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36 9 0.25 8 0.225 0.2 7 log-normal distribution 0.175 6 mlnx = -0.302 lnx = 0.414 Number of Pile-Cases 0.15 Relative Frequency 5 0.125 normal distribution 4 0.1 3 0.075 m x = 0.801 2 x = 0.337 0.05 1 0.025 0 0 0 0.5 1 1.5 2 2.5 3 KSX = Ratio of Static Load Test Results over the Pile Capacity Prediction using the -API method Figure 18. Histogram and frequency distributions of Ksx for 36 cases of concrete and pipe pile types in clay. presented in Table 18, one can conclude that the resistance the wide sources of the data. Additional graphical presenta- factors are within the range of current practice and the sub- tion of the data is included in Appendix C. categorization provides details regarding both the method of design and construction. The design methods in general pro- vide more accurate predictions than those for driven piles, as 3.2 INITIAL EXAMINATION OF RESULTS indicated by the bias being closer to one where the COVs are of similar magnitudes to those in Table 16. The "mixed" con- 3.2.1 Overview struction method represents the combination of other available construction methods. The actual numbers for the mixed case An initial examination of the results is required in order to do not necessarily add up to the sum of the individual categories assess the magnitude of values and to allow the process of as each set (individual or combined) is treated independently. transforming the large number of methods and correlations to Figures 36 through 40 present selected subsets from meaningful and inclusive categories. This is done by check- Table 18 as histograms, along with the best-fitting normal and ing the number of case histories needed to be eliminated when lognormal distributions. Four of the figures relate to the mixed limiting the set being investigated to those within the two construction case histories that include other construction standard deviation band, recalculating the resistance factors methods. The smaller subsets' databases and wider distribu- for the recommended target reliabilities, evaluating equiv- tions are the result of the variation between the methods and alent factors of safety, and examining the efficiency of the