Thesis (M.S.)--University of Florida, 2004. / Typescript. Title from title page of source document. Document formatted into pages; contains 35 pages. Includes Vita. Includes bibliographical references.

Doctor of Philosophy / Department of Civil Engineering / Hayder A. Rasheed / The use of carbon fiber reinforced polymer (CFRP) anchors can improve the performance of reinforced concrete (RC) beams strengthened in flexure with CFRP sheets. This improvement results from delaying or controlling the debonding of FRP sheets at failure. In this research, six full-scale T beams and six full-scale rectangular beams are prepared and tested as two separate series. All the specimens are strengthened identically using three layers of unidirectional CFRP sheets and one layer of bidirectional CFRP sheet. The first strengthened beam in each series is anchored with side GFRP bars inserted longitudinally to both sides of the beam. The second strengthened beam in each series is anchored with GFRP patches applied to both sides of the beam. CFRP spike anchors are utilized for the other beams in the two series. The third beam in each series is secured with CFRP spike anchors of 16 mm diameter at 140 mm spacing along the shear span. The fourth strengthened beam in each series is anchored with CFRP spike anchors of 19 mm diameter at 203 mm spacing along the shear span. Four CFRP anchors are applied to each shear span of the fifth beam in each series with 16 mm- diameter (spaced at 406 mm) to secure the flexural CFRP sheets. An end CFRP anchorage technique is considered for the last beam in each series, which includes installing one CFRP spike anchor placed at 76 mm from the free edge of CFRP sheets. The beams were tested under four-point bending until failure and the results for each series are evaluated. In addition, the outcome is compared with other anchorage techniques that have been examined by some researchers utilizing the same beam geometry and properties. The experimental testing and nonlinear analysis showed improvement in the flexural performance of anchored beams compared with those strengthened beams without anchorage. By attaining debonding or rupture failure modes for the T beams and concrete crushing failure mode for the rectangular specimens, the ultimate sectional force capacity is achieved. Accordingly, the results prove that the anchors offer an effective solution against premature debonding failure.

Made available in DSpace on 2014-06-11T19:27:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-08-27Bitstream added on 2014-06-13T20:17:28Z : No. of bitstreams: 1 kina_j_me_araca.pdf: 1193550 bytes, checksum: d217ade36af8adc9e54b137cf2f19928 (MD5) / Introdução: Para a eficiência da ancoragem, diferentes protocolos são preconizados durante a mecânica ortodôntica, principalmente quando se deseja a retração inicial do canino para o alinhamento e nivelamento anterior sem a mesialização do segmento posterior. Nesse contexto, a utilização dos minimplantes tem sido cada vez mais frequente, pois possuem características desejáveis para essa finalidade como a facilidade operacional de sua instalação, dispensa a colaboração do paciente para o desenvolvimento da mecânica ortodôntica,é favorável na estética e permite um sistema de forças mais previsível. O objetivo deste trabalho foi comparar quantitativamente por meio de telerradiografias em norma lateral e radiografias panorâmicas, a taxa de retração inicial de caninos (RIC) superiores, utilizando-se dois sistemas distintos de ancoragem. Métodos: Foram selecionados 18 pacientes, formando dois grupos aleatórios de 9 indivíduos (G1 e G2), triados para tratamento ortodôntico na UNESP - Araçatuba. Como ancoragem foi utilizado minimplantes no grupo G1 e botão de Nance no grupo G2. Para todos os pacientes foram realizadas duas telerradiografias em norma lateral (T1 e T2) e duas panorâmicas (P1 e P2). Para comparação entre as fases Início (antes do tratamento) e Após (após a retração inicial de caninos) foi utilizado o teste t pareado. Para a comparação entre os grupos de minimplante e botão de Nance foi utilizado o teste t de Student para medidas independentes. Em todos os testes foi adotado nível de significância de 5% (p<0,05). Resultados: Para a RIC no Grupo G1, obteve-se uma média de 0,63 mm/mês, enquanto para o grupo G2 a média foi de 0,56 mm/mês. Conclusões: A análise das telerradiografias em norma lateral e das radiografias panorâmicas revelou a inexistência de diferença estatisticamente significante entre os dois grupos. / Introduction: For efficiency of the anchorage, different protocols are recommended during orthodontic mechanics, especially when clinicians want to retract the initial alignment and leveling without the inclination of the posterior segment. In this context, the use of mini-implants has been frequent. For this purpose it has desirable characteristics, such as the operational facility of installation, the collaboration of the patient, exemption for the development of orthodontic mechanics, it is favorable in appearance and allows more predictable system forces. This study compared, by teleradiographs and panoramic radiographs, the initial rate of retraction of canines (ICR), using two different systems of anchoring. Methods: 18 patients were selected and divided in two random groups of 9 subjects (G1 and G2). They needed and were refered to orthodontic treatment at UNESP - Araçatuba. In G1, mini-implants were used as anchor and G2 used the Nance button appliance. Two teleradiographs (T1 and T2) and two panoramic (P1 and P2) were made for all patients. The paired T test was used for comparison between Initial (before treatment) and After (after the initial retraction of canines) phases. Student's t test for independent measures was used for comparison between groups of mini-implants and the Nance button appliance. A significance level of 5% (p <0.05) was adopted in all tests. Results: For G1, an average of 0.63 mm / month was obtained, while for G2, the average was 0.56 mm / month. Conclusions: The analysis of teleradiographs and panoramic radiographs showed the absence of statistically significant difference between the two groups.

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2017. / In South Africa, squid fishing vessels need to find and then anchor above benthic squid egg beds to effect viable catches. However, waves acting on the vessel produce a dynamic response on the anchor line. These oscillatory motions produce impact forces of the chain striking the seabed. It is hypothesised that this causes damage to the squid egg bed beneath the vessels. Different mooring systems may cause more or less damage and this is what is investigated in this research. The effect of vessel mooring lines impact on the seabed during squid fishing is investigated using a specialised hydrodynamic tool commercial package ANSYS AQWA models. This study analysed the single-point versus the two-point mooring system’s impact on the seabed. The ANSYS AQWA models were developed for both mooring systems under the influence of the wave and current loads using the 14 and 22 m vessels anchored with various chain sizes. The effect of various wave conditions was investigated as well as the analysis of three mooring line configurations. The mooring chain contact pressure on the seabed is investigated beyond what is output from ANSYS AQWA using ABAQUS finite element analysis. The real-world velocity of the mooring chain underwater was obtained using video analysis. The ABAQUS model was built by varying chain sizes at different impact velocities. The impact pressure and force due to this velocity was related to mooring line impact velocity on the seabed in ANSYS AQWA. Results show the maximum impact pressure of 191 MPa when the 20 mm diameter chain impacts the seabed at the velocity of 8 m/s from video analysis. It was found that the mooring chain impact pressure on the seabed increased with an increase in the velocity of impact and chain size. The ANSYS AQWA impact pressure on the seabed was found to be 170.86 MPa at the impact velocity of 6.4 m/s. The two-point mooring system was found to double the seabed mooring chain contact length compared to the single-point mooring system. Both mooring systems showed that the 14 m vessel mooring line causes the least seabed footprint compared to the 22 m vessel.

Orientador: Lídia Parsekian Martins / Banca: Dirceu Barnabé Raveli / Banca: Ana Cláudia de Mello / Resumo: O objetivo do presente trabalho foi avaliar in vitro, por meio de um ensaio mecânico, a força necessária para a remoção das bandas ortodônticas Grip Tite (C), Convencional (A) e banda Convencional com a superfície interna microjateada por óxido de alumínio (B). Também analisar visualmente a quantidade de cimento residual, e classificar usando uma escala de incrementos a 25%. Após, verificar, por meio de MEV, a superfície com melhores características para a retenção. Os resultados obtidos mostraram que a média de carga do Grupo B, bandas microjateadas internamente por óxido de alumínio, foi significantemente maior que as médias dos Grupos A, bandas Convencionais, e C, bandas Grip Tite. Quanto a quantidade de cimento remanescente nas bandas, o Grupo B apresentou 100% das bandas com índice 4, indicando a presença de mais de 75% de cimento residual nas bandas, enquanto que nos Grupos A e C, houve a predominância do índice 1, indicativo de menos de 25% de cimento residual nas bandas, sem diferença significativa entre esses dois grupos. Os resultados foram confirmados pela MEV, onde observou-se uma superfície com melhores características para a retenção do cimento nas bandas onde foi realizado o processo de microjateamento. Conclui-se que o processo de microjateamento por óxido de alumínio, na superfície interna das bandas convencionais, aumenta a força necessária para a remoção das bandas e aumenta a quantidade de cimento residual preso à superfície da banda. Quando analisada pela MEV, essa superfície apresenta-se como a mais áspera e rugosa, com a maior quantidade de cimento de ionômero de vidro aderido à banda. / Abstract: The purpose of this study was to evaluate in vitro, the necessary force for the removal of Grip Tite, Conventional and Sandblasted orthodontics molar bands, as well as, to analyze and to classify the amount of residual cement in the internal surface of these bands. After that, checking through scanning electron microscopy, the surface with better characteristics for the retention. The obtained results showed that the load average of the group B, Sandblasted bands, was significantly higher than the group A, Conventional bands, and C, Grip Tite bands. Observing the amount of remaining cement in the bands, group B presented 100% of the bands with index 4, indicating the presence of more than 75% of residual cement in the bands, while in the groups A and C, had the predominance of index 1, indicative of less than 25% of residual cement in the bands, without significant difference between these two groups. The results were confirmed by the scanning electronic microscopy, where the surface with better characteristics for the retention of the cement was observed, in the bands where the sandblasted process was carried through. It was concluded that the process of sandblasted, in the internal surface of the conventional bands, increases the necessary force for the removal of the bands and increases the amount of residual cement in the internal surface of the band. When analyzed by the scanning electronic microscopy, this surface appeared rougher and corrugated, with great amount of glass ionomer cement adhered to the band. / Mestre

Orientador: Armando Lopes Moreno Junior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenhaira Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-05T00:18:16Z (GMT). No. of bitstreams: 1 Tramontin_AndrePenteado_M.pdf: 3029877 bytes, checksum: d1ddf2e0086571a9cb41c8abef993f75 (MD5) Previous issue date: 2005 / Resumo: As fissuras na interface alvenaria-estrutura são comuns e pouco se conhece a respeito da sua ocorrência, embora sejam freqüentes, especialmente as que aparecem na ligação alvenaria-pilar de concreto. O objetivo deste trabalho foi estudar a melhor técnica de ancoragem entre alvenaria-estrutura, avaliando sua eficiência no combate a esse tipo de fissura. Foram utilizados para a elaboração dos ensaios, além dos materiais usados na alvenaria de vedação (bloco cerâmico, argamassa etc), diferentes materiais de ancoragem (tela metálica eletrosoldada e barras de aço) e dispositivos de ligação (adesivo epóxi, pinos, arruelas e cantoneira), analisando-se assim o melhor conjunto do ponto de vista técnico. Foram feitos ensaios de caracterização dos materiais e de arrancamento à tração direta, até a ocorrência da primeira fissura visível a olho nu. Concluiu-se finalmente que a tela metálica eletrosoldada galvanizada malha 15 x 15 mm e diâmetro do fio 1,65 mm, sem cantoneira e com tratamento de chapisco com adesivo acrílico no pilarete foi a melhor técnica de ancoragem para a prevenção do aparecimento de fissuras na interface alvenaria de vedação e pilar de concreto / Abstract: The splitting of the fair-faced masonry-structure are very usual but it is not wellknown the reason of its occurrence, although they are frequent, specially the ones that appear in the linking of the masonry-concrete column. The purpouse of this work was to study the best anchorage technique between masonrystructure, being evaluated its efficiency to prevent this type of splitting. Beyond the materials that are usually used for masonry (ceramic block, mortar etc), changeable materials of anchorage (stell welded tie and steel wire) and apparatus of linking (adhesive epoxy, bolts, washers and angle-steel) were used, analyzing the best combination for the technical view. Tests of characterization of the materials and the pullout test were made, until the occurrence of the first splitting visible by naked eye. Finally, it was concluded that the metallic wall tie, 15 x 15 mm and the diameter of wire 1,65 mm, without angle-steel and with mortar with acrylic adhesive in the concrete column was the best anchorage technique for to prevent occurrence of splitting in the fair-faced masonry-concrete structure / Mestrado / Edificações / Mestre em Engenharia Civil

Um efeito colateral indesejável do uso do aparelho de Herbst é a vestibularização excessiva dos incisivos inferiores que pode estar relacionada à retração gengival, à perda óssea marginal e à reabsorção radicular. A ancoragem esquelética do aparelho de Herbst poderia evitar estes problemas. O objetivo do presente estudo foi o de avaliar, em Minipigs br1, a resistência à flexão de protótipos de mini-implantes desenvolvidos para ancoragem do aparelho de Herbst, comparar a resistência dos protótipos entre as duas regiões escolhidas para inserção e avaliar se os protótipos de mini-implantes seriam capazes de suportar forças ortopédicas. Após o cálculo do tamanho da amostra, 13 protótipos de mini-implantes foram colocados nas regiões posterior da maxila e anterior da mandíbula de três Minipigs br1, após terem sido mortos. Corpos de prova contendo os protótipos de mini-implantes inseridos em osso foram submetidos a uma força de flexão por engastamento simples utilizandose uma máquina universal de ensaios mecânicos Instron, calculando-se a média e o desvio padrão para cada região. Com o objetivo de comparar a resistência dos protótipos entre as regiões de inserção foi utilizado o Teste t de Student para duas amostras não pareadas. O teste de hipótese foi realizado para cada região para avaliar se os protótipos de mini-implantes seriam capazes de suportar forças ortopédicas. Para fins de comparação foram consideradas forças ortopédicas acima de 1,0 kgf. O nível de significância adotado foi P < 0,05. Os protótipos de miniimplantes apresentaram resistência à força de flexão de 13,86 kgf (DP = 2,3) para a região posterior da maxila e 20,55 kgf (DP = 5,2) para a região anterior da mandíbula. Houve diferença estatisticamente significativa entre as duas regiões com relação à força de resistência dos mini-implantes (P = 0,015), sendo que a resistência maior foi na região anterior da mandíbula. A hipótese de que os protótipos de mini-implantes seriam capazes de suportar forças ortopédicas foi confirmada para as regiões posterior da maxila e anterior da mandíbula. Os autores concluíram que, em Minipigs br1, os protótipos de mini-implantes desenvolvidos para a ancoragem do aparelho de Herbst foram capazes de resistir a forças entre 13,86 e 20,55 kgf, sendo estatisticamente mais resistentes na região anterior da mandíbula e capazes de suportar forças ortopédicas. / An undesirable tooth movement resulting from use of the Herbst appliance is the excessive proclination of the anterior mandibular teeth, which is commonly associated with gingival recession, marginal bone loss, and root resorption. Skeletal anchorage of the Herbst appliance could prevent these problems. The present study was designed to evaluate, in Minipigs br1, the flexure resistance of prototype miniimplants developed for Herbst appliance anchorage, to compare the prototype resistance between the regions in which the mini-implants were placed, and to test the hypothesis that these mini-implant prototypes can withstand orthopedic forces. After calculation of sample size, 13 mini-implant prototypes (2 mm in diameter x 10 mm long) were inserted in the posterior region of the maxilla and the anterior region of the mandible, in three recently killed minipigs. The specimens were submitted to a single cantilever flexure test using an Instron testing machine. Mean and standard deviation were calculated for each region. To compare the resistance of the prototypes between the sites of mini-implant insertion, a 2-Sample Students t test was calculated. The test was carried out individually for each region, to evaluate if the prototype mini-implants developed for Herbst appliance anchorage could withstand orthopedic forces. Orthopedic forces above 1.0 kgf were considered. The level of significance was set at P < 0.05. The prototype mini-implant showed a flexure strength of 13.86 kgf (SD = 2.3) for the posterior region of the maxilla, and 20.55 kgf (SD = 5.2) for the anterior region of the mandible. A significant statistically difference was found in the resistance of the prototypes between the two regions (P = 0.015). The hypothesis that the prototype mini-implants can withstand orthopedic forces was confirmed. The authors concluded that, in Minipigs br1, the prototype mini-implants developed for Herbst appliance anchorage could resist forces from 13.86 to 20.55 kgf, were statistically more resistant in the anterior region of the mandible, and were capable of withstanding orthopedic forces.

No description available.

Linear and nonlinear finite element analyses are used for the investigation of rectangular anchorage zones with the presence of a support reaction. The investigation is conducted based on four load configurations consisting of concentric, inclined concentric, eccentric, and inclined eccentric loads. The method of model construction is illustrated thoroughly. The influence of several parameters, including anchorage ratio, inclination of prestressing load, eccentricity, magnitude of the reaction force, bearing plate ratio, and the location of the reaction force, is studied. Both graphical and numerical presentations of the results from each load configuration are given. Improved equations, which are modified from the equations presented in the AASHTO Standard Specifications (2002), are proposed. The results from the equations are compared to those from the finite element method. Nonlinear finite element analysis is used to verify the applicability of the equations and to study a new bursting steel arrangement. Linear and nonlinear finite element analyses are also used for the study of non-rectangular anchorage zones. Four basic load configurations, including concentric, eccentric, inclined concentric, and inclined eccentric loads, are investigated. The shell element is selected for the construction of the finite element models. Several parameters, consisting of anchorage ratio, inclination of prestressing load, eccentricity, web thickness, ratio of web thickness to flange thickness, and flange width, are chosen for parametric studies. The results from the studies are presented graphically and numerically. Equations to calculate the bursting force and location of the force are developed from the Strut-and-Tie Model approach. The verification of the formulations and the investigation of bursting steel arrangement are conducted using nonlinear finite element analysis. / Ph. D.

Precast/Prestressed concrete girders are commonly used in bridge construction in the United States. The application and diffusion of the prestress force in a pretensioned girder causes a vertical tension force to develop near the end of the beam. Field surveys of the beam ends of pretensioned bridge girders indicate that many of the PCBT beams used in the Commonwealth of Virginia develop cracks within the anchorage zone region. The lengths and widths of these cracks range from acceptable to poor and in need of repair. Field observations also indicate deeper cross sections, very heavily prestressed sections, and girders with lightweight concrete tend to be most susceptible to crack formation. This research examined a new strut-and-tie based design approach to the anchorage zone design of the PCBT bridge girders used in Virginia. Case study girders surveyed during site visits are discussed and used to illustrate the nature of the problem and support the calibration of the strut-and-tie based model. A parametric study was conducted using this proposed design model and the results of this study were consolidated into anchorage zone design tables. The results of the parametric study were compared to the results obtained using existing anchorage zone design models, international bridge codes, and standard anchorage zone details used by other states. A set of new standard details was developed for the PCBT girders which incorporates elements of the new design approach and is compatible with the anchorage zone design aids. A 65 ft PCBT-53 girder was fabricated to verify the new strut-and-tie based design model. This girder contained anchorage zone details designed with the new model. The new anchorage zone details were successful at controlling the development of anchorage zone cracks. The new design approach is recommended for implementation by the Virginia Department of Transportation. / Master of Science