Why determining the number of code spectrum-matched records based on usual statistics is an ill-posed problem

摘要: The most advanced analytical tool in earthquake engineering is non-linear dynamic analysis, which typically entails a computer model of a structure subjected to a set of real recorded accelerograms. Although computationally demanding, this type of analysis is gradually becoming the norm in seismic design and assessment applications. Seismic reliability calculations according to the paradigm of performance-based earthquake engineering (PBEE) use dynamic analysis results to estimate the probabilistic distribution of structural response. In this context, the uncertainty in estimation of structural seismic risk depends, among other things, on the number of records used. On the other hand, modern seismic codes that espouse PBEE principles, but do not incorporate its probabilistic framework, do not require explicit estimates of structural seismic risk and acquiesce to the use of dynamic analysis for the purpose of pass/fail verifications of a single performance level, based on comparing average response vs fixed thresholds. While structural seismic reliability studies use a few tens of records, codes often require no more than seven to eleven records for obtaining an estimate of mean response, mandating that these records be selected based on criteria of compatibility with the design spectrum. The present study addresses this issue by investigating the effect of spectrum-compatible acceleration records’ sample size on estimating average single-stripe inelastic structural response. To this end, multiple record sets are assembled, with a fixed number of records that are all selected to match-on-average the same target design spectrum, without repeating …