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52 4 0.125 3.5 0.1 3 log-normal 2.5 distribution Number of Pile-Cases 0.075 Relative Frequency mlnx = 0.326 lnx = 0.738 2 mx = 1.714 0.05 1.5 normal distribution 1 x = 1.027 0.025 0.5 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 KSX = Ratio of Static Load Test Results over the Shaft Capacity Prediction using the FHWA Method for Mixed Construction Figure 38. Histogram and frequency distributions for Ksx for 32 cases of drilled shafts in sand. 4. The determination of the required number of indicator 3.5 EVALUATION OF piles can be combined along with the required number THE RESISTANCE FACTORS of dynamic pile tests presented in Table 28. For sites at 3.5.1 Overview which fewer than 100 piles are driven, the number of indicator piles can be used as the number of tested piles Evaluation of the recommended resistance factors to be (approximately 8). Specifically, at least one pile should incorporated into a code is a complex and extensive process. be tested under each substructure, using the test results The aim of the process is to compare an existing code of as outlined in section 3.3.3. When more than 100 piles practice to the recommended new factors. Very often this are driven, particularly at sites of high variability, sep- evaluation cannot be done directly, as either the principles aration can be made between indicator piles and pro- behind the factors differ (e.g., WSD vs. LRFD), or the applied duction piles, with the former used for assigning driv- methodology is not compatible (e.g., the design and con- ing criteria and the latter used for production quality struction combined factors of the existing code). As a result, control, as outlined in section 3.3.3. Restrike testing of the evaluation can be carried out in two ways: piles should be scheduled according to equations 37 through 39, as outlined in section 3.4.6. 1. Analyzing design case histories in light of both the new 5. Resistance factors for static load tests of driven piles and factors and the existing codes. In this way what has drilled shafts should be assigned according to Table 30. been done can be compared with what would have been The driven pile tests should be scheduled according to done; and, if a sufficient number of case histories are equations 37 through 39, as outlined in section 3.4.6. analyzed, statistically valid conclusions can be derived 6. All drilled shafts should be tested using small or high regarding the effectiveness and overall performance of strain integrity testing. the recommendations.