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48 30 60 0.15 25 0.16 55 mx = 0.785 0.14 Number of Pile-Cases log-normal Relative Frequency 20 normal distribution 50 distribution 0.13 0.12 mlnx = -0.162 0.12 15 x = 0.290 45 lnx = 0.435 0.08 0.11 log-normal mx = 0.940 10 distribution 40 0.1 Number of Pile-Cases Relative Frequency mlnx = -0.304 0.04 5 lnx = 0.350 35 0.09 normal distribution 0.08 0 0 30 0 0.5 1 1.5 2 2.5 3 0.07 25 x = 0.472 Ratio of Static Load Test Results over the Pile Capacity 0.06 Prediction using the Energy Approach method 20 0.05 Figure 34. Histogram and frequency distributions for all BOR-last (153) energy approach pile-cases in PD/LT2000. 15 0.04 0.03 10 0.02 The assigned resistance factors are based on the LRFD 5 principle of a consistent prescribed reliability for either a 0.01 redundant or a nonredundant pile cap configuration. The rec- 0 0 ommended values should not be affected by the quality con- 0 0.5 1 1.5 2 2.5 >3 trol procedure to be implemented in the construction stage other than through the relationship with the anticipated ulti- Ratio of Static Load Test Results over the Pile Capacity Prediction According to the FHWA modified Gates equation mate capacity as explained in item 3 of section 3.4.7. Figure 35. Histogram and frequency distributions for all (384) FHWA modified Gates equation pile-cases in 3.4.3 Dynamic Analysis of Driven Piles PD/LT2000. Table 27 presents the recommended resistance factors to be used for dynamic monitoring of driven piles and the rele- a. Relate to each significant bearing layer, average vant method's efficiency factors. The dynamic methods are parameters used for strength analysis (e.g., N SPT) categorized according to the controlling parameter and the at each boring location. time of driving. Table 28 presents the recommended number b. Check the COV between the average values for of tests required during production, with values rounded to each identifiable significant layer obtained at each the next highest integer. Dynamic tests at EOD are carried boring location. out for capacity evaluation, monitoring the performance of c. Categorize site variability in the following way: the driving system, and establishing driving criteria. As such, i) COV < 25%--Low EOD tests are of great importance beyond the capacity eval- ii) 25% COV < 40%--Medium uation alone. iii) 40% COV--High The following comments relate to the way site variability is being established: The following recommendations apply to dynamic tests: 1. Restrike should be scheduled according to the guide- 1. Site variability relates to the variability within similar lines provided in section 3.4.6 subsurface conditions of the same site, not between sites. 2. The recommended values in Table 28 relate to similar For example, when piers are based on substantially dif- pile types driven at the same site. ferent subsurface conditions (i.e., in the stratum mostly 3. For EOD conditions: influencing the pile capacity). The criteria should be If dynamic measurements are available, evaluate pile applied independently to each pier location as a sepa- capacity using the Energy Approach; if dynamic mea- rate site. surements are not available, evaluate pile capacity 2. Site variability can be determined by judgment or using using the Gates or the FHWA modified Gates. the following approximate criteria related to borings Signal matching is recommended for EOD condi- representative of the entire site subsurface conditions: tions for end bearing piles only.