Abstract:
Static load testing is considered the gold standard for determination of pile nominal resistance; however, quantification of the point of “ failure” is not always straightforward. Numerous criteria have been developed for defining pile failure, also referred to as the pile nominal resistance. Some criteria, such as the Terzaghi (1942) and 10 Percent Diameter (Eurocode, 2004) methods, quantify the nominal resistance at a specified amount of displacement on a load displacement curve. The Davisson and Modified Davisson methods recommended in the AASHTO LRFD bridge design code determine pile nominal resistance based on a point of intersection with the load displacement curve. Other methods, such as DeBeer (1970) and Mazurkiewicz (1972), involve more subjective curve fitting procedures to define nominal resistance. As part of a recently completed FHWA study on bearing resistance of large diameter open-end piles, the authors compiled a data set of over 150-full-scale static load test on large diameter open-end piles for evaluation of existing static design methods. The analysis required determination of nominal pile resistance for each static load test. Review and evaluation of failure criteria methods found no single suitable failure criteria. Instead, the selection of the failure criteria needs to consider multiple factors, including the shape of the load displacement curve and the magnitude of the displacement corresponding to the nominal resistance. This paper evaluates different criteria to define pile failure, examines the dataset of large diameter open-end piles, and provides insights to answer the question of what is pile failure.