Effect of Uplift on Behavior of Steel Structures and Response Modification Factors

Document Type : Research Article

Authors

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

2 International Institute of Earthquake Engineering and Seismology, Tehran, Iran

3 Senior Structural Engineer, National Iranian Oil Company, Ilam, Iran

Abstract

In design of structures for applied loads, the common assumption is that the structure is tightly attached to its base, i.e. no vertical rigid-body motion can happen at the same place. During a major earthquake, the couple of axial forces associated with the overturning moment can overcome that of the gravity loads in lateral load bearing columns and result in an uplifted column. With a building losing some of its contact points to the ground, a reduced lateral stiffness can be expected. This in turn can result in a reduced seismic base shear. At the same time, the structural members around the uplifted part can undergo large local deformations and perhaps a more extensive seismic damage. Illuminating the above predictions is the incentive of this research. In this paper, in the numerical part, a number of steel frames having various numbers of stories and bays are studied in two cases of without uplift (fxed base) and with uplift. The methods of analysis are the non-linear static and dynamic analysis procedures.According to the fndings, the uplift phenomenon generally has an important role in changing the behavior of structure and reduction of its response. At the same time, it can result in locally increased damages that sometimes can add up to total failures. The results showed that uplift increases the structural period and the absorbed energy, and decreases the displacements of most parts of the structures and their internal forces.

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References

[1] A.A. Hucklebridge, R.W. Clough, Seismic Response of Uplifting Building Frame, Journal of the Structural Division, 104(8) (1978) 1211-1229.
[2] I.N. Psycharis, Effect of Base Uplift on Dynamic Response of SDOF Structures, Journal of Structural Engineering, 117(3) (1991) 733-754.
[3] S.K. Smith, Parametric Analysis of Dynamically Loaded Concenterically Braced Steel Frames Allowed to Uplift, M.Sc. thesis, University of Washington, USA, (1995).
[4] M. Midorikawa, T. Azuhata, T. Ishihara, A. Wada, Shaking table tests on seismic response of steel braced frames with column uplift, Earthquake Engineering and Structural Dynamics, 35(14) (2006) 1767-1785.
[5] M. Midorikawa, T. Sudo, T. Asari, T. Azuhata, T. Ishihara, Three-dimensional seismic response of ten-story steel frames with yielding base plates allowed to uplift, Journal of Structural and Construction Engineering, 74(637) (2009) 495-502.
[6] X. Qin, N. Chouw, Experimental investigation of uplift effect on structures in earthquakes, 2010 NZSEE Conference, Auckland, New Zealand, (2010).
[7] M.E. Boostani Darmian, M. Azhdary Moghaddam, H.R. Naseri, Soil–Structure Interaction In Steel Braced Structures With Foundation Uplift, IJRRAS, 7(2) (2011) 185–191.
[8] F. Khoshnoudian, M. Shahreza, F. Paytam, P-Delta effects on earthquake response of structures with foundation uplift, Journal of Soil Dynamics and Earthquake Engineering, 34(1) (2012) 25–36.
[9] Y. Chen, X. Qin, N. Chouw, Effect of higher vibration modes on seismic response of a structure with uplift, Proceeding of the 15th World Conference on Earthquake Engineering, Lisbon, Portugal, (2012).
[10] F. Zhou, M. Mori, N. Fukuwa, A new uplift foundation analysis model to simulate dynamic nonlinear soilstructure-interaction, Proceeding of the The 15th World Conference on Earthquake Engineering, Lisbon, Portugal, (2012).
[11] FEMA356, Prestandard and Commentary for the Seismic Rehabilitation of Buildings, Federal Emergency Management Agency, Washington D.C., (FEMA Publication No. 356), (2000).
[12] NEHRP Recommended Provisions forSeismic Regulations for New Buildings and Other Structures, prepared by the Building Seismic Safety Council for the Federal Emergency Management Agency, Washington D.C., (2009).
[13] IBC, International Building Code, International Code Council, Falls Church, Virginia. (2009).
[14] ASCE/SEI 41-13, Seismic Rehabilitation of Existing Buildings, American Society of Civil Engineers, Reston, Virginia, (2013).
Amirkabir Journal of Civil Engineering
Volume 50, Issue 2
May and June 2018
Pages 315-326

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