S - Kam Ng PhD Dissertation Final.pdf - Digital Repository of CCEE ...

218and the calibration procedure proposed in Chapter 5, the effect of pile setup was incorporatedinto the LRFD recommendations to elevate the efficiency of bridge foundations attaining theeconomic advantages of pile setup.6.3. BackgroundThe different pile design and construction practices results in a discrepancy betweendesign and field pile resistances. For instance, in current Iowa practices, piles are designedusing the Iowa DOT in-house method (Iowa Blue Book), and the designed pile performancesare verified in the field using dynamic analysis methods. The disagreement in the pileresistances incurs additional construction costs, delays the construction schedule, and mayprovoke contractual challenges. To overcome this problem, the regionally-calibrated resultswere used to minimize the difference in pile resistances through a probabilistic approach.Construction control factors (ξ) for the static analysis method (i.e., Iowa Blue Book) withrespect to different dynamic analysis methods at different soil profiles were determined. Thecorrected resistance factors were limited to ensure the corrected pile resistance remainedsmaller than the measured resistances obtained from the static load test. This proposedconstruction control procedure assimilates the construction control capability of dynamicanalysis methods in pile designs and overcomes the limitations concerning the designmethod.6.4. Development of Resistance FactorsThe development of regionally-calibrated resistance factors requires sufficient pileload test data records with good quality hammer, pile, and soil information. Both historicalIowa DOT database and 10 recently completed field test results were used in calculating theresistance factors for WEAP, while only the recent field test results containing PDA datawere used for CAPWAP. With the focus on the axial pile resistance, the AASHTO StrengthI load combination (i.e., dead and live loads only) was considered, and the FOSM methodsuggested by Barker et al. (1991) was used to determine the resistance factors. Furthermore,resistance factors for pile setup were determined using the calibration procedure proposed in