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43 records have higher amplitudes in high frequency (low- period) ranges. · The difference in spectral shape between WUS and CEUS records is more evident for the rock records. · Having larger amplitudes at long periods implies that for the same PGA, the earthquake records in WUS will have larger PGV, therefore inducing larger displacements in the structure. 5.2.6 Correlation between PGV and S1, PGA and M Several correlations between PGV and other ground mo- tion parameters such as S1, PGA, and M were developed dur- ing this study. After reviewing recent publications related to this subject, a revised form of a PGV correlation suggested by Abrahamson (2005) for the estimation of PGV from spectral acceleration at one second (S1) was selected for use, as dis- cussed in Section 5.3. It is expected that in the future, USGS will publish recom- mended PGV values for different locations nationwide. In that case the S1-PGV correlation will be replaced in favor of design PGV values, and the designers can use Newmark displace- ment correlations directly using the USGS-recommended PGV values. Figure 5-7. Strong motion information database 5.2.7 Newmark Sliding Block model. Displacement Correlations Various researchers have proposed different correlations information database, and Table 5-4 gives a description of each for predicting the permanent displacement of earth structures field in the Access database. The developed database can be used subjected to seismic loading. A summary and comparison of to efficiently explore correlations between different record char- some of these correlations can be found in a paper by Cai and acteristics. It also can be used to prepare data sets required for Bathurst (1996). The majority of these correlations are based various statistical analyses. on the results of direct Newmark sliding block analyses on a set of strong motion records. Martin and Qiu (1994) used the following general form for 5.2.5 Spectral Acceleration Characteristics estimation of Newmark displacement: To compare strong motion records from different re- d = C ( k y kmax ) (1 - ky kmax ) Aa 3V a 4 M a 5 a1 a2 gion, magnitude, and soil type bins, the normalized spec- (5-1) tral acceleration and normalized relative density graphs are plotted for each bin. The average spectrum for each region- Using a database of earthquake records with a magnitude site condition for different magnitude ranges was calcu- range between 6.0 and 7.5, published by Hynes and Franklin lated. The average normalized spectra are presented in (1984), Martin and Qiu concluded that the correlation with M Figures 5-8 and 5-9. (magnitude) is negligible. The following simplified equation Results in Figures 5-8 and 5-9 show the following trends: was proposed by Martin and Qiu and adopted in NCHRP 12-49 Project: · Records with higher magnitudes generally have higher am- d = 6.82 ( k y kmax ) (1 - ky kmax ) -0.55 5.08 A -0.86V -0.8 86 M 1.66 (5-2) plitude in the long-period range. · Records for WUS and CEUS generally have different spec- where tral shapes. WUS records have higher normalized ampli- d = permanent displacement in inches, tudes in lower frequency (long-period) ranges, while CEUS ky = yield acceleration,
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44 Table 5-4. Description of different fields in the access ground motion database. Table Field Description INFOTAB NO Earthquake event number INFOTAB EARTHQUAKE Earthquake event name INFOTAB YEAR Event year INFOTAB MODY Event date INFOTAB HRMN Event time INFOTAB MAG Earthquake magnitude INFOTAB OWN Station owner INFOTAB STNO Station number INFOTAB STATION Station name INFOTAB DIST Closest distance from source INFOTAB GEOM Geomatrix site classification code INFOTAB USGS USGS site classification code INFOTAB HP Filter corner frequency, high INFOTAB LP Filter corner frequency, low INFOTAB PGA Peak ground acceleration INFOTAB PGV Peak ground velocity INFOTAB PGD Peak ground displacement INFOTAB DUR Duration INFOTAB FILENAME Record file name INFOTAB PAA1S Pseudo spectral acceleration at 1 second INFOTAB PRV1S Pseudo relative velocity at 1 second INFOTAB RD1S Relative displacement at 1 second INFOTAB PAAMAX Peak pseudo spectral acceleration INFOTAB PRVMAX Peak pseudo relative velocity INFOTAB RDMAX Peak relative displacement INFOTAB DUR95 5%-95% Arias intensity duration INFOTAB REGION Region (WUS or CEUS) INFOTAB SITE Site type (Soil/Rock) NEWMARK FILENAME Record file name NEWMARK REGION Region (WUS or CEUS) NEWMARK SITE Site type (Soil/Rock) NEWMARK DIR Record direction (horizontal/vertical) NEWMARK MAG Earthquake magnitude NEWMARK PGA Peak ground acceleration NEWMARK KYMAX ky/kmax (ratio of yield acceleration to PGA) NEWMARK DISP Calculated permanent (Newmark) displacement Note: Rock/Soil Definitions A and B for rock, C, D and E for soil based on NEHRP classification. kmax = the maximum seismic acceleration in the sliding block, log ( d ) = b0 + b1 log ( k y kmax ) + b2 log (1 - k y kmax ) A = peak ground acceleration (in/sec2), and + b3 log ( kmax ) + b4 log ( PGV ) (5-3) V = peak ground velocity (in/sec). Using a logarithmic transformation of the data helped to A correlation based on Equation (5-2), but in logarithmic stabilize the variance of residuals and normalize the variables, form, was used for estimation of Newmark displacement hence improving the correlation in the entire range of the from peak ground acceleration and peak ground velocity. parameters. Writing Equation (5-2) in logarithmic form resulted in the The coefficients for Equation (5-3) were estimated using following equation: regression analysis. The permanent displacement data from
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45 Figure 5-8. Average normalized spectral acceleration for rock records. Figure 5-9. Average normalized spectral acceleration for soil records.