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Mathematical Problems in Engineering
Volume 2013 (2013), Article ID 125856, 15 pages
http://dx.doi.org/10.1155/2013/125856
Research Article

Time Intervals for Maintenance of Offshore Structures Based on Multiobjective Optimization

Instituto de Ingeniería, Universidad Nacional Autónoma de México, 04510 Coyoacán, DF, Mexico

Received 22 March 2013; Revised 28 June 2013; Accepted 5 July 2013

Academic Editor: Dan Simon

Copyright © 2013 Dante Tolentino and Sonia E. Ruiz. 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

With the aim of establishing adequate time intervals for maintenance of offshore structures, an approach based on multiobjective optimization for making decisions is proposed. The formulation takes into account the degradation of the mechanical properties of the structures and its influence over time on both the structural capacity and the structural demand, given a maximum wave height. The set of time intervals for maintenance corresponds to a balance between three objectives: (a) structural reliability, (b) damage index, and (c) expected cumulative total cost. Structural reliability is expressed in terms of confidence factors as functions of time by means of closed-form mathematical expressions which consider structural deterioration. The multiobjective optimization is solved using an evolutionary genetic algorithm. The approach is applied to an offshore platform located at Campeche Bay in the Gulf of Mexico. The optimization criterion includes the reconstruction of the platform. Results indicate that if the first maintenance action is made in 5 years after installing the structure, the second repair action should be made in the following 7 to 10 years; however, if the first maintenance action is made in 6 years after installing the structure, then the second should be made in the following 5 to 8 years.