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

231modified resistance factor (Пξ i φ) does not exceed the resistance factor of 0.80 (see Table6.8), as recommended by AASHTO (2010) for an SLT (φ SLT ).For an illustrative purpose, Figure 6.7 shows the primary relationship between thefactored pile resistances estimated using WEAP and the Iowa Blue Book (on the left y-axis)for a mixed soil profile together with the construction control correction factor (ξ EOD ) on thex-axis. A construction control factor (ξ EOD ) of 1.07 and a modified resistance factor (ξ EOD φ)of 0.64 as similarly found in Figure 6.5 were confirmed by equating the primary factoredresistance ratio (left y-axis) to one. Figure 6.7 also shows the secondary relationship (on theright y-axis) between the factored pile resistances measured using SLT and estimated usingthe Iowa Blue Book considering the construction control correction factor (ξ EOD ) on the x-axis. The maximum limits for ξ EOD and modified resistance factor (ξ EOD φ) are determined1.90 and 1.14, respectively, by equating the secondary factored resistance ratio (right y-axis)to one. Since the initially calculated ξ EOD value of 1.07 is smaller than the maximum limit of1.90 or the recommended ξ EOD φ of 0.64 is smaller than the calculated maximum limit of 1.14as well as 0.80, based on AASHTO (2010), the ξ EOD value of 1.07 is suggested in Table 6.8.Figure 6.8 shows the normal distribution curves of the factored resistances ratio for WEAPand the Iowa Blue Book (i.e., φ weap R weap /φ BB R BB ) before and after considering theconstruction control. The effect of construction control consideration shifts the meantowards unity and reduces the standard of deviation from 0.27 to 0.25, which indicates thatthe average pile resistances estimated using WEAP and the Iowa Blue Book has beenmatched, minimizing the overall discrepency between design and field verified pileresistances.6.5.3. Construction control resultsTable 6.8 summarized the results obtained from the foregoing construction controlevaluations. If WEAP is specified as the construction control method during pile driving, thecalculated construction controls for clay and sand are 0.87 and 0.94, respectively. In otherwords, the average factored pile resistances estimated using WEAP are smaller than thoseusing the Iowa Blue Book. The Iowa Blue Book’s value may have to be reduced to match