Issues and Approaches for Implementing Conditional Mean Spectra in Practice

Ground‐motion selection for dynamic analysis of structures is often based on the conditional mean spectrum (CMS). The CMS is a spectrum that matches the uniform hazard spectrum (UHS) at a conditioning period but that also represents the response from a single earthquake scenario more realistically than the UHS. This paper discusses and offers solutions for several issues related to implementing CMS in practice. The issues covered are the selection of the conditioning period, the number of CMS necessary to cover the range of the UHS, how to broaden the CMS to match the UHS with fewer conditioning periods, how to compute a CMS for several ground‐motion prediction equations that is consistent with probabilistic seismic‐hazard analysis, the application of correlation coefficients to hard‐rock sites, and the robustness of correlation coefficients.