DYNAMIC BEHAVIOR and SEISMIC PERFORMANCE of ELEVATED TANKS DUE to GROUND TYPES DEFINED in EC-8 and TEC-06

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1 Firt European onference on Earthquake Engineering and Seimology (a joint event of the 13 th EEE & 3 th General embly of the ES) Geneva, Switzerland, 3-8 September 26 Paper Number:1313 YNMI EHVIOR and SEISMI PERFORMNE of ELEVTE TNKS UE to GROUN TYPES EFINE in E-8 and TE-6 Ramazan LİVOĞLU 1 and dem OĞNGÜN 2 SUMMRY The aim of thi paper i firtly to ubmit a ynthei work related to how the ground type defined in Eurocode-8 (E-8 Part:1 26) and Turkih Earthquake ode (TE-6) affect repone of the elevated tank and econdly to evaluate the performance of upporting ytem according to the ground type. For thi purpoe, an elevated tank with a frame upporting ytem which ha been commonly ued in recent year by the Minitry of Public Work and Settlement ie elected in the analye. For taking into account fluid inide veel a procedure which i propoed by E-8 i adapted to the tudy. y uing thi procedure the elevated tank-fluid ytem i modelled with finite element technique. The model i analyzed via the Repone pectrum analyi for evaluating the ground type effect on the behaviour of tank. Finally, conequence of analye carried out in thi paper how that the ground type defined in E-8 generally give fewer reult than the correponding one in TE-6. Furthermore it i een from the reult that the upporting ytem of the elevated tank doen t have an adequate performance for a lot of ground type invetigated in thi tudy. 1. INTROUTION It i known that very few invetigation have been carried out about the eimic behaviour of the elevated tank. However behaviour of uch a pecial type of tructure mut be well-known and the eimic behaviour of thi type of tank need to be undertood well. Otherwie earthquake damage to the tank can take everal form and caue everal unwanted event uch a hortage of drinking and utilizing water, uncontrolled fire and pillage of dangerou liquid etc. Even uncontrolled fire and pillage of dangerou liquid ubequent to a major earthquake may caue ubtantially more damage than the earthquake itelf. ue to thee reaon, thi type of tructure which i pecial in contruction and in function from engineering point of view mut be contructed to be reitant againt earthquake. lthough numerou tudie have been done about dynamic behaviour of liquid torage tank, mot of them are concerned with ground level cylindrical tank. However, few exit among thee tudie related to underground and elevated tank,. It i generally aumed that the elevated tank are fixed the ground. So attention i given to the dynamic behaviour of the fluid and tructure. Early invetigation uggeting implified two-ma-model about thi type of tank i realized by Houner (1963) lo ome tudie uggeting imple procedure to include fluid-interaction effect for ground level cylindrical and rectangular tank exit [auer 1964, Malhotra et al., 2]. lo thee approximation and ome new other about fluid-elevated tank-oil/foundation ytem are ummarized by Livaoğlu and oğangün (26). Haroun and Ellaithy (1985) developed a model including an analyi of a variety of elevated rigid tank undergoing tranlation and rotation. The model conider fluid lohing mode and it aee the effect of tank wall flexibility on the earthquake repone of the elevated tank. Reheidat and Sunna (1986) invetigated the behavior of a rectangular elevated tank conidering the oilfoundation-tructure interaction during earthquake. They neglected the lohing effect on the eimic behavior 1 Karadeniz Technical Univerity, epartment of ivil Engineering. 29, Gümüşhane, TURKEY rliva@ktu.edu.tr 2 Karadeniz Technical Univerity, epartment of ivil Engineering. 618, Trabzon, TURKEY adem@ktu.edu.tr 1

2 of the elevated tank and the radiation damping effect of oil medium. Haroun and Temraz (1992) analyzed model of two-dimenional X-braced elevated tank upported on the iolated footing to invetigate the effect of the dynamic interaction between the tower and the upporting oil-foundation ytem, but they neglected the lohing effect. utta et al (2a, 2b) tudied on the comparion of the upporting ytem of elevated tank with reduced torional vulnerability and they uggeted approximate empirical equation to determine the value of lateral, horizontal and torional tiffnee for different frame upporting ytem. They alo invetigated how the inelatic torional behaviour of the tank ytem with accidental eccentricity varied in accordance with the increaing number of panel and column [utta et al. 21]. Some tudie were alo conducted to invetigate fluid effect on eimic behaviour of elevated tank uing FEM with added ma approximation [oğangün et.al. 1997, Livaoğlu and oğangün, 23]. Furthermore tudie taken effect of oil-tructure interaction into account exit [Reheidat et al. 199, El-amatty et al. 1997]. Finally, Livaoğlu and oğangün (24, 25) propoed a frequency-dependent imple procedure to take into account effect of both the oil-tructure and fluid tructure interaction on eimic behaviour of elevated tank. So, it can be clearly een that effect of ground type and their effect on the performance of elevated tank are not generally dicued in the above-mentioned tudie. Therefore it i aimed, in thi tudy, to invetigate the effect of ground type defined code like E-8 and TE- 6 which have been recently come into the practice. 2. ERTHQUKE NLYSES OF ELEVTE TNKS In the literature, many implified analyi procedure exit a uggeted by Houner (1963), auer (1964) and Veleto with co-worker for the ground level tank. In the Houner approach two mae (m 1 and m 2 ) are aumed to be uncoupled and the earthquake force on the upport are etimated by conidering two eparate ingle-degree-of-freedom ytem. The ma of m 2 repreent only the lohing of the convective ma, the ma of m 1 conit of the impulive ma of the fluid. The ma derived by the weight of container and by ome part of elf-weight of the upporting tructure (two-third of the upporting tructure weight i recommended in I 371R and total weight of the upporting tructure i recommended in reference by Prietley et al, (1986)). Thi two-ma model uggeted by Houner wa updated by Eptein (1976) and ha been commonly ued for eimic deign of the elevated tank. If one need to conider additional higher-mode of convective mae (m cn ), auer or Eurocode 8 model can be ued that the equivalent mae and height for thi model baed on the work of Veleto and co-worker [Malhotra et al., 2] with certain modification that make the procedure imple. The recommended deign value for the cylindrical ground upported tank in the E 8 are given in Table 1. In thi table i i the dimenionle coefficient, c i the coefficient dimenion of (/m 1/2 ), h i and h c are the height of the impulive and convective mae for overturning moment, repectively. fter determination of two mae of m 1 and m 2 with their height from ground level and tiffnee of k 1 and k 2, for the elevated tank-fluid ytem, the model can be idealized a een from Fig 1. Water urface level k cn /2 k cn /2 m cn k c1 /2 m c1 k c1 /2 h m c k c /2 k c /2 m i R hi hc m 2 =m c k 2 =k c m 1 = m i + m v +.66 m h c2 h i h c1 m i k 1 m v i the ma of the empty container m i the ma of the upporting tructure k 1 i the tiffne of the upporting tructure k 2 i equal to k c (a) Equivalent mechanical model Two-ma model Figure 1: (a) The multi ma model for the cylindrical tank, (b) their equivalent mechanical and idealized model for elevated tank 2

3 y uing tandard tructural dynamic procedure, period, bae hear and overturning moment for the deign of tank can be etimated. Modal propertie like effective modal ma, height and tiffne can be calculated from thi two degree-of-freedom ytem Table 1: Recommended deign value for the firt impulive and convective mode of vibration a a function of the tank height-to-radiu ratio (h/r) [Eurocode-8:Part 4, 26] h/r i c m i /m w m c /m w h i /h h c /h h i /h h c /h ESIGN SPETRUM FOR GROUN TYPES In thi tudy, the term of ground type i elected in accordance with E-8. Table 2 preent ground type and hear wave velocitie given in the code like TE-6 and E-8. However, the ite condition have been claified into different categorie in earthquake code, thee categorie are named ground type, oil profile type, or uboil clae. een from thi table TE-6 give more information about ground type depending on the topmot layer thickne of oil (h 1 ). Four and ix ground type are defined in TE-6 and E-8, repectively. It hould be noted that in the 1998 verion of E-8 only three ground type of, and were defined. However, five main ground type a to be,,,, E and two pecial ground type S1 and S2 have been decribed in the current verion. Table 2: Ground type defined in the TE-6 and E8 [oğangün and Livaoğlu 26]. Ground type - TE ecription Maive volcanic rock, unweathered ound metamorphic rock, tiff cemented edimentary rock V - > 1 m/; Very dene and, gravel V >7 m/; Hard clay, ilty clay V > 7 m/ Soft volcanic rock uch a tuff and agglomerate, weathered cemented edimentary rock with plane of dicontinuity V h 1 15 m 7~1; ene and, gravel V 4~7; Very tiff clay, ilty clay V 3 7 Soft volcanic rock uch a tuff and agglomerate, weathered cemented edimentary rock with plane of h 1 >15 m dicontinuity V 7~1; ene and, gravel V 4~7; Very tiff clay, ilty clay V 3~7 Highly weathered oft metamorphic rock and cemented edimentary rock with plane of dicontinuity V h 1 15 m 4~7; Medium dene and and gravel V 2~4;Stiff clay,ilty clay V 2~3 Highly weathered oft metamorphic rock and cemented edimentary rock with plane of dicontinuity V 15m<h 1 5 4~7; Medium dene and and gravel V 2~4; Stiff clay, ilty clay V 2~3 Soft, deep alluvial layer with high water table V h 1 1 m < 2; Looe and V 2; Soft clay, ilty clay V < 2 Highly weathered oft metamorphic rock and cemented edimentary rock with plane of dicontinuity V h 1 >5 m 4~7; Medium dene and and gravel V 2~4; Stiff clay, ilty clay V 2~3 Soft, deep alluvial layer with high water table V h 1 > 1 m < 2; Looe and V <2; Soft clay, ilty clay V < 2 In all eimic zone, oft, deep alluvial layer with high water table V < 2, looe and V <2 and oft clay, ilty clay V < 2 with water table le than 1 m from the the oil urface hall be invetigated and the reult hall be documented to identify whether the Liquefaction Potential exit, by uing appropriate analytical method baed on initu and laboratory tet. Ground type E S 1 S 2 E8 ecription Rock or rock-like geological formation including mot 5 m weaker material at the urface V,3 >8 m/ epoit of very dene and, gravel or very tiff clay, at leat everal ten of m in thicknee, characterized by a gradual increae of mechanical propertie with depth V,3 36~ 8 eep depoit of dene or medium-dene and, gravel or tiff clay with thickne from everal ten to many hundred of m V,3 18~36 epoit of looe-to-medium coheionle oil (with o r without ome oft coheive layer), or of predominantly oft-to-firm coheive oil. V,3 <18 oil profile coniting of a urface alluvium layer with V,3 value of cla or and thick-ne varying between about 5m and 2m, underlain by tiffer material with V,3 >8 m/ epoit coniting or containing a layer at leat 1 m thick of oft clay/ ilt with (PI>4) and height water content, V,3 <1 m/ epoit of liquefiable oil, of enitive clay, or any other oil profile not included in type -E or S 1 3

4 Since the effect of tructural propertie and oil condition affect elatic and inelatic repone in a different proportion, a factor uually ued to reduce the elatic pectral ordinate to account for inelatic behaviour depending on the tructural propertie and oil condition. The ordinate of elatic deign pectra S e and inelatic deign pectra S d for the reference return period defined by the earthquake code. In thi table, β how lower bound factor for the horizontal deign pectrum, recommended value for β i.2 and γ I how importance factor. S i the oil factor defined in E-8 depending on ground type and η i the damping correction factor with a reference value of η=1 for 5% vicou damping Table 3: Ordinate of elatic and inelatic deign pectra (S e and S d ) for TE-6, and E8-3 [oğangün and Livaoğlu 26] TE-6 E-8 T T T T T T T T Se = a gr S e = 25. a T gr S e = 25. agr T T 25. ag ag T Sd = 25. ag T S d = Ra Sd = Ra T R T T Se ag S 1 ( 25. 1) T η = + 2 T Sd = ags T q 3 S = 25. a S η e g 25. Sd = ag S q a T T T T Se = 2.5ag S η T T T T S d 2.5 T = ag S q T β ag TT T T 4 Se = 2.5ag S η 2 T 2.5 TT T T S = a S β a q 2 T d g g In thi tudy the tank are conidered a being ituated in the firt earthquake zone. Thee tank have high importance factor of 1.5 and ductility reduction factor of 2. Inelatic deign pectra were drawn and given in Fig. 2 by uing the expreion hown in Table 2-3 for all ground type defined in the code. een from Fig. 2, only TE conider the ame peak value for all ground type. E-8 give the maximum peak value for ground type excluding ground type of E S (T).g (m/2) Period () S (T).g (m/ 2 ) Figure 2: eign pectrum for different ground type defined in E-8 and TE-6 4. STRUTURL T and MOEL In thi tudy, a reinforced concrete elevated tank with a container capacity of 9 m 3 i conidered in eimic analyi (Fig. 4). The elevated tank ha a frame upporting tructure in which column are connected by the circumferential beam at regular interval at 7 m and 14 m height level. The tank container i Intze type and thi Period () 4

5 elevated tank ytem ha been ued a a typical project in Turkey up to recent year by Minitry of Public Work and Settlement. Young modulu of concrete and the weight per unit volume are taken to be 32, MPa and 25 kn/m 3, repectively. The container i filled with the water denity of 1, kg/m 3. alculated ma propertie are m t = 613,97 kg, m c = 281,3 kg, k 2 = 32,9, N/m. Other dimenion of the elevated tank are illutrated in Fig Finite Element Model of the onidered Tank Finite element model (FEM) conidered for the elevated tank-fluid ytem in thi tudy i given in Fig. 4. egree of freedom at the bae node were fixed and the other left free. olumn and beam were modelled with frame element, veel and truncated cone wall were modelled with hell element. dded ma approach i ued in thi tudy. In thi approach, two mae which are obtained in different height (calculated by Table 1) from the ground level of veel were determined. onvective ma and impulive ma and their height were calculated a m c =2813 kg and it height from veel ground level h c i 5.52 m, m i =61397 kg and it height from veel ground level h i i 3.51 m. Impulive ma added finite element of veel wall and truncated cone mehed in accordance with height level calculated for the impulive ma. The convective ma placed in the centre of veel at the level of calculated height. Thi ma connected to the finite element of wall with pring having tiffne of k 2 (k 2 =846.7 kn/m) along the axiymmetrical direction. Mode number taken into account in modal analyi i ten for all elevated tank. SP2 [SP2 25] package program i ued for carrying repone pectrum analyi of fluid elevated tank ytem. m 2 = kg onvective ma hi=3.51m hc=5.52m k 2 = 846 kn/m m 1 = kg dded ma Ma ditribution etimated from hydrodynamic preure ditribution Figure 3: Equivalent model and finite element model of the conidered ytem 5. EVLUTION OF RESULTS Eight analye due to ground type condition were carried out by uing the decribed procedure. The analye were realized via a computer program SP-2. The diplacement repone obtained along the height of the elevated tank, bae hear force and overturning moment are illutrated and dicued in the following title comparatively and alo by uing internal force reult, performance of the upporting tructure are invetigated iplacement Repone onidering totally eight ground type defined in E-8 and TE-6, eimic analye of elevated tank are done. Obtained diplacement along the height according to different ground type for the elevated tank are comparatively illutrated (Fig. 4a). lo, for the eight ground type, Fig. 4b how the drift of which limit defined via TE-6. can be een from the Fig. 4a., the maximum diplacement wa obtained for the cla a.48 m at 21 m height level and at the ame level, the minimum diplacement wa etimated for the cla a.16 m. The difference ratio obtained according to uboil cla to the, and are calculated a 26%, 119% and 24% repectively. Similarly, between the ground type of E-8, more reult are repectively 5

6 calculated for, and than the cla a 5%, 72% and 83%. On the other hand it wa generally een that the diplaced hape of the tank change while the ground type are changed from the to or to. So deterioration with tability of the tank i more clearly een for the, and clae than the other. lo the calculated diplacement how that from the imilar ground type defined in E-8 and TE-6, ground type defined in TE-6 give bigger reult than the correponding one defined in E limit drift ratio for TE-6 Height (m) iplacement (m).6.7 (a) Figure 4: ccording to the ground type (a) diplacement repone of the tank (b) drift ratio. Fig. 4.b how comparatively drift reult. Thi figure alo how that ground type defined in TE-6 caue more drift than the E-8 for the imilar ground type. a conequence, it can be eaily aid that if the reult are evaluated for the TE-6 permiible limit, the calculated repone require that any ground type do not allow the deign of thee elevated tank ae Shear Force and Overturning Moment Height (m) rift ratio (b) The comparative variation of the etimated bae reaction like bae hear and overturning moment for invetigated elevated tank are illutrated in Fig. 5. een from thee figure different repone were etimated for the tank ituated in different oil type. i.e. the maximum bae hear force reache 1316 kn for and kn for, while for and ground type minimum bae hear were obtained a 436 kn and 5464 kn, repectively. The increae between the imilar oil type defined TE-6 and E-8 i intereting that i.e. between and or and etc, the ratio occurred interval of 5%~25%. Thi how that the imilar definition made on the different code give different reult and alo how that ground type defined in TE-6 may give bigger repone than the other approximately a 25%. Furthermore, maximum deviation in the bae hear or overturning moment due to oil clae were etimated a 174% between the and and 141% between the and ground type ae Shear (kn) Overturning Moment (knm) c Local ite clae Local ite clae Figure 5: ae hear force and overturning moment for elevated tank ituated in different ground type 6

7 5.3. omparion of the Performance of the column due to Ground Type ccording to the analye carried out, to better judge the trength of the upporting column, the reult dicued are obtained for the tank. The maximum internal force like axial force and moment obtained from repone pectrum analye are comparatively illutrated in Fig. 6 according to ground type. Thee comparion clearly exhibit that the ground type play an effective role in increaing all calculated internal force. i.e. ground type caue 26% more bigger repone of axial force than. Similarly thi repone occurred 141% more for ground type. Furthermore E-8 ground type give 174% increae between the and ground type Figure 6: Maximum axial force and moment obtained from a column of the elevated tank due to ground type. Fig.7 how the calculated axial load-moment interaction diagram for a typical upporting column. For the interaction curve, an etimated concrete compreive trength of deign, f cd, of 25 MPa wa ued. In the determination of interaction diagram a een in Fig. 7, the characteritic and deign yield trength were accepted a 42 MPa and 365 MPa, repectively that thi type of reinforcement ha been commonly ued in Turkey. When the capacity of column ubjected to combined axial load and bending moment i compared with the etimated load and moment from the eimic analye, clearly one can tate that mot of them have not adequate capacity except the column of elevated tank ituated in, and ground type. Thee reult how that elevated tank invetigated here can only be built in ground type in accordance to TE-6 and due to E-8 and. they are only appropriate ground type for thee tructure. For the other ground type the internal force obtained exceed the capacity of the column. If imilar comparion are made in accordance with reult obtained by tatic analyi, it can be eaily een that both etimated axial load and bending moment are inide the limit value. 1 cm Φ8 75 mm c Typical column 8 mm - ection - 1Φ xial Force (kn) 2Φ Local ite clae xial Force (kn) (N;M)=( kn ; knm) (for ground type ) irection to excitation Perpendeciular direction to excitation (N;M)=( kn ; knm) (for ground type ) (N;M)=( kn ;283.4 knm) (for ground type ) (N;M)=( kn ; knm) (N;M)=( (for ground kn ; type ) knm) (for ground type) Moment (knm) Figure 7. xial load-moment interaction diagram and etimated maximum reaction force for a column Local ite clae Moment (knm) 7

8 ccording to Turkih ode [TS 5 2, TE-6] hear capacity of column of the nominal ductility level (V cap ) may be etimated with the below equation: N.8, 65 (1, 7 d V f ctd c ) cap + + c f d w ywd (1) Where c i gro ection area of column, f ctd i deign tenile trength of concrete, N d i factored axial force calculated under imultaneou action of vertical load and eimic load, w i ection area of tranvere reinforcement, f ywd i deign yield trength of tranvere reinforcement, d i effective interval in the ection area of column and i pacing of tranvere reinforcement. The hear capacity of the column wa etimated equal to 125 kn uing the value of c = 6, mm 2, f ctd =1.15 N/mm 2, N d 5 x16 N, w =31.5 mm 2, f ywd = 365 N/mm 2, d =75 mm and =1 mm. The hear force wa determined interval of 795~1915 kn for to and of 634~174 kn for to from the repone pectrum analyi. If thi hear force and the above capacity of column are compared, it would be een that hear capacity wa exceeded for, and ground type. Shear reinforcement however i adequate for the other ground type. 6. ONLUSIONS lthough the correponding ground type defined different code have almot imilar propertie, only one defined in TE-6 ha given almot more reult than the correponding type defined in E-8. However complex definition are given by the TE-6, the E 8 eentially trie to repreent ground type. ccording to the reult of analye, ground type except for,, are not appropriate to build the elevated tank in view of performance of upporting ytem. Furthermore, due to the limit drift defined in TE-6 any ground type are not appropriate for the tank. In pite of putting into conidering elevated tank with frame upporting ytem practice by Minitry of Public Work and Settlement of Turkey, the elevated tank couldn t be ued on 1.eimic zone and for almot all ground type. Thi type of tructure in Turkey hould be redeigned conidering new proviion and technique. KNOWLEGEMENTS The preent work i upported by Grant-in-id for Scientific Reearch (Project No.15M252) from the Scientific and Technological Reearch ouncil of Turkey (TÜİTK). 7. REFERENES thana,., Sridhar. P. (1997), Earthquake nalyi of Elevated Water Tank Uing SESM, 4th International onference on civil Engineering,. pp , May 4-6. auer, H.F., Fluid ocillation in the container of a pace vehicle and their ınfluence upon tability. NS TR R-187. oğangün.., yvaz, Y.,. urmuş (1997), Earthquake nalyi of Water Tower, 4th International onference on civil Engineering, May 4-6. oğangün,. and Livaoğlu, R. (26) comparative tudy of the deign pectra defined by Eurocode 8, U, I and Turkih Earthquake ode on R/ ample building, Journal of Seimology, (ccepted for publication) utta, S.., Jain, S. K,. and Murty,. V. R. (2a) lternate tank taging configuration with reduced torional vulnerability, Soil ynamic and Earthquake Engineering, v.19, utta, S.., Jain, S. K. and Murty,. V. R., (2b) eing the eimic torional vulnerability of elevated tank with R frame-type taging. Soil ynamic and Earthquake Engineering, v.19, utta, S.., Jain, S. K.,.and Murty,. V. R., (21), Inelatic eimic torional behavior of elevated tank, Journal of Sound and Vibration, v.242(1), El-amatty,.., Korol. M. R., and Mirza,. F. (1997), Stability of Elevated Liquid-Filled onical Tank Under Seimic Loading, Part-1-Theory, Earthquake Engineering nd Structural ynamic, Vol 26, ,. Eptein, H. I., (1976). Seimic deign of liquid-torage tank. SE Journal of Structural iviion, v.12,

9 E 8: Part1., (26), Eurocode 8: eign of tructure for earthquake reitance Part 1: General rule, eimic action and rule for building, European Norm. E 8: Part4., (24). Eurocode-8: eign of tructure for earthquake reitance Part 4: Silo, tank and pipeline. European ommittee for Standardization,. Houner, G. W., (1963), ynamic ehavior of Water Tank, ulletin of the Seimological Society of the merica, 53 pp Haroun, M.. and Ellaithy, M. H. (1985), Seimically induced fluid force on elevated tank, Journal of Technical Topic in ivil Engineering; 111 (1), Haroun, M.. and Temraz, M. K. (1992), Effect of oil-tructure interaction on eimic repone of elevated tank, Soil ynamic and Earthquake Engineering, 11(2), Livaoğlu, R, oğangün,. (23), Evaluation of dynamic repone of the elevated tank having different upporting ytem due to uboil clae defined TE-98, Sakarya Üniveritei Fen ilimleri Entitüü ergii, v.:7:3, 7-77 (in Turkih). Livaoğlu, R., oğangün,. (24), imple eimic analyi procedure for fluid-elevated tank-foundation/oil ytem, Sixth International onference on dvance in ivil Engineering (E 24), İtanbul,Turkey, v1; pp Livaoğlu, R. and oğangün,., (25), Seimic evaluation of fluid-elevated tank-foundation/oil ytem in frequency domain, Structural Engineering and Mechanic; n International Journal, v. 21(1) pp Livaoğlu, R. and oğangün,., (26), Simplified Seimic nalyi Procedure for Elevated Tank onidering Fluid-Structure-Soil Interaction, Journal of Fluid and Structure, v.22:3, Malhotra, P.K., Wenk, T. and Weiland, M. (2), Simple procedure of eimic analyi of liquid-torage tank. J. Structural Engineering International ISE. v.1 (3), Marahi, E.S., Shakib, H., Evaluation of ynamic haracteritic of Elevated Water Tank by mbient Vibration Tet, 4th International onference on civil Engineering, May 4-6,1997. Prietley, M. J. N., avidon,.j., Honey, G.., Hopkin,.., Martin, R.J., Ramey, G., Veey, J.V., Wood, J.H., (1986). Seimic eign of Storage Tank. Recommendation of a tudy group the New Zealand Society for Earthquake Engineering, New Zealand. Reheidat, R. M., Sunna, H., (199), ehavior of Elevated Storage Tank uring Earthquake, Proceeding of the 3th World onference on Earthquake Engineering, v.ii, 13,22, Mocow. SP2., (1995) Structural nalyi Program, omputer and Structure Inc., Nonlinear, erkeley, alifornia,. TE (26)., Specification for Structure to e uilt in Earthquake rea, Minitry of Public Work and Settlement Government of Republic of Turkey. TS 5, 2, Requirement for deign and contruction of reinforced concrete tructure. nkara. Turkih Standard Intitute. Turkey (in Turkih). 9