Reliability of API and ISO Guidelines for Bearing Capacity of Offshore Shallow Foundations

Conference paper (2015)
Copyright: © 2015 The Authors and IOS Press, Creative Commons CC-BY
DOI: https://doi.org/10.3233/978-1-61499-580-7-821
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Published Date

15-10-2015

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Abstract

The safe bearing capacity for offshore shallow foundations has been traditionally assessed using working stress design (WSD) methods (e.g. the API RP 2GEO guideline). Other codes of practice such as the ISO standard strive to provide designs achieving a desired target reliability level in the form of the Load and Resistance Factor Design (LRFD) approach. This study compares the levels of safety achieved for offshore shallow foundations. Calculations are made for one foundation on soft clay and one on medium dense sand, using the API RP 2GEO, API RP 2GEO-LRFD and ISO 19901-4 design guidelines. Three probabilistic models were used, the first-order, second moment (FOSM) approximation, the first order reliability method (FORM) and the Monte Carlo simulation (MC) approach, to do the reliability assessment. The results showed that the reliability level achieved with current practice varies with the design methods. The FORM and MC models yielded consistent results, while the FOSM model yielded inconsistent results when the performance function was non-linear.