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912.7.4 Recommended LRFD resistance factorsAccording to Allen (2005), the initial source of the resistance factors in the AASHTOLRFD Design Specifications (AASHTO 2004), Section 10, was based on therecommendation reported by Barker et al. (1991). However, the latest AASHTO (2010)Interim Revisions presented the resistance factors for driven piles are based on the studies byPaikowsky et al. (2004) and Allen (2005). Table 2.16 was adapted from the revisedAASHTO (2010) LRFD Bridge Design Specifications for dynamic analysis methods.Table 2.16: LRFD resistance factors for driven piles (AASHTO, 2010)ResistanceCondition/Resistance Determination MethodFactorDriving criteria established by successful static load test ofat least one pile per site condition and dynamic testing (a) of0.80at least two piles per site condition, but no less than 2% ofthe production pilesNominal Bearing Driving criteria established by successful static load test of0.75Resistance of Single at least one pile per site condition without dynamic testing0.75Load Test Methods, Driving criteria established by dynamic test (a) , qualityφ dyn control by dynamic testing (a) of at least two piles per site 0.65condition, but no less than 2% of the production pilesWave equation analysis, without pile dynamicmeasurements or load test but with field confirmation of 0.50hammer performance(a) ‒ Dynamic testing requires signal matching, and best estimates of nominal resistance are madefrom a restrike. Dynamic tests are calibrated to the static load test, when available.Pile – Dynamic Driving criteria established by dynamic testing (a) conductedAnalysis and Static on 100% of production pilesAs described in the AASHTO (2010) Section 10.5.5.2.3 for driven piles, if theresistance factors shown in Table 2.16 are to be applied to non-redundant pile groups asdescribed in Table 2.15, the factors should be reduced by 20 % to reflect a higher targetreliability index (β T ) of 3.0 or more. Furthermore, the resistance factors were determinedmainly from load test results obtained on piles with diameters of 610 mm (2 ft) or less. Astatic or dynamic load test should be considered if piles larger than 610 mm (2 ft) diameterare used during design using static analysis methods. The combination of static and/ordynamic tests should be established based on the degree of site variability, which ischaracterized using field and laboratory exploration and test program. Noted that the