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38 10 9 0.12 8 log-normal distribution 0.1 7 mlnx = -0.028 lnx = 0.544 Number of Pile-Cases 6 Relative Frequency 0.08 normal distribution 5 0.06 4 x = 0.588 3 0.04 mx = 1.115 2 0.02 1 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 Nordlund Design Method Figure 20. Histogram and frequency distributions of Ksx for 74 cases of all pile types (Concrete, Pipe, H) in sand. using DL/LL = 2, L = 1.75,and D = 1.25 (load factors taken method), which in effect represents both the actual FS and a from the structural code) for which the resistance factors measure of the economic efficiency of the method--the were calculated, results in: lower the value, the smaller the number of deep foundations required and the lower the cost, therefore the greater eco- FS 1.4167/ (33) nomic efficiency of the method. Table 22 provides a summary of Tables 19 through 21, presenting resistance factors and efficiency measures for select 3.2.4 Detailed Tables categories of method/pile/soil combinations. The LRFD principles are clearly seen in the obtained values Tables 19, 20, and 21 present detailed evaluations of the as the application of consistent target reliability produces analyzed case histories for static analyses of driven piles, values related to the individual method. While a method/ dynamic analyses of driven piles, and static analyses of drilled condition combination that has large variability (expressed as shafts, respectively. The tables include the number of case COV) results in low resistance factors, the resistance factors histories in the subset as well as the number of case histories alone do not provide a measure of the efficiency of the method. used in the analysis of resistance factors. The efficiency fac- For example, SPT 97 for H piles in sand has a resistance fac- tors, /, are calculated and presented with the resistance fac- tor ( = 2.33) = 0.63 while the Nordlund method for the same cat- tors. The approximated factors of safety associated with the egory results in a lower resistance factor = 0.46. In fact, SPT calculated resistance factors based on equation 33 are pro- 97 underestimates the capacity ( = 1.35), while Nordlund's vided as well. The factors of safety are presented along with method slightly overestimates it ( = 0.94); as a result, Nord- the mean overprediction ratio (calculated FS the bias of the lund's method has an efficiency similar to that of SPT 97