Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 49
49 Figure 5-16. Comparison between Martin-Qiu and WUS-Soil correlations for PGV = 30 kmax. PGV = 60 × kmax, respectively, with respect to the mean design 5.3 Correlation of PGV with S1 curve given by Equation (5-8). A procedure for establishing the PGV for design from the spectral acceleration at one second (S1) also was developed for 5.2.10 Design Recommendations the Project. For earth and buried structures, PGV provides a For design applications, Equation (5-8) for soil and rock direct measure of the ground deformation (as opposed to sites for WUS and CEUS and Equation (5-6) for CEUS rock ground shaking parameters represented by the spectral am- sites are recommended. The regression curves shown on plitude) and is a more meaningful parameter than PGA or Figure 5-18 and Figure 5-19 suggest that 84 percent confi- spectral accelerations for designing against kinematic loading dence levels in displacement evaluations could be reason- induced by ground deformation. Also PGV is a key parame- ably approximated by multiplying the mean curve by a ter used for Newmark deformation analysis, as described in factor of 2. Section 5.2. Figure 5-17. Comparison between Martin-Qiu and WUS-Soil correlations for PGV = 60 kmax.
OCR for page 50
50 Figure 5-18. Mean Newmark displacement and 84% confidence level, PGA = 0.3g, PGV = 30 kmax. The initial approach taken to develop the PGV-S1 correla- based on the spectral acceleration at 1 second (S1) and the tion involved performing statistical studies of the USNRC magnitude (M) of the earthquake. database. However, the resulting correlation exhibited con- ln ( PGV ) = 3.97 + 0.94 ln ( S1 ) + 0.013 ( ln ( S1 ) + 2.93) 2 siderable scatter. Subsequently a correlation being devel- oped by Dr. Norm Abrahamson of the Pacific Gas and + 0.063 M (5-9) Electric Group in San Francisco was identified through dis- cussions with seismologists involved in ground motion where PGV is in units of cm/sec, S1 is spectral acceleration at studies. Dr. Abrahamson forwarded a draft paper that he was T = 1 sec in units of g, and M is magnitude. Dr. Abrahamson writing on the topic. (A copy of the draft paper was originally reported that this equation has a standard deviation of 0.38 included in Appendix D. Copyright restrictions prevented in- natural log units. cluding this draft as part of the Final Report for the NCHRP Because the strong motion database used in Dr. Abraham- 12-70 Project.) son's regression analyses consists of exclusively the WUS In the draft of the Abrahamson's paper, the following re- database, an evaluation was performed to determine whether gression equation was recommended for determining PGV the above regression equation would be valid for representative Figure 5-19. Mean Newmark displacement and 84% confidence level, PGA = 0.3g, PGV = 60 kmax.
OCR for page 51
51 CEUS records. The NUREG/CR-6728 strong motion data, as cluded that the PGV correlation could be significantly discussed in Section 5.2.4, was used to evaluate the validity simplified by eliminating the parameter M from Equation of the Abrahamson PGV equation shown above. Figures 5- (5-9). Dr. Abrahamson concurred with this suggestion. 20 through 5-24 present comparisons between the results of 3. During discussions with Dr. Abrahamson, various other the Abrahamson PGV equation and the strong motion data- versions of the PGV predictive equation were discussed. base from NUREG/CR-6728. Other versions involve using spectral acceleration at the The following conclusions can be made from Figures 5-20 3-second period. These equations are more suitable for through 5-24: capturing peak ground velocity if there is a strong velocity pulse from near-fault earthquake records. However, for 1. The Abrahamson PGV equation gives reasonable predic- applications involving the entire United States, especially tions using the NUREG/CR-6728 database, even though for CEUS, these near-fault attenuation equations are not the strong motion database from CEUS is characterized by believed to be relevant or appropriate at this time. much lower long-period ground motion content. Part of the reason is that the spectral acceleration at 1 second has Dr. Abrahamson reported that his research found that PGV been used as a dependent variable in the regression equa- is strongly correlated with the spectral acceleration at 1 second tion. The reasonableness of the comparisons occurs when (S1); therefore, the attenuation equation used S1 to anchor the rock and soil conditions are separated for the CEUS and regression equation. Dr. Abrahamson commented that be- the WUS. sides the 1-second spectral acceleration ordinate, other spec- 2. Magnitude (M) appears to play a very small role in affect- tral values around 1 second might be used to improve the PGV ing the predicted PGV result. For example, there is very lit- prediction; however, from his experience, the PGA (that is, tle change (that is, barely 10 percent) in the resultant PGV peak ground acceleration or spectral acceleration at zero- value as the magnitude M changes from 5.5 to 7.5. The in- second period) has a frequency too far off for correlating with sensitivity of magnitude, as well as the potential difficulty PGV, and this difference tends to increase the error in the and/or ambiguity in establishing the deaggregated magni- regression equation. From these comments, a decision was tude parameter for many CEUS sites where the seismic made to use the PGV equation based solely on the 1-second sources are not well defined, was discussed with Dr. Abra- spectral acceleration ordinate (S1). In all the presented figures, hamson (2005). From a practical perspective, it was con- the PGA amplitudes are depicted in four different categories. Figure 5-20. Comparison between Abrahamson PGV equation with all data in NUREG/ CR-6728.
OCR for page 52
52 Figure 5-21. Comparison between Abrahamson PGV equation with only NUREG/CR-6728 CEUS rock data. Figure 5-22. Comparison between Abrahamson PGV equation with only NUREG/CR-6728 CEUS soil data.
OCR for page 53
53 Figure 5-23. Comparison between Abrahamson PGV equation with only NUREG/CR-6728 WUS rock data. WUS-SOIL 100 10 0.0