COMPARISON BETWEEN COLUMN SUPPORTED ESR

AND SHAFT SUPPORTED ESR

Prof. K. A. Parmar Prof. A. R. Gandhi (Faculty Guide) (Head of the Department)

GUJARAT TECHNOLOGICAL UNIVERSITY

PROJECT- I (User Defined Problem)

GROUP ID: 68470

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Team Members

Sr. No. Name of Student Email ID Enrollment No.

1. Bhola Aniket aniketbhola1996@gmail.com 130280106014

2. Chaudhari Marut marutchaudhary1995@gmail.com 130280106020

3. Patni Mo. Aamir patniaamir62@gmail.com 130280106091

4. Shrimali Biren shrimalibiren@gmail.com 130280106113

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Index

Sr. No. Content Slide No.

1 Acknowledgement 04

2 Abstract 05

3 Introduction 07

4 Failure of Shaft Staging 10

5 Review of Damage Observed to Shaft Staging 11

6 Proposed Design Forces and Response Reduction Factor 14

7 Conclusion 16

8 Future Scope 18

9 PSAR-1 to 5 19

10 References 24

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Acknowledgement

• We express our sincere appreciation to our project guide Prof. K. A. Parmar,

Assistant Professor of Civil Engineering Department, L. D. College of Engineering,

whose encouragement, guidance and support from the initial to the final level has

enabled us to develop a good understanding of the subject.

• Besides, we would like to thank Gujarat Technological University for providing their

invaluable guidance and for providing an environment to complete our project

successfully.

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Abstract

• Due to enormous need by the public, water has to be stored and supplied according

to their needs. Water demand is not constant throughout the day. It fluctuates hour to

hour. In order to supply constant amount of water, we need to store water. So to meet

the public water demand, water tank need to be constructed. Storage reservoirs and

overhead tanks are used to store water, and similar liquids. These “floating” storage

tanks reduce peak pumping rates, stabilize pressures, and increase reliability.

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Abstract

• The project deals with the design and estimation of intze tank each of with shaft

staging and beam column staging concluding it with comparison of both types of

tank. The comparison concludes the economical design within which it includes the

structural design, analysis, and detailing of structure which could be used for detail

estimation of both the type of water tank, and appropriate suggestion is given in this

project. Analysis of tanks is about the same in both column-beam and shaft staging.

• This project gives in brief, the design of liquid retaining structure (Elevated circular

water tank with domed roof and conical base) using working stress method.

Elements are design in working stress method.

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Introduction

• For large capacity storage overhead tanks, circular tanks are found economical. Intze

tank is a solution for such tanks, where domes are used in place of level slabs.

• A typical intze tank as shown in fig. 1-1 consists of:

(1) Top dome (cover roof) (6) Bottom spherical dome

(2) Top ring beam B1 (7) Bottom circular ring beam B3

(3) Side walls (circular) (8) Staging- columns and bracings

(4) Bottom ring beam B2 (9) Foundation

(5) Conical dome

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Introduction

• Domes are economical than flat floors for large spans. The bottom slab is divided into

conical dome and spherical dome in such a way that the inward thrust due to conical

dome on ring beam B3 gets balanced by the outward thrust of the spherical dome.

• The inclination of conical dome is usually 45° to 55° with the vertical so as to obtain

the net thrust as hoop compression and not the hoop tension.

• The conical dome is used to reduce the diameter of the spherical dome. The diameter of

the bottom spherical dome is usually 65% to 75% of the diameter of the tank. Figure

indicates the usual dimensions of the intze tank.

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[Intze Tank: Components and Dimensions]

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Failure of Shaft Staging

• Current designs of circular shaft-type staging of elevated water tanks are extremely

vulnerable under earthquake forces. In 2001 Bhuj earthquake, another illustration of this

vulnerability had been seen when a many water tank with shaft stagings suffered damage as

distant as 100 km from the epicentre. Shaft type stagings contains poor ductility of thin shell

sections and in addition to that it has lack of redundancy of load paths and toughness.

• Lateral strength analyses of number of damaged shaft stagings clearly shows that all of them

are either met or exceeded the requirements of IS: 1893(1984), however, they were all found

to be deficient when compared with requirements of IBC in similar seismic exposure

conditions. IS: 1893(1984) design forces are inexcusably low for these systems which do not

have enough ductility and redundancy.

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Review of Damage Observed to Shaft Support

• Bhachau water tank (200 m3) developed the tension-flexural cracks upto the one-third height of the staging. Severe cracking at the junctions of the first two lift.

• Cracks are through the shell thickness as seen from inside the shaft of Anjar Nagar Palika Tank (1000 m3)

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Review of Damage Observed to Shaft Support

• Cracks in staging of tank repaired by injecting the epoxy. This tank in Morbi (500 m3), 80 km away from epicenter, was empty at the time of the earthquake

• Collapsed water tank in Chobari (265 m3) village about 20 km from epicenter. The tank was approximately half full during the earthquake event

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List of Water tanks affected or collapsed in Gujarat

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Proposed Design Forces and Response Reduction Factor

• Recently revised version of IS: 1893/1(2002) provides the following relation for the

design base shear Vb and seismic weight W (referred as Ah, design horizontal

seismic coefficient):

Vb/W = (Z/2) x (Sa/g) x (I/R)

where, Z = seismic zone factor

I = an importance factor

R = response reduction factor

(Sa/g) = average response acceleration coefficient.

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Proposed Design Forces and Response Reduction Factor

• A value of R for elevated tanks structures to be used with above equation is currently not

available as Part 2 of IS: 1893 concerning with liquid tanks is still under preparation. A value

of R equal to 2 provides practically safe estimate of the expected seismic demand for eight

shaft supporting structures of Kachchh region affected in Bhuj earthquake. Further, it also

compares very well with the 2000 IBC design forces in a similar seismic exposure conditions.

• The Zone factor was taken as 0.36 as specified for Seismic Zone V of the Kachchh region, and

a value of 1.5 was assumed for importance factor as specified in the old version of IS: 1893.

Since the codal forces are specified at working stress level, the spectral ordinates were

multiplied by the typical load factor of 1.5 to bring it upto ultimate stress level.

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Conclusion

• The current design parameters of the Indian seismic codes for elevated tanks result in

extremely vulnerable shaft-type supporting structures as evidenced in the 2001 Bhuj

earthquake. Supporting shafts developed flexural-tension cracks were observed in tanks as

far as 100 km away from the epicentral regions, despite the fact that most had lateral strength

far greater than that specified by IS: 1893(1984). The analysis of the flexural-tension

cracking strength, ultimate-flexural strength, and ultimate-shear strength of a sample of the

damaged shaft supports clearly indicate that code design forces are currently being greatly

underestimated.

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Conclusion

• A response reduction factor is equal to 2 in the new base shear formula of new version of

IS:1893/1 (2002) appeared to provide a reasonable level of safe design forces for the

elevated tanks, and these forces are also agreed well with the forces specified in IBC (2000)

for the similar seismic exposure conditions. The value of response reduction factor as 2 can

be used for inverted pendulum type shaft-supported elevated tank structures in the IS:

1893/2, which concerns with liquid retaining tanks.

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Future Scope

• We will Design and analyse both the types of elevated tanks separately, i.e., column

supported tank and shaft supported tank.

• For this purpose first we will design them manually and after that we will perform

software modelling.

• We will prepare a detailed estimate of both the type of elevated tanks. For this

purpose we will make quantity sheets and abstract sheets.

• We will make comments over the feasibility, adaptability and performance of the

design.

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PSAR- 1: Elevated Water-Tank Floor & Construction Thereof (US5241797 A)

• The floor for a water tank on a tank support-tower is made up of a dome of steel bar-RC over a lower steel base in a

central part encircling the center access the tower, dome being surrounded by and continuous with annular rim also of

the concrete reinforced with steel bars but over the circular steel beam at base of the dome. The studs are welded from

concrete area into steel base and steel beam.

• Floor is built by first centering steel base between the bottom section of a tank support tower placed over there to start

and center access tower and then constructing a tank support tower by the slip form or by the jump form method, while

raising steel floor base, lifting the circular steel beam & placing it on the top of the tank support tower, installing lower

portion or cone of elevated water tank above the tank support tower, securing steel base of a dome in place of the

circular steel beam.

• After positioning steel reinforcing bars where concrete is to be poured & welding the studs in to the steel base and steel

beam, pouring and curing concrete there over. The floor is bounded on outside by cone or lower portion of the tank.

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PSAR- 2: Multi Purpose Elevated Water-Storage Facility (US4486988 A)

• Multi-purpose elevated water storage facility of present invention includes a pillar supporting the

elevated water storage tank which has the flute portion, there by rendering overall facility more

efficiently and aesthetically pleasing. The fluted portion of tank includes a plurality of the fluted

plates, and is coupled to pillar by a box girder in preferred personification Additional stiffening rings

are also included, and additional floor can be included above water stored in the tank.

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PSAR- 3: Water-Tank (US7487619 B2)

• The blending of geometrical shapes combines the best features of pipe tank (standpipe) and a

common multi legged elevated tank. The bowl of an elevated water tank has been designed as top

section of a standpipe or tube tank. This type of design provides the nearly constant pressure and

volume that a true elevated tank provides and also a large volume of water for emergency purposes.

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PSAR- 4: Water-Tank Floating-Support (CN103507621 A)

• This invention relates to improvement on a water tank support, and it provides a water tank floating-support

which is very simple in structure, reliable in connection and also capable of enhancing the stability. The water

tank floating-support comprises a pair of stand-columns and a base, stand columns are in an L-shape, and L-

shaped stand columns are rigidly connected to upper portions of the two ends of base.

• The base is provided with at least two vertical springs and at least two horizontal springs are arranged on

inner side face of each L shaped stand-column. The vertical springs & the horizontal springs, all of which can

absorb the vibration energy are additionally arranged between two sides of water tank and the stand-columns.

• When a car is driven in rugged road section, two sets of springs can absorb vibration energy, the water tank is

prevented from being damaged and the service life of the water tank is prolonged. The water tank floating-

support is simple in structure, practical and reliable.

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PSAR- 5: Seismic-Design Method for External Water-Tank Structure of Outer Containment of Nuclear Power-Plant with Fluid Structure Interaction

Considered (CN103886138 A)

• The invention relates to a seismic design method for an external water tank structure of an outer containment of a nuclear

power plant with fluid-structure interaction considered.

• According to the method, different finite element mesh description modes are adopted according to different material

properties of the structure and water, the wall of the plant and the water tank structure are simulated by a Lagrange mesh

mode, the water portion is simulated by a Euler mesh mode, and a fluid-structure interaction analysis method and an explicit

dynamics analysis method are adopted to really simulate interaction of the water in an external tank and the structure under

the seismic action from the aspects of different material mesh properties, mutual contact relation, a fluid state equation, a

structural dynamics equation and the like.

• By the method, the problem about analysis of interaction of the water and the structure of the water tank structure complicated

in shape and low in liquid level clearance under the seismic action can be solved.

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References• Dr. H. J. Shah (2014), REINFORCED CONCRETE VOL. II (ELEMENTARY

REINFORCED CONCRETE), ISBN: 9788192869223, CHAROTAR PUBLISHING HOUSE PVT. LTD.

• IS: 11992-1995, Indian Standard CRITERIA FOR DESIGN OF RCC STAGING FOR OVERHEAD WATER TANKS (First Reprint OCTOBER 1998), UDC628.134 :624.953.014.45, BUREAU OF INDIAN STANDARDS.

• CED38 (7811) P (2011), CRITERIA FOR DESIGN OF RCC STAGING FOR OVERHEAD WATER TANKS (First Revision of IS 11682), BUREAU OF INDIAN STANDARDS

• Durgesh C. Rai (2002), Review of Code Design Forces for Shaft Supports of Elevated Water Tanks, IIT Roorkee.

• SP: 34(1987), HANDBOOK ON CONCRETE REINFORCEMENT AND DETAILING, Bureau of Indian Standards, New Delhi.

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References• IS: 13920(1993), DUCTILE DETAILING OF REINFORCED CONCRETE

STRUCTURES SUBJECTED TO SEISMIC FORCES - CODE OF PRACTICE, Bureau of Indian Standards, New Delhi.

• IS: 1893(1984), CRITERIA FOR EARTHQUAKE RESISTANT DESIGN OF STRUCTURES, Bureau of Indian Standards, New Delhi.

• IS: 1893(2002), CRITERIA FOR EARTHQUAKE RESISTANT DESIGN OF STRUCTURES, PART 1: GENERAL PROVISIONS AND BUILDINGS, Bureau of Indian Standards, New Delhi.

• Images are taken from https://images.google.com/

• Patents are taken form https://patents.google.com/

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We are really very thankful to Prof. K.A. Parmar for their invaluable

guidance and their help in every difficult situation we came across.

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