Dissertations / Theses on the topic 'Rotation capacity'

Concrete-filled tubular (CFT) columns have been widely adopted in building structures owing to their superior structural performance, such as enhanced load bearing capacity, compared to hollow tubes. Circular, square and rectangular hollow sections are most commonly used in the past few decades. Elliptical hollow section (EHS) available recently is regarded as a new cross-section for the CFT columns due to its attractive appearance, optional orientation either on major axis or minor axis and improved structural efficiency. The state of the research in terms of elliptical columns, tubular joints between EHSs and connections with CFT columns, etc., are reviewed in this thesis, showing a lack of investigations on EHSs, especially on beam to elliptical column connections which are essential in framed structures. The structural behaviour of elliptical column to I-beam connections under bending is studied in this thesis to fill the research gap. Overall ten specimens with various joint assemblies were tested to failure to highlight the benefits of adopting concrete infill and stiffeners in the columns. A three-dimensional finite element model developed by using ABAQUS software is presented and verified against obtained experimental results, which shows acceptable accuracy and reliability in predicting failure modes of the connections and their moment capacities. Parametric studies were performed to access the main parameters that affecting the bending behaviour of the connections. A simple hand calculation method in terms of ultimate moment capacity is proposed according to experiments conducted for connections with concrete-filled columns.

O presente trabalho é uma contribuição para o esclarecimento e a quantificação das influências na deformabilidade e na capacidade portante de elementos unidimensionais de concreto armado em solicitação plana, decorrentes da não-linearidade física dos materiais concreto e aço, bem como da fissuração e do enrijecimento da armadura tracionada, também na sua fase plástica. Para aplicações práticas determinam-se a rigidez à flexão e a capacidade de rotação plástica dos elementos estruturais, o que permite limitar com mais precisão e coerência a demanda de rotação plástica obtida na análise. De início, descrevem-se os comportamentos não-lineares do concreto e do aço, aplicando-se conceitos da Mecânica da Fratura, bem como a atuação conjunta destes materiais, sob os aspectos de aderência e de fissuração. O núcleo deste trabalho concentra-se na obtenção do diagrama momento-curvatura e dos seus pontos principais, e na subseqüente determinação da capacidade de rotação plástica dos mencionados elementos. Consideram-se as seções geradas a partir da seção duplo T assimétrico, com várias camadas de armadura, sujeitas à flexão composta normal. Com dados deste diagrama e através do modelo da viga equivalente simétrica, posteriormente estendido à viga equivalente assimétrica e às vigas contínuas de pórticos planos, determina-se a capacidade de rotação plástica, considerando-se nesta suas múltiplas influências. Por fim, comparam-se os resultados teóricos e experimentais da capacidade de rotação plástica, e resumem-se as principais conclusões encontradas e os pontos que exigem subseqüente desenvolvimento.
The present study is a contribution to the enlightenment and evaluation of the influences on deformability and load carrying capacity of one-dimensional elements of reinforced concrete subject to in-plane loading, arisen from the constitutive non-linearity of concrete and steel, as well as from the concrete cracking and the tension stiffening of the reinforcement, prior and after yielding. For practical applications, the flexural rigidity and the plastic rotation capacity of structural elements are determined, which makes it possible to limit, more precisely and coherently, the plastic rotation demand coming from the analysis. Firstly, the non-linear behaviors of concrete and steel are described, applying concepts of Fracture Mechanics, and then the joint action of both materials concerning bond and cracking is studied. The core of this study lies on obtaining the bending moment-curvature diagram, specially its main points, and on the subsequent determination of the plastic rotation capacity of the aforementioned elements. The cross-sections generated from an asymmetric double T cross-section are considered, with several layers of reinforcement, acted upon simple or combined bending about one principal axis. With data based on this diagram and through the model of equivalent symmetric beam, later extended to equivalent asymmetric beam and to continuous beams of plane frames, the plastic rotation capacity is determined, considering its multiple influences. Finally, theoretical and experimental results of plastic rotation capacity are compared, and the main conclusions and points in need of subsequent development are summarized.

Михалчич Г.Ю. Обґрунтування параметрів та розробка інтегрального приводу головного руху горизонтально-фрезерного верстату. Спец. 133 – Галузеве машинобудування; Тернопільський національний технічний університет імені Івана Пулюя; м. Тернопіль, 2018р.
Mychaltchytch H.Yu. Substantiation of parameters and development of integral main motion drive of horizontal milling machine.
У дипломній роботі проведено аналіз структур приводів головного руху горизонтально-фрезерних верстатів. На основі здійсненого аналізу можливостей різних типів інструментальних матеріалів встановлено граничні частоти обертання шпинделя та необхідну максимальну потужність різання. Здійснено обґрунтування структури безступеневої частини приводу головного руху з використанням методу морфологічного аналізу. Проведено обґрунтування компоновки шпиндельного вузла на основі розробленої математичної моделі, що 8 враховує кількість підшипників в передній опорі, їх натяг, а також відстань між ними. На основі даної моделі здійснено розрахунки радіальної жорсткості шпиндельного вузла для різних його компонувальних схем. Вибрано оптимальну структуру шпиндельного вузла, а також загальну структуру приводу. Розроблено конструкції коробки швидкостей та шпиндельного вузла верстату.
Analysis of the design of the main motion drive of the horizontal milling machines is carried out in this graduation thesis. The boundary frequencies of the spindle rotation and the required maximum cutting power are determined on the basis of the carried out analysis of the possibilities of different tool materials types. The substantiation of the spindle unit arrangement is carried out on the basis of the developed mathematical model taking into account the number of bearings in the front support, their tension as well as the distance between them. The calculations of the spindle unit radial stiffness for its various arrangement schemes on the basis of the given model are performed. Both the optimal structure of the spindle unit and the drive general structure are found. The designs of the gearbox and machine tool spindle unit are developed.
Вступ, Аналітичний розділ, Обґрунтування формоутворення та компонувальної схеми, Обґрунтування кінематичних та силових параметрів приводу головного руху проектованого верстата, Науково-дослідний розділ, Конструкторський розділ, Обґрунтування економічної ефективності; Охорона праці та безпека в надзвичайних ситуаціях; Екологія; Висновки,

Severe seismic events in urban regions during the last two decades revealed that the structures constructed before the development of modern seismic codes are the most vulnerable to earthquakes. Sub-standard reinforced concrete buildings constitute an important part of this highly vulnerable urban building stock. There is urgent need for the development and improvement of methods for seismic performance assessment of existing reinforced concrete structures. As an alternative to current conventional force-based assessment methods, a performance evaluation procedure for structural members, mainly reinforced concrete columns is proposed in this study, by using an energy-based approach combined with the low cycle fatigue concept. An energy-based hysteresis model is further introduced for representing the inelastic response of column members under severe seismic excitations. The shape of the hysteresis loops are controlled by the dissipated cumulative energy whereas the ultimate strength is governed by the low cycle fatigue behavior. These two basic characteristics are obtained experimentally from full scale specimens tested under constant and variable amplitude displacement cycles. The first phase of the experimental program presented in the study constitutes of testing sub-standard non-conforming column specimens. The second phase of testing was conducted on standard, code compliant reinforced concrete columns. A total number of 13 specimens were tested. The behavior of these specimens was observed individually and comparatively according to the performance based objectives. The results obtained from the experiments were employed for developing relations between the energy dissipation capacity of specimens, the specimen properties as well as the imposed displacement history. Moreover, the measured rotation capacities at the plastic regions are evaluated comparatively with the limits proposed by modern displacement-based seismic design and assessment provisions.

Les recherches sur l’implication des processus moteurs lors des tâches de rotation mentale ne sont pas consensuelles. Selon la revue de littérature, ces divergences semblent être dues aux différences de tâches utilisées (nature des stimuli, types de jugement, caractéristiques des stimuli) impliquant différentes stratégies mentales. L’objectif de ce travail de thèse est de préciser la place des processus moteurs dans la rotation mentale par l’étude des effets de la pratique sportive. Plus précisément, il s’agit d’identifier les conditions permettant de mettre en évidence des effets sélectifs de différentes pratiques sportives dans une tâche de rotation mentale. Les résultats de ce travail montrent que l’utilisation de représentations corporelles avec un jugement de latéralité permet de révéler les effets sélectifs des pratiques sportives par l’utilisation de stratégies égocentriques et d’embodiment. De plus, ces stratégies semblent être influencées par le réalisme des stimuli. Ces résultats attestent de l’implication des processus moteurs dans ces tâches
Research on the involvement of motor processes during mental rotation tasks is not consensual. According to the literature, this lack of consensus seems to be due to differences in the tasks used (type of stimuli, types of judgment, stimuli features) involving different mental strategies. Our aim is to clarify the role of motor processes in mental rotation by studying the effects of sport on mental rotation ability. Specifically, we tried to identify the tasks requirements to highlight selective effects of different sporting activities in a mental rotation task. The results of this work show that the use of body stimuli with a laterality judgment would engage egocentric strategies and embodiment allowing revealing selective effects of sports. Further, theses strategies appear to be affected by the stimuli realism. These results indicate the involvement of motor processes in these tasks

The aim of this thesis is to assess the suitability of cold-formed rectangular hollow sections (RHS) for plastic design. The project involved an extensive range of tests on cold-formed Grade C350 and Grade C450 (DuraGal) RHS beams, joints and frames. A large number of finite element analyses was also carried out on models of RHS beams. The conclusion is that cold- formed RHS can be used in plastic design, but stricter element slenderness (b/t) limits and consideration of the connections, are required. Further research, particularly into the effect of axial compression on element slenderness limits, is required before changes to current design rules can be finalised. Bending tests were performed on cold-formed RHS to examine the web and flange slenderness required to maintain the plastic moment for a large enough rotation suitable for plastic design. The major conclusions of the beam tests were: (i) Some sections which are classified as Compact or Class 1 by current steel design specifications do not maintain plastic rotations considered sufficient for plastic design. (ii) The current design philosophy, in which flange and web slenderness limits are independent, is inappropriate. An interaction formula is required, and simple formulations are proposed for RHS. Connection tests were performed on various types of knee joints in RHS, suitable for the column - rafter connection in a portal frame. The connection types investigated were welded stiffened and unstiffened rigid knee connections, bolted plate knee joints, and welded and bolted internal sleeve knee joints, for use in RHS portal frames. The ability of the connections to act as plastic hinges in a portal frame was investigated. The most important finding of the joint tests was the unexpected fracture of the cold-formed welded connections under opening moment before significant plastic rotations occurred. The use of an internal sleeve moved the plastic hinge in the connection away from the connection centre- line thus eliminating the need for the weld between the RHS, or the RHS and the stiffening plate, to carry the majority of the load. The internal sleeve connections were capable of sustaining the plastic moment for large rotations considered suitable for plastic design. Tests on pinned-base portal frames were also performed. There were three separate tests, with two different ratios of vertical to horizontal point loads, simulating gravity and horizontal wind loads. Two grades of steel were used for comparison. The aims of the tests were to examine if a plastic collapse mechanism could form in a cold-formed RHS frame, and to investigate if plastic design was suitable for such frames. In each frame, two regions of highly concentrated curvature were observed before the onset of local buckling, which indicated the formation of plastic hinges and a plastic collapse mechanism. An advanced plastic zone structural analysis which accounted for second order effects, material non-linearity and member imperfections slightly overestimated the strength of the frames. The analysis slightly underestimated the deflections, and hence the magnitude of the second order effects. A second order plastic zone analysis, which did not account for the effects of structural imperfections, provided the best estimates of the strengths of the frames, but also underestimated the deflections. While cold-formed RHS did not satisfy the material ductility requirements specified for plastic design in some current steel design standards, plastic hinges and plastic collapse mechanisms formed. This suggests that the restriction on plastic design for cold-formed RHS based on insufficient material ductility is unnecessary, provided that the connections are suitable for plastic hinge formation, if required. A large number of finite element analyses were performed to simulate the bending tests summarised above, and to examine various parameters not studied in the experimental investigation. To simulate the experimental rotation capacity of the RHS beams, a sinusoidally varying longitudinal local imperfection was prescribed. The finite element analysis determined similar trends as observed experimentally, namely that the rotation capacity depended on both the web slenderness and flange slenderness, and that for a given section aspect ratio, the relationship between web slenderness and rotation capacity was non-linear. The main finding of the finite element study was that the size of the imperfections had an unexpectedly large influence on the rotation capacity. Larger imperfections were required in the more slender sections to simulate the experimental results. There should be further investigation into the effect of varying material properties on rotation capacity.

The aim of this thesis is to assess the suitability of cold-formed rectangular hollow sections (RHS) for plastic design. The project involved an extensive range of tests on cold-formed Grade C350 and Grade C450 (DuraGal) RHS beams, joints and frames. A large number of finite element analyses was also carried out on models of RHS beams. The conclusion is that cold- formed RHS can be used in plastic design, but stricter element slenderness (b/t) limits and consideration of the connections, are required. Further research, particularly into the effect of axial compression on element slenderness limits, is required before changes to current design rules can be finalised. Bending tests were performed on cold-formed RHS to examine the web and flange slenderness required to maintain the plastic moment for a large enough rotation suitable for plastic design. The major conclusions of the beam tests were: (i) Some sections which are classified as Compact or Class 1 by current steel design specifications do not maintain plastic rotations considered sufficient for plastic design. (ii) The current design philosophy, in which flange and web slenderness limits are independent, is inappropriate. An interaction formula is required, and simple formulations are proposed for RHS. Connection tests were performed on various types of knee joints in RHS, suitable for the column - rafter connection in a portal frame. The connection types investigated were welded stiffened and unstiffened rigid knee connections, bolted plate knee joints, and welded and bolted internal sleeve knee joints, for use in RHS portal frames. The ability of the connections to act as plastic hinges in a portal frame was investigated. The most important finding of the joint tests was the unexpected fracture of the cold-formed welded connections under opening moment before significant plastic rotations occurred. The use of an internal sleeve moved the plastic hinge in the connection away from the connection centre- line thus eliminating the need for the weld between the RHS, or the RHS and the stiffening plate, to carry the majority of the load. The internal sleeve connections were capable of sustaining the plastic moment for large rotations considered suitable for plastic design. Tests on pinned-base portal frames were also performed. There were three separate tests, with two different ratios of vertical to horizontal point loads, simulating gravity and horizontal wind loads. Two grades of steel were used for comparison. The aims of the tests were to examine if a plastic collapse mechanism could form in a cold-formed RHS frame, and to investigate if plastic design was suitable for such frames. In each frame, two regions of highly concentrated curvature were observed before the onset of local buckling, which indicated the formation of plastic hinges and a plastic collapse mechanism. An advanced plastic zone structural analysis which accounted for second order effects, material non-linearity and member imperfections slightly overestimated the strength of the frames. The analysis slightly underestimated the deflections, and hence the magnitude of the second order effects. A second order plastic zone analysis, which did not account for the effects of structural imperfections, provided the best estimates of the strengths of the frames, but also underestimated the deflections. While cold-formed RHS did not satisfy the material ductility requirements specified for plastic design in some current steel design standards, plastic hinges and plastic collapse mechanisms formed. This suggests that the restriction on plastic design for cold-formed RHS based on insufficient material ductility is unnecessary, provided that the connections are suitable for plastic hinge formation, if required. A large number of finite element analyses were performed to simulate the bending tests summarised above, and to examine various parameters not studied in the experimental investigation. To simulate the experimental rotation capacity of the RHS beams, a sinusoidally varying longitudinal local imperfection was prescribed. The finite element analysis determined similar trends as observed experimentally, namely that the rotation capacity depended on both the web slenderness and flange slenderness, and that for a given section aspect ratio, the relationship between web slenderness and rotation capacity was non-linear. The main finding of the finite element study was that the size of the imperfections had an unexpectedly large influence on the rotation capacity. Larger imperfections were required in the more slender sections to simulate the experimental results. There should be further investigation into the effect of varying material properties on rotation capacity.

Cross Laminated Timber (CLT) has in recent years become a more important building material. This means that the demand for accurate calculation methods in building standards such as Eurocode 5 has increased. There is limited knowledge about the connections in CLT buildings which is an important part of a CLT structure. This thesis was therefore focused on investigating a wall-floor-wall type connection commonly found in platform type buildings.  An experimental and numerical study on typical wall-floor-wall connections was carried out in this thesis. In the experimental part 60 tests with 8 different configurations were conducted to investigate the influence of different parameters on the connection, moment capacity and rotational stiffness. During the tests the deformation of the specimens under four load levels were investigated. Compression tests were also performed on the specimens to determine the compressive strength and stiffness of the elements. In the numerical part two different models for the connection were created. One simplified model with rotational springs and one more complex model with compression springs. With these models the influence from the number of stories, span and thickness of the wall on the global behavior of a structure was investigated.  The result from this thesis shows that there is both moment capacity and rotational stiffness in the wall-floor-wall type connection that can be utilized in the design phase of a structure. This was proven by both the experimental and the numerical study. The parameters that influence the behavior of the connection most were the load level applied on the wall and the wall thickness. The model created in the numerical study showed great potential regarding the replication of the connection behavior observed in the experimental study.

У дисертації на підставі сукупності узагальнених наукових результатів вирішено актуальне завдання розширення функціональних можливостей гвинтових транспортних механізмів шляхом розроблення та обгрунтування параметрів комбінованого робочого органу гвинтового конвеєра. Гвинтовий конвеєр складається із завантажувального бункера та кожуха. У кожусі встановлено шнек, який виконано у вигляді приводного барабана на якому по гвинтовій лінії закріплено спіральні витки. Між витками та під кутом до поперечного січення барабана встановлено ножі-подрібнювачі. Гвинтова лінія навивання ножів-подрібнювачів і спіральних витків виконана зі змінним кроком. Розширення функціональних можливостей гвинтового конвеєра досягнуто за рахунок одночасного поєднання двох роздільних операцій транспортування та подрібнення коренеплодів в одну суміжну операцію. На основі проведених аналітичних досліджень розроблено: математичну модель, яка функціонально описує процес транспортування дискретних одиниць подрібнених коренеплодів робочими органами гвинтового конвеєра на основі аналізу матеріального балансу вхідних і вихідних потоків; математичну модель продуктивності роботи гвинтового конвеєра на основі узгодження пропускної здатності шнекового конвеєра та уточненого коефіцієнта заповнення робочого простору. На основі проведених теоретичних і експериментальних досліджень обґрунтовано основні раціональні параметри гвинтового конвеєра з комбінованим робочим органом. Результати досліджень впроваджено в компанії ПАП «Агропродсервіс» Тернопільської обл. в технологічній лінії для приготування соковитих кормів.
A topical problem of screw transport mechanisms enhancement by means of development and substantiation of parameters of combined working body of a screw conveyor has been solved in the thesis on the basis of the whole set of summarized scientific results. The screw conveyor consists of a loading bin and an encasing. The encasing has an auger in the form of a drive pulley where spiral turns are fixed along helix line. Knives-cutters are placed between turns and at a certain angle to the drum transversal cross-section view. The helix line of knives-cutters and spiral turns winding is made with an adjustable pitch. Screw conveyor enhancement has been achieved due to the simultaneous combination of two separate operations, namely root crops transportation and breaking into one related operation. On the basis of conducted analytical research we have developed the following: a mathematical model describing functionally the process of transportation of discrete units of minced root crops by screw conveyor working bodies on the basis of analysis of material balance of incoming and outgoing flows; a mathematical model of a screw conveyor capacity based on the conformation of an auger-type conveyor throughput and specified factor of working space filling. Main rational parameters of a screw conveyor with combined working body have been substantiated on the basis of conducted theoretical and experimental investigations. The results of the research have been introduced into the company PJSC “Agroprodservice” of Ternopil region on the succulent feed production line.

This diploma thesis analyze reinforced concrete construction, which is loaded by new steel superstructure with brick cladding. The necessary strengthening of construction is solved by using carbon fibre reinforced polymer plates. Software RFEM 5 is used for calculation of internal forces. All checks are made in Excel.

碩士
國立中央大學
土木工程學系
85
AbstractIn this research, the 16 high-strength concrete beams were tested to observe and study the relationship between the thickness of the concrete cover and rotation capacity of beams. Because the plastic design theory which consider failure behavior of structures is accurate to estimate the rate of safety of design theory than the elastic design theory which consider elastic failure of material. In the concrete structure, the research of capacity of plastic rotation wasn't adequate understanding .So, the plastic design theory of concrete structure is very important. The ultimate cleavage length of concrete cover on the bar surface Ws and depth of crack were used to compute the rotation of the beam and analyzed. It appears that plastic rotation computed from the result of experiment has the good tendency with the theory of Mattock , Corley and Sawyer .

碩士
國立臺灣科技大學
營建工程系
98
Current ACI 318 building code the proposed formula for reinforced concrete columns without considering the axial force increases the required transverse steel bar should be improving, and TW-SRC design code evolved by the ACI 318 building code. Although the required transverse steel bar considers the effect of the confining by the steel shape, but it still doesn’t consider the effect from the axial force. This thesis to experimentally investigate seismic behavior of encased steel column research. 9 sets of large scale encased steel column specimens which included 5 new SRC columns (NSRC) and 4 traditional SRC columns (TSRC) were tested. The parameters studied in this test comprised: the required transverse steel bars for NSRC and TSRC when bending about x-axis and y-axis for plastic hinge rotation capacity; influence of axial load on the plastic hinge rotation capacity and requirement. Test resulted showed that: (1) if steel shape isn’t bi- symmetrical, the required transverse steel bar is directional when when bending about x-axis and y-axis. (2) the required transverse steel from TW-SRC is too conservative for SRC column. (3) because the required transverse steel from this thesis which considers the symmetry of steel shape, the width of flange, the depth of web and axial load, the required transverse steel bar can reduce to a reasonable range. (4) the required transverse steel of H shape when bending about x-axis which is proper in XH.

Semi-rigid composite connections with precast hollowcore slabs are a newly developed technique with few applications in current construction practice. The research on the structural behaviour of this new type of connection is limited, with no existing method available to predict its important characteristics such as moment and rotation capacities. In this paper, based on the parametric studies of the three-dimensional finite element model and full-scale tests, analytical methods to calculate the moment and rotation capacity of this type of composite joint are proposed. A comparison between the proposed calculation method and the full-scale test results was made, and good agreement was obtained.

This paper is concerned with the behaviour of beam ¿ column connections of steel ¿ concrete composite beams with precast hollow core slabs. Experiments were carried out to investigate the joint rotation characteristics and ultimate moment capacity of these connections. Details of the test specimens, instrumentation, test set-up and test procedures are described. Results obtained for the connection moment capacity, rotation capacity and failure modes are presented. It is found that through proper design and detailing, these simple steel connections display the characteristics of a semi-rigid connection with very little extra cost.

Βασικός σκοπός της παρούσης διατριβής είναι η ανάπτυξη μιας διαδικασίας προσδιορισμού της βέλτιστης στρατηγικής ενίσχυσης ενός υφιστάμενου ανεπαρκούς κτιρίου, αξιοποιώντας τα δεδομένα που προκύπτουν από την αποτίμησή του με χρήση της ανελαστικής στατικής ανάλυσης και συνεκτιμώντας τις καμπύλες που αντιστοιχούν σε εναλλακτικές λύσεις επέμβασης και προσδιορίζονται προσεγγιστικά. Επειδή η καμπύλη αντίστασης του αρχικού φορέα αποτελεί τη σημαντικότερη πληροφορία που αξιολογείται στα πλαίσια της διαδικασίας που αναπτύχθηκε, ένας έμμεσος στόχος της παρούσης διατριβής είναι η αξιολόγηση των προσομοιωμάτων συμπεριφοράς στοιχείων οπλισμένου σκυροδέματος που συμπεριλαμβάνονται στο σχέδιο του Ελληνικού Κανονισμού Επεμβάσεων (ΚΑΝ.ΕΠΕ.), τα οποία χρησιμοποιήθηκαν στα πλαίσια των αναλύσεων που πραγματοποιήθηκαν. Για τις ανάγκες της διερεύνησης των προσομοιώματων του ΚΑΝ.ΕΠΕ. και την ανάπτυξη της μεθόδου επιλογής στρατηγικής επέμβασης διενεργήθηκαν ανελαστικές αναλύσεις σε κτίρια που τα οποία είχαν μορφωθεί και διαστασιολογηθεί με βάση της επικρατούσες πριν το 1985 αντιλήψεις. Στο πρώτο κεφάλαιο της εργασίας γίνεται μια εισαγωγή στο θέμα αποτίμησης και ενίσχυσης υφιστάμενων κατασκευών. Εντοπίζονται οι δυσκολίες και οι απαιτήσεις του προβλήματος της μελέτης υφιστάμενων κτιρίων και σχολιάζονται σύντομα τα υπάρχοντα κανονιστικά σχέδια για την αποτίμηση υφιστάμενων κατασκευών. Στο δεύτερο κεφάλαιο παρουσιάζονται οι μέθοδοι που χρησιμοποιούνται για την αποτίμηση υφιστάμενων κτιρίων. Οι μέθοδοι διακρίνονται σε ελαστικές και ανελαστικές. Η στατική ανελαστική ανάλυση παρουσιάζεται εκτενέστερα, καθώς χρησιμοποιείται για τις αναλύσεις που πραγματοποιούνται. Συγκεκριμένα αναφέρονται οι παραδοχές στις οποίες βασίζεται και παρουσιάζονται τρεις διαφορετικές διαδικασίες για τον προσδιορισμό της στοχευόμενης μετατόπισης. Ιδιαίτερη αναφορά γίνεται στη μέθοδο των ανελαστικών φασμάτων απαίτησης, στην οποία βασίζεται η διαδικασία επιλογής στρατηγικής επέμβασης που αναπτύχθηκε. Το τρίτο κεφάλαιο αφορά τα προσομοιώματα συμπεριφοράς στοιχείων Ο/Σ που χρησιμοποιούνται σε ανελαστικές αναλύσεις. Συγκεκριμένα παρουσιάζεται αναλυτικά το προσομοίωμα του ΚΑΝ.ΕΠΕ. που υιοθετείται στη συνέχεια για τις ανάγκες της προσομοίωσης των κτιρίων που αναλύονται. Σύντομη αναφορά γίνεται και σε άλλα προσομοιώματα, τα οποία προτείνονται σε σχέδια κανονισμών ή ερευνητικές εργασίες. Στο τέταρτο κεφάλαιο εξετάζονται αναλυτικά τα προτεινόμενα από τον ΚΑΝ.ΕΠΕ. προσομοιώματα συμπεριφοράς των δομικών στοιχείων και η χρήση τους για την σεισμική αποτίμηση με χρήση της μη-γραμμικής στατικής ανάλυσης. Οι προτεινόμενες σχέσεις χρησιμοποιούνται για την προσομοίωση των μελών δύο ιδεατών κτιρίων και ενός πραγματικού. Εξετάζονται πιθανές αποκλίσεις μεταξύ των διατιθέμενων σχέσεων, καθώς και η επιρροή διαφορετικών παραδοχών για τις τιμές του μήκους διάτμησης και του ανηγμένου αξονικού φορτίου στα προσδιοριζόμενα μεγέθη. Τέλος ελέγχεται η επίδραση των ίδιων παραμέτρων στην τελική μορφή της καμπύλης τέμνουσας βάσης – μετατόπισης και στα συμπεράσματα της διαδικασίας αποτίμησης. Το πέμπτο κεφάλαιο αναφέρεται στις στρατηγικές ενίσχυσης υφιστάμενων κτιρίων. Συγκεκριμένα αρχικά γίνεται η διάκριση μεταξύ στρατηγικής και τεχνικής επέμβασης. Στη συνέχεια αναφέρονται και σχολιάζονται διαδικασίες για την επιλογή της κατάλληλης στρατηγικής επέμβασης που αναπτύχθηκαν παλαιότερα. Ακολούθως παρουσιάζεται η προτεινόμενη διαδικασία για την επιλογή της κατάλληλης στρατηγικής επέμβασης. Αναφέρονται οι βασικές παραδοχές που λαμβάνονται και τα βήματα υπολογισμών που πραγματοποιούνται. Τέλος η προτεινόμενη διαδικασία εφαρμόζεται σε δύο ιδεατά κτίρια και παρουσιάζονται αναλυτικά τα αποτελέσματα και τα συμπεράσματα που αφορούν τις απαιτούμενες ενισχύσεις στα κτίρια που αναλύονται. Στο έκτο κεφάλαιο επιχειρείται η σύνδεση των εκτιμώμενων καμπυλών συμπεριφοράς για τα ενισχυμένα κτίρια, οι οποίες προκύπτουν από τη διαδικασία επιλογής στρατηγικής επέμβασης που αναπτύχθηκε, με τις απαιτούμενες επεμβάσεις στα μέλη. Σκοπός είναι να προκύψει μια διαδικασία προδιαστασιολόγησης των ενισχύσεων. Ορίζονται αδιάστατες παράμετροι που συσχετίζουν τα χαρακτηριστικά του φορέα με αυτά των μελών. Αναλύονται φορείς που προκύπτουν από υλοποίηση εναλλακτικών ενισχύσεων στα κτίρια στα οποία εφαρμόστηκε η προτεινόμενη διαδικασία και εξετάζεται πως μεταβάλλεται η τιμή των παραμέτρων που ορίστηκαν. Με βάση τα αποτελέσματα των ανελαστικών αναλύσεων και των υπολογισμών που παρουσιάζονται, διατυπώνονται απλοί κανόνες για την αρχική διαστασιολόγηση των επεμβάσεων στα μέλη. Στο τελευταίο κεφάλαιο γίνεται μια προσπάθεια ερμηνείας των αποτελεσμάτων των διερευνήσεων που παρουσιάσθηκαν ώστε να προκύψουν γενικότερα συμπεράσματα για τη διαδικασία επιλογής στρατηγικής επέμβασης που αναπτύχθηκε. Από τη διερεύνηση που πραγματοποιήθηκε προκύπτει πως με χρήση της προτεινόμενης μεθόδου εκτιμώνται με ικανοποιητική ακρίβεια οι καμπύλες συμπεριφοράς των ενισχυμένων κατασκευών για δύο ακραίες περιπτώσεις επέμβασης (αύξηση αντοχής - δυσκαμψίας και αύξηση πλαστιμότητας), η αξιολόγηση των οποίων μπορεί να οδηγήσει σε μια αξιόπιστη επιλογή της βέλτιστης στρατηγικής ενίσχυσης, χωρίς να απαιτούνται εμπειρικού χαρακτήρα εκτιμήσεις. Τέλος είναι δυνατόν να γίνει μια συντηρητική εκτίμηση των απαιτούμενων επεμβάσεων στα μέλη, η οποία κατευθύνει σε μεγάλο βαθμό την τελική επιλογή λύσης.
The main aim of the present thesis is the development of a procedure to determine the optimum retrofit strategy for an existing building, using the results obtained from the assessment of the building via non-linear static analysis and evaluating the capacity curves that correspond to the application of different strengthening solutions for the building under consideration. The latter curves are approximated without further analysis. Because of the significance of the capacity curve of the original building which is taken into consideration in the proposed strategy selection procedure, a second aim of this thesis is the evaluation of the analytical models for the behavior of Reinforced Concrete (R/C) members which are included in the first and second draft versions of the Greek Retrofitting Code (GRECO). These were used to create the numerical models of the buildings that have been analyzed. In order to develop the proposed procedure for the selection of the optimum retrofit strategy, as well as to evaluate the proposed models that are referred above, three buildings have been analyzed via non-linear static analysis (pushover analysis). The dimensioning of members of these buildings complies with the regulatory demands of the prior to 1985 Greek building Codes. In the first chapter of the present thesis, a brief introduction to the topic of assessment and strengthening of existing buildings is conducted. The basic difficulties of the problem of analyzing existing structures are pointed. Finally, draft codes that have been developed for the assessment and rehabilitation of existing buildings are reviewed briefly. In the second chapter, the basic analysis procedures that are used for the assessment of existing buildings are presented. The available procedures are separated into linear and non-linear. Non-linear static (pushover) analysis is presented thoroughly since it is used for the analyses of the buildings referred above. The basic assumptions of this analysis procedure are described as well as three different methods to determine the target displacement (or performance point). The capacity spectrum method is presented in detail, since it is the basis for the development of the proposed strategy selection procedure. The third chapter refers to the analytical models for the behavior of R/C members that are used in non-linear analyses. The models proposed in GRECO, which have been used in terms of the analyses of the buildings that were examined in this thesis, are presented thoroughly. Other models included in draft codes (such as FEMA 356) or proposed by researchers are briefly reviewed. In the fourth chapter, the analytical models for the behavior of R/C members that are included in GRECO are presented in detail. Moreover, the application of the above models in the assessment of existing buildings using pushover analysis is examined. The proposed equations are applied to model the behavior of the members of three buildings, in order to examine whether the use of different equations leads to significantly different results for the inelastic deformation capacities of the members. Furthermore, the impact of different assumptions for parameters, such as the non-constant axial load, to the results of the above equations is discussed. Finally, the effect of the above parameters in the capacity curve of the building, which is being analyzed, is examined. In the fifth chapter, the strategies for the retrofit of existing buildings are discussed. The difference between retrofit techniques and retrofit strategies is stated. Available procedures for the selection of the optimum retrofit strategy are reviewed and commented. Furthermore, the procedure proposed in this thesis is presented. The basic assumptions and the required calculations are stated. Finally, the procedure is applied for the selection of the optimum retrofit strategy of two of the buildings analyzed earlier in the present thesis. The results and main conclusions are referred briefly. In the sixth chapter, the estimated capacity curves of the strengthened buildings, which arise from the strategy selection procedure that has been developed, are correlated with the required rehabilitation measures for the members. The buildings under consideration are analyzed taking into account the application of different rehabilitation scenarios and several parameters such as the strength or ductility of the retrofitted members in regard with that of the entire building are evaluated. Finally a simplified procedure for the estimation of the needed rehabilitation measures for the members in order to achieve the targeted capacity curve for the structure is proposed. In the final chapter, the results concerning the proposed procedure for the estimation of the optimum retrofit strategy for an existing building are reviewed and the main conclusions are presented. The use of the proposed procedure results in the estimation of the capacity curve of the rehabilitated building with acceptable accuracy, considering two “extreme” retrofit scenarios (system strengthening and stiffening or increasing the ductility of the building). The evaluation of these two curves leads to the selection of the optimum retrofit strategy for a building, which usually combines the effects of the above scenarios. Finally, it is possible to estimate the required retrofit measures for the members of the structure under consideration, although the results are conservative and can be used only for the needs of the initial evaluation discussed in this thesis.

碩士
高雄醫學大學
化學系碩士班
92
There are three parts in this research. The first part was to study the cycle performance of LiMn2O4 spinel and its modified cathode materials by the pouch cells. The second part was to study capacity fade of LiMn2O4 spinel and its modified cathode materials by cyclic voltammetry(CV) scan experiments. The third part was to study Mn dissolution from LiMn2O4 spinel and its modified electrodes by rotating ring-disk collection experiments. Results exhibited modifications LiMn2O4 spinel improved capacity fade rate and suppressed the dissolution of the Mn ion, especially in 612(Li1.06Al0.2Mn1.74O4) cathode material sample for cycling and CV tests. In the rotating ring-disk collection experiments, results exhibited most of Mn dissolution occurs charge state. In the tests of all spinel materials, results exhibited small capacity fade rate and suppressed the dissolution of the Mn+2 ion for the 612 spinel cathode material sample.

碩士
大葉大學
機械工程學系碩士班
91
ABSTRACT It is known that the electrorheogical (ER) fluid demonstrates better ER effect in the squeeze mode operation than in shear or flow modes. Hence, this thesis concentrates on the application of the ER fluid contained between rotating circular disks and operated in squeeze mode. When the axial loading or rotating speed of the disks has changed, the torque and axial loading capacity of this ER film damper can be controlled by adjusting the applied electric field. The result of this study can apply to the related research in the smart thrust bearing and transmission clutch. In the theoretical formulation, based on linear assumption, the rotating behavior and the squeezing dynamics of the ER fluid between two circular disks are uncoupled from each other. Therefore, the axial loading capacity and the rotation torque of the circular disks under different rotation speeds, amplitudes and fre- quencies of axial displacement are derived. The loading character- istics of this rotating ER squeeze film damper are also measured using an experimental test rig setup in this study. The measurements in axial loading capacity and rotating torque of the ER squeeze film damper under various operation circumstances verify the accuracy of the theoretical formulation. In addition, the modification on the surface morphology of the rotating electrodes can alter the local distribution of the electric field between them. These could make the suspension particles in the ER fluid aggregate into thicker chain-like structure upon the application of electric field. Thereby the ER effect can be enhanced. Accordingly, three circular electrodes with different surface morphology are studied experimentally. The result suggests the modification on the electrode surface can provide a feasible method for improving the ER effect on this rotating squeeze film damper. It is expected that the results of this study can be applied to the related field in the design of the ER smart bearings. Keywords: electrorheological fluid, squeeze mode, thrust bearing, smart bearing.

碩士
高雄醫學大學
化學系碩士班
90
The major work of the research is divided into two parts .The first part was to study the capacity fading of LiMn2O4 spinel after 20 charge-discharged cycles in comparison with a commercialized LiCoO2. The capacity loss was 14.7% for LiCoO2 and 39.8% for LiMn2O4, respectively. The second part is to study Mn2+ dissolution from LiMn2O4 spinel cathode resulting in capacity fading by rotating ring-disk collection experiments. Results showed that the anodic stripping potential (Mn2+/Mn reduction) is about 1.8V. The quantity of Mn2+ dissoluted from the spinel into the electrolyte solution was increased with the increasing of number of cycles as well as temperature. The Mn+2 leaches into the solution and leads the capacity loss.