Model Uncertainty in Pile Axial Capacity Calculations

The use of a probabilistic approach for pile design is described and its importance is discussed. The paper illustrates the effect of the uncertainties in pile capacity analysis methods on the reliability of a design. Suggestions are made for the value of model uncertainty to use with different analysis methods. Special emphasis is given to the American Petroleum Institute (API) RP2A approach (Ref. 1). Relevant model tests for calibration of the model uncertainty are few and exhibit scatter. It is therefore difficult to assign values to the parameters describing the model uncertainty. In the latest API RP2A guidelines. designers are encouraged to use all research advances available to them. The designer is therefore encouraged to use substantiated alternative analysis methods. Probabilistic analyses is one of the tools that will help judge the soundness of a design.