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Journal of Applied Mathematics
Volume 2012 (2012), Article ID 102618, 18 pages
http://dx.doi.org/10.1155/2012/102618
Research Article

A Study on the Holding Capacity Safety Factors for Torpedo Anchors

1Laboratory of Analysis and Reliability of Offshore Structures, Civil Engineering Department, Centro de Tecnologia, COPPE/UFRJ, Cidade Universitária, Bloco I-2000, Sala I-116, Ilha do Fundão, 21945-970 Rio de Janeiro, RJ, Brazil
2PETROBRAS Research and Development Center (CENPES), Cidade Universitária, Quadra 7, Ilha do Fundão, 21949-900 Rio de Janeiro, RJ, Brazil

Received 19 January 2012; Accepted 29 March 2012

Academic Editor: Ioannis K. Chatjigeorgiou

Copyright © 2012 Luís V. S. Sagrilo et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The use of powerful numerical tools based on the finite-element method has been improving the prediction of the holding capacity of fixed anchors employed by the offshore oil industry. One of the main achievements of these tools is the reduction of the uncertainty related to the holding capacity calculation of these anchors. Therefore, it is also possible to reduce the values of the associated design safety factors, which have been calibrated relying on models with higher uncertainty, without impairing the original level of structural safety. This paper presents a study on the calibration of reliability-based safety factors for the design of torpedo anchors considering the statistical model uncertainty evaluated using results from experimental tests and their correspondent finite-element-based numerical predictions. Both working stress design (WSD) and load and resistance factors design (LRFD) design methodologies are investigated. Considering the WSD design methodology, the single safety is considerably lower than the value typically employed in the design of torpedo anchors. Moreover, a LRFD design code format for torpedo anchors is more appropriate since it leads to designs having less-scattered safety levels around the target value.