Professor Neal Simon Kwong has co-authored paper titled "Determining Bi-Directional Ground Motions for Nonlinear Response History Analysis of Buildings at Far-field Sites" to be published in the Earthquake Spectra journal.

Abstract:

The current practice for selecting bi-directional ground motions (GM pairs) to conduct nonlinear response history analysis (RHA) of buildings depends on the separation between the fundamental periods along its two orthogonal structural axes. To overcome the key but subtle limitations of this practice, we propose to define these fundamental periods using the concept of effective modal masses and select GM pairs to be consistent with a pair of target spectra defined along the structural axes; this approach provides a unique azimuth for each GM pair. We develop two new target spectra: (i) the s-GCMS for two horizontal components of GM and (ii) the CMS-UHS Composite Spectrum. Based on nonlinear RHAs of buildings with both symmetric and unsymmetric plans, the CMS-UHS Composite Spectrum is observed to be the best alternative to the current practice of utilizing multiple conditional mean spectra, because it provides accurate demands with minimal computational effort and can be easily constructed using existing hazard analysis tools.