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The choice of spectral targets for ground motion selection has a strong impact on structural demands resulting from nonlinear time history analysis. In particular, the conditional mean spectrum (CMS) has been recognized as an appealing alternative to the uniform hazard spectrum (UHS) as a spectral target due to the former's more realistic shape and reduced conservatism. Using a tall building case study in a high-seismicity region, this paper evaluates the building demands generated by UHS- and CMS-based selection procedures. Theoretically rigorous implementation of CMS-based selection using 17 different conditioning periods is shown to reduce maximum considered earthquake (MCE)–level demands on the case study building by 9%–35% relative to UHS-based selection. Furthermore, the simplified CMS-based procedure in the building code with apt choice of only two conditioning periods is found to satisfactorily capture the demands generated by the theoretically rigorous approach. Findings also highlight the degree of sensitivity of CMS-based results to the choice of conditioning periods and to enforcement of lower bounds on spectral targets, such as 75% of the UHS. The presented analysis procedure can be replicated in future studies for explicit evaluation of simplified CMS ground motion selection in other structural systems or analysis cases. Since its introduction to the building code, the alternative, conditional mean spectrum-based method for ground motion selection has gained traction among practitioners due to its reduced conservatism relative to traditional selection methods. To simplify the implementation of conditional mean spectra in practice, the building code alternative method requires a minimum of only two target spectra be used, so long as their envelope satisfies a lower bound within a specified period range. However, there are few quantitative studies of the impacts of these simplifications on the resulting building demands. In this study, we demonstrate how building demands vary when a tall building in a high-seismicity region is analyzed using either a traditional or a conditional mean spectrum-based selection approach. We find that using two reasonable target spectra in accordance with the alternative method produces acceptable building demands as compared to the demands obtained from performing exhaustive nonlinear analysis with a large number of target spectra. Furthermore, we illustrate how different choices of conditional mean spectrum targets maximize different types of building demands (e.g., interstory drift, base shear, floor acceleration) and how some types of demands are more sensitive to this choice than others. This work provides a procedure for evaluating conditional mean spectrum-based ground motion selection that can be replicated in the future for other buildings or structural systems. [ABSTRACT FROM AUTHOR]

The scarcity of strong ground motion records presents a challenge for making reliable performance assessments of tall buildings whose seismic design is controlled by large‐magnitude and close‐distance earthquakes. This challenge can be addressed using broadband ground‐motion simulation methods to generate records with site‐specific characteristics of large‐magnitude events. In this paper, simulated site‐specific earthquake seismograms, developed through a related project that was organized through the Southern California Earthquake Center (SCEC) Ground Motion Simulation Validation (GMSV) Technical Activity Group, are used for nonlinear response history analyses of two archetype tall buildings for sites in San Francisco, Los Angeles, and San Bernardino. The SCEC GMSV team created the seismograms using the Broadband Platform (BBP) simulations for five site‐specific earthquake scenarios. The two buildings are evaluated using nonlinear dynamic analyses under comparable record suites selected from the simulated BBP catalog and recorded motions from the NGA‐West database. The collapse risks and structural response demands (maximum story drift ratio, peak floor acceleration, and maximum story shear) under the BBP and NGA suites are compared. In general, this study finds that use of the BBP simulations resolves concerns about estimation biases in structural response analysis which are caused by ground motion scaling, unrealistic spectral shapes, and overconservative spectral variations. While there are remaining concerns that strong coherence in some kinematic fault rupture models may lead to an overestimation of velocity pulse effects in the BBP simulations, the simulations are shown to generally yield realistic pulse‐like features of near‐fault ground motion records. [ABSTRACT FROM AUTHOR]