This research addresses the infrastructure maintenance scheduling problems under budget uncertainty. Infrastructure agencies usually face budget uncertainties that will eventually lead to suboptimal planning if maintenance decisions are made without taking the uncertainty into consideration. It is important for decision makers to adopt maintenance scheduling policies that take future budget uncertainty into consideration. The author proposes a multistage, stochastic linear programming model to address this problem. The author also develops solution procedures using the augmented Lagrangian decomposition algorithm and scenario reduction method. A case study exploring the computational characteristics of the proposed methods is conducted and the benefit of using the stochastic programming approach is discussed. In the case study, the road network in Dallas District is used with data taken from the Texas Department of Transportation’s Pavement Management Information System. The case study results reveal that the stochastic programming solutions tend to allocate more resources to preventive maintenance than deterministic solutions that ignore the uncertainty information. The proposed methodology can help decision makers effectively obtain optimal maintenance plan under budget uncertainty. / text

Maintenance planning and execution is increasingly important for the modern industrial sector. Maintenance costs can amount to a major part of industrial spending. However, it is not as simple as just reducing maintenance budgets. A balance must be struck between risking unplanned downtime and the costs of maintenance efforts, in order to keep the profit margins needed to compete in the global markets of today. One approach to improve the effectiveness of industries is to apply intelligent maintenance planners. In this thesis, a general-purpose maintenance planner based on Monte-Carlotree search and deep reinforcement learning is presented. This planner was evaluated and compared against two different periodic planners as well as the oracle lower bound on four different maintenance scenarios. These four scenarios are all based on servicing wind turbines. All scenarios include imperfect maintenance actions, as well as uncertainty in terms of the outcomes of maintenance actions. Furthermore, the four scenarios include both single and multi-component variants. The evaluation showed that the proposed method is outperforming both periodic planners in three of the four scenarios, with the forth being inconclusive. These results indicate that the maintenance planner introduced in this paper is a viable method, at least for these types of maintenance problems. However, further research is needed on this topic of maintenance planning under uncertainty. More specifically, the viability of the proposed method on a more diverse set of maintenance problems is needed to draw any clear general conclusions. Finally, possible improvements to the training process that are discussed in this thesis should be investigated.

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Problem statement: Manufacturing and production plants operate machines and equipment that deteriorate with usage and time thus requiring maintenance actions to restore them back to their original operational conditions. Approach: This study investigates the current standard of maintenance planning at a steel manufacturing facility in South Africa. The study begins with a thorough literature study to find good characteristics of planning which should be present at any facility that is optimally engaged in performing excellent maintenance planning effectively and efficiently. A number of key observations from the literature are made indicating that planning is a key component of maintenance and affects excellence in maintenance significantly. The literature recommends that planning should be set and based on key principles to allow for standardisation and efficiency. An empirical study in the form of a survey is then completed to benchmark the current maintenance-planning environment of the steel facility against the good characteristics of maintenance planning found in literature. Results: The results from the empirical study show that the current maintenance environment at the steel manufacturer is not optimal. The following issues are uncovered from the study: no schedulers employed to relieve the planners’ work overload, no guiding principles for planning and standardisation of work planning, no efficient shutdown planning and also no existent measures for tracking some of the key performance areas. Conclusion: Key recommendations to be considered for implementation for improving the status of the maintenance environment at the works include: introducing the scheduler position, standardising planning methodologies according to specific principles and rigorously focusing on overall maintenance improvement using standardised methodologies. / MBA (Business Administration), North-West University, Potchefstroom Campus, 2015

Problem statement: Manufacturing and production plants operate machines and equipment that deteriorate with usage and time thus requiring maintenance actions to restore them back to their original operational conditions. Approach: This study investigates the current standard of maintenance planning at a steel manufacturing facility in South Africa. The study begins with a thorough literature study to find good characteristics of planning which should be present at any facility that is optimally engaged in performing excellent maintenance planning effectively and efficiently. A number of key observations from the literature are made indicating that planning is a key component of maintenance and affects excellence in maintenance significantly. The literature recommends that planning should be set and based on key principles to allow for standardisation and efficiency. An empirical study in the form of a survey is then completed to benchmark the current maintenance-planning environment of the steel facility against the good characteristics of maintenance planning found in literature. Results: The results from the empirical study show that the current maintenance environment at the steel manufacturer is not optimal. The following issues are uncovered from the study: no schedulers employed to relieve the planners’ work overload, no guiding principles for planning and standardisation of work planning, no efficient shutdown planning and also no existent measures for tracking some of the key performance areas. Conclusion: Key recommendations to be considered for implementation for improving the status of the maintenance environment at the works include: introducing the scheduler position, standardising planning methodologies according to specific principles and rigorously focusing on overall maintenance improvement using standardised methodologies. / MBA (Business Administration), North-West University, Potchefstroom Campus, 2015

Thesis (MSc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: As the world-wide consumption of electricity continually increases, more and more pressure is put on the capabilities of power generating systems to maintain their levels of power provision. The electricity utility companies operating these power systems are faced with numerous challenges with respect to ensuring reliable electricity supply at cost-e ective rates. One of these challenges concerns the planned preventative maintenance of a utility's power generating units. The generator maintenance scheduling (GMS) problem refers to the problem of nding a schedule for the planned maintenance outages of generating units in a power system (i.e. determining a list of dates corresponding to the times when every unit is to be shut down so as to undergo maintenance). This is typically a large combinatorial optimisation problem, subjected to a number of power system constraints, and is usually difficult to solve. A mixed-integer programming model is presented for the GMS problem, incorporating constraints on maintenance windows, the meeting of load demand together with a safety margin, the availability of maintenance crew and general exclusion constraints. The GMS problem is modelled by adopting a reliability optimality criterion, the goal of which is to level the reserve capacity. Three objective functions are presented which may achieve this reliability goal; these objective functions are respectively quadratic, nonlinear and linear in nature. Three GMS benchmark test systems (of which one is newly created) are modelled accordingly, but prove to be too time consuming to solve exactly by means of an o -the-shelf software package. Therefore, a metaheuristic solution approach (a simulated annealing (SA) algorithm) is used to solve the GMS problem approximately. A new ejection chain neighbourhood move operator in the context of GMS is introduced into the SA algorithm, along with a local search heuristic addition to the algorithm, which results in hybridisations of the SA algorithm. Extensive experiments are performed on di erent cooling schedules within the SA algorithm, on the classical and ejection chain neighbourhood move operators, and on the modi cations to the SA algorithm by the introduction of the local search heuristic. Conclusions are drawn with respect to the e ectiveness of each variation on the SA algorithm. The best solutions obtained during the experiments for each benchmark test case are reported. It is found that the SA algorithm, with ejection chain neighbourhood move operator and a local search heuristic hybridisation, achieves very good solutions to all instances of the GMS problem. The hybridised simulated annealing algorithm is implemented in a computerised decision support system (DSS), which is capable of solving any GMS problem instance conforming to the general formulation described above. The DSS is found to determine good maintenance schedules when utilised to solve a realistic case study within the context of the South African power system. A best schedule attaining an objective function value within 6% of a theoretical lowerbound, is thus produced. / AFRIKAANSE OPSOMMING: Met die wêreldwye elektrisiteitsverbruik wat voortdurend aan die toeneem is, word daar al hoe meer druk geplaas op die vermoë van kragstelsels om aan kragvoorsieningsaanvraag te voldoen. Nutsmaatskappye wat elektrisiteit opwek, word deur talle uitdagings met betrekking tot betroubare elektrisiteitsverskaffing teen koste-e ektiewe tariewe in die gesig gestaar. Een van hierdie uitdagings het te make met die beplande, voorkomende instandhouding van 'n nutsmaatskappy se kragopwekkingseenhede. Die generator-instandhoudingskeduleringsprobleem (GISP) verwys na die probleem waarin 'n skedule vir die beplande instandhouding van kragopwekkingseenhede binne 'n kragstelsel gevind moet word ('n lys van datums moet tipies gevind word wat ooreenstem met die tye wanneer elke kragopwekkingseenheid afgeskakel moet word om instandhoudingswerk te ondergaan). Hierdie probleem is tipies 'n groot kombinatoriese optimeringsprobleem, onderworpe aan 'n aantal beperkings van die kragstelsel, en is gewoonlik moeilik om op te los. 'n Gemengde, heeltallige programmeringsmodel vir die GISP word geformuleer. Die beperkings waaruit die formulering bestaan, sluit in: venstertydperke vir instandhouding, bevrediging van die vraag na elektrisiteit tesame met 'n veiligheidsgrens, die beskikbaarheid van instandhoudingspersoneel en algemene uitsluitingsbeperkings. Die GISP-model neem as optimaliteitskriterium betroubaarheid en het ten doel om die reserwekrag wat gedurende elke tydperk beskikbaar is, gelyk te maak. Drie doelfunksies word gebruik om laasgenoemde doel te bereik (naamlik doelfunksies wat onderskeidelik kwadraties, nie-lineêr en lineêr van aard is). Drie GISP-maatstaftoetsstelsels (waarvan een nuut geskep is) is dienooreenkomstig gemodelleer, maar dit blyk uit die oplossingstye dat daar onprakties lank gewag sal moet word om eksakte oplossings deur middel van kommersiële programmatuur vir hierdie stelsels te kry. Gevolglik word 'n metaheuristiese oplossingsbenadering ('n gesimuleerde temperingsalgoritme (GTA)) gevolg om die GISP benaderd op te los. 'n Nuwe uitwerpingsketting-skuifoperator word in die konteks van GISP in die GTA gebruik. Verder word 'n lokale soekheuristiek met die GTA vermeng om 'n basteralgoritme te vorm. Uitgebreide eksperimente word uitgevoer op verskeie afkoelskedules binne die GTA, op die klassieke en uitwerpingsketting-skuifoperators en op die verbasterings van die GTA meegebring deur die lokale soekheuristiek. Gevolgtrekkings word oor elke variasie van die GTA se e ektiwiteit gemaak. Die beste oplossings vir elke toetsstelsel wat gedurende die eksperimente verkry is, word gerapporteer. Daar word bevind dat die GTA met uitwerpingsketting-skuifoperator en lokale soekheuristiek-verbastering baie goeie oplossings vir die GISP lewer. Die verbasterde GTA word in 'n gerekenariseerde besluitsteunstelsel (BSS) geïmplementeer wat 'n gebruiker in staat stel om enige GISP van die vorm soos in die wiskundige programmeringsmodel hierbo beskryf, op te los. Daar word bevind dat die BSS goeie skedules lewer wanneer dit gebruik word om 'n realistiese gevallestudie binne die konteks van die Suid-Afrikaanse kragstelsel, op te los. 'n Beste skedule met 'n doelfunksiewaarde wat binne 6% vanaf 'n teoretiese ondergrens is, word ondermeer bepaal.

The purpose of this study is to examine the nature of performance measures utilised by the maintenance function in todays business organisations. In the process, the increasing variety and significance of these measures are addressed from operational and strategic perspectives. A survey-based research method was utilised to gather the research data. Several statistical procedures were utilised to analyse the data. The findings of this study point to the multifaceted nature of the maintenance measures and measurement. Multiple categories of maintenance measures were identified. These categories varied from the machine-specific, to measures impacting organisational performance. The relative lack of emphasis placed on the environment and strategic facets of maintenance is noted. The findings of this study have direct implications to organisations, which are attempting to measure the effectiveness of their maintenance efforts. The need to align the maintenance performance efforts with the organisational strategic direction is emphasised. In this context, the integration of the maintenance performance information systems with the overall organisational performance management information system might facilitate the needed alignment. This study utilises 120 maintenance measures. As such, it represents a comprehensive view of the maintenance effort.

Several studies and government reports have indicated that a large number of apartments in Sweden built during the 1960s and 1970s require extensive refurbishment and that there is concern that some companies in the rental housing sector and in the tenant-owner cooperative (TOC) sector may have difficulties carrying out the needed activities. The overall purpose of the thesis is to increase the understanding of the factors that influence the decisions made within the multi­ faceted property management of multifamily housing in Sweden which would mitigate some of the shortcomings. Econometric analysis and semi-structured interviews as well as questionnaires carried out within the TOC sector as well as the public and the private rental housing sectors provide the basis of the conclusions arrived at. The aim is to contribute to raising efficiency in maintenance and property management within the housing sector in Sweden. The major conclusions presented in the thesis are that: maintenance as a concept is unnecessary from a decision-making perspective as the concept of investment embraces all the relevant decisions; maintenance models in manufacturing industries could be applied within the housing sector but building maintenance is different and should be grounded on a strategy that allows for the continuous adjustment of maintenance plans based on a regularly up-to-date decision support system in the company or TOC; reported maintenance costs within the municipal (public) and the private rental sectors in Sweden continuously diverge mainly due to principal-agency issues of a socio-political character, in the form of political involvement in the operations of public housing companies, as well as the way companies define maintenance together with the timing of the maintenance measures; hidden incentives in the form of cooperative members, managers or service providers that seek short term gains together with the lack of a long-term perspective in the decision-making as well as a high turnover rate of committee members are major challenges to efficient property management within the Swedish TOC sector. Similarly, the information asymmetry between the professionals (constructors as well as service providers) and the amateur decision-makers in the managing committees, especially in cooperatives with newly constructed buildings, is a substantial source of losses in efficiency within the operations of the TOCs. Major contributions of the thesis are that: it promotes the view of maintenance as an investment and highlights the possibility of cost saving through the linking together of several measures as well as the challenges involved; it points to the need within the housing sector for better decision support tools as well as knowledge transfer and sharing; it calls for the government to promote policies that would reduce the degree of information asymmetry between the procurers of services within the TOC sector and the construction companies as well as other service providers. A requirement of formal competence and certification could be a step towards increasing the degree of qualified decision making and efficiency in property management within the housing sector. How this could be implemented nationwide in the different housing sectors is an issue worth further investigation. / Flera studier och statliga rapporter har visat att ett stort antal lägenheter i Sverige som byggdes under 1960- och 1970-talet kräver omfattande renovering och att det finns oro för att vissa företag i bostadshyressektorn och i bostadsrättssektorn kan ha svårigheter att utföra nödvändiga åtgärder. Det övergripande syftet med avhandlingen är att öka förståelsen av de faktorer som påverkar beslutfattning inom den mångfacetterad fastighetsförvaltning av flerfamiljshus i Sverige, vilket skulle mildra några av bristerna. Ekonometriska analyser och semistrukturerade intervjuer samt enkäter som genomföddes inom Brf sektorn samt den offentliga och den privata hyresbostadssektorn utgör grunden för de slutsatser som dragits. Syftet är att bidra till att höja effektiviteten i underhåll och fastighetsförvaltning inom bostadssektorn i Sverige. De viktigaste slutsatserna i avhandlingen är att: underhållet som begrepp är onödigt från ett beslutsperspektiv eftersom begreppet investering omfattar alla relevanta beslut; underhållsstrategier i tillverkningsindustrin skulle kunna tillämpas inom bostadssektorn men byggnadsunderhåll skiljer sig och bör grundas på en strategi som gör det möjligt för kontinuerlig anpassning av underhållsplaner baserat på ett reguljärt uppdaterad beslutsstödsystem i företaget eller TOC; redovisade underhållskostnader inom den kommunala och den privata hyresbostadssektorn i Sverige kontinuerligt avviker från varandra främst på grund av principal-agent frågor av sociopolitisk karaktär, i form av politisk inblandning i verksamheten inom de allmännyttiga bostadsföretag, och hur företag definierar underhåll samt tidpunkten för underhållsåtgärderna; effektiv fastighetsförvaltning inom den svenska Brf sektorn kompliceras av olika aktörer (kooperativets medlemmar, che fer eller tjänsteleverantörer) med dolda incitament, avsaknaden av ett långsiktigt perspektiv i beslutsfattandet, en hög omsättning av kommittémedlemmar samt informationsasymmetri mellan yrkesverksamma (konstruktörer samt tjänsteleverantörer) och amatör beslutsfattare inom Brfer, särskilt i kooperativ med nybyggda hus, vilket utgör en stor källa till effektivitetsförluster inom verksamheten i Brf sektorn. Avhandlingens viktiga bidrag är att: det främjar synen på underhåll som en investering och understryker möjligheten till kostnadsbesparingar genom att knyta ihop flera åtgärder samt de utmaningar som kan finnas; det pekar på behovet inom bostadssektorn för bättre beslutsunderlagsverktyg liksom kunskapsöverföring och delning samt uppmuntrar den regeringen att främja en politik som skulle minska graden av informationsasymmetri mellan beställare av tjänster inom Brf sektorn och byggföretag samt andra tjänsteleverantörer. Ett krav på formell kompetens och certifiering kan vara ett steg mot att öka graden av kvalificerad beslutsfattande och effektivitet inom fastighetsförvaltning i bostadssektorn. Hur detta skulle kunna genomföras i hela landet i de olika bostadssektorerna är en fråga som ytterligare skulle kunna undersökas. / <p>QC 20160223</p>

Rail transport plays a key role in the mobility of passengers and goods. It is expected to grow the decarbonization of society. In that context, it is important to use the railway network efficiently, and jointly planning trains and network maintenance allows for better use of resources. This master thesis focuses on the integration of regular maintenance slots in a timetable while minimizing the impact on rail traffic and maintenance costs. The problem has been modeled as a mixed-integer linear programming formulation. First, we study the modeling of the interactions between trains, and we focus on the possible conflicts due to maintenance slots. Two approaches are compared: an aggregated one and a detailed one close to maintenance slots. We analyze the computation time and the quality of the solution on a real-life timetable with different maintenance scenarios. The results show while the aggregated approach is useful for finding reasonable slots, the detailed one is necessary to achieve high quality solutions with minimal traffic impact. In the second step, we reduce the computation time by using construction heuristics. We use a greedy algorithm to find realistic maintenance slots combined with a train-fixing heuristic. Our experiments have shown that theses heuristics reduces significantly the computation time (with more than 50% on the considered test instances) for solutions of equivalent quality. Limitations of the model and improvements are discussed. / Järnvägstransporter spelar en nyckelroll för passagerar- och godstransporter. Den väntas öka koldioxidminskningen i samhället. I det sammanhanget är det viktigt att använda järnvägsnätet effektivt och en gemensam planering av tåg och underhåll av nätet gör det möjligt att utnyttja resurserna bättre. Den här masteruppsatsen fokuserar på integrering av regelbundna underhållsfönster i en tidtabell samtidigt som man minimerar effekterna på järnvägstrafiken och underhållskostnaderna. Problemet har modellerats som ett linjärt optimeringsproblem med blandade heltal. Först studerar vi hur interaktioner mellan tåg kan modelleras med fokus på konflikter som uppstår vid underhållsfönster. Två tillvägagångssätt jämförs: ett aggregerat tillvägagångssätt och ett detaljerat tillvägagångssätt nära underhållstidpunkterna. Vi analyserar beräkningstiden och lösningens kvalitet på en verklig tidtabell med olika underhållsscenarier. Resultaten visar att medan det aggregerade tillvägagångssättet är användbart för att hitta rimliga tidsluckor, så är det detaljerade tillvägagångssättet nödvändigt för att hitta lösningar med hög kvalitet och minsta möjliga trafikpåverkan. I det andra steget minskar vi beräkningstiden med hjälp av konstruktionsheuristik. Vi använder en algoritm för att hitta realistiska underhållstidpunkter kombinerat med en fixeringsheuristik för tågen. Våra experiment visar att dessa heuristiker avsevärt minskar beräkningstiden (med mer än 50% för de studerade testfallen) för lösningar av likvärdig kvalitet. Begränsningar av modellen och förbättringar diskuteras.

Submitted by Joana Azevedo (joanad@id.uff.br) on 2017-08-07T19:12:15Z No. of bitstreams: 1 Dissert Fabrício Alves Nunes.pdf: 2050717 bytes, checksum: d5c4252b007b010c89e979a0c870c404 (MD5) / Approved for entry into archive by Biblioteca da Escola de Engenharia (bee@ndc.uff.br) on 2017-08-24T14:17:56Z (GMT) No. of bitstreams: 1 Dissert Fabrício Alves Nunes.pdf: 2050717 bytes, checksum: d5c4252b007b010c89e979a0c870c404 (MD5) / Made available in DSpace on 2017-08-24T14:17:56Z (GMT). No. of bitstreams: 1 Dissert Fabrício Alves Nunes.pdf: 2050717 bytes, checksum: d5c4252b007b010c89e979a0c870c404 (MD5) Previous issue date: 2016-12-21 / A garantia da distribuição de energia é central para a sociedade moderna e uma atividade que impacta diretamente a gerência de planejamento da manutenção e operação de uma das maiores distribuidoras de energia do Rio de Janeiro, a Light. Dada a relevância da constância do fornecimento, a agência reguladora do setor elétrico (ANEEL) estabelece metas rígidas relacionadas aos indicadores de disponibilidade (DEC) e frequência (FEC) de interrupções, com aplicação de rígidas sanções às distribuidoras. O objetivo da pesquisa é analisar modelos quantitativos capazes de aprender com o histórico de interrupções do sistema de distribuição de energia e simular entradas (recursos financeiros necessários a serem investidos por tipo de ação de manutenção) para provisionar os indicadores de continuidade DEC e FEC (saídas), assegurando a proximidade entre o valor obtido experimentalmente e o valor verdadeiro na medição desses indicadores. Em termos metodológicos, foi realizada uma revisão da literatura para identificar possíveis modelos para apoio à decisão sendo capaz de fornecer insumos para a tomada de decisão gerencial. Como resultados, os provisionamentos calculados para o DEC e FEC Global foram obtidos com precisão de 84% e 90%, respectivamente, o que representa uma contribuição acadêmica e gerencial orientadas ao atendimento dos requisitos impostos pela ANEEL. / The guarantee of energy distribution is central to modern society and an activity that directly impacts the management planning of the maintenance and operation of one of the largest energy distributors in Rio de Janeiro, Light. Due to the importance of supply constancy, the regulatory agency of the electricity sector (ANEEL) establishes strict targets related to the availability (DEC) and frequency (FEC) indicators of interruptions, with strict sanctions applied to distributors. The objective of the research is to analyze quantitative models able to learn from the history of disruptions of the power distribution system and simulate inputs (financial resources needed to be invested by type of maintenance action) to provide the continuity indicators DEC and FEC (Outputs), ensuring the proximity between the value obtained experimentally and the true value in the measurement of these indicators. In methodological terms, a review of the literature was carried out to identify possible models for decision support being capable of providing inputs for managerial decision making. As a result, the provisions calculated for DEC and FEC Global were obtained with an accuracy of 84% and 90%, respectively, which represents an academic and managerial contribution geared to meeting the requirements imposed by ANEEL.