Postprint version. Published in Earthquake Spectra, Volume 20, Issue 3, August 1, 2004, pages 757-778.
Copyright © 2004 Earthquake Engineering Research Institute. This article may be downloaded for personal use only. Any other use requires prior permission of the Earthquake Engineering Research Institute. The definitive version is available at http://dx.doi.org/10.1193/1.1775237.
The modal pushover analysis (MPA) procedure, which includes the contributions of all significant modes of vibration, estimates seismic demands much more accurately than current pushover procedures used in structural engineering practice. Outlined in this paper is a modified MPA (MMPA) procedure wherein the response contributions of higher vibration modes are computed by assuming the building to be linearly elastic, thus reducing the computational effort. After outlining such a modified procedure, its accuracy is evaluated for a variety of frame buildings and ground motion ensembles. Although it is not necessarily more accurate than the MPA procedure, the MMPA procedure is an attractive alternative for practical application because it leads to a larger estimate of seismic demands, improving the accuracy of the MPA results in some cases (relative to nonlinear response history analysis) and increasing their conservatism in others. However, such conservatism is unacceptably large for lightly damped systems, with damping significantly less than 5%. Thus the MMPA procedure is not recommended for such systems.
Civil and Environmental Engineering