American Petroleum Institute

Further Evaluation of Offshore Structures Performance in Hurricane Andrew - Development of Bias Factors for Pile Foundation Capacity
 N REPORT 94-81

Annotation

Executive Summary

Hurricane Andrew (hereafter called Andrew) was a very intense storm that passed through the Gulf of Mexico on August 24, 25 and 26, 1992. While most of these Gulf of Mexico platforms were not adversely impacted by Andrew, several were significantly damaged and in some cases collapsed. Recognizing that this type of experience provides a unique opportunity to further understand the performance of offshore structures in large storms, PMB solicited and gained support for a Joint Industry Project to study the effects of Andrew on offshore platforms. The Andrew JIP was completed in October 1993.

The Andrew JIP predicted failures of foundation elements in a majority of platforms, which were not observed during post-Andrew inspections. The Andrew JIP established an overall (system) correction factor, with a mean of 1.2. This correction factor was not specific to the biases associated with the foundation capacity estimates per the "recipe" followed in that project. Rather it included failures of all types within jacket and its foundation. Therefore, to further investigate the bias in the foundation capacity estimates for the steel jacket platforms, API and MMS commissioned this study specifically to evaluate the effects of Andrew on offshore platform foundations. This is the final report, which documents the approach and results of the project.

This project had two primary objectives:

1. Calibration. Perform a calibration of procedures for foundation capacity analysis (lateral and axial) for assessing existing platforms. A rigorous method for calibration developed in the Andrew Phase I is to be used. The process includes reconciling analytically predicted platform damage and failure with observed field performance during Andrew.