Earthquake Engineering Research - HKU Libraries - The University ...

292
by using the computer program SNAP-2DX (Rai et al., 1996). Strain hardening and damping values of
2 % were used for all members.
Fig. 7 shows the base shear versus roof displacement plot of the frame obtained from die static
pushover analysis. As can be seen, the yield drift and the design base shear of the frame are very close
to the values assumed in the design. Fig. 8 shows the envelopes of maximum story drifts of the frame
due to the four selected ground motions. The envelopes of maximum story drifts show that the story
drifts are generally within the target design limit of 2%, as expected.
Conclusion
A new seismic design procedure based on modified energy balance equation and plastic design concept
was presented and discussed. A new modification factor for energy was derived, which depends on the
structural ductility factor f ju^) and the ductility reduction factor (R M ). A new design lateral force
distribution based on nonlinear inelastic dynamic analysis results was used. In this proposed design
method, the story drift is specified as a design parameter and, therefore, no explicit check for ultimate
drift is required.
The example 9-story frame was designed by the proposed design method. Nonlinear static and
dynamic analyses of the frame were conducted to verify the proposed method. The results show that
the proposed method can produce structures that meet preselected performance objectives in terms of
yield mechanism and target drift.
References
Lee, Soon-Sik and Goel, S.C., U A New Lateral Force Distribution for Seismic Design of Steel
Structure," Proceedings of U.S.-Japan Workshop on Seismic Fracture Issues in Steel
Structures, San Francisco, CA, February 28-March 1, 2000.
Leelataviwat, S. (1998), Drift and Yield Mechanism based Seismic Design and Upgrading of
Steel Moment Frames, Ph.D. Thesis, Department of Civ. & Env. Engrg., University of
Michigan, Ann Arbor, MI, USA.
Miranda, E. and Bertero, V.V. (1994), "Evaluation of Strength Reduction Factors for
Earthquake-Resistant Design," Earthquake Spectra, Vol. 10, No. 2, 1994
Newmark, N.M. and Hall, W.J. (1982), Earthquake Spectra and Design, Earthquake Engrg.
Res. Inst, El Cerrito, CA.
Rai, D.C., Goel, S.C., and Firmansjah, J. (1996), U SNAP-2DX: A General Purpose Computer
Program for Nonlinear Structural Analysis," Report EERC 96-21, Dept. of Civ. & Env.
Engrg., University of Michigan, Ann Arbor, ML
Uang, C.-M. and Maarouf, A. (1994), "Deflection Amplification Factor for Seismic Design
Provisions," J. Struc. Engrg., Vol. 120, No. 8,2423-2436, ASCE
Uniform Building Code (UBC) (1997), Int. Conf. of Bldg. Officials, Whittier, Calif.