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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.
271

Fundamental solutions for beams, plates, and shells under thermomechanical actions

Khazaeinejad, Payam January 2016 (has links)
As the engineering profession moves from prescriptive or “deemed-to-satisfy” approaches towards design methodologies based on quantification of performance, sophisticated modelling tools are increasingly needed, especially when complex combinations of demand and capacity are encountered. Recourse is invariably made to advanced computational tools to provide high fidelity solutions to large and complex problems, such as the response of structural systems or components to thermomechanical actions. Software packages based on the finite element method are most commonly used for such analyses. There are some essential prerequisites to effective use of advanced computational software for complex nonlinear problems, which are often ignored, particularly in professional practice. These include a thorough understanding of the underlying mechanics of the problem under consideration; a good appreciation of the approximation methods for modelling the problem properly (e.g. the choice between elements, continuum or structural, low or high order interpolation, degree of mesh refinement necessary and so on); and perhaps most importantly ensuring that the software is reliable and is able to reproduce established fundamental solutions to an acceptable degree of accuracy. This thesis attempts to address most of these issues but focusses primarily on the last mentioned prerequisite and provides a range of novel and unprecedented fundamental solutions for beams, plates, and shallow shells subject to moderate or extreme thermomechanical loads such as those resulting from a fire. Geometric and material nonlinearities are included in the proposed formulations along with the most common idealised boundary conditions. Thermally induced deformations generate large displacements and require the solutions to account for geometric nonlinearity, while material nonlinearity arises from the degradation of the material at elevated temperatures. In the context of structural performance under extreme thermal action (such as fire), a finite element procedure is employed to analytically characterise generic temperature distributions through the thickness of a structural component arising from different types of fire exposure conditions including: a “short hot” fire leading to a high compartment temperature over a relatively short duration; and a “long cool” fire with lower compartment temperatures, but over a longer duration. Results have shown that despite the larger area under the long cool fire time-temperature curve, which traditionally represented the fire severity, the effect of the short hot fire on the nonlinear responses of beams, plates, and shallow shells is more pronounced. Also, the effect of temperature-dependent material properties is found to be more pronounced during the short hot fire rather than the long cool fire. Comparison studies have confirmed that while the current numerical and theoretical approaches for analysing of thin plates and shells are often computationally intensive, the proposed approach offers an adequate level of accuracy with a rapid convergence rate for such structures. The solutions developed can be used to: verify software used for modelling structural response to thermomechanical actions; help students and professionals appreciate the fundamental mechanics better; provide relatively quick solutions for component level analyses; and visualise internal load paths and stress trajectories in complex structural components such as composite shells that can help engineers develop deeper insights into the relevant mechanics. The formulations developed are versatile and can be used for other applications such as laminated composite or orthotropic shallow shells. A very significant by-product of developing such fundamental solutions is their potential use in the development of highly accurate hybrid elements for very efficient modelling of large problems. While this has not been fully developed and implemented in the current work, the requisite theoretical framework has been developed and reported in one of the appendices, which can be used to develop such elements and implement on an appropriate software platform.
272

Isolamento e caracterização do cDNA,produção heteróloga e análise estrutural de BbKI: um inibidor de proteinase de Bauhinia bauhinioides / cDNA cloning, heterologous production and structural analysis of BbKI: a protease inhibitor of Bauhinia bauhinioides

Débora Fernanda Vieira 22 April 2004 (has links)
Inibidores tipo Kunitz são proteínas de aproximadamente 20 kDa, que geralmente possuem de dois a quatro resíduos de cisteína, formando uma ou duas pontes dissulfeto, sendo responsáveis por inibir uma ou diversas serina proteinases com grande especificidade. Eles são importantes tanto por atuarem em situações de defesa na planta como por estarem envolvidos na inibição de diversas proteinases, como aquelas presentes na cascata de coagulação sanguínea, no processo inflamatório ou e até mesmo atuarem na supressão de tumores. Este trabalho teve como alvo o estudo de um inibidor tipo Kunitz encontrado em sementes de Bauhinia bauhinioides (Martius) Macbr., denominado BbKI (Bauhinia bauhinioides Kallikrein Inhibitor). Um fragmento gênico codificando a seqüência primária madura de BbKI foi amplificado por RT-PCR e clonado no vetor pGEM-T. Através da técnica de RACE (3 e 5) foi possível constatar que a proteína é sintetizada inicialmente como um prepropeptídeo com a seguinte estrutura: peptídeo sinal (19 resíduos de aminoácidos), proteína madura (164 resíduos), e peptídeo C-terminal (10 resíduos). A presença do peptídeo sinal demonstra que a proteína segue uma rota de síntese via retículo endoplasmático e sugere que este inibidor possa seguir para outro compartimento celular, sinalizado pelo peptídeo C-terminal. Para avaliar se este peptídeo não seria um mero inibidor da atividade biológica, foram feitas duas subclonagens em vetores do sistema pET: uma com o fragmento gênico codificador para BbKI madura, e outra adicionando a seqüência codificante para a porção C-terminal na proteína madura. As proteínas recombinantes foram expressas em células de E. coli BL21(DE3), as quais foram purificadas através de cromatografia de afinidade (Ni-NTA) e filtração em gel, apresentando a massa molecular esperada de 20 kDa. Testes de atividade com tripsina mostraram que ambas as proteínas são biologicamente ativas, embora com diferentes constantes de inibição. Estudos de Dicroísmo Circular revelaram estruturas secundárias similares para ambas as proteínas. Quando analisado por espectroscopia de fluorescência, o inibidor maduro mostrou-se estável numa ampla faixa de pH. A proteína madura recombinante foi ainda cristalizada e o cristal foi difratado por raios X até a resolução máxima de 1,9 A, permitindo a resolução e o refinamento de sua estrutura. A análise da estrutura revelou que o inibidor apresenta um enovelamento -trefoil que é típico nos inibidores tipo Kunitz previamente estudados. Sua estrutura terciária mostrou que no centro ativo o loop inibitório está exposto ao solvente e que os únicos W e C ficam escondidos no interior da proteína, rodeados por resíduos hidrofóbicos / Kunitz-type inhibitors are proteins of about 20 kDa that usually contain from 2 to 4 cystein residues used to form one or two dissulfide bridges. They are responsible for inhibiting one or severa1 serine proteinases with large specificity. Kunitz inhibitors are important both for playing defense roles in plants and also for being involved in the inhibition of many proteinases, like those present in the blood coagulation cascade, in inflammatory processes, or even for suppressing tumors. The aim of this work was to study a Kunitz-type inhibitor from Bauhinia bauhinioides (Martius) Macbr. seeds, denominated BbKI (Bauhinia buhinioides Kallikrein Inhibitor). A gene fragment codifying the mature primary sequence of BbKI was amplified by RT-PCR and was cloned in the pGEM-T vector. Using the RACE (3 and 5) technique we could verify that this protein is synthesized as a prepropeptide with the following structure: signal peptide (19 amino acid residues), mature protein (164 residues) and C-terminal peptide (10 residues). The presence of the peptide signal shows this protein follows a synthesis pathway via endoplasmatic reticulum and suggests the inhibitor can move to another cell compartment guided by the C-terminal peptide. To evaluate if this peptide was just an inhibitor of the biological activity, we performed two subclonings in the system pET vectors: one using the gene fragment codifying to mature BbKI, and another adding the codifying sequence for the C-terminal peptide to the mature protein. The recombinant proteins were expressed in E. coli BL21(DE3) cells which were purified by affinity chromatography (Ni-NTA) and gel filtration thus presenting the expected molecular mass of 20kDa. Activity assays with trypsin showed that both of proteins are biologically active, although they presented different inhibition constants. Circular Dichroism studies revealed that both proteins have similar secondary structures. When analyzed by fluorescence spectroscopy the mature inhibitor was stable in a wide pH range. The mature recombinant protein was latter crystallized and the crystal was diffracted by X-ray at 1.9A resolution, allowing the resolution and refinement of its structure. The analysis of this structure revealed the inhibitor presents a -trefoil fold, which is typical in the Kunitz-type inhibitors previously studied. Its tertiary structure showed that in the active site the inhibitory loop is exposed to solvent, and that the W and the C are buried into the protein surrounded by hydrophobic residues.
273

Estudo do efeito do escorregamento dos cabos de borda em estruturas de membranas. / Sliding cables at the boundary of membrane structures.

Carolina Banki Martins 24 April 2009 (has links)
Este trabalho apresenta a implementação computacional do elemento finito de cabo deslizando sem atrito, em ambiente MATLAB®, com a finalidade de modelar os cabos de borda não-aderentes das estruturas de membrana. Este novo elemento foi incluído no programa de análise de estruturas retesadas SATS, já previamente desenvolvido. Esta ferramenta é capaz de gerar resultados em deslocamentos, tensões e deformações em estruturas retesadas. São apresentadas as formulações utilizadas para a análise de estruturas de membrana, como a formulação do Método de Newton-Raphson para a resolução de equações não-lineares, as formulações do Elemento Finito de Treliça e do Elemento Finito de Cabo Ideal. É proposta, neste trabalho, a generalização da formulação do elemento de cabo de três nós para o super-elemento de cabo ideal de n nós. São desenvolvidas verificações da eficiência dos elementos finitos de cabo, por meio de exemplos simples de aplicação, nos quais são comparados os resultados obtidos com soluções analíticas. Por fim, é estudado o desempenho dos elementos de cabo, associados a elementos de membrana, por meio da análise da estrutura de cobertura do Memorial dos Povos de Belém do Pará. São comparados os resultados obtidos a partir da implementação das duas formulações apresentadas para os cabos, avaliando a influência da discretização e as diferenças em relação aos resultados obtidos em análises tradicionais usando elementos de treliça. Demonstra-se que a consideração do escorregamento nos cabos de borda é importante para a correta representação das tensões e deslocamentos em estruturas retesadas. / This work presents the implementation of a cable finite element, developed in MATLAB® environment, with the aim of modeling the cables at the boundary of membrane structures. It was added to a software named SATS (System for the Analysis of Taut Structures), which is able to give accurate results on displacements, stress and strains. This work also presents formulations used for the analysis of membrane structures, such as, the Newton-Raphson Method for solving non-linear equations, the Truss Finite Element and the Cable Finite Element. A generalization of the formulation from the three node cable element to an n-node cable super-element is proposed. The efficiency of the cable finite element has been verified by applying simple examples, comparing numerical results to analytical solutions. Finally, it has been studied the performance of these cable elements, along with the membrane finite elements, through the analysis of the membrane roof of the amphitheater of the Memorial dos Povos de Belém do Pará. The results from the implementation of both cable formulations and the traditional analysis using truss elements were compared. It has been shown that the consideration of the cable sliding is important for the accurate stress and displacements analysis.
274

Stress evaluation of a monolithic refractory concrete rotary calciner lining for Tioxide Southern Africa

Ilbury, M. W. January 1993 (has links)
Presented in partial fulfillment of the requirements for the Masters Diploma in Technology: Civil Engineering, Technikon Natal, 1993. / M
275

Structural check of a steel through truss bridge

Dickens, Loren E., III January 1900 (has links)
Master of Science / Department of Civil Engineering / Hani G. Melhem / The Abilene & Smoky Valley Railroad Association offers train excursions to sightseers wishing to see historic Abilene and natural Kansas scenery. Currently, a diesel powered ALCO locomotive is used to pull the passenger cars. They wish to use a 1919 Baldwin steam locomotive in the future. Part of the excursion includes a slow crossing of the Smoky Hill River over a two-span steel truss bridge. The company approached the Kansas State University Civil Engineering Department with the task of performing a structural check of the bridge. By using the Baldwin locomotive, the bridge is required to support much larger loads than when the diesel engine is used. First, a basic visual inspection and site visit of the bridge was performed. The inspection was not thorough, but was used to familiarize the team with the bridge and its components. Using the inspection and data supplied, a structural analysis was performed using the software, RISA. After completion of the analysis for both loading situations, the resulting stress increases were calculated. Other calculations performed include buckling loads of the compression members, deflections of the bottom chord and stresses in some of the connections. After completion of the analysis and calculations, large increases in member stress were found. For most of the members, the increase of live loads stress was between 80% and 100%. The largest stress found due to the dead and live load, which was under 15 ksi, occurred in the bottom chord for the steam locomotive loading situation. Some truss members experienced stress reversal, but relatively low values were noted. Deflection calculations for the two loading situations yielded similar results to the stress calculations. Again, an increase in deflection between 80% and 100% was found for the joints located on the bottom chord. It is recommended that a more detailed inspection and a more thorough analysis of the connections, supports, piers, and foundations be performed before the heavier locomotive is used.
276

Super finite elements for nonlinear static and dynamic analysis of stiffened plate structures

Koko, Tamunoiyala Stanley January 1990 (has links)
The analysis of stiffened plate structures subject to complex loads such as air-blast pressure waves from external or internal explosions, water waves, collisions or simply large static loads is still considered a difficult task. The associated response is highly nonlinear and although it can be solved with currently available commercial finite element programs, the modelling requires many elements with a huge amount of input data and very expensive computer runs. Hence this type of analysis is impractical at the preliminary design stage. The present work is aimed at improving this situation by introducing a new philosophy. That is, a new formulation is developed which is capable of representing the overall response of the complete structure with reasonable accuracy but with a sacrifice in local detailed accuracy. The resulting modelling is relatively simple thereby requiring much reduced data input and run times. It now becomes feasible to carry out design oriented response analyses. Based on the above philosophy, new plate and stiffener beam finite elements are developed for the nonlinear static and dynamic analysis of stiffened plate structures. The elements are specially designed to contain all the basic modes of deformation response which occur in stiffened plates and are called super finite elements since only one plate element per bay or one beam element per span is needed to achieve engineering design level accuracy at minimum cost. Rectangular plate elements are used so that orthogonally stiffened plates can be modelled. The von Karman large deflection theory is used to model the nonlinear geometric behaviour. Material nonlinearities are modelled by von Mises yield criterion and associated flow rule using a bi-linear stress-strain law. The finite element equations are derived using the virtual work principle and the matrix quantities are evaluated by Gauss quadrature. Temporal integration is carried out using the Newmark-β method with Newton-Raphson iteration for the nonlinear equations at each time step. A computer code has been written to implement the theory and this has been applied to the static, vibration and transient analysis of unstiffened plates, beams and plates stiffened in one or two orthogonal directions. Good approximations have been obtained for both linear and nonlinear problems with only one element representations for each plate bay or beam span with significant savings in computing time and costs. The displacement and stress responses obtained from the present analysis compare well with experimental, analytical or other numerical results. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate
277

Analýza konkurence v oblasti filmové distribuce / The analysis of competotion film distribution

Zachová, Magdalena January 2008 (has links)
This text deals with the market for film distribution in the Czech republic and it focuses mainly on the competition in this area. Its theoretical background lies in a structural analysis of sector and Porter's Competitive Forces model. This theoretical approach is confronted with contemporary situation on the market in the practical part of the text. Also, there is formulated a competitive advantage in product and in producer as a purchase motivation. These aspects of competitive advantages are discussed and some recommendations for market subjects are proposed. Brief discussion of financial indicators of main firms is also included.
278

Supervision of the Air Loop in the Columbus Module of the International Space Station

Germeys, Jasper January 2016 (has links)
Failure detection and isolation (FDI) is essential for reliable operations of complex autonomous systems or other systems where continuous observation or maintenance thereof is either very costly or for any other reason not easily accessible. Beneficial for the model based FDI is that there is no need for fault data to detect and isolate a fault in contrary to design by data clustering. However, it is limited by the accuracy and complexity of the model used. As models grow more complex, or have multiple interconnections, problems with the traditional methods for FDI emerge. The main objective of this thesis is to utilise the automated methodology presented in [Svärd, 2012] to create a model based FDI system for the Columbus air loop. A small but crucial part of the life support on board the European space laboratory Columbus. The process of creating a model based FDI, from creation of the model equations, validation thereof to the design of residuals, test quantities and evaluation logic is handled in this work. Although the latter parts only briefly which leaves room for future work. This work indicate that the methodology presented is capable to create quite decent model based FDI systems even with poor sensor placement and limited information of the actual design. [] Carl Svärd. Methods for Automated Design of Fault Detection and Isolation Systems with Automotive Applications. PhD thesis, Linköping University, Vehicular Systems, The Institute of Technology, 2012
279

Analiza i procena seizmičkih performansi grednih armiranobetonskih mostova / Аnalysis and estimation of seismic performance of gird reinforced concrete bridges

Rašeta Andrija 12 June 2014 (has links)
<p>U EN1998-1 i EN1998-2 su propisane metode za određivanje seizmičkih<br />uticaja koje koriste linearno-elastične modele u modalnoj analizi sa<br />spektrima odgovora. Za regularne konstrukcije, se može primeniti i<br />ekvivalentna statička metoda u slučaju da ne postoji značajan<br />doprinos viših tonova na odgovor sistema. U EN1998-2 su propisane,<br />kao alternativa linearno-elastičnim metodama analize, nelinearna<br />statička analiza i nelinearna dinamička analiza. U ovom radu su<br />primenjene linearne i nelinearne statičke i dinamičke analize<br />armiranobetonskih grednih mostova sa različitim kombinacijama<br />dužina stubova u cilju procene seizmičkih performansi.</p> / <p>The EN 1998-1 and EN1998-2 prescribed methods for the determination of<br />seismic action using linear-elastic models for modal analysis with response<br />spectrum. For regular structures, can be applied to the equivalent static<br />method in the action that there is a significant contribution to higher modes<br />on the response of the system. The EN1998-2 are prescribed as an<br />alternative to linear-elastic methods of analysis, nonlinear static analysis and<br />nonlinear dynamic analysis. This study applied linear and nonlinear static<br />and dynamic analysis of reinforced concrete girder bridges with different<br />combinations of length piers in order to assess the seismic performance.</p>
280

Structural Analysis of the Mitten Park Reverse Fault and Related Deformation in Dinosaur National Monument, Northwestern Colorado and Northeastern Utah

Brown, Clint M. 01 May 1996 (has links)
An integrated field and structural analysis of the Mitten Park fault-fold structure, northwestern Colorado and northeastern Utah, examines its structural origin. The Mitten Park structure is a modified fault-propagation-fold. This new model incorporates faulting, folding, and fracturing in one deformational event to produce the Mitten Park fault and associated monocline. The largest structure in the study area is the Mitten Park fault and associated monocline. The Mitten Park fault has approximately 127 meters (415 feet) of net slip, strikes S28°W and dips 55°WNW. In the footwall, net shortening was accommodated by reverse and normal faulting. Faulting was the result of northwest-southeast directed shortening. Reverse faulting accommodated the majority of the fault-related strain along the fault's trace and resulted in net shortening. However, normal faults in the overturned limb of the footwall of the Mitten Park fault also accommodated northwest-southeast directed shortening. Folds in the study area are asymmetrical and statistically cylindrical in both the footwall and the hanging wall. Folding facilitates northwest-southeast directed shortening. There is a direct correlation between changes in the strike and dip of the fault plane and changes in the trend and plunge of fold axis in the footwall. Fracture orientations show no significant variation in geometry from hanging wall to footwall. Fracture intensity increases with proximity to the Mitten Park fault. Balanced cross sections of the Mitten Park area use a modified fault-propagation- fold model and are also constrained by field observations and interlimb angles of folds. Total shortening in the study area is 13.5% and was accommodated by the hanging wall, the footwall, and the Mitten Park fault. The hanging wall accommodated 70.8% of total shortening, the footwall accommodated 14.9% of total shortening, and the Mitten Park fault accommodated 14.3% of total shortening. The significant amount of strain in the footwall of the fault is different from classical models of fault-propagation-folds, which depict a rigid undeformed footwall.

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