Reliability and Maintenance of Structures under Severe Uncertainty

Opeyemi, DA (2016) Reliability and Maintenance of Structures under Severe Uncertainty. PhD thesis, University of Liverpool.

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Abstract

Maintenance of structures and infrastructures is of increasing importance in order to reach acceptable level of safety despite the unavoidable uncertainty, and the economic efforts have to be reasonable. These two goals represent competing objectives in an overall optimization of very complex system and structure, which involve significant uncertainties. In fact, all civil engineering structures and engineering systems are subjected to degradation by fatigue cracks and corrosion due to varying loads. When the cracks propagate or corrosion grows, the structural system accumulates damage thereby leading to serviceability loss and eventual collapse. These failures can be prevented by appropriate maintenance scheduling and repair, even in the presence of uncertainties of various nature and scale, leading to a reduction in fluctuations and changes of structural and environmental parameters and conditions in the models describing the processes involved in fatigue cracks and corrosion growth. Degradation models used to predict the future state of components often involve simplifications and assumptions to compensate a lack of data, imprecision and vagueness, which cannot be ignored. To overcome these issues, the imprecise probabilities framework and markovian approach are proposed for performing reliability analysis, decision-making, and risk-based design and maintenance. It is shown how these approaches can improve the current practise based on models: B31G, Modified B31G, DNV-101 and Shell-92 failure pressure models. The reliability assessment is performed by taking into account the simultaneous action of many natural and technological loads. These loads are random by nature and can be adequately described only by stochastic processes; which are not performed due to lack of valid calculation methods. This methodology has been applied to study the reliability of arctic pipeline infrastructure. Finally, a robust and efficient probabilistic framework for optimal inspection and maintenance schedule selection for corroded pipelines and fatigue cracks in bridges is presented. Optimal solution is obtained through only one reliability assessment removing huge computational cost of the reliability-base optimization approach and making the analysis of industrial size problem feasible.

Item Type:	Thesis (PhD)
Divisions:	Faculty of Science and Engineering > School of Engineering
Depositing User:	Symplectic Admin
Date Deposited:	05 Jan 2018 13:01
Last Modified:	19 Jan 2023 07:11
DOI:	10.17638/03006432
Supervisors:	Patelli, E ORCID: 0000-0002-5007-7247 Beer, M ORCID: 0000-0002-0611-0345
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3006432