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Embedded data collector (EDC) phase II load and resistance factor design (LRFD).
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2015-09-01
[PDF-1.56 MB]
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Abstract:A total of 16 static load test results was collected in Florida and Louisiana. New static load tests on five test piles
in Florida (four of which were voided) were monitored with Embedded Data Collector (EDC) instrumentation and
contributed to the total of 16. For the voided test piles, EDC instrumentation was placed in the piles at different locations
relative to the void to compare the estimated resistances. In the four test piles, the measured top compressive stresses
measured in the solid section of the pile were typically about 25% smaller than the measured values in the voided section of
the pile. However, when the top stresses were adjusted by area (i.e., divide by 645 in2
/ 900 in2
= 0.72), then the stresses
were very comparable. Two methods were used to estimate the pile capacities: The UF method and the Tran et al. methods.
The UF method (employed in SmartPile Review) uses the Case capacity equation with variable case damping, Jc, to assess
total capacity and the Unloading Point Method for tip resistance, (i.e., skin friction = total – tip resistance). The Tran et al.
method computes side friction using a segmental approach and tip resistance using conservation of force and energy. The
Tran et al. method for side friction showed a smaller difference (6%) in predicted capacities between top solid and voided
gauge sets than the UF method (23%) using the Case Equation for the four voided test piles.
Load and Resistance Factor Design (LRFD) resistance factors () for piles with EDC were calculated for a
reliability, , of 2.33 using the First Order Second Moment (FOSM) method and the First Order Reliability Method
(FORM). For the UF method, a total of 42 pairs (measured vs. predicted; bias, = 0.998, standard deviation, = 0.212, and
CV = 0.212) were analyzed for the cases of EDC in both the solid and voided sections (four new test piles supported in
present project)). The FORM = 0.75 and FOSM = 0.64. A smaller data set of 34 pairs (measured vs. predicted; bias, =
0.918, standard deviation, = 0.172, and CV = 0.188) were analyzed for the cases of EDC only in the solid sections. The
FORM = 0.73 and FOSM = 0.62. For the Tran et al. method, a total of 39 pairs (measured vs. predicted; bias, = 0.991,
standard deviation, = 0.169, and CV = 0.17) were analyzed for the cases of EDC in both the solid and voided sections.
The FORM = 0.81 and FOSM = 0.68. A smaller data set of 33 pairs (measured vs. predicted; bias, = 0.979, standard
deviation, = 0.182, and CV = 0.186) were analyzed for the cases of EDC only in the solid sections. The FORM = 0.78 and
FOSM = 0.66. For the Fixed Jc method, FORM and FOSM were calculated for limited data sets (solid/voided and only solid
sections). The listed resistance factors should be used with caution due to the limited data set and the conditions they were
obtained (e.g., limited soil types tested, time between BOR and static load test, lack of fully instrumented tests piles).
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