consequences of the Recently Modification of Iran Seismic Design Code (No. 2800) (Due to A*B) and Proposing Forward Directivity Effect Coefficients (Na and Nv)

Document Type : Research Article

Author

Iran University of Science and Technology, Tehran, Iran

Abstract

This article intends to criticize and discuss the challenging of the design spectra in Iran seismic design (No. 2800, 4th version) mainly due to its two parametric form (A×B) and highlight its weaknesses regarding the current earthquake engineering principals. Examples of the discussed points include the predefined spectral shape as a fixed envelope of spectral ordinates at the constant maximum acceleration and velocity ranges, the dependency of corner period (Ts) to those of constant spectral acceleration, meaningless of the defined parameter (S) in spectral shape formula. The design spectral acceleration in the third and fourth 2800’s code are compared and assessed. A simple methodology for assessing the existing period dependent forward directivity effects parameter, N(T) is presented. The real spectral ordinates data at 120 near source sites from the two cities in the United State on four site soil types are used to develop the presented two parameters as representatives of FD-pulse effects; Na(T1) (for the constant maximum spectral ordinate range of period) and Nv(T) (for constant maximum velocity spectral ordinate range of period). The average values of the obtained design spectra are compared with those of the 2800’s third and fourth versions and the differences are the results are assessed. The resulted considerable differences confirm the necessary modification of the currently used design response spectra in the both period ranges of; the constant maximum acceleration spectra and acceleration spectra at the constant maximum velocity.

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References

[1] A., Nicknam; Y., Eslamian; A Hybrid Method for Simulating Near-source, Broadband Seismograms:Application to the 2003 Bam Earthquake (Mw 6.5),Tectonophysics, Vol. 487, No. 1, pp. 46‑58, 2010.
[2] A., Nicknam et al.; Modification of Seismological Parameters of Zarand Earthquake (2005 February 22), in Central Iran, Using Empirical Green’s Function Method, 2007.
[3] A., Nicknam et al.; Reproducing Fling-step and Forward Directivity at Near Source Site Using of Multiobjective Particle Swarm Optimization and Multi Taper, Earthquake Engineering and Engineering Vibration, Vol. 12, No. 4, pp. 529‑540, 2013.
[4] E., Kalkan; S. K., Kunnath; Effects of Fling Step and Forward Directivity on Seismic Response of Buildings, Earthquake Spectra, Vol. 22, No. 2, pp. 367‑390, 2006.
[5] C., Kou-Cheng et al.; An Observation of Rupture Pulses of the 20 September 1999 Chi-Chi, Taiwan, Earthquake from Near-field Seismograms, Bulletin of the Seismological Society of America, Vol. 91, No. 5, pp. 1247‑1254, 2001.
[6] S., Hartzell et al.; Calculation of Broadband Time Histories of Ground Motion: Comparison of Methods and Validation Using Strong-ground Motion from the 1994 Northridge Earthquake, Bulletin of the Seismological Society of America, Vol. 89, No. 6, pp. 1484‑1504 , 1999.
[7] M. R., Attalla; T. F., Paret; S. A., Freeman; Near Source Behavior of Buildings under Pulse-type Earthquakes, 6th National Conference on Earthquake Engineering, Consultant Eng. Wiss, Janny, Elsner A Association, 2015.
[8] P. G., Somerville et al., Modification of Empirical Strong Ground Motion Attenuation Relations to Include the Amplitude and Duration Effects of Rupture Directivity, Seismological Research Letters, Vol. 68, No. 1, pp. 199- 222, 1997.
[9] ASCE/SEI-2005 Minimum Design Loads for Buildings and Other Structures, Published by American Society of Civil Engineers, 1801 Alexander Bell Drive, Reston, Virginia 20 19 1, www.pubs.asce.org
[10] D. M., Boore, J. Watson-Lamprey, N. A., Abrahamson, Orientation-Independent Measures of Ground Motion, Bulletin of the Seismological Society of America, Vol. 96, No. 4A, pp. 1502–1511, 2006.
[11] D. M., Boore, Short Note Orientation-Independent, Nongeometric-Mean Measures of Seismic Intensity from Two Horizontal Components of Motion, Bulletin of the Seismological Society of America, Vol. 100, No. 4, pp. 1830–1835, 2010.
[12] A., Nicknam, E., Youssefi; Modification of Design Response Spectra in Iranian Standard 2800 (4th Version) Taking into Account the Directivity Effects, Amirkabir Journal of Science and Research (Civil and Environmental engineering), Vol. 46, No. 2, pp. 57-59,2014. (In Persian)
[13] A., Nicknam, E., Youssefi; Modification of Iran 2800 Standard for Near-source Sites by Use of NZS 1170.5 (Comparison of Base Shear with other Standards), Journal of ASAS, Vol. 36, 2013. (In Persian)
[14] NZS1170. 5; Structural Design Actions, Part 5: Earthquake Actions, 2004.
[15] A., Nicknam, E., Youssefi, A., Mazarei; Iran Seismic Design Loads Code Assessment through Comparing with those of NZS 1170.5 and Criticizing its Approach to Account for the Directivity Effects at Near Source Sites. Amirkabir Journal of Science and Research (Civil and Environmental Engineering), In Press. (In Persian)
[16] A., Nicknam, A., Mazarei, M., Ganjvar; Assessment of Iran Seismic Design Response Spectra (Standard No. 2800) Regarding Site-distance Effects Particularly at Near Fault Sites, Amirkabir Journal of Science and Research (Civil and Environmental Engineering), In Press. (In Persian)
[17] J., Shoja-Taheri, B. A., Bolt, A Generalized Strong-Motion Accelerogram Based on Spectral Maximization from Two Horizontal Components, Bull. Seism. Soc. Am., Vol. 67, pp. 863–876, 1977.
[18] J. W., Baker, Conditional Mean Spectrum: Tool for Ground Motion Selection, Journal of Structural Engineering, Vol. 137, No. 3, pp. 322-331, 2011.
Amirkabir Journal of Civil Engineering
Volume 49, Issue 1
June 2017
Pages 197-208

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