Dynamic Response Spectrum of Multi-Story Shear Frame Subjected to Moderate Ground Motion

Assal Hussein

doi:10.24237/djes.2021.14207

Authors

Assal Hussein
assal_hussein_eng@uodiyala.edu.iq
Civil Engineering, University of Diyala

Keywords:

Earthquake, Response spectrum, Modal analysis, Shear frame, Ground motion

Abstract

Design structures to resist natural hazards is a vital issue to mitigate the impact of such threats. Earthquakes could lead to numerous injuries and infrastructure destruction. Specifically, when structures are not designed to resist seismic load. This article presents dynamic analysis of four-story shear frame under moderate ground motion to determine the dynamic response. The proposed location of the considered frame is near Iraq-Iran border due to increase of seismic activities in last years. Structures in the considered seismic zone are essentially either residential or commercial buildings and not designed to resist seismic load, therefore structural system failure is probable. Simplified model is considered to determine response spectrum according to the International Building Code requirements. The algorithm of the analysis is developed using MATLAB^® code to get mode shapes, response spectrum acceleration, maximum displacement, maximum shear forces, and modal participation mass at each story. The article develops design response spectra curve of Erbil city. Furthermore, the analysis results showed that first mode shape has more contribution than the other modes because higher percentage of the mass of the shear frame responds to the ground motion, and 88.53% of shear-frame mass is participating responds to the ground motion in the same mode.

Conclusions

The current study computed dynamic response spectrum of multi-story shear frame located in northern of Iraq near borders with Iran due to significant activities in last years. While the topic is well known in the structural dynamics filed, but the application of the current study is ever pressing since most of structures have not been designed to resist earthquakes and casualties and losses is probable.

Numerical evaluation has been performed of four-story shear frame subjected to ground motion using MATLAB^®. The design response spectrum is predicted for Erbil city which is located north of Iraq since moderate-scale earthquakes have been noticed in last years. Design structures to resist seismic load is essential to protect occupants and reduce losses. The framework of the study consists of running modal analysis to calculate the natural frequency, period and mode shapes of the shear-frame. The response spectrum matrix is calculated according to IBC code requirements. Furthermore, peak modal displacement, total shear at each story level are determined using square root of the sum of the squares (SRSS) combination method. Finally, the results of the analysis showed 88.53% of shear-frame mass is participating responds to ground motion in the first mode.

Downloads

Download data is not yet available.

References

Said, A.I.(2010). Development of design response spectra for Baghdad area. Urban Habitat Constr. Under Catastrophic Events Proc. COST C26 Action Final Conference. (Naples, Italy, 71.

Farman, M.S., Said A.I (2018). Updated Probabilistic Seismic Hazard Assessment for Iraq. Civil Engineering Journal, 4(7), 1610–1628.

U.S. Geological Survey (2017). M 7.3-29km S of Halabjah, Iraq 2017. Retrieved,March10,2020,from https://earthquake.usgs.gov/earthquakes/eventpage/us2000bmcg/executive

Al-Heety, E. A. (2014). A complete and homogeneous magnitude earthquake catalogue of Iraq. Arabian Journal of Geosciences, 7(11), 4727-4732.

Biggs, J. M. (1964). Introduction to structural dynamics. McGraw-Hill College.

Chopra A. K. (2011). Dynamics of structures (4th ed.). New York: Pearson Higher Ed.

Wilson, E. L. (2002). Three dimensional static and dynamic analysis of structures: a physical approach with emphasis on earthquake engineering. Computers and structures,Inc.

International Code Council (COR). (2011). International Building Code, 2012. In-ternational Code Council.

Jackson J.; McKenzie, D. (1984). Active tectonics of the Alpine-Himalayan Belt between western Turkey and Pakistan. Geophysical Journal International, 77(1), 185-264.

Alsinawi, S. A., and Al-Qasrani, Z. O. (2003). Earthquake hazards consideration for Iraq. In Fourth International Conference of Earthquake Engineering and Seismology. Teh-ran, Islamic Republic of Iran, 12-14.

Alsinawi, S. A., and Ghalib,HAA. (1975). SEISMICITY AND SEISMOTECTONICS OF IRAQ.

Al-Abbasi, J. N., and Fahmi, K. J. (1985). Estimating maximum magnitude earthquakes in Iraq using extreme value statistics. Geophysical Journal International, 82(3), 535-548.

Al-Qasrani, Z. (1990). Seismological engineering considerations of Iraq. Unpubl M Sc Thesis, Coll Sci Dep Geol Univ Baghdad ,139.

Ameer, A. S., Sharma, M. L., Wason, H. R., and Alsinawi, S. A. (2005). Probabilistic seismic hazard assessment for Iraq using complete earthquake catalogue files. pure and applied geophysics, 162(5), 951-966.

Newmark, N. M. (1982). Earthquake spectra and design. Earthquake Eng. Research Institute, Berkeley, CA.

Clough, R. W., and Penzien, J. (1993). Dynamics of structures. New York: MacGraw-Hill. Inc Editor.