Abstract
In the years since the 1994 Northridge earthquake, the profession has paid significant attention to the potential effects of various forms of deterioration in connection strength and stiffness that steel moment-resisting frames can experience during severe seismic excitations. The brittle connection fractures that a number of welded steel moment-resisting frame structures experienced during recent earthquakes have been the most extensively studied to date. However, cyclic testing of post-Northridge beam-column connections demonstrates that ductile connections may suffer other forms of deterioration. Negative post-yield tangent stiffness or capping, hereafter referred to as deformation softening, is a behavior of particular interest because it may have significant adverse effects on frame system behavior. The effects of deformation softening on frames subjected to pulse excitations were examined as part of an integrated experimental and analytical investigation of the effect of various forms of hysteretic deterioration on the overall system behavior of moment resisting steel frames. Pulse excitations, and the near-field ground motions they represent, can be highly damaging to structures and are therefore the primary focus of the results presented in this paper. The experimental portion of this study consisted of a series of thirty-two shaking table tests, which were performed on a one-third scale, two-story, one bay, steel moment frame with idealized, mechanical connections. These tests and subsequent analytical studies show that, in general, significant loss of connection strength capacity, whether from deformation softening or other types of deterioration, leads to large residual drifts and, for large pulse excitations with durations longer than the fundamental period of the structure, to collapse. In particular, frames with connections exhibiting negative post-yield stiffness tend to have substantially increased peak and residual displacements when subjected to pulse excitations.
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Aschheim, M. and Black, E. (1999). “Effects of prior earthquake damage on seismic response of simple stiffness-degrading structures.” Earthquake Spectra, 15(1), pp. 1–24.
Bernal, D. (1992). “Instability of buildings subjected to earthquakes.” Journal of Structural Engineering, ASCE, 118(8), pp. 2239–2260.
Bertero, V. V., Anderson, J. C., and Krawinkler, H. (1994). Performance of steel building structures during the Northridge earthquake. Rep. No. UCB/EERC-94/09, Earthquake Engrg. Res. Ctr., University of California, Berkeley, Calif.
Federal Emergency Management Agency (FEMA) (2000a). Recommended seismic design criteria for new steel moment-frame Buildings. FEMA-350, prepared by the SEAOC-ATC-CUREE (SAC) Joint Venture for FEMA, Washington, DC.
FEMA (2000b). State of the art report on connection performance. FEMA-355D, prepared by the SAC Joint Venture for FEMA, Washington, DC.
Ibarra, L.F. and Krawinkler, H. (2005). Global collapse of frame structures under seismic excitations. Rep. No. PEER/2005/06, Pacific Earthquake Engrg. Res. Ctr., Richmond, Calif.
Lignos, D. and Krawinkler, H. (2007). Contributions to collapse prediction for frame structures. Final Report, Kajima-CUREE Joint Research Program, Phase VI: Investigation of Factors Leading to Progressive Collapse of Structures, Category 2: Analysis of Structural Component Failure, Stanford Univ., Stanford, Calif.
Mahin, S. A. and Morishita, K. (1998). “The effect of strength deterioration on the dynamic response of simple systems subjected to impulsive loading.” Proc. U.S.-Japan Workshop on Near-field Earthquake Damage in Urban Areas, published as Rep. EERL 98-01, Earthquake Engrg. Res. Lab., California Inst. of Tech., Pasadena, Calif.
Mazzoni, S., McKenna, F., Scott, M. H., Fenves, G. L., and Jeremic, B. (2003). Open system for earthquake engineering simulation (OpenSees) command language manual, Online publication 〈www.opensees.berkeley.edu〉 (April 14, 2004).
Miranda, E., and Akkar, S. D. (2003). “Dynamic instability of simple structural systems.” Journal of Structural Engineering, ASCE, 129(12), pp. 1722–1726.
Rahnama, M. and Krawinkler. (1993). “Effects of soft soil and hysteresis model on seismic demands.” Rep. BLUME-108, John A. Blume Earthquake Engrg. Ctr., Stanford Univ., Stanford, Calif.
Rodgers, J. E. and Mahin, S. A. (2004). Effects of connection hysteretic degradation on the seismic behavior of steel moment-resisting frames. Rep. No. PEER/2003/13, Pacific Earthquake Engrg. Res. Ctr., Richmond, Calif.
Rodgers, J. E., and Mahin, S. A. (2006). “Effects of connection fractures on global behavior of steel moment frames subjected to earthquakes.” Journal of Structural Engineering, ASCE, 132(1), pp. 78–88.
Rodgers, J. E., Mahin, S. A., and van Dam, M. (2006). “Versatile mechanical connections for use in research and education related to the inelastic seismic behavior of steel frames.” Proc., 4 th Int. Symp. on Steel Struct., Seoul, Korea, pp. 1214–1224.
Vamvatsikos, D. and Cornell, C. A. (2002). “Incremental dynamic analysis.” Earthquake Engineering and Structural Dynamics, 31(3), pp. 491–514.
van Dam, M. (2000). Effect of hysteretic degradation on seismic response of steel structures. M.Eng. thesis, Univ. of California, Berkeley, Calif.
Vian, D. and Bruneau, M. (2003). “Tests to collapse of single degree of freedom frames subjected to earthquake excitations.” Journal of Structural Engineering, ASCE, 129(12), pp. 1676–1785.
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Note.-Discussion open until August 1, 2011. This manuscript for this paper was submitted for review and possible publication on March 13, 2010; approved on November 17, 2010.
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Rodgers, J.E., Mahin, S.A. Effects of connection deformation softening on behavior of steel moment frames subjected to earthquakes. Int J Steel Struct 11, 29–37 (2011). https://doi.org/10.1007/S13296-011-1003-9
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DOI: https://doi.org/10.1007/S13296-011-1003-9