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Lavall, Armando Cesar Campos. "Uma formulação consistente para análise não-linear de pórticos planos de aço considerando imperfeições iniciais e tensões residuais." Universidade de São Paulo, 1996. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-02042018-112300/.
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Neste trabalho desenvolve-se uma formulação teórica consistente para a análise não-linear, física e geométrica, de pórticos planos de aço, através do Método dos Elementos Finitos (MEF), considerando barras com imperfeições iniciais e tensões residuais nas suas seções transversais, visando analisar os critérios de resistência adotados para projeto das colunas de aço, baseados no conceito de resistência-última, e estudar o comportamento não-linear dos pórticos de aço considerando estes dois fatores. São feitas considerações qualitativas sobre a influência das imperfeições iniciais e das tensões residuais no cálculo da resistência das colunas. e é dada uma visão geral sobre a evolução dos critérios usados na prática para dimensionamento das colunas de aço. Apresenta-se o desenvolvimento da teoria geral, que leva em conta a presença das tensões residuais auto-equilibradas nas equações de equilíbrio do elemento. Este desenvolvimento é feito dentro de uma formulação Lagrangiana utilizando a técnica corrotacional para a dedução consistente da matriz de rigidez tangente do elemento de pórtico plano com imperfeição inicial. Para implementação desta formulação é desenvolvido um programa em linguagem FORTRAN para micro-computador capaz de fazer a análise não-linear elasto-plástica de pórticos planos, baseado num processo incremental-iterativo. Utiliza-se o modelo de fatias para avaliar os coeficientes de rigidez do elemento, modelo este que se mostrou bastante adequado, permitindo o acompanhamento da plastificação ao longo da altura da seção e a consideração de qualquer modelo de distribuição das tensões residuais. Finalmente, os exemplos apresentados mostram a grande potencialidade da formulação desenvolvida. São analisados vários casos cujos resultados são comparados com os obtidos por outros autores, demonstrando a precisão e correção da teoria proposta. A aplicação na análise de pórticos de andares múltiplos confirma a validade da formulação e demonstra a sua aplicabilidade nos casos práticos.A consistent finite element formulation to consider material and geometric nonlinearities of steel plane frames is presented. Residual stresses and initial imperfections are considered to evaluate steel columns failure criteria based on the ultimate strength and also to investigate the nonlinear behavior of steel plane frames. Some qualitative considerations are made on the initial imperfections and residual stresses influence on the practical steel columns design. A general theory considering self equilibrated residual stresses is developed based on the Lagrangian formulation. Corotacional technique is used to obtain the tangent stiffness matrix of plane frame taking the initial imperfection into account. A stand alone code has been written in FORTRAN and implemented on a microcomputer platform to perform incremental-iterative analysis of nonlinear elastoplastic plane frame problems. The frame element is made up of layers such that the plastic region can be readily identified and any kind of residual stresses through the cross section area can be taken into account in the analysis. Some examples are presented and their results compared to others in the literature. The multistory building analyses using the plane frame element presented in this research has shown to be very effective and useful to practical applications.
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Leal, Luiz Alberto Araújo de Seixas. "Análise elástica dos efeitos da não linearidade geométrica em estruturas de aço." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/3/3144/tde-14122014-161038/.
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A análise das estruturas de aço sujeitas a ações verticais e horizontais, em termos de esforços solicitantes, deslocamentos e rotações, muitas vezes requer a consideração dos efeitos da não linearidade geométrica. Em outras palavras, a interação entre os deslocamentos e os esforços externos pode provocar uma alteração na intensidade dos esforços internos que solicitam a estrutura que, caso não seja adequadamente avaliada, pode conduzir a uma redução significativa dos níveis de segurança. Nesse contexto, destacam-se duas metodologias de avaliação desses efeitos: aquelas baseadas em análises aproximadas e aquelas baseadas em análises geometricamente exatas. As análises aproximadas podem ser caracterizadas em sua grande maioria por desenvolver um estudo baseado no equilíbrio da estrutura na configuração inicial ou indeformada (análise sob linearidade geométrica) e, em seguida, estimar os esforços solicitantes atuantes na configuração final ou deformada por meio de coeficientes majoradores. Por outro lado, a característica principal da análise geometricamente exata é verificar as condições de equilíbrio estrutural na configuração deformada e sem fazer nenhuma restrição quanto à magnitude dos deslocamentos e rotações ou, em outras palavras, observar o comportamento geometricamente exato (não linear) de maneira direta na configuração final de equilíbrio. Este trabalho propõe realizar um estudo comparativo entre um dos métodos de análise aproximada aquele baseado nos coeficientes B1 e B2, que é recomendado pela norma brasileira ABNT NBR 8800:2008 e um método baseado em análise geometricamente exata, de maneira a verificar as semelhanças e as diferenças entre os resultados. O aço é admitido como elástico. As ferramentas computacionais utilizadas são os programas FTOOL e PEFSYS, formulados segundo teorias de barras lineares e não lineares, respectivamente.The analysis of steel structures subjected to vertical and horizontal loads, regarding internal forces, displacements and rotations, often requires the consideration of geometrically nonlinear effects. In other words, the interaction between displacements and external loads may cause a changing in the intensity of internal forces acting on the structure which, if not correctly evaluated, lead to significant reducing of structural safety. In this context, there exist two main methodologies to evaluate these effects: one based on approximated analysis and another based on geometrically exact analysis. The approximated analysis can be usually characterized by a study based on the equilibrium of the structure at its initial or undeformed configuration (geometrically linear analysis) and, further, by estimating the internal forces acting at the final or deformed configuration by means of amplifier coefficients. On the other hand, the main characteristic of the geometrically exact analysis is to verify the equilibrium conditions directly at the deformed configuration, without any restrictions regarding the magnitude of displacements and rotations or, in other words, observe the geometrically exact (nonlinear) behaviour directly at the final equilibrium configuration. This work purposes to develop a comparative study between one of the approximated methods the one based on the so called B1 and B2 coefficients, recommended by the Brazilian code ABNT NBR 8800:2008 and a method based on geometrically exact analysis, to verify the similarities and differences of results. The computational tools employed are the softwares FTOOL and PEFSYS, based on linear and nonlinear rod theories, respectively.
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Sarver, George Lertin. "Energy transfer and dissipation in structures with discrete nonlinearities." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/34031.
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Xie, Feng. "Resonant optical nonlinearities in cascade and coupled quantum well structures." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-3101.
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Lee, Siu-lam Anderson, and 李韶林. "Temperature distribution in steel structures." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B3122300X.
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Lee, Siu-lam Anderson. "Temperature distribution in steel structures /." Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B21490090.
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Castanheira, Joel Filipe Gonçalves. "Steel structures design: practical applications." Master's thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/11492.
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Mestrado em Engenharia CivilO presente trabalho está inserido num estágio realizado na empresa Alstom e aborda o dimensionamento e a execução de estruturas metálicas para o suporte de tanques de arrefecimento de turbinas de gás. No presente trabalho é referido o dimensionamento da estrutura metálica no seguimento da execução de um projecto (Carrington). No dimensionamento da estrutura metálica tem-se como bastante relevante os seguintes dados: a velocidade do vento, actividade sísmica, tipo de acesso para manutenção dos tanques de arrefecimento, movimentos dos tanques, tipos de normas foram utilizadas no projecto e ainda saber se a estrutura esta situada dentro ou fora do complexo. Os movimentos dos tanques de arrefecimento da turbina de gás tem uma enorme importância no dimensionamento porque, quando conectamos os tanques à estrutura metálica é necessário implementar amortecedores para evitar o choque dos tanques com a estrutura metalica. Estes amortecedores evitam o movimento rápido quando existe actividade sismica travando o movimento dos tanques. Depois do dimensionamento da estrutura estar concretizada, é necessário proceder aos detalhes, neste caso todas as peças desta estrutura têm que ser detalhados em desenho criado em AutoCAD, de maneira a que o fabricante da estrutura saiba toda a informação necessaria para a manufactura da mesma. Também é criado, para isto, uma lista detalhada juntamente com a instrução de montagem com todos os materiais usados na construção da estrutura metálica. A tese fará uma descrição mais aprofundada dos referidos assuntos.
This thesis presentation is in association to an internship program at Alstom, and undertakes the design and execution of metallic structures used to support gas turbine cooling vessels. Specifically mentioned in this thesis is the design and execution of a steel structure for a specific project (Carrington). When designing a metallic structure, the following inputs are extremely relevant; wind velocity, seismic activity, access options for the maintenance of the vessels, the movements of the vessels, subsequent norms or criteria to be used on the project as well as whether the structure is to be located indoor or outdoor of the plant. The movement of the vessels of the gas turbine has an enormous importance on the design of the structure. When connecting the tanks to the steel structure it is necessary to install shock absorbers/ snubbers to avoid any clashes. These shock absorbers prevent any rapid movement of the tanks due to seismic activity. When the steel structure has been designed, it is necessary to finalize any remaining details. In this case, ali the specific pieces pertaining to the structure have to be detailed and illustrated on the AutoCAD program, giving the supplier ali the specific information necessary for the manufacturing process. A detailed list, called bill of material, is also put together along with an instruction assembly manual, of ali materiais used in the construction of the steel structure. The thesis will make a more detailed description of these subjects.
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Magnevall, Martin. "Methods for Simulation and Characterization of Nonlinear Mechanical Structures." Licentiate thesis, Karlskrona : Blekinge Institute of Technology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-00430.
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Trial and error and the use of highly time-consuming methods are often necessary for modeling, simulating and characterizing nonlinear dynamical systems. However, for the rather common special case when a nonlinear system has linear relations between many of its degrees of freedom there are particularly interesting opportunities for more efficient approaches. The aim of this thesis is to develop and validate new efficient methods for the theoretical and experimental study of mechanical systems that include significant zero-memory or hysteretic nonlinearities related to only small parts of the whole system. The basic idea is to take advantage of the fact that most of the system is linear and to use much of the linear theories behind forced response simulations. This is made possible by modeling the nonlinearities as external forces acting on the underlying linear system. The result is very fast simulation routines where the model is based on the residues and poles of the underlying linear system. These residues and poles can be obtained analytically, from finite element models or from experimental measurements, making these forced response routines very versatile. Using this approach, a complete nonlinear model contains both linear and nonlinear parts. Thus, it is also important to have robust and accurate methods for estimating both the linear and nonlinear system parameters from experimental data. The results of this work include robust and user-friendly routines based on sinusoidal and random noise excitation signals for characterization and description of nonlinearities from experimental measurements. These routines are used to create models of the studied systems. When combined with efficient simulation routines, complete tools are created which are both versatile and computationally inexpensive. The developed methods have been tested both by simulations and with experimental test rigs with promising results. This indicates that they are useful in practice and can provide a basis for future research and development of methods capable of handling more complex nonlinear systems.
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Oosthuizen, Daniel Rudolph. "Data modelling of industrial steel structures." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53346.
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Thesis (MScEng)--Stellenbosch University, 2003.ENGLISH ABSTRACT: AP230 of STEP is an application protocol for structural steel-framed buildings. Product data relating to steel structures is represented in a model that captures analysis, design and manufacturing views. The information requirements described in AP230 were analysed with the purpose of identifying a subset of entities that are essential for the description of simple industrial steel frames with the view to being able to describe the structural concept, and to perform the structural analysis and design of such structures. Having identified the essential entities, a relational database model for these entities was developed. Planning, analysis and design applications will use the database to collaboratively exchange data relating to the structure. The comprehensiveness of the database model was investigated by mapping a simple industrial frame to the database model. Access to the database is provided by a set of classes called the database representative classes. The data-representatives are instances that have the same selection identifiers and attributes as corresponding information units in the database. The datarepresentatives' primary tasks are to store themselves in the database and to retrieve their state from the database. A graphical user interface application, programmed in Java, used for the description of the structural concept with the capacity of storing the concept in the database and retrieving it again through the use of the database representative classes was also created as part of this project.
AFRIKAANSE OPSOMMING: AP230 van STEP is 'n toepassingsprotokol wat staal raamwerke beskryf. Die produkdata ter beskrywing van staal strukture word saamgevat in 'n model wat analise, ontwerp en vervaardigings oogmerke in aanmerking neem. Die informasie vereistes, soos beskryf in AP230, is geanaliseer om 'n subset van entiteite te identifiseer wat noodsaaklik is vir die beskrywing van 'n eenvoudige nywerheidsstruktuur om die strukturele konsep te beskryf en om die struktuur te analiseer en te ontwerp. Nadat die essensiële entiteite geïdentifiseer is, is 'n relasionele databasismodel van die entiteite geskep. Beplanning, analise en ontwerptoepassings maak van die databasis gebruik om kollaboratief data oor strukture uit te ruil. Die omvattenheid van die databasis-model is ondersoek deur 'n eenvoudige nywerheidsstruktuur daarop afte beeld. Toegang tot die databasis word verskaf deur 'n groep Java klasse wat bekend staan as die verteenwoordigende databasis klasse. Hierdie databasis-verteenwoordigers is instansies met dieselfde identifikasie eienskappe as die ooreenkomstige informasie eenhede in die databasis. Die hoofdoel van die databasis-verteenwoordigers is om hulself in die databasis te stoor asook om hul rang weer vanuit die databasis te verkry. 'n Grafiese gebruikerskoppelvlak, geprogrammeer in Java, is ontwikkel. Die koppelvlak word gebruik om die strukturele konsep te beskryf, dit te stoor na die databasis en om dit weer, met behulp van die databasis-verteenwoordigers, uit die databasis te haal.
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Narang, Vikas A. "Heat Transfer Analysis In Steel Structures." Link to electronic thesis, 2005. http://www.wpi.edu/Pubs/ETD/Available/etd-050405-133533/.
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Surampudi, Bala Anjani Vasudha. "High-Resolution Modeling of Steel Structures." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1504787210175847.
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Dergham, Serge. "A new analytical approach for assessing the effect of joint nonlinearities in space structures." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14557.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1988.Title as it appears in M.I.T. Graduate List, June 1988: A new analytical approach to study the effects of joints nonlinearities in space structures.
Includes bibliographical references.
by Serge Dergham.
M.S.
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Khorasani, Yalda. "Feasibility study of hybrid wood steel structures." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/33561.
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This thesis involves a detailed study of steel-wood hybrid structures and their applications in construction industry. Hybrid structures combine benefits of dissimilar materials to overcome their individual limitations. Various advantages and challenges of steel-timber hybrid structures are presented. Benefits include increase in tensile capacity, seismic performance, fire resistance of the structure, and cost savings. Challenges with this type of hybrid structures originate from the differences in the properties of the materials used. Connection design may be more difficult as temperature and humidity variations have different effects on steel and timber. The hybrid materials can be integrated at component levels (hybrid slab/diaphragms, hybrid beams, hybrid columns, hybrid diagonals, hybrid post-tensioned joints) and/or at the building system levels (hybrid frames, hybrid system of steel frames and wood diaphragms, vertical mixed system and hybrid trusses). To elaborate on these types of hybridization and their advantages and challenges, case studies of steel-timber, concrete-timber and steel-concrete structures are provided. Despite the obvious advantages, today’s applications of wood-steel hybrid structures have been limited. Currently there are no material and design standards for hybrid wood-steel structures. For light structures, NAHB Research Center has developed a builder’s guide to hybrid wood and steel connection details. When combining steel and wood, designers should consider the advantages and limitation of each material and optimally utilize them. The literature review has highlighted the opportunity for wood-steel hybrid buildings and existing knowledge gaps. Another aim of this thesis is to investigate technical software packages and identify the pros and cons of each software pachage for modeling hybrid structures. The considered software packages are ANSYS, SAPWood, SeismoStruct and OpenSees Navigator. Software packages are evaluated interms of their ability to model linear and non linear materials; orthotropic and istotropic materials and composite materials. among the softwares ANSYS is found to be the most suitable for modelling hybird wood and steel structures. A case study of a hybird structure consisting of steel momet frame and wood shear wall is modeled with ANSYS. Static analysis is performed on the structure and it is observed that wood shear wall significantly reduce the lateral deflection of the system.
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Kim, Uksun. "Seismic behavior of steel joist girder structures." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/20804.
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Martinsson, Johan. "Fatigue assessment of complex welded steel structures." Doctoral thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-166.
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Abu, Sha'ari. "Analysis of steel frame structures in fire." Thesis, University of Sheffield, 1991. http://etheses.whiterose.ac.uk/3065/.
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The main aim of the present research is to develop a method of analysis for structural frames exposed to fire including the effects of material and geometric non-linearities. A matrix stiffness method based on a secant stiffness approach is used providing a full temperature deformation history. The approach has previously been used for the analysis of continuous beams and is extended in the present work to include axial forces. These not only affect the longitudinal displacement, but also reduce the member stiffness and create secondary moments due to the p-delta effect. The influence of material unloading on the moment-axial force-curvature relationship is studied by examining a cross-section subjected to different combinations of bending moment and axial force at both ambient temperature and in fire. A computer program, based on the method is used to conduct a limited parametric study. This includes the influence of slenderness ratio, the magnitude of axial load and moment, the size of cross-section and grade of steel. Both uniform and non-uniform temperature profiles are considered for isolated beams, columns and simple portal frame. The importance of the p-delta effect is also investigated.
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Wu, Yu-You. "Cathodic protection of steel framed masonry structures." Thesis, Sheffield Hallam University, 2005. http://shura.shu.ac.uk/20575/.
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The identification of "Regent Street Disease" in the United Kingdom in the late 1970's highlighted the problems of the corrosion of iron and steel frames and other structural components in historically sensitive buildings. This has resulted in serious consequences with respect to serviceability, safety, aesthetics and heritage. Cathodic protection is a proven method for preventing and protecting buried and submerged steel and reinforced concrete structures from corrosion. More recently, the method has been introduced to prevent and control corrosion in steel-framed masonry structures. However, with several sizeable installations in the UK, there are no formal guidelines for the design, installation and operation of such systems and much of the knowledge is based on empirical observations. The work presented in the thesis investigates the polarisation of structural steel sections in masonry environments; the distribution of current and potential in representative cathodic protection systems for steel-framed masonry structures; the effect of masonry type and joints width on protective current and potential distribution and stray current corrosion. These studies are considered essential in the understanding of the mechanisms of cathodic protection and the design of optimised cathodic protection systems for such structures. The study has involved both experimental measurements and boundary element modelling. The results have identified how the several key factors, such as the electrolyte resitivity, anode locations, masonry types and joint width, influence the distribution of the protective current and potential on the steel surface. Furthermore, the work has confirmed that boundary element modelling can provide a powerful technique for analysing and optimising the design of cathodic protection systems for steel framed masonry structures. The technique also generates valuable information about the level of interference in terms of current density on the surface of stray current affected components and is therefore a valuable tool for the analysis of possible CP interference in steel-framed masonry buildings. It is hoped that the output from this work will help progress the development of this technology and contribute to the development of formal guidelines and standards for the cathodic protection of steel-framed masonry buildings.
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Underwood, J. "Strength assessment of damaged steel ship structures." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/355704/.
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In 2012 106 vessels over 100 gross tonnes were lost. During the damage incidents many of these vessels required assistance from shore based emergency response services with regards to their damaged strength to stabilise the situation, preserve life, prevent environmental disaster and limit financial costs to owners and insurers. The research work presented in this Engineering Doctorate Thesis surrounds the strength assessment of damaged steel ship structures, the influence of damage on the strength of steel-plated structures and methods for assessing the residual strength of a vessel in an emergency. The focus of the work is to improve the modelling of damaged steel ship structures within an emergency situation, in order to improve guidance provided to a stricken vessel during a damage incident or salvage process. Literature study has shown that structural idealisation through the use of interframe progressive collapse analysis, to be the current state of the art method for the rapid assessment of intact and damaged ship structures. However, a number of weaknesses have been identified in the method when applied to damage assessment. The literature study has also shown a lack of understanding of the effect of damage on steel-plated structures as specific analysis has not been performed previously. Significant research has been undertaken into the influence of damage, in the form of a hole, on the ultimate collapse strength of steel-plated structures. Three levels of structural modelling have been used, stiffened-plate, stiffened panel and grillage. Comparison of the predicted ultimate collapse strength by finite element analysis (FEA) with predictions using the interframe progressive collapse idealisation, has shown the calculated results to be conservative for the assessment of damaged structure when the failure mode remains in the interframe collapse form. However, changes in the failure mode lead to the interframe progressive collapse method over predicting the ultimate collapse strength. The analysis shows that even small damage events can lead to significant changes to the failure mode and resulting ultimate collapse strength of the structure. Such influences must be accounted for in any simplified method. A new method for the assessment of damaged ship structures is proposed that is capable of modelling a damage scenario more accurately. Demonstration of the method has shown the results to be less conservative than the current state of the art, when compared to FEA, for local analysis of damaged steel-plated structure. The ability of the method to account for the influence of damage, and the resulting failure modes, that may significantly influence the ultimate bending strength of the structure has also been demonstrated. The method implements a compartment level progressive collapse analysis with structural data captured through the use of the response surface method ‘kriging’, using data points provided from FEA. This method allows the critical damage variables to be captured and strength data accessible quickly for use in the analysis. The time to provide a solution to the damage scenario is equivalent to the existing interframe progressive collapse method. Therefore, the method is suitable for application within an emergency response or salvage service.
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Sarveswaran, Velautham. "Remaining capacity of corrosion damaged steel structures." Thesis, University of Bristol, 1996. http://hdl.handle.net/1983/dd074d92-3e3b-4a6c-8bed-ce7dc447307b.
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Williams, Stephen Michael. "The condition monitoring of damaged steel structures." Thesis, University of Bristol, 1997. http://hdl.handle.net/1983/1e269816-fae1-4ffc-9b7b-75ba997377b6.
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Jarrett, Jordan Alesa. "Performance Assessment of Seismic Resistant Steel Structures." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/24773.
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This work stems from two different studies related to this performance assessment of seismic resistant systems. The first study compares the performance of newly developed and traditional seismic resisting systems, and the second study investigates many of the assumptions made within provisions for nonlinear response history analyses.
In the first study, two innovative systems, which are hybrid buckling restrained braces and collapse prevention systems, are compared to their traditional counterparts using a combination of the FEMA P-695 and FEMA P-58 methodologies. Additionally, an innovative modeling assumption is investigated, where moment frames are evaluated with and without the lateral influence of the gravity system. Each system has a unique purpose from the perspective of performance-based earthquake engineering, and analyses focus on the all intensity levels of interest. The comparisons are presented in terms consequences, including repair costs, repair duration, number of casualties, and probability of receiving an unsafe placard, which are more meaningful to owners and other decision makers than traditional structural response parameters. The results show that these systems can significantly reduce the consequences, particularly the average repair costs, at the important intensity levels.
The second study focuses on the assumptions made during proposed updates to provisions for nonlinear response history analyses. The first assumption investigated is the modeling of the gravity system's lateral influence, which can have significant effect on the system behavior and should be modeled if a more accurate representation of the behavior is needed. The influence of residual drifts on the proximity to collapse is determined, and this work concludes that a residual drift check is unnecessary if the only limit state of interest is collapse prevention. This study also finds that spectrally matched ground motions should cautiously be used for near-field structures. The effects of nonlinear accidental torsion are also examined in detail and are determined to have a significant effect on the inelastic behavior of the analyzed structure. The final investigation in this study shows that even if a structure is designed per ASCE 7, it may not have the assumed probability of collapse under the maximum considered earthquake when analyzed using FEMA P-695.Ph. D.
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Gosaye, Fida Kaba Jonathan. "Behaviour and design of prestressed steel structures." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/34395.
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The behaviour and design of prestressed steel structures, with an emphasis on trussed arches, are examined in this thesis. For long-span structural systems, where self-weight becomes an increasingly dominant component of the design loading, significant material savings can be achieved through the use of high tensile strength steel cables in conjunction with conventional steelwork. Further benefits can be achieved by prestressing the cables. In the system currently being investigated, the prestressed cables, which are housed within the bottom chord of tubular arched trusses, apply a compressive force to the chord members, which is opposite in nature to the resultant forces arising from the externally applied gravity loads. The stability of the trussed elements under prestress and the load--deformation response of the prestressed elements to the subsequent application of tensile loading are examined analytically, numerically and experimentally, with good correlation achieved between the three approaches. The benefits of prestressing, in terms of increased member strength and stiffness, are demonstrated, and optimal prestress levels are investigated. In instances of load reversal (e.g. due to wind uplift) in trusses without horizontal end anchorage that would allow catenary forces to develop, the presence of prestress can become detrimental. To examine this, a total of eight pin-ended cable-in-tube systems, featuring both non-grouted and grouted members, were tested in compression. Increasing initial prestress levels was found to reduce the capacity of the system in compression, but initial prestress was shown to be less detrimental than externally applied compressive loading of the same magnitude, due to the absence of second order bending moments. Finite element models were developed and, following accurate replication of test results, were used to generate parametric results for a range of member slendernesses and prestress levels. The test and FE results were compared against capacity predictions based on a proposed modified Perry-Robertson design method. Consistent, accurate and generally safe-side predictions were achieved. Following the examination of behaviour of individual prestressed elements within the truss, a series of analytical and numerical models of the full arched truss system were developed to investigate its global structural behaviour. Parametric studies revealed that the horizontal end boundary conditions, prestress level, truss depth and diagonal member arrangements were the key parameters influencing the stiffness, load bearing capacity and failure mode of the structure.
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Walsh, Michael Thomas. "Corrosion of Steel in Submerged Concrete Structures." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/6048.
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This investigation determined that severe corrosion of steel can occur in the submerged portions of reinforced concrete structures in marine environments. Field studies of decommissioned pilings from actual bridges revealed multiple instances of strong corrosion localization, showing appreciable local loss of steel cross-section. Quantitative understanding of the phenomenon and its causes was developed and articulated in the form of a predictive model. The predictive model output was consistent with both the corrosion rate estimates and the extent of corrosion localization observed in the field observations. The most likely explanation for the observed phenomena that emerged from the understanding and modeling is that cathodic reaction rates under oxygen diffusional limitation that are negligible in cases of uniform corrosion can nevertheless support substantial corrosion rates if the corrosion becomes localized. A dynamic evolution form of the model was created based on the proposition that much of the steel in the submerged concrete zone remained in the passive condition given cathodic prevention that resulted from favorable macrocell coupling with regions of the steel that had experienced corrosion first. The model output also matched observations from the field, supporting the plausibility of the proposed scenario.
The modeling also projected that corrosion in the submerged zone could be virtually eliminated via the use of sacrificial anode cathodic protection; the rate of corrosion damage progression in the low elevation zone above water could also be significantly reduced. Continuation work should be conducted to define an alternative to the prevalent limit-state i.e., visible external cracks and spalls, for submerged reinforced concrete structures. Work should also be conducted to determine the possible structural consequences of this form of corrosion and to assess the technical feasibility and cost/benefit aspects of incorporating protective anodes in new pile construction.
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Kent, A. J. "Finite element models for the analysis of reinforced concrete shell structures with geometric and material nonlinearities." Thesis, Swansea University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280516.
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Liu, Jinbiao. "Earthquake analysis of steel moment resisting frame structures." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ27000.pdf.
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Lang, Christopher Leslie. "Composite patching of fatigue cracks in steel structures." Thesis, Heriot-Watt University, 2008. http://hdl.handle.net/10399/2041.
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Rose, Paul Stuart. "Simulation of steel/concrete composite structures in fire." Thesis, University of Sheffield, 1999. http://etheses.whiterose.ac.uk/2995/.
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A finite element code has been developed at the University of Sheffield to simulate the structural response of steel and composite framed buildings subjected to fire. The steel skeleton is represented using two-noded line elements, the steel-to-steel connections using spring elements and the flooring system by isotropic flat shell elements. Structures are therefore considered as a complete entity, allowing a more realistic prediction of structural behaviour at elevated temperature. A series of numerical simulations of fire tests carried out on the full-scale, eight-storey composite frame at the BRE laboratory at Cardington in 1995 and 1996 have been conducted. These tests have been subject to a number of significant parametric studies including slab thickness and secondary beam connection strength and stiffness. The concrete floor slab element has also been extended to a layered flat shell element allowing the inclusion of material non-linearities, thermal bowing, thermal degradation, anisotropic properties and a more advanced cracking model. Using the new concrete floor slab element the Cardington fire tests have been simulated in detail, to further understanding of the structural reaction in fire. Another series of parametric studies have been conducted considering again the thickness of the floor slab, the effect of the slab temperature gradient, the compressive strength, tensile strength and load ratios. These have all been compared to results from the Cardington fire tests. Current design methods based on isolated element design are considered by comparing the results of analyses in which the concrete floor is either included as a continuous slab in an extensive subframe, or is treated simply as forming the flanges of composite beams in a three-dimensional skeleton. These examples show clearly the effects of membrane and bridging actions of the continuous floor slab. The implications for future design developments are discussed with particular reference to the parametric studies conducted.
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Li, Hongyu. "Analysis of steel silo structures on discrete supports." Thesis, University of Edinburgh, 1994. http://webex.lib.ed.ac.uk/homes/li94.html.
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Manson, Leigh (Leigh Caroline). "Analysis and comparison of connections in steel structures." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/34593.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2006.Includes bibliographical references (leaves 54-55).
The topic of connections is often given only limited attention in structural analysis and design of buildings, despite the fact that they can play a critical role in the structure. It is customary practice in the U.S. for the structural engineer to design the structural members, but leave the connection details to the steel fabricator. While this practice is more efficient and pragmatic in some instances, it is also necessary for structural engineers to have a good knowledge of connection behavior, especially when dealing with newer or atypical connections. Both the theoretical modeling of connections and the physical geometry and components of connections are considered in this thesis. For the theoretical modeling of connections, the concept of semi-rigid connections as an alternative to the conventional idealizations of perfectly pinned or rigid connections will be addressed. Included will be methods to model and design semi-rigid connection behavior within frames. The effects of connection behavior on frames will also be considered.
(cont.) With regard to the physical components of connections, an overview of types of fasteners and joints will be presented, including types and methods of installing bolts and welds, shop-welded, field-bolted column trees, and comparisons between these options. A final section presents options for connections between hollow structural sections of both circular and rectangular cross sections. Finally, the topics covered for connections will be applied to the design project for the MIT class 1.562 as part of the MEng program in high performance structures.
by Leigh Manson.
M.Eng.
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West, Anna Elizabeth. "Contributors to waterside corrosion of soil-steel structures." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/45606.
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Soil-steel structures are designed and constructed worldwide for use in civil infrastructure and construction industries. As a result, extensive work has been devoted to understanding the corrosion of zinc and galvanized steel yielding the development of various corrosion models worldwide. Canada does not have a corrosion model required for use in design, but engineers and contractors often use that developed in the United States by the American Association of State Highway and Transportation Officials. This corrosion model defines the recommended range of pH, chloride concentration and soluble sulphate concentration as well as minimum resistivity for unsaturated soil applications. However, these design recommendations and associated corrosion model are often misused in aqueous environments. As a result, many structures have demonstrated significant evidence of premature corrosion raising concerns with the suitability of this corrosion model.
Field testing was conducted on both mechanically stabilized earth retaining walls as well as corrugated steel pipe. Steel samples were extracted for analyses with scanning electron microscope and energy dispersive x-ray spectroscopy while water samples were collected to determine the properties causing degradation. Linear polarization resistance was also completed on two mechanically stabilized earth walls to obtain in-situ corrosion rates.
To complement field work, laboratory experiments were conducted on galvanized steel samples in electrolytes simulating environments satisfying design criteria recommending by the American Association of State Highways and Transportation Officials as well as outside the scope of this model. Relative corrosion rates were calculated from results obtained from accelerated corrosion testing and sample surfaces were analyzed with the use of a scanning electron microscope.
Through laboratory experimentation and field testing it has been discovered that the hardness of water affects the formation of the outermost protective layer on zinc articles, the zinc patina. The following dissertation challenges the appropriateness of durability design criteria and associated corrosion model, defined by the American Association of State Highway and Transportation Officials, for use in aqueous environments while offering guidance on the development of more suitable guidelines for conditions other than unsaturated soil.
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Qureshi, Jawed Qureshi. "Finite element modelling of steel-concrete composite structures." Thesis, University of Leeds, 2010. http://etheses.whiterose.ac.uk/21112/.
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The main objective of this research is to contribute to the knowledge and understanding of the behaviour of the headed stud shear connector in composite beams with trapezoidal profiled metal decking laid perpendicular to the axis of the beam through experimental and numerical studies. Push tests are used to study the behaviour of composite beams. A three-dimensional finite element model of the push test is developed using the general purpose finite element program ABAQUS and the push test is analysed using different concrete material models, and analysis procedures. The Concrete Damaged Plasticity model with dynamic explicit analysis procedure is found to have matched with experimental results very well in terms of the shear connector resistance, load-slip behaviour and failure mechanisms. The post-failure behaviour of the push test, which has not been modelled in the past, is accurately predicted in this study with the help of this modelling technique. The experimental investigation is conducted with a single-sided horizontal push test arrangement to study the influence of various parameters such as normal load, number of shear studs, reinforcement bar at the bottom trough, number of layers of mesh, position of mesh, position of normalload and various push test arrangements. To assess the accuracy and reliability of the developed finite element model, it is validated against push test experiments conducted in this study and variety of push tests carried out by other authors with different steel decks and shear stud dimensions, positions of the shear stud within a rib and push test arrangements. The results obtained from the finite element analysis showed excellent agreement with the experimental studies. The validated finite element model is used in a parametric study to investigate the effect of shear stud position, thickness of the profiled sheeting, shear connector spacing and staggering of shear studs on the performance of the shear stud. The results of the parametric study are evaluated and findings are used to propose the design equations for shear connector resistance taking into account the position of the shear stud and thickness of the profiled sheeting. The coefficient of correlation between experimental and predicted results is nearly equal to one, which indicates that the predicted results are accurate, and the proposed equations are suitable for future predictions.
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Wang, Jie. "Behaviour and design of high strength steel structures." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/43758.
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High strength steels (HSS), which are generally considered to be those with yield strengths over 460 MPa, are being increasingly utilised in construction, particularly in high rise structural applications and where long and column-free spans are an important design requirement. In place of ordinary carbon steels, the use of HSS can enable structural elements with smaller cross-sections, resulting in significant material savings. However, compared to normal strength steels, the structural use of HSS is still quite rare. The European design code EN 1993-1-12 provides design rules for HSS up to S700, but was conceived as a simple extension of the rules in EN 1993-1-1 for normal strength steels. In order to contribute to the existing limited HSS data pool and to verify and develop the current Eurocode 3 design rules, a comprehensive experimental programme on hot-finished S460 and S690 square and rectangular hollow sections has been carried out. The testing programme covered different structural aspects at the material, cross-section and member levels and consisted of 40 tensile coupon tests, 11 compressive coupon tests, 11 stub column tests, 11 full section tensile tests, 22 in-plane bending tests, 12 eccentrically loaded stub column tests, 30 long column tests, as well as measurements of geometrical imperfections and residual stresses. Numerical models, validated against the test results, were also developed to examine the cross-section and member behaviour, and subsequently employed in a comprehensive parametric study in order to generate further data. Based on the combined test and numerical data set, as well as experimental results reported in the literature, the current HSS design rules in Eurocode 3, including the slenderness limits for cross-section classification, effective width equation, N-M interaction curves and column buckling curves, were assessed by means of reliability analyses in accordance with Annex D of EN 1990. To realise the potential of HSS in long span structures, a novel structural form was also examined, namely an HSS truss with prestressing cables housed within the tubular bottom chord. A total of 4 prestressed trusses, made of S460 square hollow sections with different prestress levels, were tested under static downward loading. The truss test results showed the enhanced structural efficiency brought about by the addition of prestressing cables and by the application of prestress. Additionally, 12 tensile and 10 compressive member tests with cables, representing the bottom chord of the truss under gravity and uplift loading, respectively, were carried out to investigate the behaviour of individual prestressed cable-in-tube members. Analytical models and numerical models were also established to compare with the test behaviour and to contribute to the development of design rules for prestressed cable-in-tube systems.
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Rahgozar, Reza. "Fatigue endurance of steel structures subjected to corrosion." Thesis, University of Bristol, 1998. http://hdl.handle.net/1983/ea197da9-80da-4385-a7ed-eabd7acdedec.
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Hinton, Jackson Daniel. "Corrosion of Hydraulic Steel Structures and Preventive Measures." Thesis, Mississippi State University, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=10978643.
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Hydraulic steel structures (HSS) are key components of U.S. Army Corps of Engineers infrastructure and are subject to corrosive environments, unpredictable loadings, and extreme conditions. Corrosion can take many forms and can cause costly damage to HSS due to inadequate design of protective measures. There are numerous forms of corrosion that have a negative effect on HSS, as well as material properties that need consideration when designing HSS preventive measures. Understanding corrosion and providing proper preventive measures is crucial for HSS. Proper maintenance and repair of these protection systems also play a significant part in corrosion control of HSS.
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Gowda, Sunil. "MULTI-SCALE EFFECTS OF CORROSION ON STEEL STRUCTURES." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1469007207.
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Masendeke, Rugare B. "Parametric study of stiffened steel containment shell structures." Master's thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/19019.
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Includes bibliographical references. .A FEM-based parametric study is undertaken to investigate the buckling behavior of meridionally and circumferentially stiffened steel cylindrical and conical shell frustum subjected to different load cases. This situation arises in different steel shell applications such as storage vessels (liquid, solid and gas) and in certain configurations of industrial process facilities. The stiffeners are flat strips of rectangular section welded on to the outer surface of the shell, either over the whole length of the shell meridian or around the circumference of the shell. It is required to establish how the elastic buckling load and mode shapes vary with respect to certain key parameters of the problem. The parameters of interest in the study include the number of stiffeners around the shell circumference and along the meridian, the stiffener-depth to shell-thickness ratio, and the stiffener depth-to-width ratio. This thesis reports the findings of the parametric study and also presents some results of experimental tests on laboratory small-scale models of stiffened cylindrical and conical frusta.
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Oosthuizen, Phillip. "Assessment of steel structures subjected to fire conditions." Master's thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/5013.
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RUNGTHONGBAISUREE, Somkiat. "FUNDAMENTAL INVESTIGATIONS ON CORROSION DETERIORATION OF STEEL STRUCTURES." Kyoto University, 1991. http://hdl.handle.net/2433/138450.
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Hayes, Alethea M. "Compression behavior of linear cellular steel." Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/32857.
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Theofanous, Marios. "Studies of the Nonlinear response of stainless steel structures." Thesis, Imperial College London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509809.
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Kimura, Fumiaki. "Probabilistic Design of Steel Structures Applied to Offshore Pipelines." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511814.
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Ting, Arthur Kung Kii. "Time Equivalent for Protected Steel and Reinforced Concrete Structures." Thesis, University of Canterbury. Civil Engineering, 1999. http://hdl.handle.net/10092/8296.
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This report aims to evaluate the reliability of the formulae commonly used to determine the severity of a compartment fire. It briefly explains the concept behind fire resistance rating for structural elements, describing how the severity of a 'real' compartment fire is equated to that of the 'standard' fire used in laboratories for fire resistance testing. This is followed by a discussion of the computer method used in this report in dissecting those formulae and the development of some computer techniques for calculating fire severity.
Apart from that, various physical parameters of a compartment such as the opening sizes are looked at to determine the significance of their influence on the fire severity.
This report also goes beyond the works carried out in the past and examines the validity of the formulae for scenarios that have not previously been considered and explores the validity of the calculation methods intended for steel member for reinforced concrete structure. Finally some discussions and conclusions are made from the findings.
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Lane, Barbara. "The response of steel frame structures under fire conditions." Thesis, University of Edinburgh, 1997. http://hdl.handle.net/1842/12119.
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In June 1990 a fire occurred in a large contractors' hut on the first floor of a 14 storey steel framed building in the Broadgate development. Despite large deflections the structure behaved well and there was no collapse of any of the beams, columns or floors. A major investigation was undertaken of the fire and the structural performance. It was concluded that the building behaved as a framework of elements though designed as a collection of isolated elements. The connections were able to accommodate large deformations and forces without failure. Hence when the framework acts as a total entity structural stability is significantly improved. The investigation recommended that more research and analysis was required to study the characteristics of frame action in fires. This thesis details a study of the behaviour of multi-storey frames at elevated temperatures. A series of pairs of five storey two bay plane steel frames were designed to demonstrate restrained column collapse behaviour and column collapse due to hinges forming in the restraining beams at ambient temperatures. In a pair, both frames collapse under the same applied load but each frame displays one of the collapse mechanisms. This thesis chronicles the construction of the frames and the tests carried out at ambient temperatures and under various heating configurations. A non-linear elastic frame analysis was developed based on the slope deflection method. The reduction in flexural stiffness of the critical column due to bending plasticity is modelled with a non-linear spring. This analysis is used to predict the collapse load and collapse state of each frame tested. Comparisons are made with predictions from the EC3 simple column design method. The non-linear elastic frame analysis is also used to investigate the frame responses which occur due to the presence of elevated temperatures.
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Nemir, M. T. M. "Finite element stability analysis of thin-walled steel structures." Thesis, University of Salford, 1985. http://usir.salford.ac.uk/2219/.
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Recent applications in the use of light gauge steel members have been concerned with developing large scale systems built entirely from cold-formed steel members. An explicit analysis of such structures is complicated by the different phenomena that the structure may be prone to during loading. In particular, elastic buckling phenomena is an important consideration in the design of such structures since the load at which buckling occurs often provides a close upper bound to the carrying capacity of the structure. The first part of this two-part thesis (Part I, Chaptersl-8) has been devoted to general methods of analysis of the torsional-flexural buckling of thin-walled structures. A review of previous investigations and the available methods of solution is presented. A general finite element formulation of the torsional-flexural buckling of thin-walled structures has been derived. The resulting elastic geometric matrix can be used to analyse structures with monosymmetrical members. It also includes the effect of sectorial-monosymmetry for cross-sections without any axis of symmetry. A general transformation matrix has been developed to allow for the application of the finite element method to the three-dimensional elastic stability analysis of space and portal frames. The validity and accuracy of the new finite element formulation have been checked by analysing a number of different elastic lateral buckling problems for which exact or highly accurate solutions by other techniques are available. An experimental program was carried out on simply supported cold-formed steel z-beams. The first part of this program was undertaken to check the validity of the finite element calculations of the bimoments caused by nonuniform torsion. The second part was devoted to elastic lateral buckling of z-beams under combined bending and torsion. The second part of this thesis (Part II, Chapter 9) deals with the analysis of hipped roof structures with corrugated steel roof sheeting. A simple theoretical model has been suggested. The model has been used to perform an elastic linear analysis of the behaviour of two types of the hipped roof structures. The theoretical results are compared with previous experimental results for these two structures.
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El-, Shihy A. M. "Unwelded shear connectors in composite steel and concrete structures." Thesis, University of Southampton, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374861.
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Chen, Liquan. "Steel corrosion sensing and chloride control in concrete structures /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202008%20CHEN.
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CARDOSO, DEVANEY CRISTINA LIMA. "NUMERICAL MODELING OF SEMI-RIGID CONNECTION FOR STEEL STRUCTURES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1999. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=1270@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORLigações semi-rígidas em estruturas de aço tem apresentado uso crescente na construção metálica, pois é uma opção que permite um melhor aproveitamento da capacidade da estrutura. Neste trabalho apresentam-se as características e a classificação das ligações semi-rígidas bem como a evolução da modelagem numérica e analítica do comportamento destas ligações. Apresenta-se uma metodologia com base no método dos elementos finitos para avaliar numericamente a relação momento-rotação de conexões viga-coluna em estruturas de aço. Parte essencial desta metodologia é a modelagem da ligação e de seus diversos componentes. Um modelo completo em termos da geometria, capaz de representar a interação entre os diversos componentes da conexão é proposto. Esta modelagem inclui a discretização de todos os componentes da conexão: placa e ou cantoneiras, porcas, coluna e viga, sendo a extensão da viga e da coluna a ser considerada no modelo escolhida por calibração do mesmo. O contato entre os componentes da ligação é considerado por meio de algoritmo específico de contato com base na formulação de um problema linear complementar. Considera-se contato sem atrito entre corpos deformáveis. A fim de representar com mais fidelidade as características tridimensionais do problema, adota-se uma modelagem também tridimensional com base em elementos finitos híbridos hexaédricos de oito nós, permitindo o emprego de uma discretização relativamente grosseira. Fenômenos como a presença de grandes deformações, plastificação dos componentes e a pré-tensão dos parafusos são incluídos no modelo. Os modelos apresentados são empregados para o estudo do comportamento de ligações tipo placa de extremidade estendida e tipo cantoneira de alma simples. Para validação dos modelos são comparados os resultados numéricos com dados experimentais. Analisa-se também a participação da flexibilidade dos diversos componentes da conexão, tais como: parafuso, placa de extremidade, mesa da coluna, na resposta da conexão.
Semi-rigid connections are now-a-days widely employed by steel structures. Such connections take better advantage of the overall structure capabilities. In this work the properties and classification of semi-rigid connections is discussed. Additionally numerical and analytical models for prediction of connection behavior are presented. A finite element based methodology for the numerical evaluation of moment-rotation relations and load carrying capacity of semi-rigid connections is proposed. An important feature of this model is a complete a three dimensional geometrical description of the many components of the connection, such as plates, column, beam, bolts and nuts and the interaction between them. The extension of beam and column to be modeled is determined by numerical calibration. Frictionless contact between the connection components is considered by a specific contact algorithm which ensures non- penetration and permits separation of the individual parts. In this work a solution strategy for the contact problem based on the establishment of a linear complementary problem is adopted. The three dimensional modeling is carried out by a mesh of hybrid hexahedral eight node elements, which allow the use of relatively coarse meshes. Effects such as the presence of large deformations, yielding of components and pre- stressing of bolts are present in the model. The proposed model is applied to the analysis of the behavior of extended end-plate connections and web cleat connections. The numerical results are compared to experimental data for model validation. One of the objectives of this analysis is the evaluation of the participation of each component on the overall flexibility of the connection.
El uso de ligaduras semirígidas en extructuras de acero ha experimentado un crescimiento importante en la construcción metálica. Esta opción permite un mejor aprovechamiento de la capacidad de la extructura. En este trabajo se presentan las características de las ligaduras semirígidas, su clasificación; y la evolución de los modelos numéricos y analíticos del comportamiento de estas ligaduras. Se discute una metodología con base en el método de los elementos finitos para evaluar numéricamente la relación momento-rotación de conexiones viga-columna en extructuras de acero. La parte esencial de esta metodología es el modelo de la ligadura y sus diversos componentes. Se propone un modelo completo en términos de geometría, capaz de representar la interacción entre los diversos componentes de la conexión. Este modelo incluye la discretización de todos los componentes de la conexión, siendo que la extensión de la viga y de la coluna a ser considerada en el modelo, deberá ser elegida por calibración del mismo. Para considerar el contacto entre los componentes de la ligadura se utiliza el algoritmo específico de contacto con base en la formulación de un problema lineal complementar. A fin de representar con más fidelidad las características tridimensionales del problema, se adoptó un modelo tridimensional con base en elementos finitos híbridos hexaédricos de ocho nodos, permitiendo el empleo de una discretización relativamente grosera. Se incluyen en el modelo fenómenos como la presencia de grandes deformaciones, plastificación de los componentes y la pretensión de los tornillos. Los modelos presentados se emplean en el estudio del comportamiento de ligaduras tipo placa de extremidad extendida y tipo esquinero de alma simple. Para evaluar los modelos se comparan los resultados numéricos con datos experimentales. También se incluye un análisis de la participación en la respuesta de la conexión, de la flexibilidad de los diversos componentes de la conexión, tales como: tornillo, placa de extremidad, mesa de la columna.
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Kafetsis, Nikolas K. "Applicability of undermatched welds for high strentgh steel structures." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/37813.
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Thesis (Nav.E.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1995.Includes bibliographical references (leaves 182-184).
This study presents experimental and numerical results for the strength of welded joints, made on high strength steels with different degrees of strength matching. The steels involved are the HY-100 and HY-130 U.S. Navy, quenched and tempered steels. The test methods are the self restraint cracking test, the tensile test and the fatigue test. The investigated parameters are the strength of the weld metal and the preheat temperature. The self restraint cracking test does not show clearly the expected results, that the required preheat temperature to avoid cold cracking can be reduced by applying undermatched welds at the root of the welding. This conclusion was reached in a similar experiment that was performed on HT-80 high strength steel. The tensile test and the numerical analysis show that the strength properties of the undermatched weld are not the typical properties of the unrestrained weld material. They are greatly elevated due to the restraint effect provided by both the base metal and the stronger surrounding weld metal. Results from the fatigue test show that the degree of strength undermatching, does not affect significantly the crack propagation rate at the joint.
by Nikolas K. Kafetsis.
S.M.
Nav.E.
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Boström, Staffan. "Crack location in steel structures using acoustic emission techniques." Doctoral thesis, Luleå tekniska universitet, 1999. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-16784.
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Denna avhandling utvärderar möjligheten att använda akustisk emission (AE) för att detektera och lokalisera sprickor i stora stålkonstruktioner med ett långt avstånd mellan givarna. De industriella/ekonomiska motivet för projektet är att en noggrannare undersökning av befintliga konstruktioners tillstånd medför att utbyte av dessa konstruktioner kan skjutas på framtiden med bibehållen säkerhet, vilket i sin tur medför besparingar för till exempel broägare. Motiv för långt avstånd mellan givarna är att hålla kostnaden förundersökningen nere. Fältförsöken omfattade mätningar på fyra broar och en kranbana. I korthet var resultaten att det ofta gick att detektera sprickor men att säkerheten i metoden behövde förbättras och att mättiderna behövde reduceras. MAE utvecklades och den baseras på digital signalbehandling samt användandet en ny detektor för att upptäcka AE signaler. Den största fördelen med den nya tekniken är att bruset reduceras, vilket innebär att även svaga signaler går att detektera. Resultat från laboratorieförsök och försök ute i fält visar att MAE kan användas för sprickdetektering och lokalisering med ett avstånd mellan givarna på upp till 20m. Det är dock viktigt att den verkliga våghastigheten för konstruktionen bestäms. I jämförelse med traditionell AE kan mättiderna med MAE kortas, vilket leder till enklare och billigare kontroller/undersökningar av konstruktioners tillstånd.Godkänd; 1999; 20061117 (haneit)
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Lopes, Nuno Filipe Ferreira Soares Borges. "Behaviour of stainless steel structures in case of fire." Doctoral thesis, Universidade de Aveiro, 2009. http://hdl.handle.net/10773/2412.
Full textAbstract:
Doutoramento em Engenharia CivilA presente tese resulta de um trabalho de investigação, cujo objectivo se centrou no aumento de conhecimento do comportamento estrutural do aço inoxidável, na construção. O aço inoxidável tem várias características desejáveis num material estrutural. Embora inicialmente mais caras que em aço carbono convencional, estruturas em aço inoxidável podem ser competitivas em virtude de necessitarem de uma menor quantidade de material de protecção térmica, e de terem um custo de ciclo de vida mais baixo, contribuindo assim para uma construção mais sustentável. O principal objectivo desta tese consiste em realizar uma avaliação numérica da resistência ao fogo de estruturas em aço inoxidável. Os estudos numéricos foram efectuados através do programa de elementos finitos SAFIR com análises material e geométrica não lineares, que foi especialmente desenvolvido na Universidade de Liège para o estudo de estruturas em situação de incêndio. Estas análises numéricas enquadram-se na metodologia habitualmente designada por GMNIA - geometrically and materially non-linear imperfect analysis. O programa foi também objecto de modificações tendo em vista a realização desses estudos. É demonstrado que, devido às diferenças existentes entre as leis constitutivas do aço carbono e do aço inoxidável, não é possível utilizar em ambos os materiais as mesmas fórmulas para o cálculo da estabilidade de elementos, como é proposto no Eurocódigo 3. Os resultados mostram também que, para alguns elementos estruturais, as fórmulas, preconizadas nessa norma europeia, não estão do lado da segurança, existindo assim necessidade de as melhorar. Estes estudos foram realizados em colunas, vigas e vigas-coluna em aço inoxidável tanto à temperatura ambiente como a altas temperaturas, resultando em novas propostas de dimensionamento para esses elementos. O comportamento de vigas em aço carbono sujeitas a temperaturas elevadas foi também analisado, devido a não ser suficientemente conhecido e as propostas apresentadas nesta tese, para vigas em aço inoxidável, terem sido baseadas nesse comportamento. Esta tese contém também um estudo em elementos de paredes finas em aço inoxidável sujeitos a incêndio, onde é avaliada a influência das tensões residuais nas suas cargas últimas. Por fim apresenta-se uma análise do comportamento estrutural global de duas estruturas em aço inoxidável sujeitas a incêndio, comparando os resultados obtidos com o comportamento das mesmas estruturas em aço carbono.
This thesis is a research work aimed at increasing the knowledge of the structural behaviour of the stainless steel in construction. The stainless steel has countless desirable characteristics for a structural material. Although initially more expensive than conventional carbon steel, stainless steel structures can be competitive because of its smaller need for thermal protection material, and lower life-cycle cost, thus contributing to a more sustainable construction. The main objective of this thesis consists in making a numerical evaluation of the fire resistance of stainless steel structures. The numerical studies were performed using the finite element program SAFIR, with non-linear material and geometric analysis, which was specially developed at the University of Liege, for the study of structures in case of fire. These numerical analyses fit the methodology usually designated GMNIA - geometrically and materially non-linear imperfect analysis. The program was also object of some modifications in order to enable those studies. It is demonstrated that, due to the existing differences in the constitutive laws of carbon steel and stainless steel, it is not possible to use in both materials the same formulae for the member stability calculation, as proposed in Eurocode 3. Moreover, the results show that, the formulae, prescribed on that european norm, are not on the safe side for some structural elements, being necessary their improvement. These studies were made in stainless steel columns, beams and beam-columns at room temperature and at high temperatures, resulting in new design proposals for those members. The behaviour of carbon steel beams at elevated temperatures was also analysed, due to not being sufficiently known and to the proposals presented in this thesis, for stainless steel beams, being based on that behaviour. This thesis contains also a study on thin-walled stainless steel elements in case of fire, where it is evaluated the influence of the residual stresses on their ultimate loads. Finally, an analysis on the global structural behaviour of two stainless steel structures subjected to fire is presented, followed by a comparison of their results with the behaviour of the same structures in carbon steel.