The purpose of this study is to investigate the hydrodynamic properties of an oyster floating raft system under environmental loadings. The floating raft system is an important facility for raising oyster in the near shore area of Tainan, Taiwan. The reasons for this kind of oyster culture being main income source for local fish farmers are as the following features: (1) low cost for the farming system, (2) easily to be installed in the field, and (3) easily to be harvested. Due to the raft structure could not withstand the impact of heavy storms; most of the oyster rafts are towed into harbor to avoid damage before the onset of typhoon. Since some unexpected violent sea states may occur and severely affect the integrity of raft system, the investigation of the hydrodynamic properties of a floating raft system is essential for oyster culture in the open sea. This study includes two parts: numerical simulation and physical modeling. In numerical simulation, a lumped mass method with a Morison type of relative motion equation are adopted to calculate the drag and inertial forces on raft components and then are equally divided to the associated nodes to form a system of motion equations based on Newton¡¦s second law. Through the fourth-order Runge-Kutta method, the dynamic performance of the oyster raft system can be obtained. To verify the numerical model, a physical model was carried out in a wave tank (35x1x1.2 m), and the results of dynamic performance of numerical model show good agreement with measurements. A case study of an in situ oyster farming system located near-shore of Tainan region is analyzed by the developed numerical model to investigate the maximum mooring tension, the optimal gap between rafts, and the required length of mooring line. These specifications are crucial to the shell fish farmers for their floating raft system to be survived in the strong currents and waves. The results showed that the optimum configuration for a raft system generated the lowest mooring tension is as the follows: the space between oyster rafts is about a length of oyster raft; the length of mooring line is three times of the water depth, which is consistent with the present practice of shell fish farmers adopting 3~4 times of water depth; the appropriate embedment anchor weight is 70 kg but the anchorage should be the type used by the farmers in Penghu county. Finally, this work intends to offer a guideline for the installation of oyster raft systems in the field, and anticipate minimizing the damage during the unexpected heavy sea states.

There are four types of oyster aquaculture such as oyster plug rod, horizontal hanging scaffold, pontoon-style longline, and floating raft system. This study is to investigate the mooring tension of an oyster floating raft system under environmental loadings. According to the hydrodynamic experimental test, the horizontal fluid velocity has a retarded phenomenon when encountering the front part of structure, and then gradually reduces to a stable situation after the second floating rod. The phenomenon is identified as shielding effect for the raft system and has been used as a shielding coefficient to modify the fluid velocity in the computation program. The dynamic analysis of floating raft system under random wave interaction is investigated numerically and experimentally. The lumped mass method is applied to divide the structure into many nodes and elements. A modified Morison equation dealing with moving structure components is used to calculate the environmental forces on the elements. Further, the forces on elements are divided equally into neighboring nodes to form the equation of motion based on Newton¡¦s second law. Finally, the 4th-order Runge-Kutta (RK4) method is used as a time marching scheme to predict the displacement and velocity of nodes for the next time step. The results of time series and spectrum analysis of mooring tension show good agreement between numerical predictions and experimental data. This paper has further expanded to predict the field oyster raft system in an open sea, and offers some useful information to the oyster farmers in terms of improving the structure safety.

Offshore culture becomes the most attractive industry in last decades because of overfishing and excessively pumping groundwater causing land subsidence social problems. Oyster culture is one of offshore culture with several advantages such as easy set-up and without feeding cost. In this study, we focus on a longline-style oyster aquaculture system because it is recyclable, high growing efficiency and advanced technique against traditional tidal flat culture. This study establishes a numerical model through a lumped mass method, then employs fourth order Runge-Kutta method to solve the system of motion equations and evaluates the tension on the anchor rope. The results show the discrepancy between the numerical model and experimental data is lower than 4% in current-only situation, and similarly in wave-only situation the discrepancy is lower than 6%. The comparison results indicate that the numerical model is capable to predict the environmental loadings on longline-style oyster culture system. An in-situ case study of a longline-style oyster aquaculture system via regular and random waves, located in the Penghu Bay, is investigated based on the sea-state, Chebi Typhoon occurred in June, 2001, causing a catastrophic damage to the cage aquaculture. The conclusions of dynamic responses of the case study may be utilized as guidance for the local oyster farmers to build and protect their oyster culture system in the Bay.

The purpose of this study is improve the cage net volume deformation during typhoon attacking. A special bottom collar system is to substitute the sinkers system. The Research contents include the numerical development and the hydrodynamic physical model test in a wave tank. The numerical model is based on the lumped mass method to set up the equation of motion of the whole cage net system; meanwhile the solutions of equation have been solved through the Runge-Kutta fifth order method. The hydrodynamic physical model tests have been carried out to verify the goodness of the numerical model. The research results are as follows. The sinker system¡¦s numerical model simulation indicates that the error of the maximum tension at anchor is about 4.54% higher than the physical model results, and the error of net deformation rate is about 8.04% higher. While the bottom collar system¡¦s numerical model simulation indicates that the error of the maximum tension at anchor is 6.34% lower than physical model results, and the error of net deformation rate is 3.82% lower. The physical model show that the minimum side projection area deformation rates of net in the bottom collar system is about 4~6% higher than the sinker system¡¦s. According to the conclusions of this study, the presented numerical model is capable to predict the whole cage net system performance and indicates that the bottom collar system is practically feasible in improving the cage net volume deformation.

This thesis proposes a method to simulate the dynamics of an autonomous underwater vehicle towing another autonomous underwater vehicle of equivalent size using a marine cable in the vertical and horizontal plane. There is a coupling effect between the two vehicles because the towed vehicle is of equivalent size. This means that the towed vehicle cannot be modeled as just a payload but rather, must incorporate the forces and moments experienced and acting on it. In this work, only AUVs with symmetrical hulls are considered, where the towing AUV is moving at a constant velocity with a set thrust while the towed AUV has no thrust. The rope system is another important component that needs to be modeled correctly because the rope material and type significantly impact the motion of the vehicles. The rope system in this study is modeled using a numerical approach called the lumped mass spring damper method which is easy to understand and computationally inexpensive. The rope model accounts for buoyancy differences in different ropes and permits cable flexibility. This thesis enables us to study the motion of multiple combinations of different ropes and axi-symmetric types of underwater vehicles with any fixed or movable fin configuration. / M.S. / This thesis studies the motion of an autonomous underwater vehicle towing another autonomous underwater vehicle which is a large as it is. The towed vehicle cannot be assumed to be just a mass attached to the towing vehicle. There is an interaction between the two vehicle. The towed vehicle places a force on the towed vehicle and the towed vehicle likewise places a force on the towing vehicle. This interaction needs to be modeled correctly to fully capture the impact of both vehicles and their appendages. Additionally, the rope system poses a huge impact on the two vehicle depending on what type of rope is selected. Multiple factors affect the performance of a rope such as the shape and the elasticity. Some ropes may also be denser due to their material type and are less buoyant than others. These factors are considered in the modeling of the overall system and allows us to study different combinations of ropes and symmetric hulled autonomous underwater vehicles.

As the cost of land in cities increases, the need to build multistory buildings in close proximity to each other also increases. Sometimes, construction materials, other objects and any projections from a building may also decrease the spacing provided between the buildings. This leads to the problem of pounding of these closely placed buildings when responding to earthquake ground motion. The recent advent of base isolation systems and their use as an efficient earthquake force resisting mechanism has led to their increased use in civil engineering structures. At the same time, building codes that reflect best design practice are also evolving. The movement of these base isolated buildings can also result in building pounding. Since base isolation is itself a relatively new technique, pounding phenomenon in base isolated buildings have not been adequately investigated to date. This study looks at the base isolated response of a single two story building and adjacent two story building systems. Four earthquakes with increasing intensity were used in this study. It was found that it is difficult to anticipate the response of the adjacent buildings due to non- linear behavior of pounding and base isolation. The worst case for pounding was found to occur when a fixed base and base isolated buildings were adjacent to each other.

As the cost of land in cities increases, the need to build multistory buildings in close proximity to each other also increases. Sometimes, construction materials, other objects and any projections from a building may also decrease the spacing provided between the buildings. This leads to the problem of pounding of these closely placed buildings when responding to earthquake ground motion. The recent advent of base isolation systems and their use as an efficient earthquake force resisting mechanism has led to their increased use in civil engineering structures. At the same time, building codes that reflect best design practice are also evolving. The movement of these base isolated buildings can also result in building pounding. Since base isolation is itself a relatively new technique, pounding phenomenon in base isolated buildings have not been adequately investigated to date. This study looks at the base isolated response of a single two story building and adjacent two story building systems. Four earthquakes with increasing intensity were used in this study. It was found that it is difficult to anticipate the response of the adjacent buildings due to non- linear behavior of pounding and base isolation. The worst case for pounding was found to occur when a fixed base and base isolated buildings were adjacent to each other.

Atualmente existem diversas aplicações envolvendo estmturas flexíveis, principalmente nos domínios da robótica ou ciência espacial. Geralmente, há a necessidade de projetar controladores para atenuarem, de forma ativa, as vibrações oriundas da ativação dos modos de vibração da estrutura, ativação esta provocada por algum esforço externo. A eficiência do controlador e, conseqüentemente, a sua aplicabilidade na prática dependem fundamentalmente da existência de um modelo dinâmico que seja realista e preditivo. Isto deve-se ao fato de que, significativas diferenças entre o modelo nominal (planta nominal) e a planta física podem fazer com que a lei de controle, projetada para o modelo nominal, leve a dinâmica do sistema em malha fechada à instabilidade. Portanto, dentre as etapas de um projeto envolvendo estruturas flexíveis, a fase de obtenção de um modelo dinâmico é fundamental. Entretanto, ao se realizar uma pesquisa bibliográfica envolvendo estruturas flexíveis, percebe-se um grande número de artigos devotados à teoria de controle, principalmente a partir dos anos oitenta, mas pouco se tem publicado especificamente sobre modelagem. Este foi o principal aspecto motivador da realização da presente dissertação, cujo primeiro objetivo é avaliar diversas técnicas de modelagem dinâmica para um tipo de estrutura que encontra bastante aplicação, principalmente no domínio da robótica flexível. Uma formulação analítica é desenvolvida, sendo determinadas assim as funções de transferência analíticas. Respostas freqüenciais oriundas destas funções de transferência servem de referência no processo de validação dos modelos, obtidos com as técnicas Formalismo Discreto {Lumped Mass Approach), Modos Assumidos e Deformações Polinomiais (derivada do método dos elementos finitos). Ao final, uma aplicação à robótica flexível é analisada sob a ótica da influência da dinâmica do atuador sobre a dinâmica estrutural. / Nowadays, several applications exist involvíng flexible structures, mainly in the domains of robotics or space sciences. Generally, it is necessary to project a control law to attenuate, in an active way, the vibrations originating from the structure modes activation, provoked by some externai effort. The efficiency of the control law, and consequently its practical implementation, depends fimdamentally on the existence of a realistic and predictive dynamic model. This happens because signifícant difFerences among the nominal model and the physical system may exist And so, the control law, projected for the nominal model, can lead the closed loop system to instability. Therefore, in a project involving flexible structures, the obtaining stage of a dynamic model is fundamental. However, when making a bibliographical research involving flexible structures, one noticed a great number of papers that deal with control theory, mainly starting at the eighties, but not many papers have specifícally been published on dynamic modeling. This was the main motivation aspect of the accomplishment of the present work, whose fírst objective is to evaluate several techniques of dynamic modeling for a structure with applications mainly in the domain of flexible robotics. An analytical formulation is developed and so, analytical transfer functions are determinated. Frequency responses obtained fi-om these transfer functions are references in the validation process of the models, obtained with the techniques Lumped Mass Approach, Assumed Modes and Polynomial Deformations (derived of the finite elements method). At the end, an application to the flexible robotics area is analyzed under the point of view of the actuator dynamics influence on the structural dynamics.

Atualmente existem diversas aplicações envolvendo estmturas flexíveis, principalmente nos domínios da robótica ou ciência espacial. Geralmente, há a necessidade de projetar controladores para atenuarem, de forma ativa, as vibrações oriundas da ativação dos modos de vibração da estrutura, ativação esta provocada por algum esforço externo. A eficiência do controlador e, conseqüentemente, a sua aplicabilidade na prática dependem fundamentalmente da existência de um modelo dinâmico que seja realista e preditivo. Isto deve-se ao fato de que, significativas diferenças entre o modelo nominal (planta nominal) e a planta física podem fazer com que a lei de controle, projetada para o modelo nominal, leve a dinâmica do sistema em malha fechada à instabilidade. Portanto, dentre as etapas de um projeto envolvendo estruturas flexíveis, a fase de obtenção de um modelo dinâmico é fundamental. Entretanto, ao se realizar uma pesquisa bibliográfica envolvendo estruturas flexíveis, percebe-se um grande número de artigos devotados à teoria de controle, principalmente a partir dos anos oitenta, mas pouco se tem publicado especificamente sobre modelagem. Este foi o principal aspecto motivador da realização da presente dissertação, cujo primeiro objetivo é avaliar diversas técnicas de modelagem dinâmica para um tipo de estrutura que encontra bastante aplicação, principalmente no domínio da robótica flexível. Uma formulação analítica é desenvolvida, sendo determinadas assim as funções de transferência analíticas. Respostas freqüenciais oriundas destas funções de transferência servem de referência no processo de validação dos modelos, obtidos com as técnicas Formalismo Discreto {Lumped Mass Approach), Modos Assumidos e Deformações Polinomiais (derivada do método dos elementos finitos). Ao final, uma aplicação à robótica flexível é analisada sob a ótica da influência da dinâmica do atuador sobre a dinâmica estrutural. / Nowadays, several applications exist involvíng flexible structures, mainly in the domains of robotics or space sciences. Generally, it is necessary to project a control law to attenuate, in an active way, the vibrations originating from the structure modes activation, provoked by some externai effort. The efficiency of the control law, and consequently its practical implementation, depends fimdamentally on the existence of a realistic and predictive dynamic model. This happens because signifícant difFerences among the nominal model and the physical system may exist And so, the control law, projected for the nominal model, can lead the closed loop system to instability. Therefore, in a project involving flexible structures, the obtaining stage of a dynamic model is fundamental. However, when making a bibliographical research involving flexible structures, one noticed a great number of papers that deal with control theory, mainly starting at the eighties, but not many papers have specifícally been published on dynamic modeling. This was the main motivation aspect of the accomplishment of the present work, whose fírst objective is to evaluate several techniques of dynamic modeling for a structure with applications mainly in the domain of flexible robotics. An analytical formulation is developed and so, analytical transfer functions are determinated. Frequency responses obtained fi-om these transfer functions are references in the validation process of the models, obtained with the techniques Lumped Mass Approach, Assumed Modes and Polynomial Deformations (derived of the finite elements method). At the end, an application to the flexible robotics area is analyzed under the point of view of the actuator dynamics influence on the structural dynamics.

Atualmente existem diversas aplicações envolvendo estmturas flexíveis, principalmente nos domínios da robótica ou ciência espacial. Geralmente, há a necessidade de projetar controladores para atenuarem, de forma ativa, as vibrações oriundas da ativação dos modos de vibração da estrutura, ativação esta provocada por algum esforço externo. A eficiência do controlador e, conseqüentemente, a sua aplicabilidade na prática dependem fundamentalmente da existência de um modelo dinâmico que seja realista e preditivo. Isto deve-se ao fato de que, significativas diferenças entre o modelo nominal (planta nominal) e a planta física podem fazer com que a lei de controle, projetada para o modelo nominal, leve a dinâmica do sistema em malha fechada à instabilidade. Portanto, dentre as etapas de um projeto envolvendo estruturas flexíveis, a fase de obtenção de um modelo dinâmico é fundamental. Entretanto, ao se realizar uma pesquisa bibliográfica envolvendo estruturas flexíveis, percebe-se um grande número de artigos devotados à teoria de controle, principalmente a partir dos anos oitenta, mas pouco se tem publicado especificamente sobre modelagem. Este foi o principal aspecto motivador da realização da presente dissertação, cujo primeiro objetivo é avaliar diversas técnicas de modelagem dinâmica para um tipo de estrutura que encontra bastante aplicação, principalmente no domínio da robótica flexível. Uma formulação analítica é desenvolvida, sendo determinadas assim as funções de transferência analíticas. Respostas freqüenciais oriundas destas funções de transferência servem de referência no processo de validação dos modelos, obtidos com as técnicas Formalismo Discreto {Lumped Mass Approach), Modos Assumidos e Deformações Polinomiais (derivada do método dos elementos finitos). Ao final, uma aplicação à robótica flexível é analisada sob a ótica da influência da dinâmica do atuador sobre a dinâmica estrutural. / Nowadays, several applications exist involvíng flexible structures, mainly in the domains of robotics or space sciences. Generally, it is necessary to project a control law to attenuate, in an active way, the vibrations originating from the structure modes activation, provoked by some externai effort. The efficiency of the control law, and consequently its practical implementation, depends fimdamentally on the existence of a realistic and predictive dynamic model. This happens because signifícant difFerences among the nominal model and the physical system may exist And so, the control law, projected for the nominal model, can lead the closed loop system to instability. Therefore, in a project involving flexible structures, the obtaining stage of a dynamic model is fundamental. However, when making a bibliographical research involving flexible structures, one noticed a great number of papers that deal with control theory, mainly starting at the eighties, but not many papers have specifícally been published on dynamic modeling. This was the main motivation aspect of the accomplishment of the present work, whose fírst objective is to evaluate several techniques of dynamic modeling for a structure with applications mainly in the domain of flexible robotics. An analytical formulation is developed and so, analytical transfer functions are determinated. Frequency responses obtained fi-om these transfer functions are references in the validation process of the models, obtained with the techniques Lumped Mass Approach, Assumed Modes and Polynomial Deformations (derived of the finite elements method). At the end, an application to the flexible robotics area is analyzed under the point of view of the actuator dynamics influence on the structural dynamics.