SEISMIC BEHAVIOUR OF ELEVATED RC CIRCULAR ......III. SEISMIC ANALYSIS OF CIRCULAR WATER TANK WITH SHAFT STAGING Capacity of tank is 200 kilolitres and is supported on R.C shaft staging

DOI: 10.23883/IJRTER.2017.3525.4Q54J 1

SEISMIC BEHAVIOUR OF ELEVATED RC CIRCULAR

WATER TANK OF DIFFERENT SHAFT

HEIGHTS

Kinjarapu Lakshmu Naidu1, Surapu Ramlal2 1,2Department of Civil Engineering, Aditya Institute of Technology and Management

Abstract— Water tanks are important public utility and industrial structures. Elevated water tanks

should be competent of keeping the expected performance during and after earthquake. During

the earthquake in India, R.C.C elevated water tanks are heavily damaged. This might be due to

improper geometrical selection of staging in many cases. The main aim of this study is to

understand the seismic behaviour of elevated RC circular water tank by considering five

different shaft staging heights with consideration of impulsive and convective water masses

inside the container. The analysis is carried out as per one mass model and two mass model by

considering four seismic Zones from Zone –II to Zone –V. In this study hydrodynamic forces and

sloshing wave heights are analysed for all the five different shaft staging heights.

Keywords— Base shear, Base moment, Hydrodynamic pressure, Impulsive mass, Convective mass,

Sloshing wave height.

I. INTRODUCTION

Exports are activities of selling goods to other countries. Indonesia’s main export capital is natural

wealth. From natural wealth owned, can be produced various kinds of export goods. Goods that can

be exported are goods that are in demand and needed by overseas buyers. Indonesian export

commodities consist of petroleum and gas (oil and gas) as well as non-oil and gas. Indonesia is one of

oil and gas exporter to destination country. Some of the countries that are export destinations of

Indonesia include the United States, Germany, Japan, China, Taiwan, and Australia. The country that

the main export destination of Indonesia is the United States. This study aims to analyze the value of

Indonesia’s oil and gas exports by using computer science. One of the analysis process that can be

done is forecasting the value of oil and gas exports in indonesia.

1.1 FAILURES OBSERED IN SHAFT STAGING WATER TANKS

The cylindrical shaft-type staging developed circumferential flexural tension cracks near the

base. Similar damages to support structures had been observed in past earthquakes and recently in

the Bhuj earthquake of 26th January 2001, as shown in Fig.1 (a) which is typical of the

damage sustained to a large number of water tanks of capacities ranging from 80 m3

to 1,000 m3

and as far away as 125km from the epicentre Fig.1 (b) shows a collapsed water tank in the

epicentre tract of the Bhuj earthquake.

Figure 1 (a) Damaged water (b) Collapsed water tank

International Journal of Recent Trends in Engineering & Research (IJRTER) Volume 03, Issue 11; November - 2017 [ISSN: 2455-1457]

@IJRTER-2017, All Rights Reserved 2

II. LITARATURE AND REVIEW

Housner (1963) proposed two mass model for elevated tank which is more appropriate and is being

commonly used in most of the international codes including draft code for IS: 1893 (part - II).The

pressure generated within fluid due to the dynamic motion of the tank can be separated into the

impulsive and convective parts. When a tank containing liquid with a free surface is subjected to

horizontal earthquake ground motion, tank wall and liquid are subjected to horizontal

acceleration. Kalani and Salpekar (1978) their study is regarding different staging configuration,

which give a comparative study between conventional and matrix methods of analysis for staging of

overhead water tanks. S.C. Dutta, et al, (2000), studied torsion response of RC elevated water tanks

and have failed during past earthquakes owing to large torsion response. Considerable torsional

response may occur due to accidental eccentricity if the uncoupled torsional and lateral natural

periods of the tanks are closely spaced. Durgesh (2003).The performance of elevated water

tank in7.7 magnitude Bhuj earthquake of January 26th

, 2001 was studied. Many of the elevated

water tanks which were collapsed during the Bhuj earthquake were studied.

The conclusions arrived from them were, strength analysis of a few damaged shaft type staging‟s

clearly shows that all of them either met or exceeded the strength requirements of IS:1893-1984,

however, they were all found deficient when compared with requirements of the International

Building Code.

III. SEISMIC ANALYSIS OF CIRCULAR WATER TANK WITH SHAFT STAGING

Capacity of tank is 200 kilolitres and is supported on R.C shaft staging. In this study, five

different heights of staging 8, 11, 14, 17 and 20 m are considered. Details of various components are

as shown in Table1.

Table 1 Sizes of various components

Figure 2 Details of shaft staging water tank

Component Size (mm)

Roof slab 130 thick Wall 300 thick

Floor slab 200 thick

Circular ring beam 500×600 Gallery 110 thick

Thickness of shaft 180 thick

Diameter of tank 8120

Diameter of shaft 6480



3.1 LUMPED MASS MODEL METHOD

(When the tank is empty condition and full condition)

Table 2 Base shear

Table 3 Base moment

Figure 3 Base shear (Tank empty condition)

0

50

100

150

200

250

II III IV V

Ba

se s

hea

r(k

N)

Zone

Chart-1

8m

11m

14m

17m

20m

Zone Base

shear

(kN)

(8 m)

Base

shear

(kN)

(11m)

Base

Shear

(kN)

(14 m)

Base

shear

(kN)

(17

m)

Base

shear

(kN)

(20m

) Empt

y

Ful

l

Emp

ty

Full Empt

y

Full Empt

y

Full Emp

ty

Full

II 28 6

8

3

9

9

1

44 101 48 109 5

7

118

III 56 13

5

7

9

182 88 202 98 218 114 236

IV 70 16

9

9

7

232 109 252 122 273 143 294

V 111 27

0

156 371 175 403 195 436 228 470

Zone

Base

moment

(kN_m)

(8 m)

Base

moment

(kN_m)

(11 m)

Base

moment

(kN_m)

(14 m)

Base

moment

(kN_m)

(17 m)

Base

moment

(kN_m)

(20 m) Empt

y

Full Empt

y

Full Empt

y

Full Empt

y

Full Empt

y

Full

II 273 661 494 1157 686 1584 911 2040 1235 2553

III 545 1313 998 2313 1371 3167 1823 4047 2470 5105

IV 681 1643 1235 2949 1713 3957 2278 5096 3087 6381

V 1079 2625 1976 4719 2742 6333 3644 8160 4939 1020

9



Figure 4 Base shear (Tank full condition)

Figure 5 Base moment (Tank empty condition

Figure 6 Base moment (Tank full condition)

3.2 Hydrodynamic Pressure

Table 4 Hydrodynamic pressure on tank wall for staging height 8 m, 11 m in (N/m2)

(y)

m

y/h

Zone II Zone III Zone IV Zone V

8 m 11 m 8 m 11 m 8 m 11 m 8 m 11 m

0 0 0 0 0 0 0 0 0 0

1 \0.22

2

26.84 33.04 53.69 66.08 67.1

1

82.6

0

107.38 132.1

6 2 0.44

4

46.89 57.93 93.97 115.66 117.4

6

144.5

7

187.94 231.3

2 3 0.66

6

60.42 74.36 120.85 148.73 151.0

6

185.9

2

241.70 297.4

7 4 0.88

8

67.15 82.65 134.31 165.31 167.8

9

206.6

4

268.63 330.6

2 4.5 1 68.01 83.70 136.02 167.41 187.5

8

209.2

6

300.12 334.8

2

0

100

200

300

400

500

II III IV V

Ba

se s

hea

r (k

N)

Zone

Chart-2

8m

11m

14m

17m

20m

0

1000

2000

3000

4000

5000

6000

II III IV V

Mo

men

t (k

N_

m)

Zone

Chart-3

8m

11m

14m

17m

20m

0

2000

4000

6000

8000

10000

12000

II III IV V

Mo

men

t (k

N_

m)

Zone

Chart -4

8m

11m

14m

17m

20m



Table 5 Hydrodynamic pressure on tank wall for staging height 14 m, 17 m in (N/m2)

(y)

m

y/h


14

m

17

m

14 m 17 m 14 m 17 m 14 m 17 m

0 0 0 0 0 0 0 0 0 0

1 0.22

2

37.1

6

39.3

3

74.3

3

78.4

6

92.9

2

98.0

1

148.6

7

156.9

3 2 0.44

4

65.0

5

68.6

7

130.1

1

137.3

4

162.6

4

171.5

6

260.2

3

274.6

9 3 0.66

6

83.6

6

88.3

1

167.3

3

176.6

2

209.1

6

220.6

2

334.6

6

353.2

5 4 0.88

8

92.9

8

98.1

5

185.9

7

196.3

1

232.4

7

245.2

1

371.9

5

392.6

2 4.5 1 94.1

7

99.4

0

188.3

4

198.8

0

235.4

2

248.3

3

376.6

8

397.6

0 Table 6 Hydrodynamic pressure on tank wall for staging height 20 m in (N/m2)

Table 7 Hydrodynamic pressure on bottom of the tank for various heights of staging horizontal distance

3.765 m from the centre

(y) m y/h Zone II Zone III Zone IV Zone

V 0 0 0 0 0 0

1 0.222 41.298 83.59 103.2

4

165.19

2 2 0.444 72.28 144.5

7

180.7

2

289.15

3 0.666 92.96 185.9

2

232.4

0

371.84

4 0.888 103.32 206.6

4

258.3

0

413.28

4.

5

1 104.63 209.2

6

261.5

8

418.53

Height

of

staging

Pressure on bottom of the

tank(N/mm2) Zone II Zone III Zone IV Zone

V 8 m 188.17 3

7

6

.

3

5

470.44 752.7

1 11 m 188.17 376.35 470.44 752.7

1 14 m 211.70 423.40 529.25 846.8

0 17 m 223.46 446.13 558.12 893.2

4 20 m 235.22 470.44 588.00 940.8

9



Figure 7 Hydrodynamic pressure for 8 m




0

0.2

0.4

0.6

0.8

1

1.2

0 200 400y

/h

Hydrodynamic Pressure (N/m2 )

Chart -5Zone II Zone III Zone IV Zone V

0

0.5

1

1.5

0 200 400

y/h


Chart-6Zone II Zone III Zone IV Zone V

0

0.2

0.4

0.6

0.8

1

1.2

y/h


Chart 7Zone II Zone III Zone IV Zone V

0

0.2

0.4

0.6

0.8

1

1.2

0 200 400

y/h






Figure 12 Hydrodynamic pressure bottom of the tank

3.3 TWO MASS MODEL METHOD (When the tank is empty condition and full

condition)

Table 8 Base shear

Zon

e

Base

shear

(kN)

(8 m)

Base

shear

(kN)

(11m)

Base

shear(kN

) (14 m)

Base

shear

(kN)

(17

m)

Base

shear

(kN)

(20 m)

Empty Full Empt

y

Full Empt

y

Full Empt

y

Full Empt

y

Full

I

I

76 106 101 141 128 304 134 313 141 323

III 121 147 164 226 204 485 215 500 226 515

IV 182 205 246 339 305 730 322 753 \338 776

V 274 298 368 508 458 1094 483 1129 507 1163

Table 9 Base moment

Zon

e

Base

moment

(kN-m)

(8 m)

Base

moment

(kN-m)

(11 m)

Base

moment

(kN-

m) (14

m)

Base moment

(kN-m) (17

m)

Base

moment

(kN-

m) (20

m) Empt

y

Full Empt

y

Full Empt

y

Full Empty Full Empt

y

Full

II 735 873 1285 1852 1998 4955 2374 6039 3059 7180 III 1176 1413 2080 2962 3197 7908 3798 9638 4894 1246

0 IV 1763 2120 3120 4442 4795 1191

0

5697 14514 7340 1725

8 V 2659 3177 4669 6662 7192 1785

0

8545 21770 \1101

0

2587

7

0

0.2

0.4

0.6

0.8

1

1.2

0 200 400 600y

/h



0

200

400

600

800

1000


Pre

ssu

re N

/mm

2

Zone

Chart -9

8 m

11 m

14 m

17 m

20 m



Figure 13 Base shear (tank empty condition)

Figure 14 Base shear variation (tank full condition)

Figure 15 Base moment (tank empty condition)

0

100

200

300

400

500

600

II III IV V

Ba

se s

hea

r (k

N_

m)

Zone

Chart -10

8m

11m

14m

17m

20m

0

200

400

600

800

1000

1200

1400

II III IV V

Ba

se s

hea

r (k

N_

m)

Zone

Chart-11

8m

11m

14m

17m

20m

0

2000

4000

6000

8000

10000

12000

II III IV V

Mo

men

t (k

N_

m)

Zone

Chart -12

8m

11m

14m

17m

20m



Figure 16 Base moment (tank full condition)

From the above results Base shear and Base moment increases when height of staging is increases from

8 m height of staging to 20 m height of staging.Base shear and Base moment increase from Zone –II to

Zone –V. Base shear is lower value for the tanks are having Zone-II when compared to Zone-V. Base

shear is greater value for Zone –V and staging height is 20 m.

3.4 Hydrodynamic pressure

Table 10 Hydrodynamic pressure values at the base

Table 11 Hydrodynamic pressure values at the base of the wall for 8 m, 11 m staging height of the tank.

0

5000

10000

15000

20000

25000

30000

II III IV VM

om

ent

(kN

_m

)Zone

Chart -13

8

12

14

17

20

(y) m “ Piw” values for different zones in N/mm

2

y/h Qiw Zone 2 Zone 3 Zone 4 Zone 5

0 0 0.776 3562.6

7

5686.5

8

8564.1

3

12846.1

9

1 0.222 0.738 3388.2

1

5408.1

1

8144.7

5

12217.1

2

2 0.444 0.623 2860.2

4

4565.3

8

6875.5

8

10313.3

7

3 0.666 0.431 1978.7

5

3158.3

9

4756.6

2

7134.93

4 0.888 0.163 748.34 1194.4

7

1798.9

0

2698.36

4.5 1 0 0 0 0 0

(y)

m “ Piw” values for different zones in N/mm

2

y/h Qiw Zone 2 Zone 3 Zone 4 Zone 5

0 0 0 0.776 1708.34 2730.54 4095.81

1 0.222 0.222 0.738 1624.32 2596.25 3894.38

2 0.444 0.444 0.623 1370.11 2189.94 3284.91

3 0.666 0.666 0.431 947.88 1515.05 2272.58

4 0.888 0.888 0.163 357.60 571.58 857.38

4.5 1 1 0 0 0 0



Figure 17 Hydrodynamic pressure (14 m, 17 m, 20 m)

Figure 18 Hydrodynamic pressure (8 m, 11 m)

Figure 19 Impulsive hydrodynamic pressure on the base slab

Figure 20 Fig. 20 Convective hydrodynamic pressure on wall

0

0.2

0.4

0.6

0.8

1

1.2

0 5000 10000 15000 20000

y/h


Chart -14

Zone 2 Zone 3 Zone 4 Zone 5

0

0.2

0.4

0.6

0.8

1

1.2

0 2000 4000 6000

y/h


Chart -15Zone 2 Zone 3 Zone 4 Zone 5

0

2000

4000

6000

8000

II III IV V

Hy

dro

dy

na

mic

pre

ssu

re (

N/m

2)

Zone

Chart -1611m, 8m

20 m,17 m,14 m

0

100

200

300

400

500

600

II III IV V

Pre

ssu

re N

/mm

2

zone

Chart-17 Pressure



Table 12 Convective Hydrodynamic Pressure

Table 13 Impulsive hydrodynamic pressure on the base slab (y= 0)

Table 14 Convective pressure at the base of wall

Figure 21 Convective Hydrodynamic Pressure at the base the wall

Table 15 Convective pressure on top of base slab

Zone Pressure on slab(N/m

2)

Zone – V 540

Zone – IV 360

Zone – III 240

Zone – II 150

0

500

1000

1500

2000

II III IV V

Pre

ssu

re N

/mm

2

Zone

Chart-18 Pressure

Zone Pressure on wall(N/m

2)

Zone – V 540

Zone – IV 360

Zone – III 240

Zone – II 150

ZONE Staging height

20m,17m, 14mN/m2

Staging height

11m N/m2

Staging height

8m N/m2

Zone – V 6560 3080 1837

Zone – IV 4380 2040 1225

Zone – III 2900 1360 823

Zone – II 1820 850 508

Zone Pressure on

wall(N/m2) Zone – V 1480

Zone – IV 990

Zone – III 660

Zone – II 410



Figure 22 Convective Hydrodynamic Pressure on top the base slab

Table 16 Pressure Due to Wall Inertia

Zone Pressure on wall (N/m

2)

Zone – V 440

Zone – IV 320

Zone – III 200

Zone – II 120

Figure 23 Pressure due to wall inertia

Table 17 Pressure Due to Vertical Excitation

Zone Pressure on wall (N/m2)

II 2200

III 3530

IV 5300

V 7940

Figure 24 Pressure due to vertical excitation

0

200

400

600

II III IV V

Pre

ssu

re N

/mm

2

Zone

Chart-19 Pressure

0

100

200

300

400

500

II III IV V

Pre

ssu

re N

/mm

2

Zone

Chart -20 Pressure

0

2000

4000

6000

8000

10000

II III IV V

Pre

ssu

re N

/mm

2

Zone

Chart -21 Pressure



III CONCLUSION

Seismic analysis is carried out for different shaft staging heights which are 8 m, 11 m, 14m, 17m

and 20m respectively. The analysis is carried out as per one mass model and Two mass model by

considering four seismic Zones from Zone –II to Zone –V and also analysis is carried out for

hydrodynamic pressure and sloshing wave height.

From the results, following conclusions have been made.

1. The base shear increases from Zone –II to Zone –V for any height of staging and also with

increases of staging height base shear also increases.

2. The base shear increases about 55-60% in one mass model from tank empty to tank full

condition.

3. The base shear increases about 25-30% in 8 m and 11 m height of staging and 50-60% in 14

m, 17 m, and 20 m Two mass model from tank empty to tank full condition.

4. The base shear increases about 55-65% for Tank empty condition in single mass model to

Two mass model.

5. The base shear increases about 55-65% for Tank full condition in single mass model to two

mass model.

6. The base moment increases from Zone –II to Zone –V for any height of staging and also with

increases of staging height base moment also increases.

7. The base moment increases about 55-60% in One mass model from tank empty to tank full

condition.

REFERENCES I. BIS 1984 IS: 1893-1984 Criteria for earthquake resistant design structures, Bureau of Indian Standards,

New Delhi.

II. BIS 2002 IS: 1893 (Part-1) -2002 Criteria for Earthquake Resistant Design of Structures, General Provisions

of Buildings and Bureau of Indian standards, New Delhi, India. (Fourth Revision)

III. BIS 2002 Draft IS: 1893-2002 (Part-II, Liquid Retaining Tanks) Criteria for Earthquake Resistant Design of

Structures, Bureau of Indian standards, New Delhi, India.

IV. Bojja.Devadanam , M K MV Ratnam , Dr.U RangaRaju, “Effect of Staging Height on the Seismic Performance

of RC Elevated Water Tank”, International Journal of Innovative Research in Science, Engineering and

Technology, January 2015,

V. Issue 1, Vol. 4, PP. 18568- 18575.

VI. Chirag N. Patel and H. S. Patel, ―Former Failure Assessments of RC Elevated Water Tanks: Literature

Review‖, GIT-Journal of Engineering and Technology

VII. (ISSN 2249 - 6157), 2012.

VIII. G. W. Housner, “The Dynamic Behaviour of Water Tanks, Bulletin of the Seismological Society of America,

Vol.53, No.2, pp.381-387, Feb1963” IX. Housner, G.W., “Dynamic analysis of fluids in containers subjected to acceleration”, Nuclear Reactors

and Earthquakes, Report No. TID 7024, U.S. Atomic Energy Commission, Washington D.C, 1963.

X. 8.IITK-GSDMA guidelines for seismic design of liquid storage tanks.

XI. IS: 11682-1985, Criteria for Design of RCC Staging For Overhead Tanks (1985),Bureau of Indian Standards,

New Delhi.

XII. IS: 3370 (Part II) – 2009 code of practice for concrete structures for the storage of liquids part -II reinforced

concrete structures (First Revision).

Documents

SEISMIC BEHAVIOUR OF ELEVATED RC CIRCULAR ......III. SEISMIC ANALYSIS OF CIRCULAR WATER TANK WITH SHAFT STAGING Capacity of tank is 200 kilolitres and is supported on R.C shaft staging