Predictive Equations to Quantify the Impact of Spectral Matching on Ground Motion Characteristics

Abstract

Spectral matching, the process of modifying a seed acceleration time history in intensity and frequency content until its acceleration response spectrum matches a target spectrum, is used extensively in practice. Predictive equations that quantify the impact of spectral matching on the peak ground velocity, peak ground displacement, Arias intensity, and cumulative absolute velocity of a scaled seed time history have been developed and validated on the basis of thousands of matched motions, three different earthquake scenarios, and numerous target spectra. It is found that spectral mismatch is the most critical factor affecting the changes in ground motion characteristics. The technique used for modification (e.g., time domain or frequency domain) is in many cases not critical. Based on the results, recommendations in order to minimize the impact of matching on the ground motion characteristics are provided.

A Probabilistic Approach Towards an Evaluation of Existing Code Provisions for Seismically Isolated Structures

“… The results obtained through a spectral matching procedure based on the RMSE factor [21] indicate a 5% probability of inelastic behavior and associated damage in the superstructure for the design seismic hazard level (return period of 475 years).…”

“…From the 183 ground motions used that study, 20 motions were chosen for this study, using the minimization of the root-mean-squared error (RMSE) between the selected motions' acceleration response spectrum and the target design spectrum (Fig. 2), as performed by Carlson et al [21]. RMSE is defined as follows:…”

A Metric to Screen Acceptable Velocity and Displacement Time Histories of Modified Ground Motions

“…Motions were selected from the Pacific Earthquake Engineering Research Center (Chiou et al 2008), Consortium of Organizations for Strong Motion Observation Systems (COSMOS 2014), and European Strong Motion (Ambraseys et al 2001) databases and the study performed by McGuire et al (2001). Details on the selection process used to obtain representative ground motions for all three scenarios is presented in Carlson et al (2015). Ultimately, 108, 100, and 94 ground motions were selected for Scenarios I, II, and III, respectively.…”

“…More details on the development and implementation of the TD and FD modification processes used in this study are provided in Carlson (2014). Carlson et al (2015) presented four metrics that were used to quantify spectral mismatch:…”

“…The justification for using NE to quantify spectral mismatch is that it leads to the least amount of dispersion in the data as previously discussed in Carlson et al (2015). In addition to calculating NE for the entire range of periods for the response spectrum (T ¼ 0.01 s to 5 s), NE was also calculated for short period (T ¼ 0.01 s to 0.5 s), intermediate period (T ¼ 0.5 s to 3 s), and long period (T ¼ 3.0 s to 5.0 s) ranges.…”