Modelling, simulation and optimization of maintenance considerations on condition based maintenance

Globalization has increased the pressure on organizations and companies to operate in the most efficient and economic way. This tendency promotes that companies concentrate more and more on their core businesses, outsource less profitable departments and services to reduce costs. By contrast to earlier times, companies are highly specialized and have a low real net output ratio. For being able to provide the consumers with the right products, those companies have to collaborate with other suppliers and form large supply chains. An effect of large supply chains is the deficiency of high stocks and stockholding costs. This fact has lead to the rapid spread of Just-in-Time logistic concepts aimed minimizing stock by simultaneous high availability of products. Those concurring goals, minimizing stock by simultaneous high product availability, claim for high availability of the production systems in the way that an incoming order can immediately processed. Besides of design aspects and the quality of the production system, maintenance has a strong impact on production system availability. In the last decades, there has been many attempts to create maintenance models for availability optimization. Most of them concentrated on the availability aspect only without incorporating further aspects as logistics and profitability of the overall system. However, production system operator’s main intention is to optimize the profitability of the production system and not the availability of the production system. Thus, classic models, limited to represent and optimize maintenance strategies under the light of availability, fail. A novel approach, incorporating all financial impacting processes of and around a production system, is needed. The proposed model is subdivided into three parts, maintenance module, production module and connection module. This subdivision provides easy maintainability and simple extendability. Within those modules, all aspect of production process are modeled. Main part of the work lies in the extended maintenance and failure module that offers a representation of different maintenance strategies but also incorporates the effect of over-maintaining and failed maintenance (maintenance induced failures). Order release and seizing of the production system are modeled in the production part. Due to computational power limitation, it was not possible to run the simulation and the optimization with the fully developed production model. Thus, the production model was reduced to a black-box without higher degree of details.

Life cycle assessment in construction field: A life cycle cost analysis of reinforcement concrete bridge

The present work is included in the context of the assessment of sustainability in the construction field and is aimed at estimating and analyzing life cycle cost of the existing reinforced concrete bridge “Viadotto delle Capre” during its entire life. This was accomplished by a comprehensive data collection and results evaluation. In detail, the economic analysis of the project is performed. The work has investigated possible design alternatives for maintenance/rehabilitation and end-of-life operations, when structural, functional, economic and also environmental requirements have to be fulfilled. In detail, the economic impact of different design options for the given reinforced concrete bridge have been assessed, whereupon the most economically, structurally and environmentally efficient scenario was chosen. The Integrated Life-Cycle Analysis procedure and Environmental Impact Assessment were also discussed in this work. The scope of this thesis is to illustrate that Life Cycle Cost analysis as part of Life Cycle Assessment approach could be effectively used to drive the design and management strategy of new and existing structures. The final objective of this contribution is to show how an economic analysis can influence decision-making in the definition of the most sustainable design alternatives. The designers can monitor the economic impact of different design strategies in order to identify the most appropriate option.