Tesi sul tema "Service life (Engineering)"

Pipelines are extensively used engineering structures for conveying of fluid from one place to another. Most of the time, pipelines are placed underground, surcharged by soil weight and traffic loads. Corrosion of pipe material is the most common form of pipeline deterioration and should be considered in both the strength and serviceability analysis of pipes. The study in this research focuses on two different types of buried pipes including concrete pipes in sewage systems (concrete sewers) and cast iron water pipes used in water distribution systems. This research firstly investigates how to involve the effect of corrosion as a time dependent process of deterioration in the structural and failure analysis of these two types of pipes. Then two probabilistic time dependent reliability analysis methods including first passage probability theory and the gamma distributed degradation model are developed and applied for service life prediction of the pipes. The obtained results are verified by using Monte Carlo simulation technique. Sensitivity analysis is also performed to identify the most important parameters that affect pipe failure. For each type of the pipelines both individual failure mode and multi failure mode assessment are considered. The factors that affect and control the process of deterioration and their effects on the remaining service life are studied in a quantitative manner. The reliability analysis methods which have been developed in this research, contribute as rational tools for decision makers with regard to strengthening and rehabilitation of existing pipelines. The results can be used to obtain a cost-effective strategy for the management of the pipeline system. The output of this research is a methodology that will help infrastructure managers and design professionals to predict service life of pipeline systems and to optimize materials selection and design parameters for designing pipelines with longer service life.

Thesis: S.M. in Mechanical Engineering, and S.M in Naval Architecture and Marine Engineering, Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 71-74).
New regulations in the United States and Europe, designed to address climate change concerns by reducing greenhouse gas emissions, are causing increased use of gasoline direct-injection (GDI) engines in light-duty vehicles (LDV). Separate new regulations that aim to reduce particulate emissions to address air pollution concerns are taking effect concurrent with greenhouse gas limitations in both jurisdictions. GDI engines are proven to create more particulate emissions than previously utilized port-injection technology. Increasing particulate emissions rates combined with falling regulatory particulate emissions limits requires new strategies to reduce these emissions from gasoline powered LDVs. Particulate filters have been successfully implemented to reduce particulate emissions from diesel engine exhaust for over a decade. Diesel particulate filters have a demonstrated filtration efficiency of 95% or greater and have reduced diesel particulate mass (PM) emissions by one to two orders of magnitude. GDI engines require no more than one order of magnitude reduction in particulate emissions to meet new regulations. Existing particulate filter technology in use in diesel vehicles is capable of reducing GDI engine emissions to new regulatory levels; however, it is proposed that these reduction may be achievable through means other than gasoline particulate filters (GPF). A GPF will create an additional back-pressure in the engine exhaust system that will reduce engine power and efficiency. This backpressure will increase as PM is trapped in the filter and decrease as combustible PM removed. A buildup of incombustible ash present in engine-out PM will increase the baseline backpressure of the filter during the course of its service life. It is important to understand the impact of ash on the filter pressure drop performance before implementing GPF to meet new emissions regulations. This study builds on existing diesel particulate filter technology and demonstrates through experimental results the mechanisms by which ash increases GPF pressure drop. Ash deposits are also shown to increase the light-off temperature of three-way catalyst coatings in GPF.
by Nicholas C. Custer.
S.M. in Mechanical Engineering, and S.M in Naval Architecture and Marine Engineering

Over the last few decades, the increasing premature deterioration of reinforced concrete structures, mainly due to rebar corrosion, has become a worldwide concern. This has been attributed to insufficient quality and quantity of cover concrete resulting from inadequate mix design and poor onsite workmanship respectively. Engineers also often lack understanding of concrete durability and prescribe insufficient cover depths relative to the exposure conditions. Concrete degradation has many financial and social implications on a larger scale. Direct costs relate to the repair and rehabilitation of existing structures to maintain serviceability while indirect costs include loss in productivity and reduced economic growth. With increasing demand for infrastructure and subsequent expansion of the built environment, there is greater need for concrete to withstand and perform in corrosive environments. Hence, designing for durability has gained significant importance amongst engineers and other stakeholders in the construction industry. Furthermore, the appearance of cracks can be considered as an inevitable phenomenon in the design life of reinforced concrete structures, due to concrete being an inherently cracked material. The presence of cracks within the cover zone changes the dynamics of transport mechanisms and corrosion development. Cracks provide preferential ingress paths for deleterious species such as chlorides and this leads to a reduction in the time taken for reinforcement corrosion initiation and thus reduces the service life of the structure. Most service life models also consider concrete only in the uncracked state, leading to an overestimation of the actual performance and design life of reinforced concrete infrastructure. Extensive research has been carried out to find means to promote the service life of reinforced concrete structures in aggressive environments. Hydrophobic (silane) impregnation represents a cost-effective way to increase the durability of concrete structures in cases where insufficient cover quality and depth have been achieved. The hydrophobic impregnation agent lines the internal capillary pore structure and provides a water-repellent surface without affecting the external appearance of the concrete. Thus, the risk of reinforcement corrosion and subsequent deterioration can be reduced as the ingress of water-dissolved aggressive species is minimised or prevented. The influence of silane impregnation on chloride ingress is well documented in literature and several experiments have been carried out over the last decades. However, there is limited work on the service life modelling of silane treated concrete. Hence, the purpose of this study was to investigate and quantify the influence of silane impregnation as a remedial measure for poor quality cover or insufficient cover depth in newly constructed structures and ultimately predict the time to corrosion initiation for specific cover depths and concrete types. The effectiveness of silane impregnation in cracked concrete was also studied. Two w/b ratios (w/b = 0.45 and w/b = 0.60) and four binder types (CEM I 52.5N, Fly-ash (FA), Ground granulated Corex slag (GGCS) and CEM III/B 42.5N) were selected. Hence, a total of 8 main (normal) concrete mixes and 4 poor quality mixes were used. Poor quality concrete was produced by exposing the concrete specimens to relatively high temperature at early age. Cracked concrete was obtained by loading notched reinforced beams until the formation of cracks. Steel spacers were then placed in the notch and the beams were unloaded to create crack widths of 0.2 mm and 0.6 mm (below and above the commonly assumed crack width threshold of 0.4 mm). Silane treatment was performed at a specimen age of 28 days by applying Sikagard®-706 Thixo at a consumption rate of 400 g/m2 . Several experimental tests were performed on untreated and silane treated concrete. Compressive strength and Durability Index (DI) tests were carried out to characterise the concrete mixes. Accelerated carbonation and moisture profiling tests were undertaken to assess the influence of silane impregnation on concrete carbonation and relative humidity. Finally, uncracked and cracked (untreated and treated) concrete mixes were ponded in sodium chloride (NaCl) solution for 80 days, followed by chloride profiling. The data for the uncracked concrete was curve fitted using a solution to Fick’s second law of diffusion. The regression parameters obtained (surface chloride concentration (Cs) and apparent chloride diffusion coefficient (Da)) were then incorporated in a mathematical solution to Fick’s second law to obtain suitable expressions that describe the penetration of chlorides with time for silane treated and untreated concrete mixes. Hence by determining the time taken for chloride concentration at the rebar level to reach the critical threshold (assumed to be 0.4% by mass of binder), the time to corrosion initiation of untreated and silane treated concrete was predicted for particular cover depths. The results indicate that the silane penetration depth is highly dependent on the quality (porosity) and moisture content of the near surface zone as deeper penetration was recorded in the higher w/b ratio and poor-quality concrete mixes. Silane impregnation also reduced the capillary absorption and chloride conductivity for all the mixes. In terms of the bulk diffusion test, chloride ingress in the treated concrete mixes was suppressed and lower chloride surface concentration (Cs) and apparent chloride diffusion coefficient (Da) were recorded. The influence of silane impregnation on carbonation was negligible in the w/b = 0.45 concrete mixes while a slight decrease in carbonation depth was observed in the w/b = 0.60 concrete mixes. The relative humidity of treated concrete (near the surface) initially increased relative to the untreated concrete. However, the difference in relative humidity between silane-treated and untreated concrete is reduced with time. Higher chloride concentrations were measured in the cracked concrete at depths of 50-60 mm compared to the uncracked concrete. Greater chloride ingress was also recorded in the 0.6 mm crack width relative to the 0.2 mm crack width. For a particular crack width, chloride ingress in cracked concrete was influenced by the type of binder; a significant reduction in chloride content was recorded in the cracked slag (GGCS and CEM III/B) concrete mixes relative to the CEM I mix. The results also suggest that silane impregnation reduces chloride ingress in cracked concrete (up to a crack with of 0.6 mm) and consequently minimises the risk of premature reinforcement corrosion initiation, especially in slag concrete. The service life prediction results emphasized the importance of adequate cover depths in the extreme marine exposure class (XS3) and highlighted the superior performance of slag concrete relative to CEM I concrete. A lower rate of chloride ingress was predicted in the silane treated concrete and consequently to achieve the same time to corrosion initiation, smaller cover depths are required. Alternatively, the results also show that the initiation period of rebar corrosion in structures with insufficient cover depth and quality can be effectively extended using silane impregnation.

Les Systèmes Produit-Service (PSS) résultent d'une intégration de composants hétérogènes couvrant à la fois des aspects matériels et immatériels (mécanique, électrique,logiciel, processus, organisation, etc.). Le processus de développement d’un PSS est fortement collaboratif impliquant des acteurs métier très variés.Ce caractère interdisciplinaire nécessite des référentiels sémantiques standardisés pour gérer la multitude des points de vue métier et faciliter l’intégration de tous les composants hétérogènes dans un système unique. Ceci est encore plus complexe dans le cas des PSS personnalisables, majoritaires dans le milieu industriel. Malgré les nombreuses méthodologies dans littérature, la gestion des processus de développement du PSS reste encore limitée face à cette complexité. Dans ce contexte, l'Ingénierie des systèmes (IS) pourrait être une solution avantageuse au regard de ses qualités bien prouvé pour la modélisation et la gestion de systèmes complexes. Cette thèse vise à explorer le potentiel d'utilisation de l'Ingénierie des systèmes (IS) comme fondement conceptuel pour représenter d’une façon intégrée tous les différents points de vue métier associés au cycle de vie du PSS. Dans ce cadre, un méta-modèle de PSS est proposé et exemplifié dans des cas industriels. Un modèle ontologique est aussi présenté comme une application d’une partie des modèles pour structurer le référentiel commun de la plateforme ICP4Life
Product-service systems (PSS) result from the integration of heterogeneous components covering both tangible and intangible aspects(mechanical, electrical, software, process, organization, etc.). The process of developing PSS is highly collaborative involving a wide variety of stakeholders. This interdisciplinary nature requires standardized semantic repositories to handle the multitude of business views and facilitate the integration of all heterogeneous components into a single system. This is even more complex in the case of customizable PSS in the industrial sector. Despite the many methodologies in literature, the management of the development processes of the PSS is still limited to face this complexity. In this context, Systems Engineering (SE) could bean advantageous solution in terms of its proven qualities for the modeling and management of complex systems. This thesis aims at exploring the potentials of Systems Engineering (SE) as a conceptual foundation to represent various different business perspectives associated with the life cycle of the PSS. In this context, a meta-model for PSS is proposed and verified in industrial cases. An ontological model is also presented as an application of a part of the model to structure the common repository of the ICP4Life platform

Dissertation (Ph.D.)--University of Toledo, 2005.
Typescript. "A dissertation [submitted] as partial fulfillment of the requirements of the Doctor of Philosophy degree in Engineering." Bibliography: leaves 69-74.

This research aims at enhancing the service life of the prestressed concrete bridge girders, using fiber-reinforced polymer (FRP) composite shell on the lower flange to impede the ingress of deleterious elements into the concrete. The FRP shell would help to retard the resulting deterioration reactions and achieve more durable bridges for a considerably increased service life. The behavior of prestressed concrete bridge girders with FRP shells on the tension flange was investigated experimentally.The flexural characteristics of FRP shell and concrete interface along with the effect of the steel reinforcement ratio were studied experimentally. This FRP shell was bonded around the lower part of the concrete beams, constructed with four different reinforcement ratios. The beam specimens with the FRP shell showed a significant enhancement in their strength, stiffness and energy absorption capacities, as compared with the associated control beams. The flexural behavior of cast-in-place prestressed concrete beams with FRP shell was studied to examine the contribution of the bonded FRP shell to the strength, stiffness, ductility and energy absorption capacity of prestressed concrete beam specimens, for five different levels of prestressing. The initial cracking, yield and ultimate strengths of the beam specimens with FRP shell were significantly higher than those of the associated control beam specimens. The FRP shell and the prestressing force enhanced the strength and stiffness of the beams. The long-term durability of the FRP shell to act as a barrier against ingress of aggressive elements, such as moisture and chlorides into the proposed FRP shell-concrete system, was examined experimentally in a preliminary manner. Detailed tests on concrete specimens reinforced externally with FRP shells subjected to accelerated moisture and salt solution at control temperatures were performed. In addition, scanning electron microscopy (SEM) was used to determine the effects caused by aging, with time, temperature and chloride injection pressure. The FRP shell, acting as a barrier, showed a significant resistance against chloride ingress by significantly slowing down the chlorides ingress rate and the total amount of chlorides. For a prestressed concrete girder with an FRP shell, the accumulated time for chloride penetration and reaching the level of prestressing steel strands was predicted to be more than 135 years. These results suggest that the FRP shell is quite effective in improving the durability characteristics of prestressed concrete girders and can significantly extend their service life.
Cette recherche vise à améliorer la durée de vie des poutres de pont en béton précontraint à l'aide de coquilles de composite de polymères renforcés de fibres (FRP) appliquées à la semelle inférieure pour empêcher l'infiltration d'éléments nocifs dans le béton. La coque en FRP permettrait de retarder les réactions de détérioration et de réaliser des ponts plus durables ayant une durée de vie considérablement accrue. Le comportement de ces poutres de a été étudié expérimentalement. Les caractéristiques en flexion de la coquille en FRP et de son interface de béton ainsi que de l'effet du pourcentage d'armature d'acier ont été étudiés expérimentalement. La coquille en FRP a été collée autour de la partie inférieure de poutres béton construites avec quatre pourcentages d'armature. Les spécimens de poutres avec la coquille de FRP ont montré une amélioration significative dans leurs résistances, rigidités et capacités d'absorption d'énergie par rapport aux poutres sans coquilles. Le comportement en flexion de poutres de béton précontraint coulées en place avec la coquille de FRP a été étudié afin d'examiner la contribution de la coquille à la résistance, rigidité, ductilité et capacité d'absorption d'énergie pour cinq pourcentages de précontraintes. La limite de fissuration, la limite d'élasticité et la limite ultime des spécimens avec FRP étaient sensiblement supérieures à ceux des spécimens sans coquille. La coquille en FRP et la force de précontrainte a amélioré la résistance et la rigidité des poutres. La contribution à la durabilité à long terme de la coquille de FRP contre les infiltrations d'éléments agressifs dans la coquille et le béton, tels que l'humidité et les chlorures, a été étudiée expérimentalement de façon préliminaire. Des tests accélérés sur des échantillons de béton renforcés extérieurement avec des coquilles de FRP ont été effectuées en les soumettant à l'humidité et une solution saline à température contrôlées. La microscopie électronique (SEM) a aussi été utilisée pour déterminer les effets du vieillissement par rapport au temps d'exposition, à la pression d'injection, à la température et aux chlorures. La coquille de FRP, agissant comme une barrière, a augmenté significativement la résistance contre la pénétration des chlorures en réduisant significativement le taux de pénétration des chlorures et de la quantité totale d'ions chlorure. Pour une poutre en béton précontraint avec une coque en FRP, le temps total pour que les ions chlorure atteignent les câbles d'acier de précontrainte est estimé à 135 ans. Ces résultats suggèrent que la coquille de FRP est très efficace pour améliorer la longévité des poutres en béton précontraints et peut allonger considérablement leur durée de vie.

Vacuum insulation panels, VIPs, constitute a new insulation material, 6 to 8 times better than traditional insulation materials, which utilizes the positive influence vacuum has on the thermal properties of certain materials. A VIP is a composite with a flat core enclosed by an envelope preventing the core to fill with gas. The vacuum in the core is vital to reach thermal conductivities down to 0,0035 W/(m K), if the vacuum is lost the panel has reached the end of its service life time. Metal sheets would the preferred material to create an impermeable envelope but would creates a large thermal bridge at the edges of a panel when it folds over the edges of the panel.

A serpentine edge has been proposed in order to deal with this large thermal bridge. This serpentine edge has been evaluated first as a numeric model in software and then by measuring on a prototype edge element in a hot and cold plate instrument. Measured temperatures were used to validate the numerical model. Results show that a serpentine edge can greatly reduce the thermal bridge if designed correctly.

Another direction taken in the development of the VIP barrier is to use very thin metal layers, metallization layer or coating, incorporated into multi layered polymer composite film. This creates barrier films with very good barrier properties and only small thermal bridges. The modeling of gas flux through films with more than one coating has only just started. Existing models for flux through multi coated films all assume that flux is only taking place through defects in the coating layers, that all defects are of the same size and that all defects are positioned in square lattices. The model discussed herein use the same assumption of flux through pinholes only but it does take defect sizes and positions into account. Barrier film, from a regular vacuum insulation panel, with double coatings has been evaluated in light microscopy to characterize the defects in each of the coatings. The data found have been fed into the model and the results comply well with reported permeabilities of similar barrier films.

Thesis (M.S.)--Missouri University of Science and Technology, 2010.
Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed June 7, 2010) Includes bibliographical references (p. 44-46).

The built environment usually constitutes a very important part of the real capital of a nation, and the construction sector represents more than 10% of the yearly Gross National Product of the industrialised world. Good planning of all construction is important, and consideration of the service life of the work is of great interest and is a significant aspect of sustainability considerations. The need for more knowledge about degradation of materials, for structured methodology, and for working tools for those involved in the planning process, has resulted in an extensive effort in pre-normative research and standardisation regarding this field.

This thesis presents a discussion on service life planning and the role of the Factor Method in such work, and especially, discussion of modification and development of the methodology. In the design process, the need to evaluate the service life of products is a great challenge, as the results will depend on both material properties and the environment in which the material is placed or used. A practical solution has to be based on a good knowledge in the field, but also on a sound working strategy, to ensure that different design scenarios can be compared in a standardised or structured way. The Factor Method is a promising working tool for such an evaluation and comparison, but is as such, still more of a methodology, than a method. Examples of the use of the methodology are still very limited, and the method as such, is much discussed by researchers. However, its future will depend upon how practical it will be to apply in use. The method is useful to estimate the service life of products, based on a known reference service life and a number of modifying factors. These factors in turn depend on the conditional differences between the specific project and the reference, in-use conditions. This thesis discusses the required precision of such a methodology, especially in light of inherent distributions in material properties, and the fact that the consequences of failure are often very limited. In such cases, the standardised Factor Method is considered to be quite useful, and should give the parties involved a good means for working in a structured and systematic way.

This research identifies realistic timelines for human survivability during accidental dwelling fires (ADF). It also establishes a time window within which the fire service is likely to affect a rescue of the occupants from ADFs. Through a comparison of these two timelines, the likelihood that the fire service will rescue an occupant before they receive a fatal dose of heat and/or smoke (asphyxiant gases) is established. The dependence of fire service intervention times is also assessed in the context of increasing intervention times resulting from cuts to fire authority budgets. The results show that an increase in the time taken to affect a rescue will lead to an increase in the number of fatalities and the severity of injuries which occur when the occupants of a dwelling become trapped by (or are otherwise unable to escape from) fire within the property. Around 80% of all fire deaths and injuries in Great Britain occur in dwellings. This study analyses national and local fire statistics to identify the typical fire situations and common circumstances which lead to fire deaths and injuries. This statistical analysis has been used to inform the carrying out of thirteen large-scale fire experiments. Asphyxiant gas concentrations and compartment temperatures were gathered during these experiments, in order to establish human survival times resulting from the adverse effects of exposure to these. Statistics have also been analysed and a methodology developed to establish fire service intervention times. Establishing survival times on the basis of an analysis of national statistics constitutes new work within the field of community fire safety. In addition, the author is in a preferential position to establish realistic times for fire service interventions, and there is no evidence that these timelines have previously been developed to this extent or compared to timelines for occupant survival. The findings of this research should be considered by fire authorities as they make important decisions for the development of local fire service resourcing activities in continuing times of austerity.

The use of Phase Change Material, PCM, to change the thermal inertia of lightweight buildings is investigated in the CRAFT project C-TIDE. It is a joint project with Italian and Swedish partners, representing both industry and research. PCMs are materials where the phase change enthalpy can be used for thermal storage. The Swedish application is a night ventilation system where cold night air is used to solidify the PCM. The PCM is melted in the day with warm indoor air and thereby the indoor air is cooled. The system is intended for light weight buildings with an overproduction of heat during daytime. In the thesis, the results of experiments and numerical simulations of the application are presented. The theoretical background in order design the heat exchanger and applying the installation in thermal simulation software is presented. An extensive program is set up, in order to develop test methods and carry tests to evaluate the performance over time of the PCM. Testing procedures are set up according to ISO standards concerning service life testing. The tests are focused on the change over time of the Thermal Storage Capacity (TSC) in different temperature spans. Measurements are carried out on large samples with a water bath calorimeter. The service life estimation of a material is based on the performance of one or more critical properties over time. When the performances of these properties are below the performance requirements, the material has reached its service life. The critical properties of the PCM are evaluated by simulation of the application. The performance requirements of the material are set up according to general requirements of PCM and requirements according to building legislation. The critical properties of a PCM are the transition temperature, the melting temperature range and the TSC in the operative temperature interval. The critical property of the application is its energy efficiency.

The results of the study show that the night cooling system will lower the indoor air temperature during daytime. It also shows that the tested PCM does not have a clear phase change, but an increased specific heat in the operative temperature interval. Increasing the amount of material, used in the application, can compensate this. Finally, the tested PCM is thermally stable and the service life of the product is within the range of the design lives of the building services. It is essential to for all designers to know the performance over time of the properties of PCMs. Therefore it is desirable that standardized testing methods of PCM are established and standardized classification systems of PCMs are developed.

The internal combustion engine requires clean air in order to operate without problems the entire service life. The air filter acts as a barrier between the ambient air ridden with particulate matter, and the sensitive interior of the engine. Several factors affect the air filter performance, such as pressure drop, efficiency, and dust holding capacity. Many external factors affect the air filter too, such as driving style, engine type, if the car is equipped with hybrid propulsion et cetera. The scope for this thesis work aims to extend the knowledge of air filtration for the customer, in this case, Volvo Cars. A comprehensive literature study along with benchmarking of competitors acts as a foundational approach. Regarding air filter service life, three parameters are identified as the most significant: dust holding capacity, efficiency and pressure drop over the filter element. Reverse engineering shows some competitor design decisions. A model of estimating air consumption is developed using a data-driven approach with real-world driving data as a basis. The model shows how much the actual air consumption varies between different markets and various engines. As a result, the service lifetime of air filters in certain cars with certain engines may be extended or allow for a smaller filter size for the same service lifetime.

The transportation engineering community of the United States faces a tremendous problem: the gradual deterioration of the nation's bridges. A major component of the overall bridge deterioration problem is the corrosion-induced deterioration of reinforced concrete bridge components that are exposed to de-icing salts. The progression of events resulting from corrosion of the reinforcing steel includes cracking, delamination, spalling, and patching of the surface concrete.

Bridge components reach the end of their functional service life when the level of damage warrants rehabilitation. The objective of this study was to determine the end of functional service life for concrete bridge decks, piers, and abutments by quantifying terminal levels of physical damage. The approach for quantifying terminal damage levels involved obtaining recommendations from state Department of Transportation (DOT) bridge engineers via an opinion survey.

A field study of 18 existing concrete bridges that had been designated for rehabilitation was conducted to develop concrete bridge component maps showing areas of physical damage. Deck damage maps were produced using a ground-based photogrammetry system developed in this study, while pier and abutment damage maps were drawn by hand in the field. Survey Kits based on the component damage maps were distributed to bridge engineers in 25 states that use de-icing salts. The engineers evaluated the maps and recommended when each component should be, or should have been, rehabilitated~ Based on the engineers' responses, linear regression prediction models were developed to relate the recommended bridge component rehabilitation time point to the physical damage level. Based on the prediction models, two viable terminal damage levels for concrete bridge decks, and a partial terminal damage level for concrete bridge piers, were quantified.

Master of Science

Nowadays, circular economy is becoming more relevant in society. In the context of the automotive industry, we no longer simply work on emissions emitted during the vehicle use phase but rather on the environmental impacts induced during all phases of the vehicle's life cycle (manufacturing, logistics, use, maintenance and end of life). For this purpose, many automakers, including the Group PSA, use life cycle assessment (LCA) to determine these environmental impacts. Also, the economy of sharing is gradually established and follows innovative uses of the car. New mobility systems emerge and compete with the classical system of sales of vehicles. These new uses of the automobile mainly take the form of car-sharing. In the future, it will become essential to evaluate these services from an environmental point of view.Some studies of the use of car-sharing already demonstrate important consequences such as reductions in the number of vehicles and in the number of kilometers traveled but also an increase in the use of other means of transport. However, to my knowledge, there is no LCA-based method to quantify the environmental benefit of the use of a car-sharing service in relation to the use of vehicles for exclusive use by the owner but also which would eco-design these services and the vehicles intended for these services.As part of this six-month project, a LCA approach was implemented to a PSA B2C (business-to-consumers) car-sharing service called “Emov” with a fleet of 500 Citroën C-Zero electric vehicles. The goal was to compare the use of Emov in Madrid, Spain with the urban use of a private Internal Combustion Engine (ICE) vehicle and a battery electric vehicle for one user characterized by its frequency, its average time and its average distance of use over a defined period. Thanks to a modeling of the service on the LCA software Gabi and by controlling over the input parameters related to the Emov service and the parameters related to the user's use of the service (variable parameters), it was therefore possible to show the influence of these parameters on the final results. Furthermore, it was possible to show also in which scenario it was more environmentally beneficial to use the service rather than a private vehicle. For the study, six impact indicators were chosen: the potentials for global warming, photochemical oxidation, air acidification, water eutrophication, resource depletion and primary energy demand.Using Emov’s big data to inform the service parameters and then varying the service user's usage parameters, it was possible to conclude that whatever the user's urban mobility needs, it is more beneficial to use the service than a private ICE vehicle for five of the six impact indicators. Only the acidification potential indicator (SO2 equivalent) is worse when using the service, which can be explained by the manufacture of the batteries of the Emov vehicles.

Includes bibliographical references.
There is an urgent need for economic and technically sound concrete repair technologies in South Africa as the number of deteriorating RC structures needing repair is increasing. Currently, the South African concrete repair industry mainly relies on the application of patch repairs and corrosion inhibitors while other potentially successful methods such as sacrificial anodes are rarely applied. Sacrificial anode cathodic protection (SACP) systems use metals that are higher than steel in the electrochemical series. These metals corrode preferentially to steel thereby supplying electrons to the cathodic steel surface. Common SACP systems include discrete zinc anodes installed in slots or drilled holes, non -structural jacket encasements, and overlays made from expanded zinc mesh or any other convenient form. The effectiveness of discrete SACP systems in service life extension of chloride contaminated RC slabs has been investigated in this study. Similarly, the extent to which discrete sacrificial anodes can be used to extend the service life of corroding chloride contaminated RC structures has been assessed through an extensive review of literature a s well as laboratory experiments on corroding chloride contaminated RC slabs . This study evaluates the performance of discrete SACP systems with respect to binder type, corrosion rate and the level of chloride contamination with an objective of developing guidelines for rational concrete repair when using SACP systems to repair RC structures that are deteriorating from corrosion of reinforcing steel in South Africa. Eight slabs were investigated. Four slabs were cast using 100% PC CEM 1, 42.5N while the other four were cast using a blend of 70/30 PC CEM 1, 42.5N/FA. Each slab comprised two portions: one half of each slab was cast using concrete that was admixed with 0.6% chloride by mass of binder while the other half was cast using concrete that was admixed with 1.8% chloride by mass of binder. The corrosion in the slabs was induced and accelerated using direct anodic current. The SACP system that was used in this study comprised discrete zinc disks put in a cylinder of a proprietary high alkaline mortar. The se anodes were installed in 1 0 0 x 10 0 x 60 mm deep cavities that had been made in concrete. The anodes were connected to the reinforcement cage using tie wires and thereafter backfilled with a repair mortar. The cavities in which the anodes were installed were arranged in a square grid of 450 x 450 mm. The corrosion rate and half-cell potential of the steel as well as the resistivity of concrete in the slabs were monitored over a duration of five month s. The discrete SACP system that has been investigated in this study can increase the service life of chloride contaminated RC structures that are deteriorating as a result of rebar corrosion. The discrete anodes reduced the corrosion rate of steel in the test slabs. The percentage reduction in the average corrosion rate was higher within the slabs that were cast using 100% PC CEM 1, 42.5N than in the slabs that were cast using a blend of 70/30 PC CEM 1, 42.5N/FA. The reduction in average corrosion rate within the slabs cast using 100% PC CEM 1, 42.5N ranged between 45-95%. Similarly, the reduction in the average corrosion rate of within the slabs that were cast using a blend of 70/30 PC CEM, 42.5N 1/ FA ranged between 54-75%. Throughout the test specimens, the portions of the slabs that was admixed with 0.6% chloride by mass of binder exhibited superior performance. These portions (admixed with 0.6% chloride by mass of binder) experienced the greatest reduction in average corrosion rate as well as the greatest shift in average half -cell potential towards values that are more negative. Finally, in order to achieve the long-term objective of increasing the service life of RC structures that are deteriorating as a result of rebar corrosion, lo ng-term studies ought to be undertaken to ascertain, with surety, the effectiveness of discrete SACP systems in corroding structures.

The current fiscally austere environment prevalent in the military and industry is driving extreme measures to save money. In the United States Air Force, this has driven enormous efforts to trim sustainment spending on extended life aircraft. The challenge to the aerospace engineer is to ensure flight safety in the midst of this economic pressure.

One method of cutting costs is to increase the time an aircraft is in service by delaying the point when the aircraft is taken out of service for depot maintenance. To ensure flight safety, in depth fatigue and fracture analysis needs to be accomplished to assess increasing the inspection interval.

The purpose of this study was to determine the sensitivity of Aluminum 2024-T351 alloy, a common material used in tension dominated aerospace applications, to two different loading spectra—one that is aggressive and the other that is benign. This was accomplished by conducting five different combinations of the two spectra, developing computer simulations using the AFGROW software and comparing with the measured data. The results showed that the material demonstrated significantly different behavior between the two spectra. These results provide a valuable tool for the aerospace engineer for fatigue life prediction and inspection interval evaluation.

The focus in environmental management has during the last decades in many cases shifted to include all the phases in a product’s (or a service’s) life – the life-cycle perspective. The transport system has a large environmental pressure on the environment. Train traffic is habitually regarded as an environmentally preferable mean of transport, mainly depending on that trains often are driven by electricity. This view is also true when the operation phase alone is considered; at least if the electricity derives from renewable sources. In a life-cycle perspective the advantages of this mean of transport get less apparent. The extraction of the raw materials requires plenty of energy, energy which often is produced by fossil fuels. A dominating part of the material-related energy requirements in the railway infrastructure can be referred to a few materials. The main part of these materials can be found in a few products; rails, railway ties, ballast materials, cables and the contact wire system. It is here that the effort to reduce the environmental impact of the railway infrastructure should lie to become most efficient. The aim of the thesis is to investigate how the environmental pressure is affected by the service lives, i.e. the technical durability as well as the durability in practise, of the most energy-intense railway products, as well as reuse of them. The objective is to map estimated service lives and reuse in order to create scenarios representing the present state of how the products are used and reused in Sweden. The scenarios are used in order to analyse the importance of focusing on service lives and reuse when reducing environmental pressure. The objective is also to find out which possibilities and hindrances there are to increase the service lives and the reuse of the products.

To investigate the environmental pressure of the railway infrastructure, embodied energy is used as indicator. Embodied energy represents the energy needed to produce a product, from extracting the materials to the production phase. The present state concerning service lives and reuse of the studied products are mapped through interviews with employees at Banverket and at VTI. The empirical material is analysed and scenarios are created in order to evaluate the environmental importance of service lives and reuse. Organizational issues concerning service lives and reuse are also investigated.

The present state service lives varies between 25 and 100 years for the realistic scenarios for all the products. The estimated service lives varies between 25 and 100 years for the new technology scenarios. When it comes to the best-case scenarios the estimated service lives varies between 60 and 120 years, depending on railway product. The only products reused today are rails and railway ties. There are considerable improvements to be made by increasing service lives, and this pertains to all the studied products. The reductions in embodied energy per year go up to 75 % if the New-Technology Scenario is applied and to 33 % if the Realistic Scenarios are applied. If the Low Realistic Scenarios are applied the reductions goes up to 50 %. A great improvement potential exist for all the products if the New-Technology Scenarios are applied. The products where the main improvement potential when it comes to the Realistic and the Low Realistic Scenarios exist are the macadam-ballast, the cables, the rails and the railway ties. If the New-Technology Scenarios are applied for all the products the total improvement span is as much as 69 % altogether. If the Low Realistic Scenario instead is applied, the improvement span is calculated to 38-39 % (depending on the exchange level of macadam-ballast). If the Realistic Scenario is applied, the improvement span is calculated to 23 % and if the Best-Case Scenario is applied the span is calculated to 7 %, depending on that the most energy efficient strategy is to reuse the products possible to reuse. The main part of this improvement potential derives from the rails and the railway ties.

In reducing the environmental pressure it is important to make use of the products as much as possible, i.e. to reuse them and use them as long as possible. If rails and railway ties are reused and made use of during their entire service life, all energy invested in the products is made use of. The most environmental sound alternative is to reuse the products which are reusable and to use these products as long as they last. This gives a need for embodied energy of 16 GJ/yr and km for the railway ties and 38 GJ/yr for the rails on the mainline track. The energy allocated to the tracks where the products are reused is calculated to 3 GJ/yr and km for the railway ties and to 7 GJ/yr and km for the rails. Actions of maintenance prolong the durability of the products, e.g. by increasing the stability in the embankment and hence reduce the wearing. The administration of the used material is the main problem in order to create a well-functioning reuse of railway articles. This includes transports, storage and documentation of products. Tradition and routines also stand in the way of creating a sustainable reuse of these products.

Maintenance is constantly challenged with increasing productivity by maximizing up-time and reliability while at the same time reducing expenditure and investment. In the last few years it has become evident through the development of maintenance concepts that maintenance is more than just a non-productive support function, it is a profit- generating function. In the past decades, hundreds of models that address maintenance strategy have been presented. The vast majority of those models rely purely on mathematical modeling to describe the maintenance function. Due to the complex nature of the maintenance function, and its complex interaction with other functions, it is almost impossible to accurately model maintenance using mathematical modeling without sacrificing accuracy and validity with unfeasible simplifications and assumptions. Analysis presented as part of this thesis shows that stochastic simulation offers a viable alternative and a powerful technique for tackling maintenance problems. Stochastic simulation is a method of modeling a system or process (on a computer) based on random events generated by the software so that system performance can be evaluated without experimenting or interfering with the actual system. The methodology developed as part of this thesis addresses most of the shortcomings found in literature, specifically by allowing the modeling of most of the complexities of an advanced maintenance system, such as one that is employed in the airline industry. This technique also allows sensitivity analysis to be carried out resulting in an understanding of how critical variables may affect the maintenance and asset management decision-making process. In many heavy industries (e.g. airline maintenance) where high utilization is essential for the success of the organization, subsystems are often of a rotable nature, i.e. they rotate among different systems throughout their life-cycle. This causes a system to be composed of a number of subsystems of different ages, and therefore different reliability characteristics. This makes it difficult for analysts to estimate its reliability behavior, and therefore may result in a less-than-optimal maintenance plan. Traditional reliability models are based on detailed statistical analysis of individual component failures. For complex machinery, especially involving many rotable parts, such analyses are difficult and time consuming. In this work, a model is proposed that combines the well-established Weibull method with discrete simulation to estimate the reliability of complex machinery with rotable subsystems or modules. Each module is characterized by an empirically derived failure distribution. The simulation model consists of a number of stages including operational up-time, maintenance down-time and a user-interface allowing decisions on maintenance and replacement strategies as well as inventory levels and logistics. This enables the optimization of a maintenance plan by comparing different maintenance and removal policies using the Cost per Unit Time (CPUT) measure as the decision variable. Five different removal strategies were tested. These include: On-failure replacements, block replacements, time-based replacements, condition-based replacements and a combination of time-based and condition-based strategies. Initial analyses performed on aircraft gas-turbine data yielded an optimal combination of modules out of a pool of multiple spares, resulting in an increased machine up-time of 16%. In addition, it was shown that condition-based replacement is a cost-effective strategy; however, it was noted that the combination of time and condition-based strategy can produce slightly better results. Furthermore, a sensitivity analysis was performed to optimize decision variables (module soft-time), and to provide an insight to the level of accuracy with which it has to be estimated. It is imperative as part of the overall reliability and life-cycle cost program to focus not only on reducing levels of unplanned (i.e. breakdown) maintenance through preventive and predictive maintenance tasks, but also optimizing inventory of spare parts management, sometimes called float hardware. It is well known that the unavailability of a spare part may result in loss of revenue, which is associated with an increase in system downtime. On the other hand increasing the number of spares will lead to an increase in capital investment and holding cost. The results obtained from the simulation model were used in a discounted NPV (Net Present Value) analysis to determine the optimal number of spare engines. The benefits of this methodology are that it is capable of providing reliability trends and forecasts in a short time frame and based on available data. In addition, it takes into account the rotable nature of many components by tracking the life and service history of individual parts and allowing the user to simulate different combinations of rotables, operating scenarios, and replacement strategies. It is also capable of optimizing stock and spares levels as well as other related key parameters like the average waiting time, unavailability cost, and the number of maintenance events that result in extensive durations due to the unavailability of spare parts. Importantly, as more data becomes available or as greater accuracy is demanded, the model or database can be updated or expanded, thereby approaching the results obtainable by pure statistical reliability analysis.

Concrete substructures are often subjected to environmental deterioration, such as sulfate and acid attack, which leads to severe damage and causes structure degradation or even failure. In order to improve the durability of concrete, the High Performance Concrete (HPC) has become widely used by partially replacing cement with pozzolanic materials. However, HPC degradation mechanisms in sulfate and acidic environments are not completely understood. It is therefore important to evaluate the performance of the HPC in such conditions and predict concrete service life by establishing degradation models. This study began with a review of available environmental data in the State of Florida. A total of seven bridges have been inspected. Concrete cores were taken from these bridge piles and were subjected for microstructural analysis using Scanning Electron Microscope (SEM). Ettringite is found to be the products of sulfate attack in sulfate and acidic condition. In order to quantitatively analyze concrete deterioration level, an image processing program is designed using Matlab to obtain quantitative data. Crack percentage (Acrack/Asurface) is used to evaluate concrete deterioration. Thereafter, correlation analysis was performed to find the correlation between five related variables and concrete deterioration. Environmental sulfate concentration and bridge age were found to be positively correlated, while environmental pH level was found to be negatively correlated. Besides environmental conditions, concrete property factor was also included in the equation. It was derived from laboratory testing data. Experimental tests were carried out implementing accelerated expansion test under controlled environment. Specimens of eight different mix designs were prepared. The effect of pozzolanic replacement rate was taken into consideration in the empirical equation. And the empirical equation was validated with existing bridges. Results show that the proposed equations compared well with field test results with a maximum deviation of ± 20%. Two examples showing how to use the proposed equations are provided to guide the practical implementation. In conclusion, the proposed approach of relating microcracks to deterioration is a better method than existing diffusion and sorption models since sulfate attack cause cracking in concrete. Imaging technique provided in this study can also be used to quantitatively analyze concrete samples.

Thesis (MScEng (Industrial Engineering))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: The problem with which many organisations struggle in the current economical environment is that of focus. They are trapped in a situation where limited resources or lack of inherent knowledge withhold them from increasing shareholder value. This research focuses on the strategy which an organisation pursues when outsourcing those business functions which are outside their core competencies. The outcome of this decision involves them entering into a partnership with a service organisation (or consultancy). The duration of the relationship between these parties is dependent on the value (actual plus perceived) which the service organisation contributes to its customer. Pragma (a service organisation in the physical asset management (PAM) environment) is, due to the current economic turmoil, in a situation where they need to indicate the value created through the acquirement of their service. This leads to a search for a model which would provide them with the required justification. A study was conducted on current available frameworks but none of those identified suited this type of measurement. This led to the development of a unique model (based on the principles of the Balanced Scorecard) called the performance measurement value index (PMVI) which identifies the generic elements required to measure the value of a service partnership. These elements are: 1. financial perspective; 2. customer engagement; 3. risk management; and 4. internal business processes. These elements are weighted (using the analytical hierarchical process) to represent the change in value, as contributed by the elements, and is then represented as a single value (ten is used as this arbitrary value in this research). The PMVI is introduced into the PAM environment which then produces the asset management value index (AMVI). The four elements of the PMVI are broken down into five elements required for the AMVI. These elements are: 1. cost reduction; 2. asset performance improvement; 3. customer satisfaction; 4. risk reduction; and 5. asset management maturity. The model was applied to three of Pragma’s customers. The type of application (within this environment) is dependent on the nature of both the customer and service. The first two customers are both from a manufacturing environment but they differ in the type of service (ACC@Pragma vs ACC@Client) rendered. The third customer operates within the utilities and facilities environment and receives an ACC@Client service. The period over which the model was applied varies due to the use and availability of historical data of these customers. An increase in value was noted for the two ACC@Client customers (from 7.68 to 8.51 and 4.54 to 7.73 respectively), where the service partnership is still in its early stages (one to three years old). However, the ACC@Pragma customer reflected a stagnating value (6.62 to 6.59) where the service partnership is older than ten years. These results reflect the expectations which Pragma had at the beginning of the study and consequently proves that they do add value to their customers.
AFRIKAANSE OPSOMMING: Die huidige ekonomiese omgewing veroorsaak dat baie ondernemings sukkel om te fokus. Hulle word vasgevang in ‘n situasie waar ‘n beperking in hulpbronne of ‘n tekort aan nodige kennis hulle verhoed om waarde te verskaf aan hulle aandeelhouers. Hierdie navorsing ondersoek daardie strategie van ‘n onderneming wat daartoe lei dat hulle sekere besigheids funksies, wat hulle nie beskou as hul eie sterktepunte nie, uitkontrakteer en gevolglik kan fokus op hul sterktepunte. Die gevolg van hierdie besluit verg dat die onderneming ‘n ooreenkoms aangaan met ‘n dienste onderneming. Die tydperk van hierdie verhouding word bepaal deur die waarde (beide werklik en aangevoelde) wat die dienste onderneming toevoeg tot hul klient. Pragma (‘n dienste onderneming in die fisiese bates bestuur bedryf) word huidiglik gekonfronteer met die situasie waar hulle die waarde wat, weens die lewering van hul diens, toegevoeg word tot die klient. Dit lei tot die soeke na ‘n model om die lewering van hulle diens te valideer. ‘n Studie was uitgevoer op die huidige beskikbare modele wat doeltreffendheid in ‘n onderneming meet, maar geen van die geїdentifiseerdes was toepaslik op hiersie situasie nie. Dit het gelei tot die ontwikkeling van ‘n unieke model (gebaseer op die beginsels van die Balanced Scorecard) genaamd die Performance Measurement Value Index (PMVI) wat die nodige elemente vir die meting van hierdie tipe doeltreffenheid identifiseer. Hierdie elemente sluit in die: • finansiële perspektief; • kliënte interaksie; • risiko bestuur; en • interne besigheids prosesse. Die geweegde uikomste van hierdie elemente (soos bepaal deur die Analytical Hierarchical Process) word gebruik om ‘n verandering in waarde aan te dui as ‘n enkele waarde (tien in die geval van hierdie studie).Die PMVI word aangepas vir gebruik in die fisiese bate bestuur omgewing en die gevolge hiervan is die skepping van die Asset Management Value Index (AMVI). Die vier elemente, soos gebruik in die PMVI, word aangepas na vyf elemente in die AMVI. Hierdie elemente sluit in die: • verlaging van uitgawes; • bate doeltreffenheid verhoging; • kliënt tevredenheid; • risiko verlaging; en • bate bestuur verbetering (verbetering in die interne besigheids funksies van bate bestuur). Die model was toegepas op drie van Pragma se kliente. Die tipe van toepassing (binne hierdie omgewing) is afhanklik van beide die kliënt en dienste gelewer. Die eerste twee kliënte is beide afkomstig van ‘n hoofsaaklik vervaardigings-omgewing, maar die dienste gelewer aan die kliënte verskil (ACC@Pragma vs ACC@Client). Die ander klient is afkomstig vanuit ‘n dienste en geboue omgewing en ontvang die dienste van ‘n ACC@Client. Die tydperk waaroor die AMVI toegepas is verskil weens die toepaslikheid en beskikbaarheid van historiese inligting. ‘n Toename in waarde is bevind by beide van die ACC@Client kliënte (vanaf 7.68 na 8.51 en 4.54 na 7.73 onderskeidelik). Dit kan toeskryf word aan die vroeë fase waarin hierdie diens ooreenkoms funksioneer (vanaf een tot drie jaar). Die uitkomste van die ACC@Pragma, aan die anderkant, dui op stagnerende waarde (6.62 na 6.59) vir die kliënt waar die diens ooreenkoms alreeds ouer as tien jaar is. Die uitkomste van hierdie studie bewys die verwagtinge wat Pragma aan die begin van hierdie studie gehad het en bewys gevolglik dat hulle wel waarde toevoeg tot hul kliënte.

The required useful service lives of gas turbine components and parts are naturally one of the major design constraints limiting the gas turbine design space. For example, the required service life of a turbine blade limits the firing temperature in the combustor, which in turn limits the performance of the gas turbine. For a cooled turbine blade, it also determines the necessary cooling flow, which has a strong impact on the turbine efficiency. In most gas turbine design practices, the life prediction is only emphasized during or after the detailed design has been completed. Limited life prediction efforts have been made in the early design stages, but these efforts capture only a few of the necessary key factors, such as centrifugal stress. Furthermore, the early stage prediction methods are usually hard coded in the gas turbine system design tools and hidden from the system designer s view. The common failure mechanisms affecting the service life, such as creep, fatigue and oxidation, are highly sensitive to the material temperatures and/or stresses. Calculation of these temperatures and stresses requires that the geometry, material properties, and operating conditions be known; information not typically available in early stages of design. Even without awareness of the errors, the resulting inaccuracy in the life prediction may mislead the system designers when examining a design space which is bounded indirectly by the inaccurate required life constraints. Furthermore, because intensive creep lifing analysis is possible only towards the end of the design process, any errors or changes will cost the engine manufacturer significant money; money that could be saved if more comprehensive creep lifing predictions were possible in the early stages of design. A rapid, physics-based life prediction method could address this problem by enabling the system designer to investigate the design space more thoroughly and accurately. Although not meant as a final decision method, the realistic trends will help to reduce risk, by providing greater insight into the bounded space at an earlier stage of the design. The method proposed by this thesis was developed by first identifying the missing pieces in the system design tools. Then, by bringing some key features from later stages of design and analysis forward through 0/1/2Ds dimensional modeling and simulation, the method allows estimation of the geometry, material selection, and the loading stemming from the operating conditions. Finally, after integration with a system design platform, the method provides a rapid and more complete way to allow system designers to better investigate the required life constraints. It also extracts the creep life as a system level metric to allow the designers to see the impact of their design decisions on life. The method is to be first applied to a cooled gas turbine blade and could be further development for other critical parts. These new developments are integrated to allow the system designers to better capture the blade creep life as well as its impact on the overall design.

The building sector is resource intensive and contributes significantly to Climate change. In recent times, many initiatives are being undertaken to make today’s situation better. Among them, the Circular economy has become an attractive topic for implementation of sustainability in various sectors.  A case study has been performed to assess the environmental impacts of a ‘circular’ kitchen at Chainable company in the Netherlands through life cycle assessment. This kitchen is different from other standard kitchens as it is offered as kitchen-as-a-service for a long period of time. It follows circular design strategies such as extension of service life, use of recycled materials, design-for- disassembly and design for light weight construction. The company maintains the kitchen and ensures that it is circular by either recycling, reusing or recovering the waste at the end-of-life of the kitchen. This could potentially reduce the impacts of construction of more kitchens if people and different organizations keep it for the long term.  The kitchen is made of various components such as frame, panels, sink, tap, drawers, countertop, handles and electric socket. The use phase of the kitchen includes repair and maintenance scenarios for the whole lifecycle of the kitchen.  The results indicate production and replacement of Chipboard panels, production of steel frame and transports linked to repair and maintenance scenarios as hotspots of the kitchen in Climate change and Resource use impact categories.
Byggsektorn är resurskrävande och bidrar avsevärt till klimatförändringarna. På senare tid har många initiativ tagits för att göra dagens situation bättre. Bland dem har cirkulär ekonomi blivit ett attraktivt ämne för genomförandet av hållbarhet inom olika sektorer.  En fallstudie med hjälp av livscykelanalys har utförts för att bedöma miljöeffekterna av ett “cirkulärt” kök från Chainable, ett företag i Nederländerna. Detta kök skiljer sig från andra vanliga kök eftersom det erbjuds som kök-som-en-service under en längre tid. Det följer cirkulära designstrategier som förlängning av livslängden, användning av återvunnet material, design för demontering och design för lätt konstruktion. Företaget underhåller köket och ser till att det är cirkulärt genom att antingen återvinna, återanvända eller återhämta avfallet i slutet av kökets livscykel. Detta kan eventuellt minska påverkan av byggandet av fler kök om människor och olika organisationer behåller dem på lång sikt.  Köket är tillverkat av olika komponenter som ram, paneler, handfat, kran, lådor, bänkskiva, handtag och eluttag. Kökets användningsfas inkluderar reparations- och underhållsscenarier för hela kökets livscykel.  Resultaten indikerar att produktionen och utbytet av spånskivor, tillverkningen av stålram och transporter kopplade till reparations- och underhållsscenarier har störst påverkan i kökets livscykel inom kategorierna klimatförändring och resursanvändning.

Aerospace design requirements mandate acceptable levels of structural failure risk. Probabilistic fatigue models enable estimation of the likelihood of fatigue failure. A key step in the development of these models is the accurate inference of the probability distributions for dominant parameters. Since data sets for these inferences are of limited size, the fatigue model parameter distributions are themselves uncertain. A hierarchical Bayesian approach is adopted to account for the uncertainties in both the parameters and their distribution. Variables specifying the distribution of the fatigue model parameters are cast as hyperparameters whose uncertainty is modeled with a hyperprior distribution. Bayes' rule is used to determine the posterior hyperparameter distribution, given available data, thus specifying the probabilistic model. The Bayesian formulation provides an additional advantage by allowing the posterior distribution to be updated as new data becomes available through inspections. By updating the probabilistic model, uncertainty in the hyperparameters can be reduced, and the appropriate level of conservatism can be achieved. In this work, techniques for Bayesian inference and updating of probabilistic fatigue models for metallic components are developed. Both safe-life and damage-tolerant methods are considered. Uncertainty in damage rates, crack growth behavior, damage, and initial flaws are quantified. Efficient computational techniques are developed to perform the inference and updating analyses. The developed capabilities are demonstrated through a series of case studies.

Aluminized steel pipes are expected to have a long service life, e.g. 75 years. Spiral ribbed aluminized pipes (SRAP) have been widely specified and used by the Florida Department of Transportation (FDOT) for drainage of runoff water. Confidence in the long term durability of SRAP has been challenged by recent unexpected early corrosion failures in various Florida locations. SRAP premature corrosion incidents have occurred in two modalities. Mode A has taken place in near-neutral soil environments and has often been associated with either gross manufacturing defects (i.e. helical cuts) or corrosion concentration at or near the ribs. Mode B took place in pipes in contact with limestone backfill and corrosion damage was in the form of perforations, not preferentially located at the ribs, and not necessarily associated with other deficiencies. These failures motivated this research. The objectives of this work are to establish to what extent the Mode A corrosion incidents can be ascribed to manufacturing defects, that can be rectified by appropriate quality control, as opposed to an intrinsic vulnerability to corrosion of regularly produced SRAP due to ordinary forming strains and to determine the mechanism responsible for Mode B corrosion including the role that limestone backfill played in that deterioration. To achieve those objectives, laboratory experiments were conducted to replicate the conditions for Mode A and Mode B. Overall, the findings of this and previous work suggest that much of the corrosion damage observed in the Mode A incidents were promoted more by manufacturing deficiencies and less by any possible inherent susceptibility of corrosion at the ribs of SRAP that was produced following appropriate quality control. Experiments to explore the causes of Mode B corrosion showed that high pH values, sufficient to cause dissolution of the passive film on aluminum, can develop under exposure of limestone to flowing natural water. The findings substantiate, for the first time, an important vulnerability of aluminized steel in limestone soils and provide an explanation for the rapid onset deterioration observed at the field under Mode B. The findings also provide strong evidence in support of service guidelines to disallow the use of limestone bedding for aluminized steel pipe, including SRAP.

Material damage such as dislocations and microcracks are characteristic of early stages of fatigue. Accumulation of these nascent cracks leads to non-linear elastic response of the material. These non-linearities can be detected from harmonic generation for propagating elastic waves. The long term goal of this study is to investigate the non-linear elastic propagation in parts with complex geometry. Cellular Automata is introduced as a new simulation method, in order to develop new analysis on quadratic non-linearities. An existing linear code was progressively modified to take into account a different constitutive law. Also the boundary conditions need to be reviewed to ensure free stress with the non-linear behavior. The propagation of the longitudinal wave is investigated in detail. Numerical accuracy is validated from comparison with a closed, for both linear and non-linear code. The reflection of the non-linear P-wave gives confirmation for the correct treatment of the boundary condition. Finally the capabilities of the Cellular Automata code are underlined for reflection of Lamb waves for various boundary conditions.

The trend in many countries is to outsource maintenance with competitive tendering. The design of the tender is then a crucial issue. A new type of tendering contract, called "Integrated Bridge Maintenance", was introduced in one experimental area in Sweden. In this case the preventive bridge maintenance is separated from the standard road maintenance contract. The ideas behind these changes are that the new approach can increase efficiency through a combination of in­creased specialization, economies of scale and through giving the private contractor a greater degree of freedom concerning exactly what to do and exactly when to do it. A pilot project has been running since 2004 for all bridges in Uppsala County with about 400 bridges and since 2007 for all bridges in Örebro County with about 700 bridges.   The experiences and lessons from this pilot project are presented in this thesis together with guidelines on how to procure Integrated Bridge Maintenance in the future. An important feature of the contract was that it contained a combination of specific measures that the contractor should carry out and properties of the bridges that the contractor was responsible to maintain. This created a balance between predictability and flexibility for the contractor. The contractor could make long term planning for the work. The client was satisfied because of increased com­petence and a low price. The latter can partly be explained by the possibility for the specialised bridge crew to receive additional work from other clients. As information about old bridges always is incomplete a partnering structure needs to be built into the contract. Experi­ence has also shown that a conscious policy to maintain long run competition is important. The general conclusion is that the project was seen as successful and as creating more "value for money".   To manage a bridge stock optimally from a life cycle perspective is a very complex task, since the condi­tions for the individual bridge can vary greatly from place to place which the answers from the research questions indicate. Besides following-up and evaluating the Integrated Bridge Maintenance projects a number of research questions have been studied.   Is Integrated Bridge Maintenance a successful method to increase the effectiveness and to increase the standard in bridge maintenance alternatively increasing the service life for the bridge stock at an optimal cost, i.e., will IBM lead to lower LCC? It is difficult to answer this question with exact numbers after so short time, but so far the opinion is that the effectiveness has increased. How can a bridge stock develop over a long time e.g. 15 years? Based on historical data one can calculate, for instance, new construction rate, demolition rate and average age for the bridge stock. This information could together with different future scenarios be a basis for different bridge management strategies for the actual bridge stock. What is the real service life for a bridge? Survival analysis for the different types of bridges in the actual bridge stock will give a good estimate of the different expected service life. Why and at which age are bridges de­molished? Two main reasons were found in this study: deterioration process of the bridge had gone too far and/or load bearing capacity was too low, and road were rerouted. What is the real service life for a bridge edge beam, one of the most often repaired element of Swedish bridges? Survival analysis of edge beams located on different types of roads will give a good estimate of the different expected service life.   How should a long-term contract for bridge maintenance and specially Integrated Bridge Maintenance be procured? The bridge manager should have a good understanding of the answers on the research ques­tions above when the tender documents are to be prepared for the actual bridge stock. Thereafter the area that the contract should cover could be chosen, a good balance between properties and measures, defining the working cycle for properties, a flexible partnering structure in the contract and a suitable length of the contract (x years) inclusive an option (+ y years) and finally good incentives in the contract.   To sum up, the main purpose with the doctoral project has been reached. A model for procurement of bridge maintenance has been developed; see the projects in Uppsala and Örebro. The contractor has deve­loped more effective methods for bridge maintenance. The doctoral project has been a step closer to the end goal of reducing the society’s costs for bridge maintenance in the future. The bridges should be func­tional to the lowest possible cost during its expected service life (LCC). The doctoral project has also con­tributed with new knowledge in the area of bridge maintenance, the actual development of a bridge stock over time, real service life for road bridges in Sweden and survival analysis.
QC 20100826

Increasing awareness of anthropogenic impacts on the planet has lead to efforts to reduce negative environmental impacts in product development for several decades. Benefits to companies who focus on sustainability initiatives have been put forth more recently, leading to many efforts to incorporate sustainability considerations in their product innovation processes. The majority of current sustainability considerations in industry constrain design space by emphasizing reduced material and energy flows across the product’s life cycle. However, there is also an opportunity to use awareness of sustainability to bring attention to new facets of design space and to drive innovation. Specifically there is an opportunity for product-service systems (PSS) to be a vehicle through which sustainability-driven innovation occurs. A framework for strategic sustainable development (FSSD) provides the basis for understanding sustainability in this work, and provides clarity with regard to how to think about sustainable products and service innovations. The “backcasting” approach included in this framework also provides insight into how incremental and radical approaches could be aligned within the product innovation working environment. This thesis explores how sustainability considerations can be better integrated into existing product innovation working environments in order to drive innovation processes within firms, with a specific emphasis on opportunities that occur as sustainability knowledge leads to innovation through a product-service system approach. It endeavors to contribute to both theory development within the emerging sustainable PSS design research area, and also to advance the state of practice within industry by connecting dots between the state of theory and the state of practice. Society’s opportunity to become more sustainable and industry’s desire for innovation in order to lead to or increase profitability are often in conflict. However, this thesis argues that knowledge of global social and ecological sustainability can be used to drive innovation processes, and that there are win-win opportunities that can often be achieved through a PSS approach. There is some, but not sufficient, support for the inclusion of sustainability considerations in the product innovation process, and even fewer tools to support the use of sustainability to drive innovation. In response, an approach to providing support that brings together the FSSD and various approaches to systems modeling and simulation is presented. Opportunities to use sustainability-friendly attributes of existing products through a PSS-approach are also presented.

To decouple ever-increasing production and the related environmental impacts, collaborative use of products and product-service-systems including rental services can help to intensify the use of products during their designed lifetimes. While these approaches present potential to decrease environmental impacts compared to traditional linear product sales, they need to be assessed with a holistic scope to avoid counterintuitive trade-offs. This study evaluates the potential environment impacts of Husqvarna’s tool rental service with a hypothetical case example from Stockholm, Sweden. The objectives are to analyse the potential environmental impacts of the rental service, to identify hotspots for improvement and to compare the potential impacts of the rental system to a sales alternative. The annual service of one electric chainsaw is analysed using Life Cycle Assessment (LCA) methodology with different user scenarios. The potential impacts are analysed for global warming potential, fossil and mineral resource scarcity, marine ecotoxicity and human carcinogenic and non-carcinogenic toxicity. The analysis for the rental system shows that user transport back-and-forth to the rental service is a key contributor to all the environmental impacts analysed, if done by private cars. The comparative results to sales business model indicate that while the rental service can help to reduce the potential impacts in mineral resource scarcity and toxicities due to the lower number of products needed, the user transport may outweigh the potential improvements in global warming potential and fossil resource scarcity, depending on the distances and modes of transport. Different scenarios illustrate that the results are however sensitive to the assumptions made. Based on the results, it can be recommended to optimally place the service close to the users and to take efforts to reduce user transports around the service, to reach the environmental potential of the service. The sensitivity analyses also indicate the importance for accounting detailed data for LCAs for product-service-systems and covering the service holistically in system boundaries. Further studies on user behaviour are suggested to reach more robust analyses on consumer services, to cover also potential rebound effects.
Gemensam konsumtion av produkter kan minska dess miljöpåverkan, sett över produktens livstid, genom intensifiering av produktanvändning och minskad nyproduktion. Även om detta koncept har potential att minska miljöpåverkan, jämfört med traditionell linjär produktförsäljning, måste det granskas på ett systematiskt sätt. Denna studie utvärderar den potentiella miljöpåverkan av ett verktygshyrningssystem av Husqvarna med ett hypotetiskt exempel från Stockholm, Sverige. Målen är att analysera den potentiella miljöpåverkan av hyrestjänsten, identifiera förbättringspunkter och jämföra de potentiella effekterna av hyressystemet med ett försäljningsalternativ. Miljöpåverkan av en motorsåg under ett år är analyserad genom livscykelanalysmetod med olika scenarier. Analysen för hyressystemet visar att den högsta miljöpåverkan kommer från transporten av användare fram och tillbaka till hyresdepån, om transporten är gjord med personbilar. Resultaten indikerar att hyrestjänsten kan bidra till att minska potentiella effekter av mineralresursbrist och toxicitet, jämfört med försäljningsmodellen, på grund av det lägre antal producerade produkter. Hyrestjänsten kan dock riskera att öka växthuseffekten och påverkan på fossilresursbrist, beroende på transportens längd och transportsätt. Olika scenarier illustrerar att resultaten är känsliga för andantagen. Resultaten visar att det kan rekommenderas att placera tjänsten optimalt nära användarna och att försöka minska användartransporten runt tjänsten för att nå tjänstens optimala miljöpotential. Känslighetsanalyserna indikerar också att detaljerade data och omfattande systemgränser är viktiga med LCA studier om produktrelaterade tjänster. Ytterligare studier om användarbeteende föreslås för att nå mer robusta analyser av konsumenttjänster, för att utvärdera även potentiella rekyl-effekter.

As a consequence of the recent deregulation in the electrical power production industry, there has been a shift in the traditional ownership of power plants and the way they are operated. To hedge their business risks, the many new private entrepreneurs enter into long-term service agreement (LTSA) with third parties for their operation and maintenance activities. As the major LTSA providers, original equipment manufacturers have invested huge amounts of money to develop preventive maintenance strategies to minimize the occurrence of costly unplanned outages resulting from failures of the equipments covered under LTSA contracts. As a matter of fact, a recent study by the Electric Power Research Institute estimates the cost benefit of preventing a failure of a General Electric 7FA or 9FA technology compressor at $10 to $20 million. Therefore, in this dissertation, a two-phase data analytics approach is proposed to use the existing monitoring gas path and vibration sensors data to first develop a proactive strategy that systematically detects and validates catastrophic failure precursors so as to avoid the failure; and secondly to estimate the residual time to failure of the unhealthy items. For the first part of this work, the time-frequency technique of the wavelet packet transforms is used to de-noise the noisy sensor data. Next, the time-series signal of each sensor is decomposed to perform a multi-resolution analysis to extract its features. After that, the probabilistic principal component analysis is applied as a data fusion technique to reduce the number of the potentially correlated multi-sensors measurement into a few uncorrelated principal components. The last step of the failure precursor detection methodology, the anomaly detection decision, is in itself a multi-stage process. The obtained principal components from the data fusion step are first combined into a one-dimensional reconstructed signal representing the overall health assessment of the monitored systems. Then, two damage indicators of the reconstructed signal are defined and monitored for defect using a statistical process control approach. Finally, the Bayesian evaluation method for hypothesis testing is applied to a computed threshold to test for deviations from the healthy band. To model the residual time to failure, the anomaly severity index and the anomaly duration index are defined as defects characteristics. Two modeling techniques are investigated for the prognostication of the survival time after an anomaly is detected: the deterministic regression approach, and parametric approximation of the non-parametric Kaplan-Meier plot estimator. It is established that the deterministic regression provides poor prediction estimation. The non parametric survival data analysis technique of the Kaplan-Meier estimator provides the empirical survivor function of the data set comprised of both non-censored and right censored data. Though powerful because no a-priori predefined lifetime distribution is made, the Kaplan-Meier result lacks the flexibility to be transplanted to other units of a given fleet. The parametric analysis of survival data is performed with two popular failure analysis distributions: the exponential distribution and the Weibull distribution. The conclusion from the parametric analysis of the Kaplan-Meier plot is that the larger the data set, the more accurate is the prognostication ability of the residual time to failure model.

The KENTRACK program is a finite element based railway trackbed structural design program that can be utilized to analyze trackbeds having various combinations of all-granular and asphalt-bound layered support. It is applicable for calculating compressive stresses at the top of subgrade, indicative of potential long-term trackbed settlement failure. Furthermore, for trackbeds containing asphalt layer, it is applicable for calculating tensile strains at the bottom of the asphalt layer, indicative of potential fatigue cracking. The program was recently expanded to include both English and international units. A procedure has been incorporated to provide a path to save results in a text formation in post-Windows XP operating systems. More importantly, properties of performance graded (PG) asphalt binders and the Witczak E* predictive model have been incorporated in the 4.0 Version of the program. Component layers of typical trackbed support systems are analyzed while predicting the significance of layer thicknesses and material properties on design and performance. The effect of various material parameters and loading magnitudes on trackbed design and evaluation, as determined and predicted by the computer program, are presented. Variances in subgrade modulus and axle loads and the incorporation of a layer of asphalt within the track structure have significant effects on subgrade vertical compressive stresses and predicted trackbed service lives. The parameter assessments are presented and evaluated using sensitivity analysis. Recommendations for future research are suggested.

Thesis (M. S.)--Aerospace Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Mavris, Dimitri; Committee Member: Bishop, Carlee; Committee Member: Costello, Mark; Committee Member: Nam, Taewoo; Committee Member: Schrage, Daniel.

Volvo Construction Equipment (Volvo CE) is one of the world's largest manufacturers of construction machines. Now they want to access a sustainability-focused mining field – urban mining. This study is to find a solution helping Volvo CE quickly access to urban mining with a Product-Service System (PSS) development concept. To do this, the authors completed surveys and several interviews with construction companies, to understand the user and customer needs. The authors also go through a functional analysis on a new prototype of their collaboration partner - Stanford University. The result of this thesis is a PSS concept for urban mining, developed with machine selection guidelines combined with Life Cycle Assessment, and Quality Function Deployment. Recommendations include: 1) Improve the communication between Volvo CE and their Customers. 2) Adding more visible services. 3) Adding multiple business solutions provide to customers. 4) Understanding relevant stakeholders in urban mining 5) Expand research on urban mining.

Este trabalho foi elaborado, na tentativa de se aplicar as técnicas e os conceitos que são empregadas na Análise de Sobrevivência, na medicina e aplicá-los na Engenharia Civil, na área de construção. Essas técnicas recebe o nome de Confiabilidade, onde permite estimar a vida útil de componentes construtivos, através de modelos probabilísticos mais usados nessa área. Esses modelos foram desenvolvidos e aplicados nos dados colhidos, com uma confiabilidade de 95%. Esse assunto, nessa área, já vem sendo estudado na comunidade científica, mas especificamente na área da construção civil pouco se conhece, encontrando-se ainda a fase embrionária, merecendo um estudo mais aprofundado. Logo nossa proposição foi a de a partir de análise feita em uma amostra para estudo, tirar algum proveito ou alguma informação que possa ajudar para trabalhos futuros. Foram coletados 60 amostras para estudo, sendo que 10 delas foram censuradas, onde o estudo terminou com um numero pré-determinado de amostras estudadas. Os resultados foram obtidos através do software R, sendo comparados os modelos Exponencial, Weibull e Log-normal, com o estimador de Kaplan-Meier, mostrando tanto graficamente como através de testes, qual melhor modelo se ajusta aos dados coletados. O modelo que melhor se ajustou foi o Log-normal
This Work was developed as an effort to utilize the techniques and concepts that are employed in Survival Analysis in medicine, in order to apply them in Civil Engineering in the construction area. These techniques is called Reliability, which allows estimating the life time of building components through probabilistic models commonly used in that area. These models were developed and applied to the collected data, with a reliability of 95%. This subject, in this area have been studied in the scientific community, but specifically in the construction area is poorly known and is still in its beginning and, deserves further study. Thus, our proposition was to take some benefit or some information that might help for future work from analysis of a sample to study. 60 samples were collected for study, and 10 of them were censored, so that the study ended with a predetermined number of samples. The results were obtained using the software R and compared the models Exponential, Weibull and Log-normal, with the Kaplan-Meier estimator showing both graphically and through tests, which model best fits the data collected. The model that best fitted was the lognormal