New Lateral Force Distribution for Seismic Design of Structures Based on Seismic Demand Ratio

Document Type: Regular Paper

Authors

1 Department of Civil Engineering, Isfahan Science and Research Branch, Islamic Azad University, Isfahan, Iran and Department of Civil Engineering, Isfahan (Khorasgan) Branch, Islamic Azad University, Isfahan, Iran

2 Department of Civil Engineering, Isfahan University of Technology, Isfahan, Iran

Abstract

The design of earthquake-resistant buildings starts with defining the maximum lateral earthquake forces or their resultant. The amount of these forces depends on various factors, including coefficient of system behavior which depends on over strength and its ductility. In this study, a method is proposed in order to design an earthquake-resistant system in which the distribution of lateral forces is adjusted based on equal distribution of the seismic demand ratio in structural elements for the optimum use of seismic capability of the structure. To this end, three types of 4-, 7-, and 10-story structures are Applied. Firstly, the above-mentioned structures are designed based on gravity loads and consequently analyzed based on linear and nonlinear dynamic analyses, applying the accelerograms of some major earthquakes. Pursuant to that, the average loading ratio to the allowed capacity of the elements of each story in linear analysis and the average ratios of plastic rotations to the allowed capacity of elements in nonlinear analysis are applied as the modified shear ratio in the Iranian National Seismic Code. On that account, the new lateral loading distribution is measured and identified. Based on this new distribution, the above-mentioned structures are designed and their seismic behaviors are identified, applying linear and nonlinear dynamic analyses of the same accelerograms. The findings indicate an ameliorated seismic behavior of the beams and the columns. Moreover, the distribution of the seismic demand ratios attains more uniformity along the height of the structures.

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Main Subjects


[1] Elnashai, A. s. (2002). “A Very Brief History of Earthquake Engineering with Emphasis on Developments in and from the British Isles”. Chaos Solitons & Fractals, Vol. 13, pp. 967-972.

[2] Moghaddam, H., Hosseini Gelekolai, S. M., Hajirasouliha, I., and Tajali, F. (2012). “Evaluation of Various Proposed Lateral Lload Patterns for Seismic Design of Steel Moment Resisting Frames”. 15th World Conference on Earthquake Engineering, Lisbon, Portugal, September 24-28.

[3] Newmark, N. M., Hall, W. J. (1982). “Earthquake Spectra and Design”. Berkeley, Earthquake Engineering Research Institute, ISBN: 0943198224.

[4] Fajfar, P. (1992). “Equivalent Ductility Factors, Taking in to Account Low-Cycle Fatigue”. Journal of Earthquake Engineering and Structural Dynamics, Vol. 21, pp. 837-848.

[5] Mezgebo MG, Lui EM., (2017). “A new methodology for energy-based seismic design of steel moment frames”. Journal of Earthquake Engineering and Engineering Vibration. Vol. 16, No. 1, pp. 131-52.

[6] Barrera, A.C., Bonet, J.L., Romero, M.L., Fernández, M.A. (2012). “Ductility of Slender Reinforced Concrete Columns under Monotonic Flexure and Constant Axial Load”. Journal of Engineering Structures, Vol. 40, pp. 398–412.

[7] Bazzaz M., Andalib Z., Kheyroddin A. and Kafi M.A., (2015). “Numerical Comparison of the seismic Performance of Steel Rings in Off-centre Bracing System and Diagonal Bracing System”. Journal of Steel and Composite Structures, Vol. 19, No. 4, 917-937.

[8] Bazzaz M., Andalib Z., Kafi M.A. and Kheyroddin A., (2015). “Evaluating the Performance of OBS-C-O in Steel Frames under Monotonic Load”, Journal of Earthquakes and Structures, Vol. 8, No.3, 697-710.

[9] FEMA356. (2000). “Pre-Standard and Commentary for the Seismic Rehabilitation of Buildings”, Federal Emergency Management Agency, Washington, DC.

[10] Prak. Y. J., Ang. A. H-S., Wen. Y. K. (1984). “Seismic Damage Analysis and Damage-Limiting Design of RC Building”. Technical Report of Research Supported by the National Science Foundation Division of Civil & Environmental Engineering (Under Grants CEE 80-02584 and CEE 82-13729), USA.

[11] Moghadam, H., and KaramiMohammadi, R. (2006). “More Efficient Seismic Loading for Multi Degrees of Freedom Structures”. Journal of structural Engineering, ASCE, Vol. 132, pp.1673-1677.

[12] Hajirasouliha, I., and Moghadam, H. (2009). “New Lateral Force Distribution for Seismic Design of Structures”. Journal of structural Engineering, ASCE, Vol. 135, pp. 906–915.

[13] Rahami.M.A., Moghaddam H, Hajirasouliha I. (2007). “Optimum Performance-Based Design of Steel Moment Resistant Frames for Seismic Excitations”. 5th international Conference on Seismology & Earthquake Engineering, Tehran, Iran, May 13-16.

[14] Building and housing research center. (2007). “Iranian code of practice for seismic resistant design of buildings", Iranian National Seismic Code, Tehran, Iran.

[15] Ministry of Housing and Urban Development. (2006). “Iranian National Building Code for Structural Loadings-Part 6”, Tehran, Iran.

[16] Computers and Structures. (2010). Inc., CSI Analysis Reference Manual for SAP2000, Computer and Structures, Inc., Berkley, California.

[17] Ministry of Housing and Urban Development. (2008). “Iranian National Building Code for Steel Structures-Part 10”, Tehran, Iran.

[18] PEER: NGA Database, Pacific Earthquake Engineering Research Center, University of California, Berkeley, http://peer.berkeley.edu/nga/.

[19] ASCE/SEI 7-10., (2010), “Seismic Rehabilitation of Existing Buildings”. American Society of Civil Engineers

[20] Mazzoni, S., Mckenna, F., Scott, M.H., Fenves, G., (2004). “OpenSees user’s Manual”, www.opensees.berkeley.edu

[21] Safi. M, Tehranizadeh. M. (2004). “Effectof Ductility Demand Distribution on Displacement Based Design of Steel Frames”. 13th World Conference on Earthquake Engineering, Vancouver, B.C., Canada, August 1-6.