A rapid beyond-design-basis check for critical building structures based on energy-bound critical excitation

Critical facilities must remain operational after rare earthquakes. However, spectrum-compatible analysis may underrepresent resonance-amplified structural responses. This limitation persists even when a beyond-design-basis earthquake (BDBE) philosophy—used initially for nuclear facilities—is desired for essential buildings. The contribution of this study is a supplementary BDBE screening framework for critical buildings that integrates established energy-bounded critical excitation (CE) mechanics with conventional ASCE nonlinear response-history analysis. The approach compares conventional responses obtained from PEER NGA-West2 recorded motions spectrally matched to the site-specific design basis earthquake (DBE) and risk-targeted maximum considered earthquake (MCE R ) target spectra with synthesized CE motions constrained by Arias intensity, peak ground acceleration (PGA), and peak ground velocity (PGV), and shaped to concentrate admissible energy near the dominant modal range. The three CE responses are summarized by their minimum, mean, and maximum values for base shear and interstory-drift. We evaluated 8- and 20-story steel buildings in both fixed-base and base-isolated configurations under conventional DBE and MCER suites and CE motions. The comparisons show that the relationship between conventional suite-mean demands and the CE response range varies with building height, support configuration, and response quantity, with CE demands exceeding the conventional MCE R suite mean in some cases. The CE range is conditional on the three adopted historical constraint sets and has no assigned exceedance probability or return period. Exceedances of the conventional MCE R suite mean are therefore interpreted as demand observations relevant to beyond-design-basis screening, rather than as evidence of a calibrated BDBE hazard level. Overall, the CE approach provides a supplementary structural-demand screening tool for identifying resonance-sensitive differences between the conventional suite and the CE-derived demand range. Where such differences occur, the results can motivate further review of the selected ground-motion suite and, where necessary, a separate structural-capacity assessment. This study is limited to base-shear and interstory-drift demands and does not, by itself, establish structural acceptance, functional continuity, downtime, or retrofit effectiveness.