Dissertations / Theses on the topic 'Deterioration behavior'

The population structure of the United States is changing; the older age group is increasing in size relative to the younger generation. The trend is expected to continue, especially starting in 2020, when the baby boomer population---estimated at 80 million---will be reaching their 65 th birthday, a time associated with increasing health complications, including depression and dementia. The study employed a holistic paradigm as the conceptual framework to examine the association between depression and dementia in older adults, and generated a grounded theory to illuminate the relationship between depression and dementia. This theory was then used to assess the efficacy of stimulation, a nurturing environment, and treatment provided by an adult day health care (ADHC) in ameliorating the symptoms and progression of both dementia and depression. The sample consisted of 60 clients from a California ADHC center who were diagnosed with depression and dementia and who had received at least 6 months of services at the center. Paired t tests tested the validity of the hypotheses on depression among older adults and its correlation with their cognitive abilities. The results of paired t tests indicated a significant reduction in the client's level of depression between the time of their admission and the time of their reassessment 6 months later. This study can provide data for the larger social change discussion as to what resources should be allocated to meet the quickly escalating health, economic, and humanitarian pressures of the baby boom cohort.

Les défauts de production dus aux variations dans le processus de fabrication et aux pannes inattendues des équipements rendent difficile la conservation d'un rendement élevé de production dans l'industrie de fabrication de semi-conducteurs. l'objectif de ce travail de thèse est de proposer un pronostic efficace du comportement des équipements ainsi qu'un diagnostic des pannes dans le processus de fabrication de semi-conducteurs. avec des capteurs plus performants, des proches efficaces basées sur des données sont proposées pour le pronostic et le diagnostic. pour le diagnostic, cette recherche applique d'abord la méthode de machines `a vecteurs de support (support vector machine) pour détecter les anomalies constatées dans les observations. la dynamique du processus normale est ensuite décomposée en différentes groupes par la méthode de partitionnement `a k -moyennes. l'analyse en composantes principales (acp) est utilisée pour modéliser chaque partie de la dynamique du processus. les empreintes de défaut peuvent enfin être extraites en consolidant les scénarios hors contrôle après avoir projeté les anomalies dans les modèles acp. en pronostic, une approche de modélisation et de surveillance de la dégradation des équipements pour le processus de fabrication par lots est développée avec deux objectifs : exploiter les données temporelles de détection et classification des fautes (fdc) pour caractériser le comportement des équipements et modéliser la tendance de détérioration avec les causes potentielles. la transformation en ondelettes discrète (dwt) décompose les données temporelles en composantes d'approximation détaillées afin de détecter deux types de détérioration provoquée par des variations au niveau macro et micro. les résultats montrent que les approches proposées permettent de prédire efficacement le comportement des équipements et de diagnostiquer la défaillance avec les causes premières
Moving toward advanced technologies requires the modern industries, in particular, the semiconductor, to keep their equipment at a high utilization level and lowenvironmental risk. production deficiencies such as process variations and unexpected equipment breakdowns have made it difficult (if not impossible) to stay at high-grade product yield and significant equipment utilization. in this thesis, the aim is to propose efficient equipment behavior prognosis, and equipment failure diagnosis approaches in batch manufacturing processes that are pervasive modes in today's semiconductor fab. with the advancement of sensor information technology, efficient data-driven approaches are proposed for both prognostic and diagnostic purposes. in the fault diagnosis, this research firstly applies the support vector machine (svm) classifier to detect the abnormal observations. the normal process dynamics are then decomposed into different clusters by k-means clustering. principal component analysis (pca) is used to model each part of the process dynamics. fault fingerprints can be extracted finally by consolidating the out of control scenarios after projecting the abnormal observations into the pca models. in prognostics, an equipment deterioration modeling and monitoring approach for batch processes is developed with two aims: exploiting the temporal fdc (fault detection and classification) data to characterize the equipment behavior and modeling the deterioration trend with the potential causes. by using the discrete wavelet transformation (dwt), the temporal data are decomposed into approximation and detail components to detect two types of deterioration caused by macro- and micro-level variations. several scenarios of case studies are conducted based on the practical dataset provided by a local IC maker. the results show that the proposed approaches can effectively prognose the equipment behavior and diagnose the equipment failure with the correct causes

Internet-based cognitive behavior therapy (ICBT) has the potential of providing many patients with an effective form of psychological treatment. However, despite helping to improve mental health and well-being, far from everyone seem to benefit. In some cases, negative effects may also emerge. The overall aim of the present thesis was to establish the occurrence and characteristics of such incidents in ICBT using a combination of quantitative and qualitative methods. Study I determined deterioration, non-response, and adverse and unwanted events in a sample of 133 patients undergoing ICBT for social anxiety disorder. The results indicated that up to 6.8% fared worse during the treatment period, depending on the self-report measure and time point, as determined using the Reliable Change Index (RCI), while the non-response rate was between 29.3 to 86.5% at post treatment assessment, and 12.9% experienced other negative effects. Study II investigated the responses to open-ended questions on adverse and unwanted events among 556 patients in four separate clinical trials of ICBT; social anxiety disorder, panic disorder, major depressive disorder, and procrastination. In total, 9.3% reported negative effects, with a qualitative content analysis revealing two categories and four subcategories; patient-related, i.e., gaining insight and experiencing new symptoms, and treatment-related, i.e., difficulties applying the treatment interventions and problems related to the treatment format. Study III explored the number of patients achieving reliable deterioration, as determined using the RCI on the individual raw scores of 2866 patients from 29 clinical trials of ICBT. The results showed that the deterioration rate was higher among patients in a control condition, 17.4%, in comparison to treatment, 5.8%. Predictors were related to decreased odds of deterioration for patients receiving treatment; clinical severity at pre treatment assessment, being in a relationship, having a university degree, and being older. As for the control condition, only clinical severity at pre treatment assessment was associated with decreased odds of deterioration. Study IV examined a newly developed self-report measure for monitoring and reporting adverse and unwanted events, the Negative Effects Questionnaire. The results suggested a six-factor solution with 32 items; symptoms, quality, dependency, stigma, hopelessness, and failure. One-third of the patients reported experiencing unpleasant memories, stress, and anxiety, with novel symptoms and a lack of quality in the treatment and therapeutic relationship having the greatest negative impact. The general finding of the present thesis is that negative effects do occur in ICBT and that they are characterized by deterioration, non-response, and adverse and unwanted events, similar to psychological treatments delivered face-to-face. Researchers and clinicians in ICBT are recommended to monitor and report negative effects to prevent a negative treatment trend and further the understanding of what might contribute to their incidents. Future research should investigate the relationship between negative effects and treatment outcome, especially at follow-up, to examine if they are transient or enduring. Also, interviews could be conducted with those achieving reliable deterioration to explore if and how it is experienced by the patients and to see if it is attributed to the treatment interventions or other circumstances.
Internetbaserad kognitiv beteendeterapi (IKBT) har goda förutsättningar att kunna bli en form av psykologisk behandling som på ett effektivt sätt hjälper patienter med att hantera sin psykiska ohälsa och förbättra sitt välmående. Trots detta är det dock långtifrån alla som tycks bli bättre. För en del kan det till och med resultera i negativa effekter. Det övergripande syftet med denna avhandling har således varit att undersöka förekomsten av sådana fall och hur dessa uttrycks, såväl med kvantitativa som kvalitativa metoder. Studie I fastställde andelen försämrade, oförändrade samt andra ogynnsamma eller oönskade händelser bland 133 personer som behandlades med IKBT för social ångest. Resultatet visade att uppemot 6,8 % försämrades under sin behandlingsperiod beroende på vilket självskattningsformulär respektive tidpunkt som studerades, beräknat enligt metoden Reliable Change Index (RCI). Likaså var 29,3 % till 86,5 % oförändrade vid eftermätningen samt att 12,9 % rapporterade andra former av negativa effekter. Studie II undersökte svaren på öppna frågor som gällde ogynnsamma eller oönskade händelser bland 556 patienter i fyra olika kliniska studier med IKBT; social ångest, paniksyndrom, egentlig depressionsepisod och prokrastinering. Totalt sett rapporterade 9,3 % att de hade erfarit negativa effekter, vilka analyserades med hjälp av kvalitativ innehållsanalys. Två övergripande kategorier och fyra subkategorier framkom; patientrelaterade, som ökad insikt respektive nya symptom, samt behandlingsrelaterade, som svårigheter att implementera behandlingsinterventionerna respektive problem med behandlingsformatet. Studie III utrönte andelen patienter som försämrades i enlighet med RCI, baserat på insamlad rådata från 2866 personer i 29 olika kliniska studier med IKBT. Resultatet visade att försämring var mer förekommande hos de som var i en kontrollgrupp, 17,4 %, jämfört med de som fick behandling, 5,8 %. Bland de som genomgick behandling existerade det även ett par prediktorer som innebar lägre odds för försämring; större svårigheter vid förmätningen, att befinna sig i en relation, att ha en universitetsutbildning respektive att vara äldre. För de som var i en kontrollgrupp var enbart större svårigheter vid förmätningen relaterat till lägre odds för försämring. Studie IV testade ett nykonstruerat självskattningsformulär; Negative Effects Questionnaire. Resultatet visade på en faktorlösning med sex faktorer och 32 påståenden; symptom, kvalitet, beroende, stigma, hopplöshet respektive misslyckande. En tredjedel av personerna svarade att de hade upplevt obehagliga minnen, stress och ångest, samtidigt som nya symptom och bristande kvalitet i både behandlingen respektive den terapeutiska relationen hade haft störst negativ inverkan på dem. Den generella slutsatsen av denna avhandling är således att negativa effekter förekommer i IKBT och att de kännetecknas av försämring, ett oförändrat tillstånd samt andra ogynnsamma eller oönskade händelser, något som liknar tidigare forskning av psykologisk behandling som bedrivs ansikte-mot-ansikte. Forskare och behandlare i IKBT rekommenderas att övervaka och rapportera negativa effekter i syfte att förhindra en negativ utveckling i behandlingen samt för att öka kunskapen om vad som kan bidra till deras förekomst. Framtida forskning bör undersöka relationen mellan negativa effekter och behandlingsutfall utifrån längre tidsperspektiv för att se om dess påverkan är övergående eller ihållande. Vidare kan till exempel intervjuer utföras med de patienter som har försämrats för att ta reda på om och hur det uppfattas samt huruvida det har förorsakats av behandlingen eller andra omständigheter.

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: In press.

Depuis quelques années les matériaux composites à base de fibres naturelles sont de plus en plus utilisés pour les nouvelles performances qu’ils proposent. C’est surtout au niveau des fibres naturelles que de nouvelles propriétés sont proposées. Dans ce travail, nous nous sommes essentiellement intéressés aux fibres naturelles de chanvre. Ces fibres sont déjà fortement utilisées dans l’automobile et la construction. En Europe, ces fibres sont produites principalement en France et plus particulièrement dans l’Aube. Pour développer des agro-composites hautes performances, c’est sous la forme de fibres longues et de tissus que nous avons choisi d’orienter ce travail de thèse. Nous avons choisi la thermocompression pour élaborer des plaques avec des tissus de chanvre et une matrice en polypropylène (PP). Ce travail permet de voir l’influence des conditions d’élaboration sur le comportement mécaniques de ces agro-composites. Cette thèse permet aussi de voir l’effet du vieillissement aux UV et à l’Humidité sur les performances de ces matériaux. Enfin une analyse des contraintes résiduelles par la méthode du trou incrémental permet de voir leurs effets sur ces agro-matériaux
In recent years composite materials based on natural fibers are more and more used for their new performances. Natural fibers propose attractive environmental, mechanical and thermal properties.In this work, we are firstly interested in hemp fibers. These fibers are already used in the automotive and construction industry. In Europe, these fibers are produced mainly in France and especially in Aube. To develop agro-composites with high performances, we have focused this thesis on hemp woven. We chose to elaborate the plates with hemp woven and a polypropylene matrix (PP) by compression molding. This work allows us to see the influence of elaboration conditions on the mechanical behavior of these agro-composites. This thesis also allows us to see the effect of aging conditions UV and humidity on the performance of these materials. Finally an analysis of residual stresses determined by the hole drilling method is proposed to see their effects on the agro-materials

The creep and shrinkage of concrete and the relaxation of cables cause long-term redistribution of internal forces and time-dependent deformations in concrete structures, steel-concrete composite structures and concrete cable-stayed bridges. They should be properly modelled for accurate prediction of their long-term behaviour and its effect on instantaneous structural responses at service. An equivalent stress relaxation model is proposed for prestressing tendons based on the intrinsic stress relaxation, from which the equivalent creep coefficients can be obtained through a recursive algorithm. Based on the equivalent stress relaxation model, an accurate finite element analysis of time-dependent behaviour by time integration has been devised considering concrete creep, concrete shrinkage and cable relaxation. Concrete members are modelled by beam-column elements while tendons are modelled by truss elements with nodes connected to the beam axis by perpendicular rigid arms. It is found that the proposed relaxation model with time integration can provide a reliable method as well as benchmark solutions for time-dependent analysis. The numerical results obtained indicate that the interactions among these factors should be properly considered in analysing the long-term performance of concrete bridges. Although time integration provides a reliable method for time-dependent analysis, both the computing time and memory requirement increase drastically with the number of time steps as the time-dependent strains of concrete and tendons within a time interval depend on the loading history up to that time. It is therefore necessary to develop a more efficient method to conduct time-dependent analysis. The relaxation-adjusted elasticity modulus is introduced on the basis of equivalent creep coefficients of tendons. Then, an efficient tendon sub-element is put forward to cope with cables with arbitrary profiles. Finally, a more general single-step method is devised using the classical age-adjusted elasticity modulus to account for external loading and creep effect, the shrinkage-adjusted elasticity modulus to consider shrinkage effect and its interaction with concrete creep, and the relaxation-adjusted elasticity modulus to consider the effect of cable relaxation based on the finite element method. The numerical results obtained indicate not only the accuracy of the single-step method but also the significance of interaction among various time-varying factors. Based on the time integration or single-step method, a systematic method is developed to monitor the long-term variations of dynamic properties of cable-stayed bridges taking into account various time-varying factors and geometric nonlinearities. Numerical studies show that, although geometric nonlinearities tend to reduce the natural frequencies, the time-dependent behaviour of concrete more than offsets it and tends to increase the natural frequencies in the long run. A generic method is further presented to investigate the long-term dynamic response of vehicle-bridge interaction systems taking account of time-dependent behaviour. The vehicles are represented by a combination of mass-spring-damper systems while the bridge is modelled by finite elements. The surface roughness of bridge deck is simulated by spectral representation method and introduced to the coupled system properly. Based on the method, the individual and combined effects of various time-varying factors are studied in detail using various numerical examples.
published_or_final_version
Civil Engineering
Doctoral
Doctor of Philosophy

Reinforcement corrosion is the most common deterioration problem observed in reinforced concrete (RC) structures located at coastal or cold regions. The corrosion process can impact the performance of these structures by inducing damage on the bonding action between concrete and steel, either by the splitting of the concrete cover due to the volumetric expansion of corrosion products or the lubricant effect at the steel/concrete interface as the corrosion by-products accumulate. The current research aims at investigating corrosion-induced deterioration of bond between steel and concrete through finite element (FE) analysis of the flexural behaviour of corroded RC components. By treating the concrete cover as a thick-wall cylinder subjected to internal pressure, the analytical evaluation of impaired bond capacity is studied first and verified against published bonding tests. Then, the formulation of a numerical model is performed using ABAQUS, wherein a link element to simulate the bond behaviour is formulated and implemented through the ABAQUS user-subroutine (UEL) feature according to the validated analytical model. By introducing corrosion-induced damages, i.e., smaller cross-sectional area of reinforcement, splitting of concrete and bond deterioration, in the FE analyses, the results of the numerical model show good agreement with experimental observations. Upon validation of the analytical and FE models, a parametric investigation is conducted, wherein the effects of concrete strength, dimension of reinforcing bars, properties of oxide products, different corrosion damage mechanisms and the corrosion location along the longitudinal reinforcement on the flexural behaviour of RC beams are studied. The results show that the analytical evaluation for bond degradation is impacted by the selection of the post-cracking material model and the thickness of cover that determine the ‘holding capacity’ after cracking initiation. Also, the density of rust by-products affects the results of the analytical model at high corrosion levels. From the FE model results, it was observed that each damage mechanism due to corrosion contribute to different levels of flexural degradation, although the flexural strength degradation is mainly due to the loss of bonding action. The parametric study also demonstrates that flexural members which have reinforcement corrosion initiated near the supports suffer greater deterioration in flexural capacity than those with damages at mid span. Finally, based on these observations, suggestions for the application of both analytical and numerical models are made.

Les systèmes de piles à combustible à membrane d'échange de protons (PEMFC) conviennent à diverses applications dans le domaine des transports, mais leur coût élevé et leur manque de durabilité restent les principaux facteurs limitant leur commercialisation à grande échelle. Dans les applications de transport, la détérioration des PEMFC est aggravée par des conditions de charge variables, ce qui entraîne une diminution de leur durée de vie utile restante (RUL). La gestion des pronostics et de la santé (PHM) est un outil efficace pour prévoir les risques du système, gérer les calendriers de contrôle/maintenance du système, améliorer la sécurité et la fiabilité du système, prolonger la durée de vie du système et réduire les coûts d'exploitation/maintenance. Le pronostic est une base importante et un support clé pour le PHM, et ses tâches principales incluent l'extraction d'indicateurs de santé, la prédiction des tendances de dégradation et l'estimation de la RUL. Les caractéristiques de dégradation à long terme des PEMFC sont dissimulées dans des conditions de charge variables, ce qui augmente la difficulté d'extraction des indicateurs de santé, réduit la précision de la prédiction de la dégradation et inhibe la fiabilité de l'estimation de la durée de vie. Dans cette optique, le travail de thèse part de la modélisation du comportement de dégradation des PEMFC dans des conditions de charge variables et mène des travaux de recherche sur l'extraction d'indicateurs de santé, la prédiction des tendances de dégradation à court/long terme, l'estimation RUL et l'évaluation de la fiabilité
Proton exchange membrane fuel cell (PEMFC) systems are suitable for various transportation applications thanks to their compact structure, high power density, low start/running temperature, and zero carbon emissions. High cost and lack of durability of PEMFC are still the core factors limiting their large-scale commercialization. In transportation applications, the deterioration of PEMFCs is aggravated by variable load conditions, resulting in a decrease in their Remaining Useful Life (RUL). Prognostics and health management (PHM) is an effective tool to forecast potential system risks, manage system control/maintenance schedules, improve system safety and reliability, extend system life, and reduce operation/maintenance costs. Prognostics is an important foundation and key support for PHM, and its core tasks include health indicator extraction, degradation trend prediction, and RUL estimation. The long-term degradation characteristics of PEMFC are concealed in variable load conditions, which increases the difficulty of health indicator extraction, reduces the accuracy of degradation prediction, and inhibits the reliability of life estimation. In view of this, the thesis work starts from modeling the degradation behavior of PEMFC under variable load conditions and carries out research work on health indicator extraction, short/long-term degradation trend prediction, RUL estimation and reliability evaluation

Diese Arbeit bietet eine solide theoretische Grundlage zu Philanthropie und religiös motivierten Spendenaktivitäten und deren Einfluss auf Wohltätigkeitstrends, Entwicklungszusammenarbeit und einer auf dem Gedanken der sozialen Gerechtigkeit beruhenden Philanthropie. Untersucht werden dafür die Strukturen religiös motivierte Spenden, für die in der islamischen Tradition die Begriffe „zakat“, „Waqf“ oder im Plural auch „awqaf-“ oder „Sadaqa“ verwendet werden, der christliche Begriff dafür lautet „tithes“ oder „ushour“. Aufbauend auf diesem theoretischen Rahmenwerk analysiert die qualitative und quantitative Feldstudie auf nationaler Ebene, wie die ägyptische Öffentlichkeit Philanthropie, soziale Gerechtigkeit, Menschenrechte, Spenden, Freiwilligenarbeit und andere Konzepte des zivilgesellschaftlichen Engagements wahrnimmt. Um eine umfassende und repräsentative Datengrundlage zu erhalten, wurden 2000 Haushalte, 200 zivilgesellschaftliche Organisationen erfasst, sowie Spender, Empfänger, religiöse Wohltäter und andere Akteure interviewt. Die so gewonnen Erkenntnisse lassen aussagekräftige Aufschlüsse über philanthropische Trends zu. Erstmals wird so auch eine finanzielle Einschätzung und Bewertung der Aktivitäten im lokalen Wohltätigkeitsbereich möglich, die sich auf mehr als eine Billion US-Dollar beziffern lassen. Die Erhebung weist nach, dass gemessen an den Pro-Kopf-Aufwendungen die privaten Spendenaktivitäten weitaus wichtiger sind als auswärtige wirtschaftliche Hilfe für Ägypten. Das wiederum lässt Rückschlüsse zu, welche Bedeutung lokale Wohltätigkeit erlangen kann, wenn sie richtig gesteuert wird und nicht wie bislang oft im Teufelskreis von ad-hoc-Spenden oder Hilfen von Privatperson an Privatperson gefangen ist. Die Studie stellt außerdem eine Verbindung her zwischen lokalen Wohltätigkeits-Mechanismen, die meist auf religiösen und kulturellen Werten beruhen, und modernen Strukturen, wie etwa Gemeinde-Stiftungen oder Gemeinde-„waqf“, innerhalb derer die Spenden eine nachhaltige Veränderung bewirken können. Daher bietet diese Arbeit also eine umfassende wissenschaftliche Grundlage, die nicht nur ein besseres Verständnis, sondern auch den nachhaltiger Aus- und Aufbau lokaler Wohltätigkeitsstrukturen in Ägypten ermöglicht. Zentral ist dabei vor allem die Rolle lokaler, individueller Spenden, die beispielsweise für Stiftungen auf der Gemeindeebene eingesetzt, wesentlich zu einer nachhaltigen Entwicklung beitragen könnten – und das nicht nur in Ägypten, sondern in der gesamten arabischen Region. Als konkretes Ergebnis dieser Arbeit, wurde ein innovatives Modell entwickelt, dass neben den wissenschaftlichen Daten das Konzept der „waqf“ berücksichtigt. Der Wissenschaftlerin und einem engagierten Vorstand ist es auf dieser Grundlage gelungen, die Waqfeyat al Maadi Community Foundation (WMCF) zu gründen, die nicht nur ein Modell für eine Bürgerstiftung ist, sondern auch das tradierte Konzept der „waqf“ als praktikable und verbürgte Wohlstätigkeitsstruktur sinnvoll weiterentwickelt.
This work provides a solid theoretical base on philanthropy, religious giving (Islamic zakat, ‘ushour, Waqf -plural: awqaf-, Sadaqa and Christian tithes or ‘ushour), and their implications on giving trends, development work, social justice philanthropy. The field study (quantitative and qualitative) that supports the theoretical framework reflects at a national level the Egyptian public’s perceptions on philanthropy, social justice, human rights, giving and volunteering and other concepts that determine the peoples’ civic engagement. The statistics cover 2000 households, 200 Civil Society Organizations distributed all over Egypt and interviews donors, recipients, religious people and other stakeholders. The numbers reflect philanthropic trends and for the first time provide a monetary estimate of local philanthropy of over USD 1 Billion annually. The survey proves that the per capita share of philanthropy outweighs the per capita share of foreign economic assistance to Egypt, which implies the significance of local giving if properly channeled, and not as it is actually consumed in the vicious circle of ad-hoc, person to person charity. In addition, the study relates local giving mechanisms derived from religion and culture to modern actual structures, like community foundations or community waqf that could bring about sustainable change in the communities. In sum, the work provides a comprehensive scientific base to help understand- and build on local philanthropy in Egypt. It explores the role that local individual giving could play in achieving sustainable development and building a new wave of community foundations not only in Egypt but in the Arab region at large. As a tangible result of this thesis, an innovative model that revives the concept of waqf and builds on the study’s results was created by the researcher and a dedicated board of trustees who succeeded in establishing Waqfeyat al Maadi Community Foundation (WMCF) that not only introduces the community foundation model to Egypt, but revives and modernizes the waqf as a practical authentic philanthropic structure.

Concrete highway bridges are important elements of our country's transportation infrastructure; however, only few studies that address their seismic behavior using data collected from instrumented structures are available in the literature. This gap of knowledge impairs full exploitation of structural health monitoring techniques for seismic damage assessment, and improvement of design recommendations. This research is particularly concerned with curved concrete box-girder highway bridges, whose seismic behavior is still widely unexplored due to lack of field monitoring data. By taking advantage of vibration records collected during six earthquake events at the West Street on Ramp, a curved concrete box-girder highway bridge located in Anaheim, California, this research aims at advancing knowledge about the seismic behavior of these bridges. Modal identification of the bridge during the earthquakes is conducted, and sensitivity analysis is carried out to reconcile the observed dynamic characteristics of the bridge with the behavior of its structural elements. Data collected from an instrumented large-scale bridge specimen during shaking table tests are also analyzed to gain insight about the response of the bridge bents during the earthquakes, and propose a strategy to model their seismic behavior. Information from modal identification and the shaking table tests analyses are instrumental in developing a nonlinear finite element model of the bridge, calibrated employing a multistage finite element model updating strategy. In order to evaluate the significance of using the structural-health-monitoring-informed structural model obtained, seismic performance assessment through incremental dynamic analysis is conducted, and results are compared with the predicted performance estimated with a conventional finite element model of the bridge. By advancing knowledge about the seismic behavior of concrete highway bridges, this research may ultimately contribute to improve structural health monitoring practices and design guidelines for this type of structures.

The collapse of the I-35W Bridge in Minneapolis, MN on August 1, 2007 brought into question the design and inspection of gusset plates in steel truss bridges. The experimental tests performed in this research study the sway-buckling strength and behavior of large-scale steel gusset plates in an isolated truss connection. Parameters studied include plate thickness,combination member loading, initial out-of-plane imperfection, diagonal compression member out-of-plane flexural stiffness, corrosion, and alternative retrofits to increase lateral stiffness. The flexural stiffness of the diagonal compression member and retrofit designs were unique to the testing program. The variables monitored during testing include gusset plate surface stresses and strains, member axial strains, out-of-plane displacement of the gusset plate free edge, and buckling capacity. The results were compared with previously established design models for predicting buckling capacity of gusset plates which include the Whitmore effective width, the Modified-Thornton method, and the FHWA Load Rating Guidelines. A parametric finite element model was developed to determine the lateral stiffness of the gusset plate connection and the additional stiffness provided by the alternative retrofit options. The results showed interaction between the diagonal compression member and gusset plate occurs, which affects sway-buckling capacity. Combination of member loads showed evidence of detrimental effects on sway-buckling capacity. Corrosion of the gusset plates along the top edge of the bottom chord did not lead to significant reduction in sway-buckling capacity. The two retrofit designs showed increases in both lateral stiffness and buckling capacity as well as economic benefits over traditional retrofit methods. Comparison of the results to the current design guidelines showed that the current methods are conservative and do not accurately represent the true behavior of gusset plate connections. The research concludes with two proposed models for future use in design and retrofit of gusset plates. The first is a member-gusset plate interaction model based on a stepped column analogy that takes into account the effects of member flexural stiffness and gusset plate stiffness. The second is a general design guideline developed for retrofit of gusset plate connections dominated by sway-buckling behavior which uses a stiffness based approach to increase the capacity of gusset plate connections.
Graduation date: 2012

Adjacent precast, prestressed box beam bridges have a history of poor performance and have been observed to exhibit common types of deterioration including longitudinal cracking, concrete spalling, and deterioration of the concrete top flange. The nature of these types of deterioration leads to uncertainty of the extent and effect of deterioration on structural behavior. Due to limitations in previous research and understanding of the strength of deteriorated box beam bridges, conservative assumptions are being made for the assessment and load rating of these bridges. Furthermore, the design of new box beam bridges, which can offer an efficient and economical solution, is often discouraged due to poor past performance. Therefore, the objective of this research is to develop improved recommendations for the inspection, load rating, and design of adjacent box beam bridges. Through a series of bridge inspections, deteriorated box beams were identified and acquired for experimental testing. The extent of corrosion was determined through visual inspection, non-destructive evaluation, and destructive evaluation. Non-destructive tests (NDT) included the use of connectionless electrical pulse response analysis (CEPRA), ground penetrating radar (GPR), and half-cell potentials. The deteriorated capacity was determined through structural testing, and an analysis procedure was developed to estimate deteriorated behavior. A rehabilitation procedure was also developed to restore load transfer of adjacent beams in cases where shear key failures are suspected. Based on the understanding of deterioration developed through study of deteriorated adjacent box beam bridges, improved inspection and load rating procedure are provided along with design recommendations for the next generation of box beam bridges.

博士
中原大學
工業工程研究所
101
Most items deteriorate in the real world. Deterioration can include decay, evaporation, and spoilage, and will result in imperfect products during the manufacturing process. Therefore, an optimized replenishment strategy is the key to success. Our objective is to derive integrated replenishment strategies for deteriorating products from different business perspectives. We have developed optimal integrated models that consider the major factors in both manufacturer-centric and retailer-centric supply chains. Both models have been validated and analyzed using numerical examples. In addition, this research also provides a rapid solution to solve the above complex problems in the real world.

M.Tech. (Civil Engineering)
Every year, millions of Rands are being spent in rehabilitation, repairs and maintenance of reinforced concrete structures projects around the country due to corrosion. There are a number of studies and investigations that have been done recently to address the effect of corrosion on reinforced concrete structures. Concrete provides an ideal environment for steel, supplying both physical and chemical protection from corrosive attack. The effect of corrosion on reinforced concrete structures contributes to the reduction of steel cross sectional area, weakening the bond strength between steel and concrete and thereby reducing the ductility, deflection capacities and load carrying capacity of the structure. In this research, five series of three samples each of reinforced concrete beams were fabricated, some with reduced cross-sectional area and with exposed bars to simulate loss of bonding through spalling. The structural performance of these beams was tested in terms of maximum load carrying capacity, deflections and ductility ratio. The main conclusions are as follows:  As little as 1 % loss in mass of tension steel resulted in a load carrying capacity decrease of 6.9 %  Beam deflection increased by a factor of 1.5 times when the steel mass loss level was 14%  5 % steel loss in mass resulted in a 16.5 % decrease in relative ductility.

The damaging impact of continuous utility cuts on flexible pavement performance has been shown to be a major problem for urban roads and pavement mangers due to high reconstruction and maintenance costs. Horizontal Directional Drilling (HDD) is a trenchless construction method that does not require continuous trenching. HDD pipe installation techniques can reduce reinstatement costs, shorten construction periods, and lower social costs due to reduced user traffic delays. In this thesis, a detailed field study and numerical investigations was completed to quantify pavement deterioration and polyethylene (PE) pipe performance when pipelines are installed under flexible pavements using both traditional open-cut and HDD construction methods. Two 200mm SDR-17 DIPS HDPE pipes were installed 1.5m below a flexible pavement using open-cut and HDD construction technique. A state-of-the-art instrumentation and data acquisition systems were developed to measure HDD drill rig, PE pipes and pavement responses during pipe installations and for a period of about three years afterwards. Field data from (GPR) surveys, falling weight deflectometer (FWD) tests, surface distress surveys, and ground surface elevation survey were used to evaluate pavement deterioration due to the pipeline installations. The mechanisms of ground deformations during HDD and open-cut pipe installation were numerically investigated with FLAC3D, a commercial finite difference program. A hybrid constitutive model consisting of the traditional Duncan-Chang hyperbolic model and Mohr-Coulomb perfectly plastic model was developed and implemented in FLAC3D to simulate the non-linear stress-strain and stress dependent behavior of granular materials. Field test results show that the HDD installed pipe have significantly lower construction induced strains and ring deflections when compared to the open cut-and-cover installation and the mechanism of pipe deformation differs for the two construction techniques. The two pipes performed satisfactory over the long-term monitoring period as deflections and strain levels were below acceptable limits and there was no apparent deterioration of the pipe. Pipe deflections resulting from environmental effects (freeze and thaw) were found to be more significant than those due to material creep. Furthermore, the modified Iowa’s and Plastic Pipe Institute’s (PPI) ring deflection equations were found to over estimate pipe deflection for the open-cut and HDD installed pipes by about 114 and 50 percent, respectively. Results from field tests found that the HDD installation did not results in any observable change in the condition of the pavement structure performance, while the structure and integrity of pavement section in the vicinity of the open-cut was adversely impacted by utility cut excavation. It was determined numerically that when an unsupported excavation is created within a typical flexible pavement structure, distress zones that extend laterally from the face of the excavation to a distance of approximately 80% of the depth of excavation is developed. The results of the analyses suggests that better restoration techniques are required to eliminate the adverse effect caused by the stress relief within the pavement structure during a utility cut. Furthermore, the area of potential pavement deterioration should be extended beyond the edge of the utility cut to encompass the ‘distress zones’ when determining fees to cover pavement damage and restoration costs. Results obtained from numerical simulations advanced the understanding of the mechanism, magnitude, and extent of deformation within the pavement structure during HDD pipe installation in frictional and cohesive subgrade soils. Relationship between HDD annular bore pressures and displacements have been incorporated into design Charts and Tables for use in estimating maximum allowable bore pressures for HDD installation beneath flexible pavements. Critical bore pressures that would limit ground deformations and prevent excessive pavement deformations are presented. Critical bore pressures were compared to estimated allowable bore pressures obtained from the widely used Delft Geotechnics equation. The Delft Geotechnics equation was found to over estimate allowable bore pressure for HDD installation beneath flexible pavement. HDD pipeline installations under flexible pavement were found to have significantly lower restoration costs, social costs and maintenance cost than open-cut pipeline installations.

Research Doctorate - Doctor of Philosophy (PhD)
Subsidence is one of the most challenging and controversial problems in rock mechanics and geotechnical engineering. In particular, the expansion of urbanised areas over abandoned mining excavations has brought about several questions concerning the long term stability of such excavations and the duration of the subsidence development. This study, therefore, aims to investigate the mechanisms of post mining subsidence. The role of the effective factors on the mechanisms of excavation induced ground movements are assessed through some case studies of actual subsidence incidents. Clearly, one of the fundamental stages of conducting numerical or theoretical analyses for calculating the magnitudes of subsidence is to reliably estimate the mechanical parameters of rock masses. A simple and practical approach is developed in this study, based on the concept of rock mass classification methods to approximate the rock mass parameters. Additionally, the mechanisms of mining induced subsidence in sloping terrain are investigated through numerical modelling. An interesting example of mining beneath escarpments in New South Wales, Australia, is investigated to capture the effects of the surface topography on the mechanisms of subsidence. Furthermore, the role of the gradual deterioration of a rock mass on the duration of the subsidence development in shallow abandoned coal mines is investigated. The conventional Tributary Area Method (TAM) is augmented to incorporate the effects of the gradual deterioration on the loads of pillars. Moreover, the conventional pillar strength methods are modified to take into account the effects of the gradual deterioration. The combination of these two approaches provides a suitable ground for assessing the life times of pillars. Furthermore, a simple and practical approach is proposed to take into account the role of gradual deterioration in the numerical modelling. The proposed approach is then employed for assessing the formation of subsidence over an abandoned shallow coal mine around the village of Dolphingstone, UK. The outcomes of the numerical modelling are then verified against the results of the empirical methods for estimating the stand up time of room and pillar mining excavations. Creep is the other time dependent behaviour of rocks, controlling the long term stability of excavations. The role of this factor on the mechanisms of post mining subsidence is also investigated in this study. The theories of visco elasticity and visco plasticity are employed in the frameworks of the analytical and numerical modelling to study the effects of creep on the gradual development of subsidence over abandoned room and pillar mines. The outcomes of the study show that creep plays a pronounced role on the values of the time dependent displacements over mining excavations. Moreover, a procedure is developed to take into account the effects of gradual weakening due to mechanical factors (e.g., creep) or environmental factors (e.g., weathering and moisture softening) on the formation of sinkholes. The proposed approaches are then employed for investigating the mechanisms of the subsidence over an abandoned limestone mine in the West Midlands, UK.

An ageing population challenges healthcare systems and resources. Efforts are underway in Australia and around the world to find alternatives to hospitalisation for older persons, particularly those transferred from residential aged care facilities (RACFs), where emergency transfers are frequent, costly, stressful for residents, and often considered unnecessary or preventable. RACF nursing staff play a pivotal role in managing residents with deteriorating health and hospital avoidance efforts; therefore, information on their intentions and perceptions regarding this area of their work is needed to underpin programs that aim to enhance nursing skills and confidence. The overarching aim of the study presented in this thesis is to understand and identify factors that influence RACF nursing staff management of residents with deteriorating health.

Text in Afrikaans
Summaries in Afrikaans and English
Vigs is 'n "sluipende moordenaar "_ Dit toon geen respek vir kultuur, status,ouderdom of geslag nie. Vigs veroorsaak 'n onnnatuurlike dood wat vriende en familie bedreig en vervreem, lank na die dood van die vigsslagoffer. Die navorsingsdoel van hierdie studie was om riglyne daar te stel vir die psigoterapeutiese hantering van die vigslyer en sy gesin. Die navorsing het getoon dat 'n stigma en skuldgevoelens rondom die vigslyer en sy gesin ontstaan het, en dat hulle direk verantwoordelik gehou word vir die siekte bloot omdat hulle betrokke is by mekaar. 'n Vraelys wat aspekte (soos dit uit die literatuurstudie geblyk het) inkorporeer, is opgestel en aan die vigslyer en sy gesin gegee om te voltooi. Van die belangrikste elemente wat na vore gekom het, is die vrees vir die onbekende, die stigma verbonde aan die siekte en die pad wat die siekte loop ten opsigte van naiwiteit en valse gerugte ten opsigte van die siekte. 'n Verdere hoofstuk fokus op die literatuur om die hoofaspekte van die probleem vas le stel, en sodoende riglyne vir 'n terapieprogram daar te stel om die vrese te onderskep en die familie te help om die siekte beter te begryp_ Die doel is om die samelewing te laat begryp dat vigs nie 'n kulturele of "klas" siekte is nie, maar dat dit alle lae van die samelewing kan tref. 'n Afdeling is gewy aan 'n wye verskeidenheid terapeutiese tegnieke wat geimplimenteer kan word tydens hulpverlening aan die vigslyer en sy gesinslede. Verder verskaf hierdie studie ook riglyne om ondersteuning en hulp aan die vigslyer en sy gesin te bied, om sodoende hulle selfkonsep te verbeter.
Aids is a "stalking killer''. It has no respect for culture, breeding, age or sex. It is an unnatural death which offends and alienates many friends and family, even after the victim has died. A questionnaire incorporating important aspects of the cause and effect of aids was compiled and given to the aids sufferers and family to complete. From the responses it was clearly evident that the fears of the unknown, the stigma attached to the victim's close associates and family, was a problem, and the route course of incredible naive and false rumours. A chapter of the research focused on literature to establish what was the major aspects of the problem expressed by the media. Guidelines were provided whereby therapy could address and allay these fears to assist the family to better understand the illness and it's effects. This chapter has in mind to provide the Psychologist with guidelines to provide therapy to both the victim and the family in this regard. This study confirms that the survivors are the actual victims.
Educational studies
M.Ed. (Voorligting)

Import sanctions were used to a very limited extent against South Africa in the early sixties and latter half of the seventies to clearly signal the international community's disapproval of the country's apartheid policy. In the middle eighties South Africa was further exposed to a two year wave of export and financial sanctions. This was after the government had already committed itself to move away from apartheid as a policy that was no longer deemed feasible. All these sanctions were lifted in the early nineties after the abolition of apartheid but before negotiations for a new constitutional dispensation had firmly got under way. Contrary to some popular impressions, the 1985-87 sanctions were also severe1y limited in scope and nature, with the result that their economic impact was only marginal at best. They were introduced at a time when the country unexpectedly had to face a foreign debt crisis and had to drastically adjust the economy downward, not unlike that experienced by many other developing countries. The severe recession and greater socio-political unrest that followed did not lead to an escalation of sanctions, but nevertheless threatened to make large parts of the country ungovernable. The evidence is that sanctions only played a minor role in bringing about this poor and deteriorating state of affairs. The political aims of abolishing apartheid and preparing the way for negotiations was achieved mainly as a result of certain internal political developments, together with the political implications of such major other outside developments as the economic collapse of Sub-Saharan Africa and the Soviet Union. South Africa's experience with sanctions confirms that as elsewhere their economic impact as an instrument of foreign policy was invariably exaggerated, whereas their contribution in explaining the subsequent course of political events was at best uncertain.
Department of Economics
Ph.D. (Economics)