The API RP2A (RP2GEO) and ISO 19902 guidelines include four CPT-methods for calculating the axial capacity of piles insands. The guidelines require that if newer methods are to be implemented in design, the same level of safety shall be documentedfor these methods as for existing methods. The designer is required to select an appropriate safety factor when usingthe newer design methods. The challenge lies in deciding which safety factor will ensure a consistent safety level for differentsoil conditions and pile dimensions. To evaluate the required material factor, the probability of failure was quantified in twocase studies for piles designed with the API method and with the newer NGI, ICP and Fugro methods. A calibration of therequired material factor for a target probability of failure of 10~(-4)/yr was also performed. The results show that the annual reliabilityindex and probability of failure vary with the axial pile capacity calculation method. The study provides a contribution tothe discussion on the reliability of the API, the NGI, the ICP and the Fugro methods. The material factor needs to be associatedwith the characteristic soil parameters selected for design. A large number of case studies should be added to quantify the reliabilityand the required material factor for each pile capacity method. The findings on margin of safety and the definition of thecharacteristic shear strength have important implications for the design of piles offshore and can result in significant savings.
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