99,254 research outputs found
Optimal Inspection and Maintenance Planning for Deteriorating Structural Components through Dynamic Bayesian Networks and Markov Decision Processes
Civil and maritime engineering systems, among others, from bridges to
offshore platforms and wind turbines, must be efficiently managed as they are
exposed to deterioration mechanisms throughout their operational life, such as
fatigue or corrosion. Identifying optimal inspection and maintenance policies
demands the solution of a complex sequential decision-making problem under
uncertainty, with the main objective of efficiently controlling the risk
associated with structural failures. Addressing this complexity, risk-based
inspection planning methodologies, supported often by dynamic Bayesian
networks, evaluate a set of pre-defined heuristic decision rules to reasonably
simplify the decision problem. However, the resulting policies may be
compromised by the limited space considered in the definition of the decision
rules. Avoiding this limitation, Partially Observable Markov Decision Processes
(POMDPs) provide a principled mathematical methodology for stochastic optimal
control under uncertain action outcomes and observations, in which the optimal
actions are prescribed as a function of the entire, dynamically updated, state
probability distribution. In this paper, we combine dynamic Bayesian networks
with POMDPs in a joint framework for optimal inspection and maintenance
planning, and we provide the formulation for developing both infinite and
finite horizon POMDPs in a structural reliability context. The proposed
methodology is implemented and tested for the case of a structural component
subject to fatigue deterioration, demonstrating the capability of
state-of-the-art point-based POMDP solvers for solving the underlying planning
optimization problem. Within the numerical experiments, POMDP and
heuristic-based policies are thoroughly compared, and results showcase that
POMDPs achieve substantially lower costs as compared to their counterparts,
even for traditional problem settings
Monitoring of Critical Metallic Assets in Oil and Gas Industry Using Ultrasonic Guided Waves
This chapter presents advancements in structural health monitoring (SHM) using ultrasonic guided waves (UGW) technology for metallic structures to support their integrity and maintenance management. The focus is on pipelines and storage tanks, which are critical assets in the Oil and Gas industry, whose operational conditions can greatly accelerate damage mechanisms. Conventional routine inspections are both costly and time consuming and affect the plant reliability and availability. These operational and economic disadvantages have led to development of SHM systems which can be permanently installed on these critical structures to provide information about developing damage and optimise maintenance planning and ensure structural integrity. These technology advancements enable inspection without interruption to operations, and generate diagnosis and prognosis data for condition-based maintenance, hence increasing safety and operational efficiency. The fundamentals, architecture and development of such SHM systems for pipes and above ground storage tanks are described here
Life-cycle of fatigue sensitive structures under uncertainty
Fatigue is the one of the main contributors to problems related to structural safety of civil and marine structures. Life-cycle management (LCM) techniques considering various uncertainties can be used to predict the safe service life of fatigue sensitive structures, plan for their future inspections and support the decision making process regarding maintenance and repair actions. This paper provides a brief overview of the LCM of fatigue sensitive civil and marine structures under uncertainty. Probabilistic performance prediction, inspection scheduling and maintenance optimization for such structures are discussed
Condition monitoring benefit for offshore wind turbines
As more offshore wind parks are commissioned, the focus will inevitably shift from a planning, construction and warranty focus to an operation, maintenance and investment payback focus. In this latter case, both short-term risks associated with wind turbine component assemblies, and longterm risks related to structural integrity of the support structure, are highly important. This research focuses on the role of condition monitoring to lower costs associated with short-term reliability and long-term asset integrity. This enables comparative estimates of life cycle costs and reduction in uncertainty, both of which are of value to investors
A multi-objective framework for the optimisation of life-cycle costs of wind turbines
Peer reviewedPublisher PD
Classes of decision analysis
The ultimate task of an engineer consists of developing a consistent decision procedure for the
planning, design, construction and use and management of a project. Moreover, the utility over the
entire lifetime of the project should be maximized, considering requirements with respect to safety
of individuals and the environment as specified in regulations. Due to the fact that the information
with respect to design parameters is usually incomplete or uncertain, decisions are made under
uncertainty. In order to cope with this, Bayesian statistical decision theory can be used to incorporate
objective as well as subjective information (e.g. engineering judgement). In this factsheet, the
decision tree is presented and answers are given for questions on how new data can be combined
with prior probabilities that have been assigned, and whether it is beneficial or not to collect more
information before the final decision is made. Decision making based on prior analysis and posterior
analysis is briefly explained. Pre-posterior analysis is considered in more detail and the Value of
Information (VoI) is defined
The safety case and the lessons learned for the reliability and maintainability case
This paper examine the safety case and the lessons learned for the reliability and maintainability case
Risk based bridge data collection and asset management and the role of structural health monitoring
Peer reviewedPostprin
Report on visit to four North American airlines
The object of the visits was to discuss the current state-of-the-art
with the Engineering Departments of several North American airlines which were
known to be leading the field in the application of certain advanced techniques.
In the limited time available it was decided to confine the talks mainly to
those topics on which the chosen operators were known to have had unique
experience.
This note is presented in chronological sequence and is only intended
to be a record of the information gathered; no derivations, or comparisons with
other operators, are made.
United Air Lines were visited first and reliability programmes are
detailed, although the application of critical path techniques to aircraft and
engine overhaul is summarised. Continental Air Lines are noted for their use
of the continuous maintenance philosophy, and this is reported next. The third
visit was to Air Canada where talks ranged from the applications of operations
research and electronic data processing (EDP) techniques to aircraft evaluation
procedures. Finally the PanAm aircraft system reliability programme is reviewed,
together with a note on their general LDP engineering and maintenance activities.
A bibliography is given, although it should be appreciated that some
of the items listed contain information which may be commercially secure
- …