Seismic response of liquid storage steel tanks with variable frequency pendulum isolator
Tóm tắt
The seismic response of liquid storage steel tanks (slender and broad) isolated with Variable Frequency Pendulum Isolators (VFPIs) is investigated under normal component of six near-fault ground motions. The continuous liquid mass is lumped as convective mass, impulsive mass and rigid mass. The corresponding stiffness associated with these lumped masses is worked out depending upon the properties of the tank wall and liquid mass. The frictional forces mobilized at the interface of the VFPI are assumed to be velocity independent. The governing equations of motion of liquid storage steel tanks isolated with the VFPIs are derived and solved in the incremental form using Newmark’s step-by-step method assuming linear variation of acceleration over small time interval. For comparative study, the seismic response of liquid storage steel tanks with the VFPIs is compared with that of the same liquid storage steel tanks isolated using the Friction Pendulum Systems (FPSs). In order to measure the effectiveness of isolation system, the seismic response of isolated steel tanks is compared with that of the non-isolated steel tanks. Further, a parametric study has been carried out to critically examine the behaviour of liquid storage steel tanks isolated with VFPIs. The important parameters considered are the friction coefficient of the VFPI, the Frequency Variation Factor (FVF) of the VFPI and the tank aspect ratio. The difference between the liquid storage tanks isolated with the VFPI and the FPS isolators subjected to the harmonic and far-field ground motions was also investigated in this study. Effect of vertical component of ground motions on the behaviour of the VFPI-isolated liquid storage tanks is investigated under triaxial ground excitations by considering the interaction of forces in two orthogonal directions. From these investigations, it is concluded that seismic response, viz. the base shear, the sloshing displacement and the impulsive displacement, of liquid storage steel tanks during near-fault ground motions can be controlled within a desirable range with the installation of the VFPI. Under strong harmonic excitations, the base shear of the VFPI reduces than that of the FPS whereas the sloshing displacement, the impulsive displacement and the isolator displacement of the VFPI exceeds than that of the FPS. It is also found that the isolation by the FPS and VFPI isolators has almost the same effect in the tank to the far-field ground motions. The triaxial ground motions have noticeable effect on the response of the VFPI-isolated liquid storage tanks relative to unilateral ground motion and if ignored, the sliding displacement and base shear will be underestimated.
Tài liệu tham khảo
Abali, E. and Uçkan, E. (2010). “Parametric analysis of liquid storage tanks base isolated by curved surface sliding bearings.” Soil Dynamics and Earthquake Engineering, Vol. 30, Nos. 1–2, pp. 21–31.
Akköse, M., Ateş, Ş., Bayraktar, A., and Dumanolu, A. A. (2007). “The seismic response of liquid storage tanks isolated by double concave friction pendulum bearings to near-fault ground motions.” 10th World Conference on Seismic Isolation, Energy Dissipation and Active Vibrations Control of Structures, Istanbul, Turkey.
Alavi, B. and Krawinkler, H. (2004). “Behaviour of moment-resisting frame structures subjected to near-fault ground motions.” Earthquake Engineering and Structural Dynamics, Vol. 33, No. 6, pp. 687–706.
Almazan, J. L., De la llera, J. C., and Inaudi, J. A. (1998). “Modeling aspects of structures isolated with the frictional pendulum system.” Earthquake Engineering and Structural Dynamics, Vol. 27, No. 8, pp. 845–867.
Chalhoub, M. S. and Kelly, J. (1988). “Theoretical and experimental studies of cylindrical water tanks in base isolated structures.” A Report No. UCB/EERC-88/07, USA, Berkeley.
Chalhoub, M. S. and Kelly, J. (1990). “Shake table test of cylindrical water tanks in base isolated structures.” Journal of Engineering Mechanics, ASCE., Vol. 116, No. 7, pp. 1451–1472.
Christovasilis, I. P. and Whittaker, A. S. (2008). “Seismic analysis of conventional and isolated LNG tanks using mechanical analogs.” Earthquake Spectra, Vol. 24, No. 3, pp. 599–616.
Fan, F.-G., Ahmadi, G., and Tadjbakhsh, I. G. (1990). “Multi-story baseisolated buildings under a harmonic ground motion-Part II: Sensitivity analysis.” Nuclear Engineering and Design, Vol. 123, No. 1, pp. 17–26.
Haroun, M. A. (1983). “Vibration studies and test of liquid storage tanks.” Earthquake Engineering and Structural Dynamics, Vol. 11, No. 2, pp. 179–206.
Haroun, M. A. and Housner, G. W. (1981). “Seismic design of liquid storage tanks.” Journal of Technical Councils, ASCE, Vol. 107, No. TC1, pp. 191–207.
Housner, G. W. (1957). “Dynamic pressures on accelerated fluid containers.” Bulletin of Seismological Society of America, Vol. 1, No. 4, pp. 15–37.
Housner, G. W. (1963). “Dynamic behaviour of water tanks.” Bulletin of Seismological Society of America, Vol. 53, No. 1, pp. 381–387.
Hwang, J. S. and Hsu, T. Y. (2000). “Experimental study of isolated building under triaxial ground excitations.” Journal of Structural Engineering, ASCE, Vol. 126, No. 8, pp. 879–886.
International Conference of Building Officials. (1997). Uniform building code, earthquake regulations for seismic isolated structures, Appendix Chapter 16, Whittier, CA.
Jadhav, M. B. and Jangid, R. S. (2006). “Response of base-isolated liquid storage tanks to near-fault motions.” Structural Engineering and Mechanics, Vol. 23, No. 6, pp. 615–634.
Jangid, R. S. and Kelly, J. M. (2001). “Base isolation for near-fault motions.” Earthquake Engineering and Structural Dynamics, Vol. 30, No. 5, pp. 691–707.
Kim, N. S. and Lee, D. G. (1995). “Pseudodynamic test for evaluation of seismic performance of base-isolated liquid storage tanks.” Engineering Structures, Vol. 17, No. 3, pp. 198–208.
Liaw, T. C., Tian, Q. L., and Cheung, Y. K. (1988). “Structures on sliding base subjected to horizontal and vertical motions.” Journal of Structural Engineering, ASCE, Vol. 114, No. 9, pp. 2119–2129.
Lin, B. C. and Tadjbakhsh, I. G. (1986). “Effect of vertical motion on friction driven systems.” Earthquake Engineering and Structural Dynamics, Vol. 14, No. 4, pp. 609–622.
Loh, C.-H., Liao, W.-I., and Chai, J.-F. (2002). “Effect of near-fault earthquake on bridges: Lessons learned from Chi-Chi earthquake.” Proceedings of 3 rd National Seismic Conference and Workshop on Bridges and Highways, FHWA Western Resource Center and MCEER, Portland, Ore, pp. 211–222.
Makris, N. and Chang, S.-P. (2000). “Effect of viscous, viscoplastic and friction damping on the response of seismic isolated structures.” Earthquake Engineering and Structural Dynamics, Vol. 29, No. 1, pp. 85–107.
Malhotra, P. K. (1997a). “Method for seismic base isolation of liquidstorage tanks.” Journal of Structural Engineering, ASCE, Vol. 123, No. 1, pp. 113–116.
Malhotra, P. K. (1997b). “New methods for seismic isolation of liquidstorage tanks.” Earthquake Engineering and Structural Dynamics, Vol. 26, No. 8, pp. 839–847.
Panchal, V. R. and Jangid, R. S. (2008). “Variable friction pendulum system for seismic isolation of liquid storage tanks.” Nuclear Engineering and Design, Vol. 238, No. 6, pp. 1304–1315.
Pranesh, M. and Sinha, R. (2000). “VFPI: An isolation device for aseismic design.” Earthquake Engineering and Structural Dynamics, Vol. 29, No. 5, pp. 603–627.
Rao, P. B. and Jangid, R. S. (2001). “Performance of sliding systems under near-fault motions.” Nuclear Engineering and Design, Vol. 203, Nos. 2–3, pp. 259–272.
Shakib, H. and Fuladgar, A. (2003). “Response of pure-friction sliding structures to three components of earthquake excitation.” Computers and Structures, Vol. 81, No. 4, pp. 189–196.
Shenton III, H. W. and Hampton, F. P. (1999). “Seismic response of isolated elevated water tanks.” Journal of Structural Engineering, ASCE, Vol. 125, No. 9, pp. 965–976.
Shrimali, M. K. and Jangid, R. S. (2002). “Non-linear seismic response of base-isolated liquid storage tanks to bi-directional excitation.” Nuclear Engineering and Design, Vol. 217, Nos. 1–2, pp. 1–20.
Shrimali, M. K. and Jangid, R. S. (2003). “Earthquake response of isolated elevated liquid storage steel tanks.” Journal of Constructional Steel Research, Vol. 59, No. 10, pp. 1267–1288.
Shrimali, M. K. and Jangid, R. S. (2004). “Seismic analysis of baseisolated liquid storage tank.” Journal of Sound Vibration, Vol. 275, Nos. 1–2, pp. 59–75.
Su, L. and Ahmedi, G. (1988). “Response of frictional base isolation systems to horizontal-vertical random earthquake excitations.” Probabilistic Engineering Mechanics, Vol. 3, No. 1, pp. 12–21.
Wang, Y.-P., Teng, M.-C., and Chung, K.-W. (2001). “Seismic isolation of rigid cylindrical tanks using friction pendulum bearings.” Earthquake Engineering and Structural Dynamics, Vol. 30, No. 7, pp. 1083–1099.