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39
9 0.16
8
0.14
7
log-normal 0.12
distribution
6 mlnx = 4.53x10-4
lnx = 0.552
0.1
Number of Pile-Cases
Relative Frequency
5
0.08
normal distribution
4
0.06
3
0.04
2
mx = 1.150
0.02
1
x = 0.596
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 Design Method
Figure 21. Histogram and frequency distributions of Ksx for 56
cases of pipe and concrete pile types in sand.
(COV 0.40 vs. 0.43) in spite of the large difference in the resis- The available data were analyzed and the resulting statistical
tance factors. Examining the efficiency factors, one clearly parameters and associated resistance factors are presented in
sees that the method that provides the highest / ratio also Table 23. The results, though based on limited data, seem to be
provides the lowest "actual" factor of safety (FS × ). The fac- consistent with expected behavior. Comparing the data in
tors of safety presented in Table 22 for = 3.0 (the lower of Table 23 to that presented in Table 19 for driven piles under
the two values in the last column) are in line with what one compression, the following can be observed: (1) large dis-
would expect, ranging from 2.59 to 5.63, with an average of placement piles in clay develop similar friction under com-
3.73. The use of lower target reliability for redundant piles pression or tension, (2) friction for small displacement piles (H)
( = 2.33) provided factors of safety ranging from 2.11 to 4.00 is smaller in tension than in compression, and (3) friction under
(avg. 2.94), which are judged to be reasonable as well. pullout of all piles in sand is smaller than that which develops
The recommended resistance factors based on Tables 18 under compression. The recommended resistance factors for
through 22 are presented in section 3.4. pullout tests are presented and discussed in section 3.4.
3.2.5 Resistance Factors 3.3 PILE TESTING
for Pullout of Driven Piles
3.3.1 Overview
Utilizing the University of Massachusetts Lowell static pile
database, a limited number of case histories were identified for Deep foundation testing is carried out as a quality control
which a static pile load test in tension (pullout) was carried out. to check or verify pile capacity and integrity. Quality control
