The seismic response of elevated liquid storage tanks isolated by lead-rubber bearings
DOI:
https://doi.org/10.5459/bnzsee.36.3.141-164Abstract
The seismic response of elevated liquid storage tanks isolated by the lead-rubber bearing is investigated under real earthquake ground motion. Two types of isolated tank models are considered in which the bearings are placed at the base and top of the tower structure. The tank liquid is modelled as lumped masses referred as convective mass, impulsive mass and rigid mass. The corresponding stiffness associated with these lumped masses has been worked out using the properties of the tank wall and liquid mass based on simple single-degree-of-freedom concepts. The mass of the tower structure is lumped equally at top and bottom. The assembled equations of motion are solved by Newmark's step-by-step method with iteration. The seismic response of two types of tanks, namely slender and broad tanks is obtained and a parametric study is carried out to study the effects of important system parameters on the effectiveness of seismic isolation. The various important parameters considered are the tank aspect ratio, the time period of the tower structure, damping and the lime period of the isolation system. It has been observed that the earthquake response of the isolated tank is reduced significantly. Further, it is observed that the isolation is more effective for the tank with a stiff tower structure in comparison to flexible towers. In addition, a simplified analysis is also presented to evaluate the response of the elevated tanks using a two-degrees-of-freedom model and two single degree-of-freedom models. It is observed that the proposed methods predict accurately the seismic response of elevated liquid storage tanks with less computational efforts.
References
Steinbrugge, K.V. and Rodrigo, F.A. (1963). The Chilean earthquakes of May 1960: A structural engineering viewpoint. Bulletin of Seismological Society of America, 53, 225-307.
Housner, G.W. (1963). Dynamic behavior of water tanks. Bulletin of Seismological Society o f America, 53, 381-387.
Rosenblueth, E. and Newmark, N.M. (1971). Fundamentals of Earthquake Engineering. Prience-Hall: NJ.
Epstein, H.J. (1976). Seismic design of liquid storage tanks. Journal of structural Division, ASCE, 102, 1659-1673.
Haroun, M.A. (1983). Vibration studies and test of liquid storage tanks. Earthquake Engineering and Structural Dynamics, 11, 179-206. DOI: https://doi.org/10.1002/eqe.4290110204
Kelly, J.M. (1986). Aseismic base isolation: Review and bibliography. Soil Dynamics and Earthquake Engineering, 5, 202-216. DOI: https://doi.org/10.1016/0267-7261(86)90006-0
Robinson, W.H. (1995). Recent research and application of seismic isolation in New Zealand. Bulletin of the New Zealand National Society for Earthquake Engineering, 28, 253-264. DOI: https://doi.org/10.5459/bnzsee.28.4.253-264
Jangid, R.S. and Datta, T.K. (1995). Seismic behaviour of base-isolated buildings: A-state-of-the-art review. Journal of Structures and Buildings, ICE, 110(2), 186-203. DOI: https://doi.org/10.1680/istbu.1995.27599
Chalhoub, M.S. and Kelly, J.M. (1990). Shake table test of cylindrical water tanks in base-isolated structures. Journal of Engineering Mechanics, ASCE, 116(7), 1451-1472. DOI: https://doi.org/10.1061/(ASCE)0733-9399(1990)116:7(1451)
Kim, N.S., Lee, D.G. (1995). Pseudo-dynamic test for evaluation of seismic performance of base-isolated liquid storage tanks. Engineering Structures, 17(3), 198-208. DOI: https://doi.org/10.1016/0141-0296(95)00076-J
Malhotra, P.K. (1997). Method for seismic base isolation of liquid storage tanks. Journal of Structural Engineering, ASCE, 123(1), 113-116. DOI: https://doi.org/10.1061/(ASCE)0733-9445(1997)123:1(113)
Malhotra, P .K. (1997). New methods for seismic isolation of liquid-storage tanks. Earthquake Engineering and Structural Dynamics, 26, 839-847. DOI: https://doi.org/10.1002/(SICI)1096-9845(199708)26:8<839::AID-EQE679>3.0.CO;2-Y
Bleiman, D. and Kim S. (1993). Base isolation of high volume elevated water tanks. Proceeding, Seminar on seismic isolation, passive energy dissipation and active control, ATC 17-1, Applied Technology Council, Redwood city, California, USA.
Shenton, III H.W. and Hampton, F.P. (1997). Seismic response of isolated elevated water tanks. Journal of Structural Engineering, ASCE, 125(9), 965-976. DOI: https://doi.org/10.1061/(ASCE)0733-9445(1999)125:9(965)
Robinson, W.H. and Tucker, A.G. (1977). A lead rubber shear damper. Bulletin of the New Zealand National Society for Earthquake Engineering, 10, 151-153.
Robinson, W.H. and Tucker, A.G. (1981). Test results for lead rubber bearings for Wm. Clayton Building, Toe Toe Bridge and Waiotukupuna Bridge. Bulletin of the New Zealand National Society for Earthquake Engineering, 14, 21-33.
Robinson, W.H. (1982). Lead rubber hysteretic bearing suitable for protecting structures during earthquakes. Earthquake Engineering and Structural Dynamics, 10, 593-604. DOI: https://doi.org/10.1002/eqe.4290100408
Wen, Y.K. (1976). Method of random vibration of hysteretic system. Journal of Engineering Mechanics, ASCE, 102, 249-263.