PSI - Issue 18

Bilal L. Khan et al. / Procedia Structural Integrity 18 (2019) 108–118

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Bilal L. Khan et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig.9. Comparison of Relative Displacement between Passive Base Isolators under Landers Earthquake Excitation (Far Field).

5. Conclusions

Following are the conclusions drawn from the dynamic analysis of various base isolated systems under the influence of near and far field earthquakes: • Under the influence of near field earthquake excitation, the inter-storey drift varied from 22 mm to 52 mm for all the three base isolated systems. Whereas for far field earthquake excitation, the inter-storey drift varied from 5 mm to 60 mm. • Overall the transmissibility ratio was reduced in base isolated systems as compared to fixed base system. Under the influence of near field earthquake excitation, the reduction transmissibility ratio varied from 44 % to 52 % for all the three base isolated system. For far field earthquake excitation, the reduction transmissibility ratio varied from 35 % to 47 % for all the three base isolated system. • The trend observed in global peak displacement for various base isolated systems also varied for near and far field earthquakes. Under the influence of near field earthquake excitation, peak global displacement/ drift varied from 290 mm to 300 mm for all the three base isolated systems. For far field earthquake excitation, peak global displacement varied from 150 mm to 210 mm for all the three base isolated systems. • During the dynamic analysis under far field earthquake excitation, the peak displacement measured for low damping rubber bearing system was more than that of un-isolated system, this shows that dynamic response of structure is influenced by the source of excitation and can affect the response of structure in a negative way if care is not taken in choosing the right base isolator. In the light of above conclusions, it is recommended that the designer must analyze the base isolated structure under near and far field earthquakes to efficiently control its dynamic response. As different base isolators respond to various earthquake excitations differently, their effects should be considered. In some cases, a combination of base isolators may be installed to overcome the deficiency of one damper with the other one (Usman et al., 2009 (a), 2009 (b)). References Cheng, F. Y., Jiang, H., Lou, K. (2008). Smart structures: innovative systems for seismic response control: CRC Press. Chiou, B., Darragh, R., Gregor, N., & Silva, W. (2008). NGA project strong-motion database. Earthquake Spectra, 24(1), 23-44. Chopra, A. K. (2001). Dynamics of structures: theory and applications to earthquake engineering: Prentice-Hall. Clemente, P., & Buffarini, G. (2010). Base isolation: design and optimization criteria. Seismic Isolation and Protection Systems, 1(1), 17-40. Desai, M., & John, R. (2015). Seismic Performance of Base Isolated Multi-Storey Building. Griffin, C. T. (2017). Multi-performance retrofits to commercial buildings in seismic zones. Journal of Structural Integrity and Maintenance, 2(3), 133-142. doi:10.1080/24705314.2017.1360171 Ismail, M., Rodellar, J., Ikhouane, F. (2010). An innovative isolation device for aseismic design. Engineering Structures, 32(4), 1168-1183.