Probabilistic Modelling of Updating Pile Capacity Prediction for Offshore Structure using Proof Loads and Survived Piles

Abstract eng:
Friction capacity prediction of pile foundation driven in clay soils may be estimated using the conventional methods such as the α, β, or λ methods. Comparison between measured and predicted capacity for each method exhibits scatter of friction capacity due to several factors, namely, simplified modelling in the pile capacity formula, rate of loafing effect, etc. The model error N has been introduced to denote this discrepancy. Statistics of N have been evaluated based on data gathered from various sites where each site is characterized by specific driving process, soil properties, measuring techniques etc. Therefore, statistics of N obtained from such a wide range of friction piles may be considered only as a general-error trend in friction capacity prediction. If information is available for a specific site, these prior statistics of N may be updated accordingly. This study is devoted to the development of procedures for updating model error N, and subsequently the predicted pile capacity, with proof load test results or survived piles after a recorded extreme loads, in this case wave loads, for an offshore structure. The effect of correlation between individual pile test values is included in the formulation. The updated model error N will be utilized to update the reliability and the safety of pile foundation, for example, using first order second moment method.

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