Maintenance Management Research of a Large-span Continuous Rigid Frame Bridge Based on Reliability Assessment by Using Strain Monitored Data

When the bridge components needing maintenance are the world problem at present,and the health monitoring system is considered to be a very help­ful tool for solving this problem.In this paper,a large number of strain data acquired from the structural health monitoring system(SHMS)installed on a continuous rigid frame bridge are adopted to do reliability assessment.Firstly,a calculation method of punctiform time-dependent reliability is proposed based on the basic reliability theory,and introduced how to cal­culate reliability of the bridge by using the stress data transformed from the strain data.Secondly,combined with“Three Sigma”principle and the basic pressure safety reserve requirement,the critical load effects distribu­tion function of the bridge is defined,and then the maintenance reliability threshold for controlling the unfavorable load state which appears in the early operation stage of this type bridge is suggested,and then the combi­nation of bridge maintenance management and health monitoring system is realized.Finally,the transformed stress distribution certifies that the load effects of concrete bridges practically have a normal distribution;as for the concrete continuous rigid frame bridge with C50 strength grade concrete,the retrofit reliability threshold should be valued at 6.13.The methodology suggested in this article can help bridge engineers do effective maintenance of bridges,which can effectively extend the service life of the bridge and bring better economic and social benefits.

Imperfect preventive maintenance for numerical control machine tools with log-linear virtual age process

Based on the log-linear virtual age process, an imperfect preventive maintenance policy for numerical control(NC)machine tools with random maintenance quality is proposed. The proposed model is a combination of the Kijima type virtual age model and the failure intensity adjustment model. Maintenance intervals of the proposed hybrid model are derived when the failure intensity increase factor and the restoration factor are both random variables with uniform distribution. The optimal maintenance policy in infinite time horizon is presented. A numerical example is given when the failures of NC machine tools are described by the log-linear process. Finally, a discussion is presented to show how the optimal results depend on the different cost parameters.

Maintenance in Marginal Oilfield Production Facilities: A Review

Natural decline in various mainstream oilfield reserves and the high investment capital in upstream exploration and project development have promoted attention towards smaller oilfields referred to as Marginal fields. This provides operators the opportunity to commence exploration and production with minimum requirements of design, installation, and operations. Although the low Capital Expenditure (CAPEX) requirement favors the start-up of marginal oilfield operations, several operators are not able to sustain the field’s operations due to the high Operational Expenditure (OPEX), particularly arising from facilities’ maintenance. The aim of this paper is to review the maintenance strategies adopted in marginal oilfields, assess their effectiveness, and provide a pointer towards efficient and viable maintenance strategies for the sustainability of marginal oilfields. The study showed that time-based preventive maintenance is predominant in the oil industry, which constitutes up to 40% of net operational expenses. In other cases, reactive maintenance is adopted, which often results in an unplanned shutdown, known to be responsible for nearly half of the overall losses of an oil facility. A paradigm shift in maintenance to Reliability Centered Maintenance (RCM) was explored for marginal oilfield, with a comprehensive review of various maintenance strategies, ranging from maintenance optimization strategies, Heuristics and Metaheuristics, Artificial Intelligence (AI), and Data Mining techniques. It was observed that the application of AI best addresses the proposed RCM for marginal oilfields. This was drawn from the recorded limitations of the other concepts from verifiable similar works, where different AI techniques and Data analytics methods have been successfully applied to aid RCM.

A Functional Inspection Model for the Immeasurable Potential Failure State

Functional inspection is a type of preventive maintenance of Reliability Centered Maintenance （ RCM）. We, in this paper, establish a functional inspection model（ FIM） the cost model and the availability model for the immeasurable potential failure state based on the delay time concept. This model can be used to determine the appropriate Functional Inspection Interval（FII） to achieve the goal of specific cost and availability and to assist in maintenance decision making.