Maintenance,Repair,and Reinforcement Measures for Dilapidated Small and Medium-Sized Bridges

The paper initiates by exploring the importance of maintaining,repairing,and reinforcing bridges.Subsequently,it delves into routine and preventative maintenance measures tailored for small to medium-sized bridges.Additionally,the paper examines repair and reinforcement techniques specifically designed for deteriorated small and medium-sized bridges,encompassing methods for fortifying both the bridge foundation and upper and lower structures.Lastly,the paper proposes suggestions aimed at fostering discussions and exchanges on the development of maintenance and repair processes for deteriorated small and medium-sized bridges.

Statistical approach to determination of overhaul and maintenance cost of loading equipment in surface mining

The purpose of this research was to develop a new approach in determination of overhaul and maintenance cost of loading equipment in surface mining. Two statistical models including univariate exponential regression (UER) and multivariate linear regression (MLR) were used in this study. Loading equipment parameters such as bucket capacity, machine weight, engine power, boom length, digging depth, and dumping height were considered as variables. The results obtained by models and mean absolute error rate indicate that these models can be applied as the useful tool in determination of overhaul and maintenance cost of loading equipment. The results of this study can be used by the decision-makers for the specific surface mining operations.

Analysis of a POMDP Model for an Optimal Maintenance Problem with Multiple Imperfect Repairs

I consider a system whose deterioration follows a discrete-time and discrete-state Markov chain with an absorbing state. When the system is put into practice, I may select operation (wait), imperfect repair, or replacement at each discrete-time point. The true state of the system is not known when it is operated. Instead, the system is monitored after operation and some incomplete information concerned with the deterioration is obtained for decision making. Since there are multiple imperfect repairs, I can select one option from them when the imperfect repair is preferable to operation and replacement. To express this situation, I propose a POMDP model and theoretically investigate the structure of an optimal maintenance policy minimizing a total expected discounted cost for an unbounded horizon. Then two stochastic orders are used for the analysis of our problem.

Forest Roads Maintenance and Repair

Forestry intensification requires the construction of new forest roads and quality maintenance of the existing forest-road system.The powerful modern equipment used for forestry processes mechanization puts new requirements on the pavement of the constructed roads but also on their maintenance in good technical condition.Therefore,new roadway requirements are imposed in terms of road pavement and maintenance,i.e.there are new requirements regarding the operational qualitative indicators.

Optimum Maintenance and Availability of Series Systems Subject to Imperfect Repair

Optimum maintenance and availability of a series system whose components are subject to imperfect repairs are studied in this paper. Imperfect corrective maintenance is treated in a way that after it the life of each component in the system will be decreased to a fraction of its immediately previous one and the repair time will be increased to a multiple of the one immediately preceding it, where successive failure free times are independent and so are successive repair times. Under such an assumption, the limiting system availability, mean time between system failures or repairs are derived based on some related results. A numerical example is presented to compare with Barlow and Proschan's availability model. Two classes of maintenance cost models are proposed and the optimum maintenance policies are also discussed for series system with n components in this paper.

Heath Assessment Method of EMU Trains in Level 3-5 Maintenance and Repair

An accurate and objective assessment of the health status of EMU trains is of great importance.In order to make sure the trains are functional,reliable,and endurable in their full life cycle(FLC),health assessment method for EMU trains after Level 3-5 maintenance and repair is studied.First,the element-selection principles and the assessment rules are defined;second,to present the complex topological relationship between the elements in assessment,a functional logical structure construction method is proposed;third,a health value calculation model is defined based on the element’s characteristics and their logical structures.The health variables of each element is calculated and fitted following the steps in the corresponding weight calculation methods.The assessment method is proved to be applicable and effective.

Optimum Maintenance Policy for a One-Shot System with Series Structure Considering Minimal Repair

One-shot systems such as missiles and extinguishers are placed in storage for a long time and used only once during their lives. Their reliability deteriorates with time even when they are in storage, and their failures are detected only through inspections for their characteristics. Thus, we need to decide an appropriate inspection policy for such systems. In this paper, we deal with a system comprising non-identical units in series, where only minimal repairs are performed when unit failures are detected by periodic inspections. The system is replaced and becomes “as good as new” when the nth failure of the system is detected. Our objective is to find the optimal inspection interval and number of failures before replacement that minimize the expected total system cost per unit of time.

Component reallocation and system replacement maintenance based on availability and cost in series systems

Component reallocation(CR)is receiving increasing attention in many engineering systems with functionally interchangeable and unbalanced degradation components.This paper studies a CR and system replacement maintenance policy of series repairable systems,which undergoes minimal repairs for each emergency failure of components,and considers constant downtime and cost of minimal repair,CR and system replacement.Two binary mixed integer nonlinear programming models are respectively established to determine the assignment of CR,and the uptime right before CR and system replacement with the objective of minimizing the system average maintenance cost and maximizing the system availability.Further,we derive the optimal uptime right before system replacement with maximization of the system availability,and then give the relationship between the system availability and the component failure rate.Finally,numerical examples show that the CR and system replacement maintenance policy can effectively reduce the system average maintenance cost and improve the system availability,and further give the sensitivity analysis and insights of the CR and system replacement maintenance policy.

Warranty Cost Model Based on Optimal Preventive Maintenance Operations for Repairable Products

Most warranty cost models based on preventive maintenance operations are assumed that products improve at each preventive maintenance(PM)operation and the failure rate is reduced to the failure rate of new products or to some specified level.To make warranty cost models more suitable to real operations,a modeling method of the PM warranty cost was proposed with the situation where each PM operation slowed the rate of product degradation.A warranty cost model was built on PM operations.On the basis of the cost model,both without and with reliability limit PM warranty policy,algorithms were presented to derive the optimal PM number and the optimal PM interval with an objective of minimizing expected total warranty cost over a finite warranty period.Finally,to demonstrate the feasibility of the presented modeling method,Weibull distribution cases were tested by numerical simulations.The simulation results indicate that the proposed modeling method is feasible and valid for resolving the optimal solution of the product warranty cost.

Availability modelling for periodically inspected systems under mixed maintenance policies

The availability of a periodic inspection system under mixed maintenance policies is studied in this paper.To accommodate the characteristic of multiple failure modes for complex systems,the system failures can be divided into two failure modes:hard failure and soft failure.When hard failure occurs,the corresponding corrective maintenance will be performed,taking a random time under the perfect maintenance policy;in contrast,if the soft failure is found,the corresponding preventive maintenance will be performed,taking a random time under the imperfect maintenance policy.The dynamic age setback model is adopted for imperfect maintenance,which can accurately reflect the fault characteristics of the degraded system.Then an analytical model for system steady state availability and instantaneous availability are derived.Moreover,the optimal method to maximize the system steady-state availability through adjusting the inspection interval is researched.According to the above research,the optimization of system unit time cost,preventive maintenance intervals and availability is researched.Finally,the developed approach is demonstrated by a numerical example.

Artificial neural network-based repair and maintenance cost estimation model for rice combine harvesters

This research proposes an artificial neural network(ANN)-based repair and maintenance(R&M)cost estimation model for agricultural machinery.The proposed ANN model can achieve high estimation accuracy with small data requirement.In the study,the proposed ANN model is implemented to estimate the R&M costs using a sample of locally-made rice combine harvesters.The model inputs are geographical regions,harvest area,and curve fitting coefficients related to historical cost data;and the ANN output is the estimated R&M cost.Multilayer feed-forward is adopted as the processing algorithm and Levenberg-Marquardt backpropagation learning as the training algorithm.The R&M costs are estimated using the ANN-based model,and results are compared with those of conventional mathematical estimation model.The results reveal that the percentage error between the conventional and ANN-based estimation models is below 1%,indicating the proposed ANN model’s high predictive accuracy.The proposed ANN-based model is useful for setting the service rates of agricultural machinery,given the significance of R&M cost in profitability.The novelty of this research lies in the use of curve-fitting coefficients in the ANN-based estimation model to improve estimation accuracy.Besides,the proposed ANN model could be further developed into web-based applications using a programming language to enable ease of use and greater user accessibility.Moreover,with minor modifications,the ANN estimation model is also applicable to other geographical areas and tractors or combine harvesters of different countries of origin.

Subsea Maintenance Service Delivery:Mapping Factors Influencing Scheduled Service Duration

The oil and gas （O＆G） industry on the Norwegian continental shelf （NCS） leads the world in terms of the number of subsea O＆G installations. Ensuring the dependability of these assets is critical. Non-intrusive inspection, maintenance and repair （IMR） services are therefore needed to reduce risks. These services are planned and executed using a mono-hull offshore vessel complete with remotely operated vehicles （ROVs）, a module handling system and an active heave compensated crane. Vessel time is shared between competing jobs, using a prioritized forward-looking schedule. Extension in planned job duration may have an impact on O＆G production, service costs and health, safety, and environmental （HSE） risks. This paper maps factors influencing the job schedule efficiency. The influence factors are identified through reviews of literature as well as interviews with experts in one of the large IMR subsea service providers active on the Norwegian Continental Shelf. The findings show that the most obvious factors are weather disruption and water depth. Other factors include job complexity, job uncertainty, IMR equipment availability, as well as the mix of job complexity.

Optimal Extended Warranty Policies under Different Maintenance Options

Extended warranty has recently obtained increasing attention from both manufacturers and customers in China. In this paper,given the reality of China, two types of non-renewing extended warranty were proposed: one-dimensional extended warranty and two-dimensional extended warranty. And a combined warranty policy including pro-rata warranty policy and free-repair warranty policy was applied in these two types of warranty. Then the expected life-cycle cost models from the manufacturer and consumer's perspectives were developed considering different maintenance options. The optimal warranty policy, maintenance options,and warranty price were adopted in terms of a win-win interval which was determined by the maximum extra cost the consumer should pay and the minimum price the manufacture should sell at the extended warranty. Finally,a case study was given to prove the effectiveness and validity of the model.

Model for Failure Point Process of a Repairable System and Application

A engineering system is usually repairable, and failure process of a repairable by a failure point process. The power law model is a commonly used approach to model syst the em is often described failure point process. This paper introduces the concept and model for the failure process of repairable system. The method of parameter estimation is developed, and failure observations are fitted into a power-law model by using the least square method. Two applications of the pressent model are discussed according to the practical failure data of the central cooling system of a nuclear power plant. One application is determining the optimal overhaul time, and the other is evaluating the quality of maintenance. This paper provides references for the overhaul decision making and maintenance quality evaluation in reality.

Study and Analysis of Obstacles and Challenges Facing Ship-Repair Industry in Iran

Nowadays, shipping industry which is the backbone of economic development has affiliated to ship maintenance and repair industry. This industry provides technical maintenance services to ships in a way to enable them to meet the requirements and regulations of the International Maritime Organization and maintaining the vessels at high technical standard & continual seaworthiness condition. Maintaining the minimum requirement of classification societies on the ships is solely taken place with repairs. The research method is an applied study in sake of aim and a descriptive study in sake of nature. This research has been conducted to examine causes and factors contributed to failures repairing in dry docks in the country;using the obtained results, an approach has been presented to reduce obstacles existing in country and reach to standard international levels. The problems include lack of suitable strategy, lack of government support, governmental facet of the structure of this sector, cumbersome laws, customs problems, lack of specialized workshops, low levels of technology and lack of new technology etc. Thus, by taking amendment to the cumbersome rules, taking advantage of industry and modern technology experts, increasing productivity and competitiveness, centralizing active domestic and foreign workshops at private sector, facilitating timely supply of parts and accessories, using research and development sector, increasing quality, reducing costs and repair time, selecting secure industrial- trade partner and etc. can pave the way in this context.

核磁共振谱仪升级改造实践与成效

核磁共振谱仪是有机化合物结构鉴定的通用表征设备.核磁共振谱仪的特点在于磁体稳定,而机柜和工作站等硬件随着时间推移逐步老化,导致故障频发,并且随着仪器软件和探头硬件的不断更新换代,原有仪器存在配置不齐、功能不全等问题.在教育部改善基本办学条件专项资金以及学校各部门的大力支持下,天津大学分析测试中心顺利完成核磁共振谱仪的升级改造,优化了资源配置,增加了仪器功能,并完善了基础设施.实践成效表明,仪器升级改造后促进了仪器的功能开发利用,提升了工作效率,进一步提高了开放共享水平.