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

292logarithmic trend. The amount of pile setup not only depends on the proportionof the cohesive soil layers to the embedded pile length, but also depends on thestratigraphic layers of cohesive and cohesionless soils.8.2.2. Pile setup in LRFDThe implementation of the proposed pile setup quantification method into the LRFDapproach was addressed in Chapter 5. Statistical studies show different uncertainties areassociated with the initial pile resistance estimated using dynamic analysis methods and thepile setup resistance quantified using the proposed method. However, the existing calibrationprocedure cannot separately account for these different sources of uncertainties. Hence, anew and general calibration procedure was developed using the First Order Second Moment(FOSM) method to separately calculate the resistance factors for both resistance componentsand to ensure both resistance components reach a target reliability level. Compared with theconcept of using a single resistance factor to both resistance components, it is concluded thatthe proposed procedure provides a more dependable pile foundation design. Constantresistance factors for both resistance components can be calculated based upon any regionaldatabase that reflects the local soil conditions, pile types, and setup quantification methods.Based on a total 28 data points provided in Chapter 5 on steel H-piles embedded in cohesivesoils, the resistance bias (λ R ) and the coefficient of consolidation (COV R ) for pile setupresistance (R setup ) were determined to be 0.95 and 0.317, respectively. The resistance factorsfor pile setup were found to be 0.32 and 0.26 for β T values of 2.33 and 3.00, respectively.8.2.3. Regional resistance factorsChapter 6 presents the establishment of regional Load and Resistance Factor Design(LRFD) recommendations for dynamic analysis methods, based on the historical databaseand ten recently completed field tests. When compared with the recommendations presentedin the NCHRP Report 507 by Paikowsky et al. (2004) and the latest AASHTO (2010) LRFDBridge Design Specifications, the regionally calibrated resistance factors calculated using theFOSM method for steel H-piles embedded in sand, clay, and mixed soil profiles were