http://repub.eur.nl/res/aut/5381/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/15272/ 2001-02-01T00:00:00Z In this paper we show how the marginal-cost approach can be used to optimise multi-parameter replacement rules. We will illustrate this for an opportunity-based age replacement rule that consists of two parameters. The first parameter is a control limit t, which indicates from what age on a unit is replaced preventively at the first arising opportunity. The second parameter is a planned replacement age T, which indicates at what age the unit is replaced if it has not been replaced yet. The unit can fail and is immediately replaced upon failure. It can be shown that this replacement rule belongs to a class of policies for which the long-run average-cost function is unimodal. The marginal cost approach is based on the following assertion: any point, in which the marginal cost(s) of deferring maintenance equals the average-cost, is an average-cost minimum. Assuming unimodality the minimisation problem can be solved as a root-finding problem, for which there are numerous efficient routines. It appears that the marginal cost approach is very practical for the optimisation of the considered replacement rule, especially because a quick assessment can be made of the optimal parameter values. The marginal cost approach can be used for many other multi-parameter problems, insofar as they can be modelled as a regenerative process. http://repub.eur.nl/res/pub/2260/ 1998-03-01T00:00:00Z Asphalt roads gradually deteriorate over time and need mending to remain in a good state. Inspections are performed to obtain information about the current state of the road; when the level of damage reaches the established standards, the road is repaired through a maintenance action that is considered most cost-effective. Because of econonomies of scale, it is to a certain extent economical to limit the number of maintenance services by integrating neighbouring segments into a homogeneous section which is completely repaired. In this report we consider the question of whether it is economically justified to adopt a maintenance concept in which the road is occasionally regenerated from junction to junction with a distance of several kilometers. The big advantage of junction-to-junction maintenance is that it can be done within special road barrier constructions which reduce the road capacity only slightly, so that the road can be maintained 24 hours a day. 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/7783/ 1997-12-09T00:00:00Z Asphalt roads are gradually deteriorating over time and need road mending to remain in a good state. Inspections are performed to obtain information about the current state of the road; when the damage achieves the established standards, the road is repaired through a maintenance action that is considered as most cost-effective. Because of economies of scale it is to a certain extent economical to limit the number of maintenance services by integrating neighboring segments into a homogeneous section which is completely repaired. In this report we consider the question whether it is economically justified to adopt a maintenance concept in which the road is occasionally regenerated from junction to junction with a distance of several kilometers. The big advantage of junction-to-junction maintenance is that it can be done within special road barrier constructions which reduce the road capacity only slightly, so that the road can be maintained 24 hours a day. 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%.