Common use of Conclusions and Recommendations Clause in Contracts

Conclusions and Recommendations. In this article we have statistically tested the VS30-slope (or more specifically the NEHRP class-slope) correlations published by Wald and ▇▇▇▇▇ (2007) for Europe and parts of the Middle East. In total 706 sites with VS30 measurements were used. It is found that the technique leads to a site classification that is better than chance for all NEHRP site classes in active areas. For stable areas, there are still limited data to enable firm conclusions but our results suggest that the proposed correlations perform poorly in these zones. Based on our findings we reiterate the recommendations of ▇▇▇▇ and ▇▇▇▇▇ (2007) that site classifications based on VS30-slope correlations should only be used for regional or national (and not local or site- specific) first-order studies. In addition, they are only to be used in the absence of other more detailed information (e.g. microzonation studies) and not for sites inside small, relative to the DEM resolution, basins or those with special geological conditions that may affect results (e.g. flat-lying volcanic plateaux, carbonate rocks, glaciated continental terrain or coastal pixels if the slope is not calculated using bathymetric data). Again many of these limitations were stated by ▇▇▇▇ and ▇▇▇▇▇ (2007). Site classifications based on VS30-slope correlations are not sufficiently accurate to replace actual field measurements and they should not be used for site-specific studies. Consequences of erroneous estimation could be serious, so the user of such correlations should be aware that they only provide a first approximation and the true site class for a given site could be incorrect by one or, even, two classes (in either direction). At a local scale, further investigations should be carried out based on geology and measurements. In addition, the slope limits used for estimating VS30 are dependent on the slope-calculation algorithm and, as previously shown by ▇▇▇▇▇ and ▇▇▇▇ (2009) and ▇▇▇▇▇▇ et al. (2010), on the DEM resolution. We prefer predicting a site class rather than VS30 even when this is associated with a (large) standard deviation because we believe it gives a better indication that the site class is only an estimate and is not based on a measured VS30 value. We fear that the reporting of a numerical estimate for VS30 with a measure of its uncertainty would lead to the temptation to use the value and forget about the scatter.

Conclusions and Recommendations. In this article we have statistically tested the VS30Vs,30-slope (or more specifically the NEHRP class-slope) correlations published by Wald and ▇▇▇▇▇ (2007) for Europe and parts of the Middle East. In total 706 sites with VS30 Vs,30 measurements were used. It is found that the technique leads to a site classification that is better than chance for all NEHRP site classes in active areas. For stable areas, there are still limited data to enable firm conclusions but our results suggest that the proposed correlations perform poorly in these zones. Based on our findings we reiterate the recommendations of ▇▇▇▇ and ▇▇▇▇▇ (2007) that site classifications based on VS30Vs,30-slope correlations should only be used for regional or national (and not local or site- specific) first-order studies. In addition, they are only to be used in the absence of other more detailed information (e.g. microzonation studies) and not for sites inside small, relative to the DEM resolution, basins or those with special geological conditions that may affect results (e.g. flat-lying volcanic plateaux, carbonate rocks, glaciated continental terrain or coastal pixels if the slope is not calculated using bathymetric data). Again many of these limitations were stated by ▇▇▇▇ and ▇▇▇▇▇ (2007). Site classifications based on VS30Vs,30-slope correlations are not sufficiently accurate to replace actual field measurements and they should not be used for site-specific studies. Consequences of erroneous estimation could be serious, so the user of such correlations should be aware that they only provide a first approximation and the true site class for a given site could be incorrect by one or, even, two classes (in either direction). At a local scale, further investigations should be carried out based on geology and measurements. In addition, the slope limits used for estimating VS30 Vs,30 are dependent on the slope-calculation algorithm and, as previously shown by ▇▇▇▇▇ and ▇▇▇▇ (2009) and ▇▇▇▇▇▇ et al. (2010, 2012), on the DEM resolution. We prefer predicting a site class rather than VS30 Vs,30 even when this is associated with a (large) standard deviation because we believe it gives a better indication that the site class is only an estimate and is not based on a measured VS30 Vs,30 value. We fear that the reporting of a numerical estimate for VS30 Vs,30 with a measure of its uncertainty would lead to the temptation to use the value and forget about the scatter.

Conclusions and Recommendations. In this article we have statistically tested the VS30Vs,30-slope (or more specifically the NEHRP class-slope) correlations published by Wald and ▇▇▇▇▇ (2007) for Europe and parts of the Middle East. In total 706 sites with VS30 Vs,30 measurements were used. It is found that the technique leads to a site classification that is better than chance for all NEHRP site classes in active areas. For stable areas, there are still limited data to enable firm conclusions but our results suggest that the proposed correlations perform poorly in these zones. Based on our findings we reiterate the recommendations of ▇▇▇▇ and ▇▇▇▇▇ (2007) that site classifications based on VS30Vs,30-slope correlations should only be used for regional or national (and not local or site- specific) first-order studies. In addition, they are only to be used in the absence of other more detailed information (e.g. microzonation studies) and not for sites inside small, relative to the DEM resolution, basins or those with and special geological conditions that may affect results (e.g. flat-lying volcanic plateaux, carbonate rocks, glaciated continental terrain or coastal pixels if the slope is not calculated using bathymetric data). Again many of these limitations were stated by ▇▇▇▇ and ▇▇▇▇▇ (2007). Site classifications based on VS30Vs,30-slope correlations are not sufficiently accurate to replace actual field measurements and they should not be used for site-specific studies. Consequences of erroneous estimation could be serious, so the user of such correlations should be aware that they only provide a first approximation and the true site class for a given site could be incorrect by one or, even, two classes (in either direction). At a local scale, further investigations should be carried out based on geology and measurements. In addition, the slope limits used for estimating VS30 are dependent on the slope-calculation algorithm and, as previously shown by ▇▇▇▇▇ and ▇▇▇▇ (2009) and ▇▇▇▇▇▇ et al. (2010), on the DEM resolution. We prefer predicting a site class rather than VS30 Vs,30 even when this is associated with a (large) standard deviation because we believe it gives a better indication that the site class is only an estimate and is not based on a measured VS30 Vs,30 value. We fear that the reporting of a numerical estimate for VS30 Vs,30 with a measure of its uncertainty would lead to the temptation to use the value and forget about the scatter.