http://repub.eur.nl/res/aut/4317/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/2262/ 1998-02-01T00:00:00Z This paper discusses several strategies for the maintenance of light-standards, where each light-standard consists of n independent and identical lamps screwed on a lamp assembly. The lamps are subject to stochastic failures, and must be correctly replaced if the number of failed lamps reaches a prespecified number m, a norm that is set by the local management to guarantee a minimum luminance. As lamps have an increasing hazard rate and there is a fixed cost of hoisting the assembly, we propose various variants of the m-failure group replacement rule which have in particular an age-criterion to indicate which of the non-failed lamps must be preventively replaced at the time that the assembly is lowered for a corrective lamp replacement. We show how the optimal threshold age can be determined. It appears that this modification reduces the long run average maintenance cost of the Europe Combined Terminals by approximately 8.3%. http://repub.eur.nl/res/pub/15261/ 1997-10-01T00:00:00Z In this paper we review the literature on multi-component maintenance models with economic dependence. The emphasis is on papers that appeared after 1991, but there is an overlap with Section 2 of the most recent review paper by Cho and Parlar (1991). We distinguish between stationary models, where a long-term stable situation is assumed, and dynamic models, which can take information into account that becomes available only on the short term. Within the stationary models we choose a classification scheme that is primarily based on the various options of grouping maintenance activities: grouping either corrective or preventive maintenance, or combining preventive-maintenance actions with corrective actions. As such, this classification links up with the possibilities for grouped maintenance activities that exist in practice. http://repub.eur.nl/res/pub/15265/ 1997-07-01T00:00:00Z Most maintenance-optimisation models assume an infinite planning horizon and suppose that the failure process is stationary. Hence, information which is not known beforehand and which beocmes available in the short term only, must be ignored. We consider in this paper a multi-component system with economically dependent components, and we compare the costs of a stationary-planning method with the costs according to an approach which can adapt this long-term plan to dynamically changing information (such as a variable use of components and the occurrence of maintenance opportunities). With numerical experiments we show that incorporating short-term information can yield considerable cost savings. http://repub.eur.nl/res/pub/15256/ 1997-06-16T00:00:00Z A maintenance activity carried out on a technical system often involves a system-dependent set-up cost that is the same for all maintenance activities carried out on that system. Grouping activities thus saves costs since execution of a group of activities requires only one set-up. Many maintenance models consider the grouping of maintenance activities on a long-term basis with an infinite horizon. This makes it very difficult to incorporate short-term circumstances such as opportunities or a varying use of components because these are either not known beforehand or make the problem intractable. In this paper we propose a rolling-horizon approach that takes a long-term tentative plan as a basis for a subsequent adaptation according to information that becomes available on the short term. This yields a dynamic grouping policy that assists the maintenance manager in his planning job. We present a fast approach that allows interactive planning by showing how shifts from the tentative planning work out. We illustrate our approach with examples. http://repub.eur.nl/res/pub/15306/ 1997-06-01T00:00:00Z During the last two decades, many heuristic procedures for the joint replenishment problem have appeared in the literature. The only available optimal solution procedure was based on an enumerative approach and was computationally prohibitive. In this paper we present an alternative optimal approach based on global optimisation theory. By applying Lipschitz optimisation one can find a solution with an arbitrarily small deviation from an optimal value. An efficient procedure is presented which uses a dynamic Lipschitz constant and generates a solution in little time. The running time of this procedure grows only linearly in the number of items. http://repub.eur.nl/res/pub/2222/ 1997-05-24T00:00:00Z We consider the problem of combining replacements of multiple components in an operational planning phase. Within an infinite or finite time horizon, decisions concerning replacement of components are made at discrete time epochs. The optimal solution of this problem is limited to only a small number of components. We present a heuristic rolling horizon approach that decomposes the problem; at each decision epoch an initial plan is made that http://repub.eur.nl/res/pub/7825/ 1996-11-08T00:00:00Z This paper discusses several strategies for the maintenance of light standards, where each light standard consists of n independent and identical lamps screwed on a chandelier. The lamps are subject to stochastic failures, and must be correctively replaced if the number of failed lamps reaches a prespecified number m; a norm that is set by the local management to guarantee a minimum luminance. As lamps have an increasing failure rate, and there is a fixed cost of hoisting the chandelier, we propose various variants of the m-failure group replacement rule which have in particular an age-criterion to indicate which of the non-failed lamps must be preventively replaced at the time that the chandelier is lowered for a corrective lamp replacement; we show how the optimal threshold age can be determined. It appears that this modification reduces the long run average maintenance cost of the Europe Combined Terminals with approximately 8.3%. http://repub.eur.nl/res/pub/1372/ 1996-01-01T00:00:00Z In this paper we review the literature on multi-component maintenance models with economic dependence. The emphasis is on papers that appeared after 1991, but there is an overlap with Section 2 of the most recent review paper by Cho and Parlar (1991). The classification scheme that we choose is primarily based on the various options of grouping maintenance activities: grouping either corrective or preventive maintenance actions, or combining preventive maintenance activities with corrective actions. As such, this classification links up with the possibilities for grouped maintenance activities that exist in practice. http://repub.eur.nl/res/pub/1386/ 1996-01-01T00:00:00Z Most maintenance-optimisation models assume an infinite planning horizon and suppose that the failure process is stationary. Hence, information which is not known beforehand and which becomes available on the short term only, must be ignored. We consider in this paper a multi-component system with economically dependent components, and we compare the costs of a stationary-planning method with the costs according to an approach which can adapt this long-term plan to dynamically changing information (such as a variable use of components and the occurrence of maintenance opportunities). With numerical experiments we show that incorporating short-term information can yield considerable cost savings. http://repub.eur.nl/res/pub/2224/ 1996-01-01T00:00:00Z http://repub.eur.nl/res/pub/1357/ 1995-01-01T00:00:00Z A maintenance activity carried out on a technical system often involves a system-dependent set-up cost that is the same for all maintenance activities carried out on that system. Grouping activities thus saves costs since execution of a group of activities requires only one set-up. Many maintenance models consider the grouping of maintenance activities on a long-term basis with an infinite horizon. This makes it very difficult to incorporate short-term circumstances such as opportunities or a varying use of components because these are either not known beforehand or make the problem intractable. In this paper we propose a rolling-horizon approach that takes a long-term tentative plan as a basis for a subsequent adaptation according to information that becomes available on the short term. This yields a dynamic grouping policy that assists the maintenance manager in his planning job. We present a fast approach that allows interactive planning by showing how shifts from the tentative planning work out. We illustrate our approach with examples. http://repub.eur.nl/res/pub/1358/ 1995-01-01T00:00:00Z A maintenance activity carried out on a technical system often involves a system-dependent set-up cost that is the same for all maintenance activities carried out on that system. Grouping activities thus saves costs since execution of a group of activities requires only one set-up. By now, there are several multi-component maintenance models available in the literature, but most of them suffer from intractability when the number of components grows, unless a special structure is assumed. An approach that can handle many components was introduced in the literature by Goyal et al. However, this approach requires a specific deterioration structure for components. Moreover, the authors present an algorithm that is not optimal and there is no information of how good the obtained solutions are. In this paper we present an approach that solves the model of Goyal et al. to optimality. Furthermore, we extend the approach to deal with more general maintenance models like minimal repair and inspection that can be solved to optimality as well. Even block replacement can be incorporated, in which case our approach is a good heuristic. http://repub.eur.nl/res/pub/1359/ 1995-01-01T00:00:00Z During the last two decades, many heuristic procedures for the joint replenishment problem have appeared in the literature. The only available optimal solution procedure was based on an enumerative approach and was computationally prohibitive. In this paper we present an alternative optimal approach based on global optimisation theory. By applying Lipschitz optimisation one can find a solution with an arbitrarily small deviation from an optimal value. An efficient procedure is presented which uses a dynamic Lipschitz constant and generates a solution in little time. The running time of this procedure grows only linearly in the number of items. http://repub.eur.nl/res/pub/2219/ 1995-01-01T00:00:00Z