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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
201

A scaled physical model for underwater sound radiation from a partially submerged cylindrical shell under impact

Woolfe, Katherine 06 July 2012 (has links)
The motivation for this study is to create a scaled laboratory model of a steel construction pile being driven by an impact hammer, which can provide controlled data to aid understanding and development of a structural acoustics numerical model simulating full-scale impact pile driving. The scaled model is approximately thirty times shorter than a typical 30-meter long Cast-in-Shell-Steel (CISS) pile. The relationship between the impact force, structural vibrations, and radiated sound field is analyzed. The time-domain acoustic intensity in the radial direction is found to be predominately negative immediately following excitation by the impact force. Analysis of the radial intensity shows that during the hammer strike, there is a net flow of energy from the structure into the water; however, because the structure and water are acoustically coupled a significant portion of the energy immediately flows back into the cylinder following hammer impact. This fluid-structure interaction results in a highly damped acoustic pulse in the water that propagates to the far field. In addition, the frequency spectra of the impact force, model pile wall acceleration in the radial direction in air and water, and underwater acoustic pressure are analyzed to find transfer functions between these variables. The transfer function between impact force and sound pressure is of particular interest because it can be used to calculate the system response for any other applied hammer force. This transfer function analysis has potential applications in mitigating noise generated by impact pile driving.
202

Sistemas de terminação de cordeiros do grupo genético pantaneiro / Finishing systems of lambs pantaneiro genetic group

Villafuerte, Sergio Giovanni Espinosa 08 March 2016 (has links)
Submitted by Cássia Santos (cassia.bcufg@gmail.com) on 2016-06-29T15:20:33Z No. of bitstreams: 2 Dissertação - Sergio Giovanni Espinosa Villafuerte - 2016.pdf: 5665796 bytes, checksum: 265521cbc03e90b213938b3b6896dc46 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-06-30T11:14:18Z (GMT) No. of bitstreams: 2 Dissertação - Sergio Giovanni Espinosa Villafuerte - 2016.pdf: 5665796 bytes, checksum: 265521cbc03e90b213938b3b6896dc46 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2016-06-30T11:14:18Z (GMT). No. of bitstreams: 2 Dissertação - Sergio Giovanni Espinosa Villafuerte - 2016.pdf: 5665796 bytes, checksum: 265521cbc03e90b213938b3b6896dc46 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-03-08 / Pantaneiro genetic sheep group are native to the Pantanal Biome, in the Midwest region of Brazil, which is characterized by the production of meat. They are usually created under pasture, and the lambs usually finished in confinement. But should be considered sustainable and intensive finishing systems, adapted to the region. The aim of this study was to evaluate four finishing systems, including the productive performance and economic results as profitability indicators. Were used 54 lambs, 24 males and 30 females, wormed at weaning, with initial weight of 16.70 kg, with a mean age of 74 ± 9 days. Finishing systems were; Feedlot with corn silage (Zea mays) (CS) as roughage; Feedlot with mix corn silage and Pigeon pea (Cajanus cajan cv Mandarin) as roughage (CPS); Integration Crop-Livestock (ICL) grazing Brachiaria brizantha cv. BRS Piatã grass with Pigeon pea (Cajanus cajan cv Mandarin) in succession to mixed cultivation; stockpiled pasture (SP) with Brachiaria brizantha cv. BRS Piatã grass. All treatments the animals received energy-protein concentrate supplementation (16% CP and 82% TDN) equivalent to 2% of body weight. The experimental design was completely randomized in a factorial design, with four finishing systems and two sexes. The variables were final weight (FW) and average daily gain (ADG), and economic evaluation. Finishing systems under CS and ICL, obtained better productive performance not differing significantly from the CPS, which in turn did not differ statistically from SP. However, the economic evaluation demonstrated that the ICL and CPS systems were more profitable in finishing lambs. The pasture system formed in Integration Crop-Livestock with supplement of 2% of body weight, proved to be the most appropriate for the Midwest region in the finishing of Pantaneiro lambs in the dry season. / Ovinos Pantaneiros são nativos do Bioma Pantanal, na região Centro Oeste do Brasil, que tem como característica a produção de carne. Normalmente são criados em pastagens, sendo os cordeiros terminados geralmente no confinamento. Porém deve-se considerar sistemas de terminação sustentáveis e intensivos, adaptados a região. Neste sentido foram avaliados quatro sistemas de terminação, incluindo o desempenho produtivo e a eficiência econômica e indicadores de rentabilidade. Foram utilizados 54 cordeiros, 24 machos e 30 fêmeas, desverminados no desmame, com peso inicial de 16,70 kg, com idade média de 74±9 dias. Os sistemas de terminação avaliados foram o confinamento a base de volumoso de silagem de milho (Zea mays) (M); confinamento a base de volumoso de silagem de milho mais guandú (Cajanus cajan cv Mandarim) (MG); Integração Lavoura Pecuária (ILP) pastejo em Brachiaria brizantha cv. BRS Piatã mais guandú (Cajanus cajan cv Mandarim) em sucessão ao cultivo consorciado; pasto vedado (V) com Brachiaria brizantha cv. BRS Piatã. Em todos tratamentos os animais receberam suplementação de concentrado energético-proteico (16% PB e 82% NDT) equivalente a 2% do peso vivo. O delineamento experimental utilizado foi o inteiramente casualizado em esquema fatorial, sendo 4 sistemas de terminação e 2 sexos. As variáveis avaliadas foram, peso final (PVF) e ganho de peso médio diário (GMD), e a projeção econômica. Os sistemas de terminação sob M e ILP, obtiveram melhores desempenhos produtivos, não diferindo significativamente do MG, que por sua vez não diferiu estatisticamente do V. No entanto, na avaliação econômica ficou demonstrado que os sistemas ILP e MG foram mais rentáveis na terminação de cordeiros. O sistema a pasto formado em Integração Lavoura-Pecuária, com suplementação correspondente a 2% do peso corporal, mostrou-se o mais indicado para a região Centro-Oeste na terminação de cordeiros Pantaneiros no período seco.
203

Estimation of Pile Capacity by Optimizing Dynamic Pile Driving Formulae

Rauf, Awais January 2012 (has links)
Piles have been used since prehistoric times in areas with weak subsurface conditions either to reinforce existing ground, create new ground for habitation or trade, and support bridges and buildings. Originally piles were composed of timber and driven with drop hammers using very heavy ram weights. As technology improved so did the materials that piles are composed of as well as the equipment itself. Currently, piling is a multibillion dollar a year industry, thus the need to develop more accurate prediction methods can potentially represent a significant savings in cost, material, and man power. Multiple predictive methods have been developed to estimate developed pile capacity. These range from static theoretical formulae based on geotechnical investigation prior to pile driving even occurring using specific pile and hammer types to semi empirically based dynamic formulae used during actual driving operations to more recently developed computer modeling and signal matching programs which are calibrated with site condition during initial geotechnical investigations or test piling to full scale static load tests where piles are loaded to some predetermined value or failure condition. In this thesis, dynamic formulae are used to predict pile capacity from those installed by drop and diesel hammers and are compared to the results from pile load tests, which are taken as the true measure of developed bearing capacity. The dynamic formulae examined are the Engineering News Record (ENR), Gates, Federal Highway Administration (FHWA) modified Gates, Hiley, and Ontario Ministry of Transportation (MTO) modified Hiley formulae. Methods of investigation include calculating pile capacities from the formulae as they are, omitting the factors of safety, revising the formulae with averaged coefficients and conducting multi regression analysis to solve for one or two coefficients simultaneously and revising the dynamic formula to determine if more accurate bearing capacity prediction are possible. To objectively determine which formulae provide the most accurate bearing capacities, the predicted capacities will be compared to results obtained from static pile load tests and simple statistics on the resulting data set will be calculated including regression analysis, standard deviations, coefficients of variation, coefficients of determination, and correlation values.
204

Estimation of Pile Capacity by Optimizing Dynamic Pile Driving Formulae

Rauf, Awais January 2012 (has links)
Piles have been used since prehistoric times in areas with weak subsurface conditions either to reinforce existing ground, create new ground for habitation or trade, and support bridges and buildings. Originally piles were composed of timber and driven with drop hammers using very heavy ram weights. As technology improved so did the materials that piles are composed of as well as the equipment itself. Currently, piling is a multibillion dollar a year industry, thus the need to develop more accurate prediction methods can potentially represent a significant savings in cost, material, and man power. Multiple predictive methods have been developed to estimate developed pile capacity. These range from static theoretical formulae based on geotechnical investigation prior to pile driving even occurring using specific pile and hammer types to semi empirically based dynamic formulae used during actual driving operations to more recently developed computer modeling and signal matching programs which are calibrated with site condition during initial geotechnical investigations or test piling to full scale static load tests where piles are loaded to some predetermined value or failure condition. In this thesis, dynamic formulae are used to predict pile capacity from those installed by drop and diesel hammers and are compared to the results from pile load tests, which are taken as the true measure of developed bearing capacity. The dynamic formulae examined are the Engineering News Record (ENR), Gates, Federal Highway Administration (FHWA) modified Gates, Hiley, and Ontario Ministry of Transportation (MTO) modified Hiley formulae. Methods of investigation include calculating pile capacities from the formulae as they are, omitting the factors of safety, revising the formulae with averaged coefficients and conducting multi regression analysis to solve for one or two coefficients simultaneously and revising the dynamic formula to determine if more accurate bearing capacity prediction are possible. To objectively determine which formulae provide the most accurate bearing capacities, the predicted capacities will be compared to results obtained from static pile load tests and simple statistics on the resulting data set will be calculated including regression analysis, standard deviations, coefficients of variation, coefficients of determination, and correlation values.
205

Calibration of deterministic parameters for reassessment of offshore platforms in the Arabian Gulf using reliability-based method

Zaghloul, Hassan January 2009 (has links)
[Truncated abstract] The Arabian Gulf oil and gas production reserves have made it one of the world's strategic producers since early 1960s, with many of the existing platforms stretched beyond their original design life. Advances in drilling technology and reservoir assessments have extended the requirement for the service life of those existing platforms even further. Extension of the life span of an existing platform requires satisfactory reassessment of its various structural components, including piled foundations. The American Petroleum Institute Recommended Practice 2A (API RP2A) is commonly used in the Arabian Gulf for reassessment of existing platforms. The API guidelines have been developed for conditions in the Gulf of Mexico, the waters off Alaska and the Pacific and Atlantic seaboards of the USA. However, the Arabian Gulf conditions are fundamentally different to those encountered in US waters. Hence, there is a need to develop guidelines for reassessment of existing offshore structures to account for the specific conditions of the Arabian Gulf. This thesis performs statistical analyses on databases collected during this research from existing platforms to calibrate relevant load and resistance factors for the required guidelines. The developed guidelines are based on established approaches used in developing international codes and standards such as API RP2A-LRFD. The outcome of this research revolves around the following three main issues: 1. Calibration of resistance factors for axial capacity of piles driven in the carbonate soils API RP2A (1993, 2000) does not quantify limiting soil parameters for piles driven in carbonate soils and provides a single factor to predict the capacity of piled foundations. This research identifies a set of limiting engineering parameters and calibrates corresponding capacity reduction factors to predict axial capacity of driven piles in the carbonate soils of the Arabian Gulf. ... This contrasts with Section 'R' of API RP2A (1993, 2000), which focuses on extreme environmental conditions when performing reassessment. The probabilities of failure considered in this research do not include errors and omissions (controlled by quality assurance procedures) or material deterioration (controlled by choice of materials, detailing, protective devices, and inspection and repair procedures) or reliability-based maintenance. Addressing operating overload conditions requires attending to two issues, namely the capacity of piles driven in carbonate soils and OALL, which have been addressed in this research. The operational overload situation is likely to occur during shutdown condition or during drilling or work over activities where significant OALL are usually applied to platform decks. Such operational overload can be managed by placing signs at various open areas on the platform nominating the maximum load limits (kPa), introducing procedures that ensure that maximum load limits are not exceeded during operation and management of human behavior by reinforcing the importance of following the procedures. The outcomes of this research are expected to have a profound influence on reassessment of existing platforms in the Arabian Gulf.
206

Modelling multi-directional behaviour of piles using energy principles

Levy, Nina Hannah January 2007 (has links)
The loads applied to pile foundations installed offshore vary greatly from those encountered onshore, with more substantial lateral and torsional loads. For combined axial and lateral loading the current design practice involves applying an axial load to a deep foundation and assessing the pile behaviour and then considering a lateral load separately. For the problem of an altering directions of lateral loads (e.g. due to changes in the wind directions acting on offshore wind turbines) a clear design procedure is not available. There is thus a need for a clearly established methodology to effectively introduce the interaction between the four different loading directions (two lateral, one axial and one torsional). In this thesis, a model is presented that introduces a series of Winkler elasto-plastic elements coupled between the different directions via local interaction yield surfaces along the pile. The energy based method that is used allows the soil-pile system to be defined explicitly using two equations: the energy potential and the dissipation potential. One of the most interesting applications of this model is to piles subjected to a change in lateral loading direction, where the loading history can significantly influence the pile behaviour. This effect was verified by a series of experimental tests, undertaken using the Geotechnical Centrifuge at UWA. The same theory was then applied to cyclic loading in two dimensions, leading to some very useful conclusions regarding shakedown behaviour. A theoretically based relationship was applied to the local yielding behaviour for a pile subjected to a combination of lateral and axial loading, allowing predictions to be made of the influence of load inclination on the pile behaviour. The ability of this model to represent interaction between four degrees of freedom allows a more realistic approach to be taken to this problem than that considered in current design practice.
207

Estudo da interação solo-estaca sujeito a carregamento horizontal em ambientes submersos

Christan, Priscila de 21 December 2012 (has links)
Este trabalho tem por objetivo fazer um estudo da interação solo-estaca em ambientes submersos. Para as análises foram utilizadas as seguintes condições: dois tipos de estacas, concreto e mista (tubo metálico preenchido com concreto); quatro condições para o solo (arenoso, coesivo e dois solos estratificados); dois casos de carregamento (caso I com cargas vertical, horizontal e momento e caso II somente carga horizontal e momento). Os modelos de cálculo foram gerados no programa SAP2000, sendo a estaca modelada como elemento de barra e solo representado por molas linearmente elásticas espaçadas a cada metro, baseado no modelo de Winkler. Os coeficientes de mola (Ki) foram calculados por três métodos, Terzaghi, Bowles e com equações que correlacionam às propriedades elásticas do solo. Para o solo arenoso, o método escolhido para a aplicação nos modelos de cálculo foi o de Bowles, e para o solo coesivo a equação proposta por Vesic, que correlaciona os valores de Ki com as propriedades elásticas do solo. Os resultados dos modelos de cálculo do SAP2000 mostraram que: as estacas utilizadas nas análises apresentaram o comportamento de estacas flexíveis, no qual tem os seus deslocamentos ocasionados devidos a flexão; a região que mostra o comportamento relevante da estaca, para o solo arenoso e coesivo, está de acordo com as conclusões indicadas pelos pesquisadores Matlock & Reese (1960) e Davisson & Gill (1963); a atuação da carga vertical não exerce influência nos resultados referentes ao comportamento horizontal da estaca; a estaca mista, em função da maior rigidez a flexão (EI), transfere uma tensão menor para o solo que a estaca de concreto. Os resultados dos modelos de cálculo do SAP2000, para os máximos deslocamentos horizontais e momentos fletores, ficaram muito próximos do valores obtidos com o método de Navdocks DM-7 para o solo arenoso. Já para solo coesivo os resultados ficaram próximos dos valores obtidos pelo método clássico da equação diferencial. / This work aims to make a study of the soil-pile interaction in submerged environments. For the analysis we used the following conditions: two types of piles, concrete pile and composite pile (steel pipe filled with concrete), four conditions for the soil (sandy, cohesive and two stratified soil), two load cases (case I with vertical and horizontal loads and moment, case II with horizontal load and moment). The calculation models were generated in the software SAP2000. The pile was modeled as a bar element and the soil represented by linearly elastic springs spaced each meter, based on the model of Winkler. The spring coefficients (Ki) were calculated by three methods, Terzaghi, Bowles and equations that correlates to the elastic properties of the soil. For the sandy soil, the method chosen for applying the model calculations was the Bowles, and for the cohesive soil the equation proposed by Vesic, which correlates with Ki values of the elastic properties of the soil. The results of the model calculations (SAP2000) show that: the piles used in the analysis presented flexible behavior, which have their displacements caused due to bending, the region that shows the relevant behavior of the piles for the sandy and cohesive soil agrees with the conclusions stated by researchers Matlock & Reese (1960) and Davisson & Gill (1963), the performance of vertical load does not influence the results concerning the horizontal behavior of the pile; the composite pile, due to the higher stiffness bending (EI), transfers a lower stress to the soil than a concrete pile. The model calculations results of SAP2000 to the maximum horizontal displacement and bending moments were very close to the values obtained with the method of Navdocks DM-7 to the sandy soil. However, the results for the cohesive soil were close to the values obtained by the classical method of the differential equation.
208

Design method for axially loaded piled raft foundation with fully mobilised friction piles

Ayfan, Emad 16 November 2012 (has links)
In the present work, a settlement-based method is proposed to design piled raft foundation. The proposed design method is found to be very efficient, economical and requires less calculation time. Simple software can be used to execute all the interactions and loop calculations.<p>Unlike methods with numerical techniques, there are practically no limitations for the number of individual piles under the raft, size of the group and the group shape or layout. It can also be applied to piles with different length or piles that are located within multi-layered soils.<p>The raft is designed first according to the allowable settlement that is pre-defined by the structural requirements and with the necessary factor of safety. When raft suffers excessive settlement, then the load that causes excess raft settlement beyond the required limit is to be transferred to the fully mobilised frictional piles. <p>The fully mobilised shaft (with no end bearing) piles are designed with factor of safety close to unity since their function is only to reduce raft settlement and since the raft has an adequate bearing capacity.<p>Geometry of these piles is chosen to fully mobilise their shafts capacity with low settlement level in order to comply with load/settlement requirement and reduce raft settlement to the pre-defined level. <p> / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished
209

Comportamento de estacas Mega de concreto, implantadas em solo colapsivel / Behavior of concrete "mega" piles, installed in collapsible soil

Donadon, Emanuelle Fazendeiro 14 August 2018 (has links)
Orientador: Claudio Vidrih Ferreira / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-14T15:24:59Z (GMT). No. of bitstreams: 1 Donadon_EmanuelleFazendeiro_M.pdf: 6376843 bytes, checksum: a721bbfe8b90f930873fde3fdf8d5cfe (MD5) Previous issue date: 2009 / Resumo: São muito comuns os casos de obras que tem problemas de fundações devidos ao colapso do solo e, em sua grande maioria, essas obras têm como correção o reforço de fundações com estacas "Mega" de concreto que, apesar da grande utilização, ainda existem poucos estudos sobre este tipo de estaca. Com o objetivo adicionar parâmetros ao meio técnico sobre este tipo de fundação e sobre a influência do colapso do solo em sua capacidade de carga, foi feito provas de carga em estacas "Mega" de concreto com comprimentos de 6 e 8 metros, em solo com umidade natural e pré-inundado. Com os resultados obtidos foi possível verificar que a perda na capacidade de carga neste tipo de estaca é significativa e deve ser considerada quando utilizada em solos colapsíveis. / Abstract: There are very common cases of works that have problems due to the collapse of foundations and soil, and in the most of the works, the solution applied is the underpinning with Mega piles of concrete that, despite the wide use, there are few studies on this type of foundation. With the aim of add parameters to the technical means about this type of foundation and the influence of the collapse of the soil in its load capacity, load tests were performed on concrete Mega piles with lengths of 6 and 8 meters, in soil with natural moisture and pre-flooded. With the results it was possible to verify that the decrease in the load capacity in this type of foundations is significant and should be considered when used in collapsible soils. / Mestrado / Geotecnia / Mestre em Engenharia Civil
210

A Parabolic Equation Analysis of the Underwater Noise Radiated by Impact Pile Driving

Laws, Nathan 05 July 2013 (has links)
Impact pile driving can produce extremely high underwater sound levels, which are of increasing environmental concern due to their deleterious effects on marine wildlife. Prediction of underwater sound levels is important to the assessment and mitigation of the environmental impacts caused by pile driving. Current prediction methods are limited and do not account for the dynamic pile driving source, inhomogeneities in bathymetry and sediment, or physics-based sound wave propagation. In this thesis, a computational model is presented that analyzes and predicts the underwater noise radiated by pile driving and is suitable for shallow, inhomogeneous environments and long propagation ranges. The computational model uses dynamic source models from recent developments in the technical literature. Pile source models are coupled to a broadband application of the range-dependent acoustic model (RAMPE), a standard parabolic equation (PE) propagation code capable of modeling wave propagation through complex, range dependent environments. Simulation results are shown to be in good agreement with several observations of pile driving operations in the Columbia River between Portland, Oregon and Vancouver, Washington. The model is further applied to extend sound level predictions over the entire river and study the effects of sediment and bathymetry on the underwater sound levels present in the environment.

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