International Journal of Engineering and Innovative Technology (IJEIT) Volume 1, Issue 5, May 2012

Comparison of Different Bearing Types Performance for Water Tank Kishor S. Sable, Jayashri S. Khose, Madhuri K. Rathi Abstract: For improvement of seismic performance of the structures base isolation technique is used. Application of bearing in between foundation and the base soil is one of method of base isolation. In this paper comparative study of three types of bearings viz. electrometric bearing, lead bearing and friction bearing for elevated water tank is done. Three cases of elevated water tank like tank full case, tank partially full and tank empty are studied. From experiment it is conclude that the friction type bearings are giving good performance in all cases of the water tank. Index Terms—Base Isolation, Bearing, Elevated water tank etc.

the use of shear walls, braced frames or momentresistant frames. However, these traditional methods often result in high floor accelerations for stiff buildings or large interstorey drifts for flexible buildings. Due to this, the building contents and non-structural components may suffer significant damage during a major earthquake, even if the structure itself remains basically intact. This is not tolerable for buildings whose contents are more costly and valuable than the buildings themselves. High-precision production factories are one example of buildings that contain extremely costly and sensitive equipment. Additionally hospitals, police and fire stations, and telecommunication canters are examples of facilities that contain valuable equipment and should remain operational immediately after an earthquake. b. Base Isolation Systems- When a structure is subjected to a strong earthquake, the system energy of the structure can be conceptually expressed as: KE + DE + SE = IE Where, KE=kinetic energy, DE = dissipated energy, which equals the sum of VE and HE, with VE denoting the viscous energy and HE the hysteretic energy; SE is the strain energy and IE the seismic input energy. B. Types of base isolator used for research: Elastomeric rubber bearing (EMB) Lead rubber bearing (LRB) Friction bearing (FPS) C. Modeling Of Structure Assumption Following assumptions are made for the structural system under consideration: 1. the superstructure is considered to remain within the elastic limit during the earthquake excitation. This is a reasonable assumption as the isolation attempts to reduce the earthquake which response in such a way that the structure remains within the elastic range. 2. The floors are assumed rigid in its plane and the mass is supposed to be lumped at each floor level. 3. The columns are providing the lateral stiffness. 4. The system is subjected to single horizontal component of the earthquake ground motion. 5. The effects of soil–structure interaction are not taken into consideration. Near fault motion effect is ignored .Restoring force (pounding effect) is neglected. . Harmonic ground motion effect, liquid structure interaction effect, after applying Base isolator base shear and bearing displacement effect on building and water tank is neglected.

I. INTRODUCTION A. General Many efforts have been taken by researchers to improve the seismic performance of the structure since last two decades. By introducing earthquake protection systems for structures, their response is improved when excited by earthquakes. This includes passive, active or semi active structures or hybrid devices. Also the base isolation technique is introduced for improvement in dynamic performance of structure. Base isolation may be done by introducing different types of bearings in the foundation & base soil. This can be achieved by providing rollers and /or spring in between foundation & base soil. In seismically base-isolated systems, the superstructure is decoupled from the earthquake ground motion by introducing a flexible interface between the foundation and the base of structure. Thereby, the isolation system shifts the fundamental time period of the structure to a large value and/or dissipates the energy in damping, limiting the amount of force that can be transferred to the superstructure such that inter-story drift and floor accelerations are reduced drastically. The matching of fundamental frequencies of base-isolated structures and the predominant frequency contents of earthquakes is also consequently avoided, leading to a flexible structural system more suitable from earthquake resistance from viewpoint. A part of the liquid moves independent of the tank wall motion, which is termed as 'convective' or 'sloshing' while another part of the liquid, which moves in unison with rigid tank wall is known as 'Impulsive mass'. II. METHODOLOGY A. EARTHQUAKE RESISTANCE DEVICES a. General-Conventionally-seismic design of building structures is based on the concept of increasing the resistance capacity of the structures against earthquakes by employing. For example,

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Structural model Fig. (a) Shows the idealized mathematical model of the base-isolated elevated water tank considered for the present study.

3 . 4 . 5 . 6 . 7 .

Fig.1 (A): Mathematical Model of Elevated Water Tank

8 .

III. DESCRIPTION OF STRUCTURE DESCRIPTION OF WATER TANKAn RC circular water container of 250 m3 capacities has internal diameter 8m and height 4m, container is supported on RC staging of 8 columns with horizontal bracings of 300 x 600 mm at three levels of 2.5m height. Staging conforms to ductile detailing as per IS 13920. Roof Slab 120 mm thick, Wall 200 mm thick, Floor Slab 200 mm thick, Gallery 110 mm thick, Floor Beams 250 x 600 mm, Braces 300 x 450 mm ,Columns 650 mm diameter. Density of concrete is 25 KN/m3, density of water is 1000kg/m3, modulus of elasticity E=25000 N/mm2, fck= 25 N/mm2, fe=415 N/mm2.The continuous liquid mass is lumped as sloshing, impulsive and rigid masses for tank full and tank half full are mc= 837KN and 636KN, mi= 982.85KN and 262.32KN mr =1004.142KN and 293.67 KN, respectively. The sloshing and impulsive masses are connected to the tank wall by corresponding equivalent springs having stiffness constants kc and kI, are 465.7 x10 3KN and 112.27 KN respectively. The effective stiffness kb and effective viscous damping ratio ξeff of elastomeric bearing, lead rubber bearing and friction pendulum system are 96.58 KN/m and 142.41 (0.2), 96.58 KN/m and 71.20(0.1), 136.0 KN and 142.41(0.2) respectively and coefficient of friction of friction pendulum system is µ =0.05. The weight of elastomeric bearing, lead rubber bearing and friction pendulum system are 1.0193 KN, 2.0059KN and 0.493 KN respectively. Density of rubber, lead and steel are 960 kg/ m3, 11340 kg/ m3 and 7800 kg/m3 respectively. A. Bearing Details of ESR Sr. No. 1 . 2 .

Table I: Bearing Details Elastom Lead Dimension of eric Isolated bearing Isolated Base Base Diameter of the 760 610 mm bearing mm Total height of 250 225 mm bearing/depth mm

9 .

Numbers of rubber layer Thickness of individual rubber layer Numbers of steel plates Thickness of individual plates Thickness of bottom and top plates Radius of curvature of spherical surface Diameter of lead core

23

18

-

8 mm

10 mm

-

17

-

2 mm

2.5 mm

-

25 mm

25 mm

-

-

-

1500 mm

-

-

22

160 mm

B. Displacement at top of the tank Case-I (Water tank full):

Table II: Displacement of tank (Water tank full) with different type of bearings and w/o Bearing w/o base Deflection in isolator(mm) Time isolator (sec) EMB LRB FPS (mm) 0 0 0 0 0 5 4.6414 9.467772 5.6806632 1.980294 10 13.073 6.917611 4.1505666 9.52783 15 8.0956 4.383712 2.6302272 -8.5977 20 4.364 4 0.12061 0.0723636 3.98168 25 3.0811 2.24724 1.3483458 6.588086 30 1.02376 1.215105 0.729063 1.69903 35 0.9657 0.163803 0.0982818 0.273852 40 0.48346 0.51303 0.3078162 2.4044 45 0.0927 0.05667 0.0339996 1.375981 50 0.45254 0.01022 0.0061344 1.02938 55 0.4406 0.87269 0.5236146 0.37586 60 0.0093 0.217929 0.1307574 1.332531 64 0.07043 0.007833 0.0046998 -0.0556

X axis – Time (s) Y axis - Displacement

FPS

500 mm 160 mm

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tank (full) height and difference in displacement of storey drift is less, The Water tank (full) top level displacement is influenced by the bearing displacement. Difference between displacement at base and at top level is less in with base isolator as compare to w/o base isolator .From this figure, it is observed that the lead bearing giving good performance as compare to other two types of bearing. Case-II (Water tank partially full):

Fig. 1.(b): Displacement –Time graph for tank (Water tank full) with different type of bearings and w/o Bearing

From Fig. 1. (b), it is obvious that elevated water tank displacement is more in without base isolator. The maximum displacement of tank is 30 mm for without isolator and nearly 10 mm to 15 mm for all types of isolator between 5 to 10 second, further the displacement is reduces with time and LRB shows better performance compare to EMB and FPS.

Table III: Mode shape of tank (Water tank full) with different type of bearings and w/o Bearing w/o Deflection in base isolator Storey base (mm) height isolator (m) EMB LRB FPS ( mm ) 0 0 6.114 3.6684 10.9149 1.5 4.7616 9.5481 5.72886 13.8566 4 14.0985 12.8706 7.72236 16.2525 6.5 23.3258 15.4735 9.2841 17.7165 9 28.132 16.6892 10.01352 18.2438 11.5 28.3909 16.7587 10.05522 18.2535 13.85 28.5632 16.8055 10.0833 18.2652 15.39 28.7735 16.8626 10.11756 18.8538

Table IV: Displacement of (Water tank partially full) with different type of bearings and w/o Bearing w/o base Deflection in isolator (mm) Time isolator (sec) EMB LRB FPS (mm) 0 0 0 0 0 5 5.940996 12.11875 2.534776 0.00261 10 8.854542 16.7339 0.01387 12.1956 15 5.611151 10.3624 0.03104 11.005 20 5.586432 0.15438 0.05006 5.09654 25 8.43275 3.94383 2.87647 0.07454 30 1.3104 18 1.555334 0.09503 2.17475 35 1.2361 0.209668 0.10682 0.350531 40 0.6188 34 0.65667 0.10506 3.07763 45 0.11864 0.07253 0.08054 1.761256 50 0.5792 49 0.01309 0.02194 1.317606 55 0.56398 1.11704 0.020321 0.4811 60 0.01187 0.278949 0.06356 1.70564 64 0.0901 54 0.010026 0.020007 0.07117

X axis – Time (s) Y axis - Displacement

Fig. 1.(c): Mode shape of tank (Water tank full) with different type of bearings and w/o Bearing

Fig. 1 (c) Shows, storey displacement of elevated water tank (full) without base isolator is increase according to the Water tank (full) height and difference in storey drift is more. Storey displacement of Water tank (full) with base isolator is decrease according to the elevated water

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Fig. 1 (d): Displacement –Time graph for (Water tank partially full) with different type of bearings and w/o Bearing

25 30 35 40

From Fig. 1 (d), it shows that elevated water tank (partially full) displacement is more in without base isolator. The maximum displacement of water tank is 40 mm for without isolator and nearly 10 mm to 15 mm for all types of isolator between 5 to 10 second, further the displacement is reduces with time and LRB shows better performance compare to EMB and FPS.

45 50 55

0.345964

0.108496

0.0650976

0.605238 0.961895 0.09283 0.84247 0.59242 0.22293

0.189802 0.30165 0.02911 0.26419 0.185783 0.0699 12

0.1138812 0.18099

0.052639 0.030571

0.016507 0.009586

0.0099042 0.0005752

-0.01766 0.158514 0.1114698 0.04194 72

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Table V: Mode shape of (Water tank partially full) with different type of bearings and w/o Bearing Deflection in base isolator (mm Storey w/o base ) height isolator (m) ( mm ) EMB LRB FPS 0 0 8.8653 5.319 15.827 1.5 6.904 13.845 8.307 20.092 20.44 11.19 4 18.66 23.566 5 77 33.82 13.46 6.5 22.436 25.688 2 2 9 40.79 24.199 14.52 26.45 41.16 11.5 24.3 14.58 26.468 7 13.8 41.41 14.62 24.368 26.485 5 7 1 15.3 41.72 24.451 14.67 27.338 9 2

64

1.750579 5.63561 4.20445 4.44125 1.376964 2.14939 0.117622 0.51455 0.505763

X axis – Time (s) Y axis - Displacement

Fig. 1 (f): Displacement –Time graph for w/o base isolator and Electrometric bearing of water tank (empty) at top

From Fig. 1 (f). Displacement-time graph, it is observed that displacement of the water tank (empty) is more in case of without isolator as compare to elastomeric bearing. The maximum displacement of Water tank (empty) is nearly 25 mm for without isolator and nearly 15 mm for friction pendulum system between 5 to 10 second.

Fig. 1 (e): Mode shape of (Water tank partially full) with different type of bearings and w/o Bearing

Case-III (Water tank empty):

Time (sec) 0 5 10 15 20

Table VI: Displacement of (Water tank empty) with different type of bearings and w/o Bearing w/o base Deflection in isolator isolator EMB LRB FPS (mm) 0 0 0 0 2.18598 0.68552 0.411312 9.096821 8.58201 2.691318 1.614709 12.5807 4.008793 1.257156 0.7544294 2.30341 0.423662 0.13286 0.079719 3.053869

Fig. 1 (g): Displacement –Time graph for (Water tank empty) with different type of bearings and w/o Bearing

From Fig. 1 (g), the maximum displacement of water tank is 25 mm for without isolator and

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nearly 5 mm to 10 mm for all types of isolator between 5 to 10 second, further the displacement is reduces with time and LRB shows better performance compare to EMB and FPS. Tanks without isolator having more displacement compare to tank with isolator.

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Table VII: Mode shape of (Water tank empty) with different type of bearings and w/o Bearing Deflection in base isolator (mm Storey w/o base ) height isolator (m) ( mm ) EMB LRB FPS 0 0 3.974 2.384 7.094685 1.5 3.095 6.206 3.724 9.00679 4 9.164 8.366 5.019 10.564125 6.5 15.162 10.058 6.035 11.515725 9 18.286 10.848 6.508 11.858 11.5 18.454 10.893 6.536 11.865 13.85 18.567 10.924 6.554 11.872 15.39 18.703 10.961 6.576 12.255

15 20 25

-21.9384

-16.084

40

-18.7744

-13.764

50 55 60 64

22.92633 31.13985 7.057658 16.65203 1.176066

-16.808 22.8308 -5.1744

86.7343 1.58365 13.6475 11.6793 14.2621 19.3716 4.39045

-12.208 0.86225

-10.358 0.73161

99.1250 1.80988 -15.597 13.3477 16.2995 22.1389 5.01766 -11.838 0.83612

.X axis – Time (s) Y axis – Acceleration in mm/s2

Fig. 1 (i): Acceleration –Time graph for (Water tank full) with different type of bearings and w/o Bearing

From Fig.1 (i), it is obvious that elevated water (full) tank acceleration is more in without bearing. The maximum acceleration of water tank (full) is 1m/ s2 for without isolator and nearly 0.5 m/ s2 to 0.75 mm/ s2 for all types of isolator between 5 to 10 second, further the acceleration is reduce with time and LRB shows better performance compare to EMB and FPS.

Fig. 1 (h) Shows, storey displacement of water tank (empty) without base isolator is increase according to the elevated water tank (empty) height and difference in storey drift is more. Storey displacement of Water tank (empty) with base isolator is decrease according to the Water tank (empty) height and difference in displacement of storey drift is less, The elevated water tank (empty) top level displacement is influenced by the bearing displacement. Difference between displacement at base and at top level is less in with bearing as compare to w/o bearing. Acceleration of Water Tank sat Top Case-I (Water tank full):

10

1.86644

35

45

Fig. 1 (h): Mode shape of (Water tank empty) with different type of bearings and w/o Bearing

Time (sec) 0 5

139.4255 2.545720

Table IX: Mode shape of (Water tank full) with different type of bearings and w/o Bearing Acceleration with bearing Storey w/o (mm/s2 ) height bearing (m) (mm/s2 ) EMB LRB FPS 0 0 80.114 63.668 100.915 1.5 200.315 180.382 165.65 230.857 4 330.82 238.39 222.325 380.305 6.5 480.325 380.324 375.89 420.305 9 630.325 605.35 575.265 600.311 11.5 780.3 627.3 585.356 635.38 13.85 840.3 690.958 632.658 712.368 15.39 1074.14 787.703 668.354 763.833

Table: VIII Acceleration of (Water tank full) with different type of bearings and w/o Bearing Deflection in isolator (mm/ s2 ) w/o bearing 2 (mm/ s ) EMB LRB FPS 0 0 0 0 14.42489 10.57590 8.973496 10.25542 -216.943 -184.07 -210.36 295.8978 -153.403 -130.16 -148.75 209.2328 -77.8897 -66.088 -75.529 106.2368 -102.222 -

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Fig. 1(j): Mode shape of Water tank (full) for w/o bearing and with Bearing. Fig. 1 (j) Shows, storey acceleration of Water tank (full) without bearing is increase according to the Water tank (full) height and difference in storey drift is more. Storey acceleration of Water tank (full) with bearing is decrease according to the Water tank (full) height and difference in acceleration of storey drift is less, The Water tank (full) top level acceleration is influenced by the bearing acceleration. Difference between acceleration at base and at top level is less in with bearing as compare to w/o bearing. Case-II (Water tank partially full):

Fig. 1 (K): Acceleration –Time Graph For (Water Tank Partially Full) With Different Type of Bearings and W/O Bearing .

Table X: Acceleration of (Water tank partially full) with different type of bearings and w/o Bearing

Ti me (se c) 0 5 10 15 20 25

w/o bearing (mm/s2)

Deflection in isolator (mm/s2) EMB LRB FPS

0 17.6297148

0 12.49879

40 45 50 55 60

0 4.16626

2

8

6

6

361.638326 255.718661 129.839828 170.402112

256.3878 181.2948 92.05151 120.8086

3.11131059 26.8125341 22.9456611 8 28.0199486 38.0582834 3 8.62567802 20.3516646

2.205801 19.00907 16.26760 19.86508 26.98187 7 6.115278 14.42856

1.43735629

1.019031

85.4626 60.4316 30.6838 40.2695 0.73526 7 6.33636 5.42253 6.62169 8.99395 9 2.03843 4.80952 0.33967 7

85.4626 60.4316 30.6838 40.2695 0.73526 7 6.33636 5.42253 6.62169 8.99395 9 2.03843 4.80952 0.33967 7

30 35

0 4.16626

64

From Fig. 1 (k), it shows that water (partially full) tank acceleration is more in without bearing. The maximum acceleration of water tank (partially full) is 1.25m/ s2 for without isolator and nearly 0.25 m/ s2 to 0.75 mm/ s2 for all types of isolator between 5 to 10 second, further the acceleration is reduces with time and FPS shows better performance compare to EMB and LRB. Table XI: Mode shape of (Water tank partially full) with different type of bearings and w/o Bearing Acceleration with bearing Storey w/o (mm/s2 ) height bearing (m) (mm/s2) EMB LRB FPS 88.92 70.6 112.0 0 0 7 7 2 222.3 200.2 183. 256.2 1.5 5 2 87 5 367.2 264.6 246. 422.1 4 1 2 78 4 533.1 422.1 417. 466.5 6.5 6 6 24 4 699.6 671.9 638. 666.3 9 6 4 54 4 866.1 649. 705.2 11.5 696.3 3 74 7 932.7 766.9 702. 790.7 13.85 3 6 25 3 1192. 874.3 741. 847.8 15.39 3 5 87 5

X axis – Time (s) Y axis – Acceleration in mm/s2

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0 5 5 6 0

3.92005 9.249075

2.038426 4.809519

1.56802 3.69963

2.038426 4.809519

0.653225

0.339677

0.26129

0.339677

6 4

X axis – Time (s) Y axis – Acceleration in mm/s2

Fig .1. (l): Mode shape of (Water tank partially full) with different type of bearings and w/o Bearing

Fig. (l) Shows, storey acceleration of Water tank (partially full) without bearing is increase according to the Water tank (partially full) height and difference in storey drift is more. Storey acceleration of Water tank (partially full) with bearing is decrease according to the Water tank (partially full) height and difference in acceleration of storey drift is less, The Water tank (partially full) top level acceleration is influenced by the bearing acceleration. Difference between acceleration at base and at top level is less in with bearing as compare to w/o bearing.

Fig. 1 (m): Acceleration –Time graph for (Water tank empty) with different type of bearings and w/o Bearing

From Fig. 1 (m), The maximum acceleration of water tank (empty) is 0.6m/s2 for without isolator and nearly 0.2 m/ s2 to 0.3 mm/ s2 for all types of isolator between 5 to 10 second, further the acceleration is reduce with time and LRB shows better performance compare to EMB and LRB. It is obvious that water (empty) tank acceleration is more in without bearing.

Table XIII: Mode shape of (Water tank empty) with different type of bearings and w/o Bearing Acceleration with Storey w/o bearing bearing (mm/s2 ) height (mm/s2) (m) EMB LRB FPS 35. 28. 44. 0 0 65 332 907 102.7 1.5 89.14 80.27 73.71 3 106.0 98.93 169.2 4 147.2 8 5 3 169.2 167.2 187.0 6.5 213.7 4 7 4 269.3 255.9 267.1 9 280.49 8 9 4 279.1 260.4 282.7 11.5 347.23 5 8 4 307.4 281.5 317.0 13.85 373.93 8 3 0 350.5 297.4 339.9 15.39 477.99 3 1 1

Case-III (Water tank empty): Table XII: Acceleration of (Water tank empty) with different type of bearings and w/o Bearing Time w/o Deflection in isolator (mm/s2) (sec) bearing EMB LRB FPS (mm/s2 ) 0 0 0 0 0 5 8.01205 4.166266 3.20482 4.166266 1 0 164.35118 85.46261 65.7405 85.46261 1 5 116.21463 60.43161 46.4859 60.43161 2 0 59.007375 30.68384 23.6030 30.68384 2 5 77.441425 40.26954 30.9765 40.26954 3 0 1.413975 0.735267 0.56559 0.735267 3 5 12.1853 6.336356 4.87412 6.336356 4 0 10.42795 5.422534 4.17118 5.422534 4 5 12.734025 6.621693 5.09361 6.621693 5 17.296075 8.993959 6.91843 8.993959

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lead rubber bearings.” Bulletin of the New Zealand Society for Earthquake Engineering, 36 (3), 141164. [5] Shrimali, M. K. and Jangid, R. S. (2002). “Earthquake response of liquid storage tanks with Sliding Systems.” Journal of Seismology and Earthquake Engineering, 4, 51-61. [6] Kelly, J.M., 1986. A seismic base isolation: a review and bibliography. Soil Dynamics and Earthquake Engineering 5, 202–216. AUTHOR BIOGRAPHY

Prof. Kishor S. Sable, Civil Engg. Dept, Amrutvahini college of Engg ([email protected]) DistAhmednagar, Maharastra, India. Mobile No-09890532111

Fig. 1(n): Mode shape of (Water tank empty) with Different Type of bearings and w/o Bearing

Prof. Jayashri S. Khose, Civil Engg Dept, Amrutvahini college of Engg ([email protected]) DistAhmednagar, Maharastra, India. Mobile No-09860005146

Fig.1 (n) Shows, storey acceleration of Water tank (empty) without bearing is increase according to the Water tank (empty) height and difference in storey drift is more. Storey acceleration of Water tank (empty) with bearing is decrease according to the Water tank (empty) height and difference in acceleration of storey drift is less, The Water tank (empty) top level acceleration is influenced by the bearing acceleration. Difference between acceleration at base and at top level is less in with bearing as compare to w/o bearing.

Prof. Madhuri K. Rathi, Civil Engg Dept, Amrutvahini college of Engg ([email protected]) DistAhmednagar, Maharastra, India.Mobile No-09922191315

IV. CONCLUSION A. From result and discussion it concludes that the performance of base isolated structure is good compare with non base isolated structure. B. For all three conditions tank full, tank partially full and tank empty case, friction type of bearing giving good performance compare to elastomeric and lead rubber bearing. The shear transmitted to the superstructure across the isolation interface is limited by the static friction force, which is equal to the product of the coefficient of friction and the weight of the superstructure. REFERENCES [1] Matsagar, V. A. and Jangid, R. S., 2003, “Seismic response of base-isolated structures during impact with adjacent structures,” Engineering Structures 25(10), 1311–1323.

[2] Matsagar, V. A. and Jangid, R. S., 2004, “Influence of isolator characteristics on the response of baseisolated structures,” Engineering Structures 26(12), 1735–1749. [3] Matsagar, V. A. and Jangid, R. S., 2005, “Baseisolated building with asymmetries due to the isolator parameters,” Advances in Structural Engineering 8(6), 603–622. [4] Shrimali, M. K. and Jangid R. S. (2003). “Seismic response of elevated liquid storage tanks isolated by

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