with vertical prestressing.

Precast concrete walls usually consist of precast panels curved to the tank radius with joints between panels filledwith high-strength concrete. the panels are post-tensioned circumferentially by high strength strand tendons. thetendons maybe embedded within the precast panels or placed on the external surface of the wall and protected byshortcreat .the wall panels may be prestessesd vertically with pretensioned strands or post-tensioned tendons.nonprestesses reinforcement may be provided vertically with or without vertical prestressing.

Construction MethodologyThe construction of the tanks is in the following sequence. First, the concrete core is cast and cured. The surface isprepared by sand or hydro blasting. Next, the circumferential prestressing is applied by strand wrapping machine.Shotcrete is applied to provide a coat of concrete over the prestressing strands. A few photographs are provided forillustration.

IS: 3370 (Code of Practice for Concrete Structures for the Storage of Liquids) provides guidelines for the analysisand design of liquid storage tanks. The four sections of the code are titled as follows.Part 1: General RequirementPart 2: Reinforced Concrete StructuresPart 3: Prestressed Concrete StructuresPart 4: Design TablesThe following types of boundary conditions are considered in the analysis of the cylindrical wall.a) For base: fixed or hingedb) For top: free or hinged or framed.1)For baseFixed: When the wall is built continuous with its footing, then the base can be considered to be fixed as the firstapproximation.

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Hinged: If the sub grade is susceptible to settlement, then a hinged base is a conservative assumption. Since theactual rotational restraint from the footing is somewhere in between fixed and hinged, a hinged base can beassumed. The base can be made sliding with appropriate polyvinyl chloride (PVC) water-stops for liquid tightness.

2) For topFree: The top of the wall is considered free when there is no restraint in expansion.Hinged: When the top is connected to the roof slab by dowels for shear transfer, the boundary condition isconsidered to be hinged.

The hydrostatic pressure on the wall increases linearly from the top to the bottom of the liquid of maximum possibledepth. If the vapour pressure in the free board is negligible, then the pressure at the top is zero. Else, it is added tothe pressure of the liquid throughout the depth. The forces generated in the tank due to circumferential prestress areopposite in nature to that due to hydrostatic pressure. If the tank is built underground, then the earth pressure needsto be considered.The hoop tension in the wall, generated due to a triangular hydrostatic pressure is given as T = CTw H RiThe bending moment in the vertical direction is given asM = CMwH3

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The shear at the base is given by the expression V = CVw HWhere,CT = coefficient for hoop tensionCM = coefficient for bending momentCV = coefficient for shearw = unit weight of liquidH = height of the liquidRi = inner radius of the wall.

The values of the coefficients are tabulated in IS:3370 – 1967, Part 4, for various values of H2/Dt, at different depthsof the liquid. D and t represent the inner diameter and the thickness of the wall, respectively. The typical variations ofCT and CM with depth, for two sets of boundary conditions are illustrated. The roof can be made of a domesupported at the edges on the cylindrical wall. Else, the roof can be a flat slab supported on columns along with theedges. IS:3370 – 1967, Part 4, provides coefficients for the analysis of the floor and roof slabs.

Design steps• Calculate diameter and height of water tank• Assumed suitable thickness• Calculate designed constants• Calculate hoop tension, maximum bending moment by using IS 1370 part IV.• Check the assume thickness with given permissible values of tensile stresses of concrete in direct tension for thegiven grade of concrete.• Actual circumferential prestress i.e. actual direct compressive stress (fc)• Provide circumferential steel , Provide vertical steel• Check for ultimate collapse and cracking• Non prestressing steel /untensioned steel• Design base slab• Draw detail

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Comparison of R.C.C. water tank and Prestrssed water tankThe tanks to be consider having some common data such as the tanks are having same capacity, same diameter,same height, same grade of concrete i. e. (M40) & (M50), the thickness of tank floor should be taken either 150mmor equal to the wall thickness(if greater than 150mm) for RCC water tank and minimum thickness for priestessesconcrete water tank is 120mm.We consider tank capacity for both the cases (i.e. RCC & Priestesses) reimagingfrom 1000 m3 to 9000 m3. for both the grade of concrete i.e. (M40 & M50). The result so obtained as given infollowing table3

Schedule For RCC Water Tanks & Prestressed Concrete Water Tanks Estimate Details

CAPACITY GRADE OFCONCRETE

COST OF P.C. WATERTANK

% OFCOST

COST OF R.C. C.WATERTANK

m3 Rs Rs

1000 M40 2056116 11.47 1844521

M50 2101677 9.43 1920546

2000 M40 2777828 -20.33 3486806

M50 2845004 -21.69 3633328

3000 M40 3811166 -24.87 5072773

M50 3897242 -26.22 5282492

4000 M40 5268049 -21.06 6673611

M50 5404513 -22.50 6973950

5000 M40 6696401 -18.14 8180441

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M50 6852226 -20.01 8567341

6000 M40 7901981 -22.35 10177486

M50 8143194 -23.45 10637885

7000 M40 8988532 -19.34 11144740

M50 9255833 -21.42 11778868

8000 M40 1169380 -15.02 13761735

M50 1199296 -16.63 14385223

9000 M40 1277439 -16.45 15290975

M50 1309013 -18.05 15975177

NOTE: (Negative value of % saving indicates that prestressed concrete tank is economical than RCC water tankand vice-à-versa)

Figure 1: Variation Of Cost With Capacity Of Water Tank & Grade Of Concrete

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Figure 2 Variation Of Cost For Both Type Of Water Tank With Same Grade Of Concrete(M40)

Figure 3 Variation Of Cost For Both Type Of Water Tank With Same Grade Of Concrete(M50)

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Figure 4 Variation of % of saving for given capacity with given grade of concrete(M40)

Figure 5 Variation of % of saving for given capacity with given grade of concrete(M50)

The aim of this paper is to compare the cost of R.C.C. water tanks resting over firm ground with the cost ofPrestressed concrete water tanks. In India at least, most of the small & medium sized water tanks are constructed inRCC. Senior engineers and those in the know maintain that prestressed concrete water tanks are not worth tryingfor smaller capacities. Besides cost, other reason may be that prestressed concrete construction involves skilledlabor & supervision. Furthermore, prestressing is a closely guarded technology in this country & information is notavailable that easily.

There is no clear-cut definition of “Medium Size”. The thumb rule passed on in the field from one generation ofengineers to the next, fixes a value around 10 lac liters. Therefore, this study encompasses tanks from 10 lac litercapacity to 90 lac liter capacity. A couple of cases of both varieties were designed manually. Design & Estimationprograms were developed in MS EXCEL for both RCC & Prestressed concrete. The programs were finalized after a

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number of trial runs & corrections.

Results obtained are compiled in figures numbered 1 to 5 & Table numbered 3. D/H ratio for all the tanks ismaintained at 4 based on the recommendations of the Preload Engineering Company of the US, a world leader inthe field of prestressed concrete water tanks. It should be noted that an increase in tank wall thickness results indecreased flexural steel in case of RCC. However, in case of prestressed concrete, an increased thickness leads toa greater prestressing force & consequently more prestressing steel. Thus, increased thickness leads to increasedcost in case of prestressed concrete.

Table3 presents the total cost of each tank along with the % difference. “+” means costlier prestressing & “-“ meanscheaper prestressing. As the tank capacity increases, the cost of tank increases. But the concept of “economics ofscale” holds good i.e. the cost of a tank of 20 lac liter capacity is less than double the cost of a tank of 10 lac litercapacity. Similarly, the cost of a tank of 90 lac liter capacity is less than 9 times the cost of a tank of 10 lac litercapacity. It can be clearly established that the grade of concrete hardly makes any difference in the costing.Because of its nature, the water tank design is never an impending or boundary line design. The factor of safety ishigh & the actual stresses are much lower than the permissible ones. An increased permissible stress for a highergrade of concrete hardly makes any difference to the final outcome.

Finally, a study of the same Table3 confirms that the RCC tank is cheaper only for 10 lac liter capacity. For highercapacities, prestress concrete tank is always cheaper by @ (20 +/- 5) %. This is because the thickness of an RCCtank increases many-folds for higher capacities. Thickness in fact seems to be an important criterion even forprestressed tanks. An increased thickness leads to an increased prestressing force. More steel is required togenerate this higher prestressing force resulting in higher cost.

CONCLUSION RCC tanks are cheaper only for smaller capacities up to 10-12 lac liters. For bigger tanks, Prestressing is thesuperior choice resulting in a saving of @ 20%.

REFERENCES:1 Tanetal (1966) “Minimum Cost Design Of Reinforced Concrete Cylindrical Water Tanks Based On The BritishCode For Water Tanks, Using A Direct Search Method And The (SUMT). European Journal Of Scientific ResearchISSN 1450 -216XVol.49No.4(2011),pp.510-520.2 Thakkar and Sridhar Rao (1974)”Cost Optimization Of Cylindrical Composite Type Prestesses Concrete PipesBased On The Indian Code” Journal of Structural Engineering 131: 6.3 Al-Badri (2005) “Cost Optimization Of Reinforced Concrete Circular Grain Silo Based On ACI Code(2002)American Concrete Institute Structural Journal, May- June 2006.4 Hassan Jasim Mohammed “ Economical Design Of Water Tanks” European Journal Of Scientific Research ISSN1450 -216XVol.49No.4(2011),pp.510-520.5 Abdul-Aziz & A. Rashed “Rational Design Of Priestesses And Reinforced Concrete Tanks” Dept Of Civil &Environmental Engineering. University Of Alberta, Edmontan, Alberta Canada T6g-267.Eurojournals Publishing.Inc.20116 Chetan Kumar Gautam “Comparison Of Circular RC And PSC Underground Shelters” The Indian ConcreteJournal April 2006.7 Precon “Designing Of Circular Prestressed Concrete Tanks To The Industry Standards Of The AWWA And ACI”journal of priestesses concrete institute vol.12,apr. 19678 IS: 456-2000. Indian Standard Code of Practice For Reinforced Concrete.9 IS 3370-Part I,II,III,IV 1965 & IS Code 1343-1980 Indian Standard Code of Practice For Liquid RetainingStructures.10 IS: 1343- 1980. Indian Standard Code of Practice For Prestressed Concrete (First Revision).11 Lin, T.Y, and NED H BURNS “Prestressed Concrete”, Third Edition , John Wiley & Sons[ ASIA] Pt e Ltd. ,Singapore 129809.

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12 N. Krishna Raju, 2007. “Prestressed Concrete”, Fourth Edition, Tata McGraw- Hill Company Ltd., New Delhi.13 A.K Jain Reinforced concrete (vol-1,vol-2)14 B.N Dutta, 2009 “Estimating and Costing In Civil Engineering”, Twenty- Sixth Revised Edition UBS Publishers’Distributors Pvt. Ltd. New Delhi.15 Current Schedule of Rates (CSR), 2010-2011, for Public Works Region, Amravati.16 Schedule Of Rates Year 2010-2011, For Maharashtra Jeevan Pradhikaran, Nagpur Region17 Bundy , B. D. , 1984. ” Basic Optimization Methods “, Edward Arnold Publishers.18 Fintel, M., ,1974. ” Handbook of Concrete Engineering”, USA.19 Gray ,W.S. and Manning ,G.P., 1960. ” Concrete Water Tower, Bunkers, Silos and Other Elevated Structures” ,3rd ed. , London.20 Manning, G.P., 1973. ” Reinforced Concrete Reservoirs and Tanks,1st ed. London.

We at engineeringcivil.com are thankful to MS. SNEHAL R. METKAR for submitting this useful information to us.We hope this will be of great help to all those who are looking forward for Economics of R.C.C. Water tank Restingover Firm Ground vis-a-vis Pre-stressed Concrete Water Tank Resting over Firm Ground.

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