Dissertations / Theses on the topic 'Axial bending'
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Agarwal, Rohit. "Tube bending with axial pull and internal pressure." Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/442.
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Tube bending is a widely used manufacturing process in the aerospace, automotive, and other industries. During tube bending, considerable in-plane distortion and thickness variation occurs. The thickness increases at the intrados (surface of tube in contact with the die) and it reduces at the extrados (outer surface of the tube). In some cases, when the bend die radius is small, wrinkling occurs at the intrados. In industry a mandrel is used to eliminate wrinkling and reduce distortion. However, in the case of a close bend die radius, use of a mandrel should be avoided as bending with the mandrel increases the thinning of the wall at the extrados, which is undesirable in the manufacturing operation. The present research focuses on additional loadings such as axial force and internal pressure which can be used to achieve better shape control and thickness distribution of the tube. Based on plasticity theories, an analytical model is developed to predict cross section distortion and thickness change of tubes under various loading conditions. Results from both the FEA and analytical model indicated that at the intrados the increase in thickness for bending with internal pressure and bending with combined axial pull and internal pressure was nearly the same. But in the case of bending with the combination of axial pull and internal pressure there was a significant reduction of thickness at the extrados. A parametric study was conducted for the case of bending with combined internal pressure and axial pull and it was seen that with proper selection of the pressure and axial pull wrinkling can be eliminated, thickness distribution around the tube can be optimized, and cross section distortion of the tube can be reduced. Predictions of the analytical model are in good agreement with finite element simulations and published experimental results. The model can be used to evaluate tooling and process design in tube bending.
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Rahman, Muhammad Motiur. "Geopolymer concrete columns subjected to axial load and biaxial bending." Thesis, Curtin University, 2013. http://hdl.handle.net/20.500.11937/1410.
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This thesis focuses on the behaviour of fly ash based geopolymer concrete columns under axial load and biaxial bending. Tests showed that failure load of columns increased with the increase of concrete compressive strength and longitudinal reinforcement ratio, and decreased with the increase of load eccentricity. Use of the Bresler’s reciprocal load formula with an iterative procedure for slender columns in uniaxial bending conservatively predicted the strength of the test columns.
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Chenaghlou, Mohammad Reza. "Semi-rigidity of connections in space structures." Thesis, University of Surrey, 1997. http://epubs.surrey.ac.uk/800044/.
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Nanou, Katerina. "Design of open cold rolled sections under axial force and bending moment." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324988.
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Castori, Giulia. "Interaction between axial force, shear and bending moment in reinforced concrete elements." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8519/.
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Il collasso di diverse colonne, caratterizzate da danneggiamenti simili, quali ampie fessure fortemente inclinate ad entrambe le estremità dell’elemento, lo schiacciamento del calcestruzzo e l’instabilità dei ferri longitudinali, ha portato ad interrogarsi riguardo gli effetti dell’interazione tra lo sforzo normale, il taglio ed il momento flettente.
Lo studio è iniziato con una ricerca bibliografica che ha evidenziato una sostanziale carenza nella trattazione dell’argomento.
Il problema è stato approcciato attraverso una ricerca di formule della scienza delle costruzioni, allo scopo di mettere in relazione lo sforzo assiale, il taglio ed il momento; la ricerca si è principalmente concentrata sulla teoria di Mohr.
In un primo momento è stata considerata l’interazione tra solo due componenti di sollecitazione: sforzo assiale e taglio. L’analisi ha condotto alla costruzione di un dominio elastico di taglio e sforzo assiale che, confrontato con il dominio della Modified Compression Field Theory, trovata tramite ricerca bibliografica, ha permesso di concludere che i risultati sono assolutamente paragonabili.
L’analisi si è poi orientata verso l’interazione tra sforzo assiale, taglio e momento flettente. Imponendo due criteri di rottura, il raggiungimento della resistenza a trazione ed a compressione del calcestruzzo, inserendo le componenti di sollecitazione tramite le formule di Navier e Jourawsky, sono state definite due formule che mettono in relazione le tre azioni e che, implementate nel software Matlab, hanno permesso la costruzione di un dominio tridimensionale. In questo caso non è stato possibile confrontare i risultati, non avendo la ricerca bibliografica mostrato niente di paragonabile.
Lo studio si è poi concentrato sullo sviluppo di una procedura che tenta di analizzare il comportamento di una sezione sottoposta a sforzo normale, taglio e momento: è stato sviluppato un modello a fibre della sezione nel tentativo di condurre un calcolo non lineare, corrispondente ad una sequenza di analisi lineari.
La procedura è stata applicata a casi reali di crollo, confermando l’avvenimento dei collassi.
6
LIMA, LUCIANO RODRIGUES ORNELAS DE. "BEHAVIOUR OF STRUCTURAL STEEL ENDPLATE JOINTS SUBJECTED TO BENDING MOMENT AND AXIAL FORCE." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2003. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=4165@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOTradicionalmente, o projeto de pórticos em estruturas de aço assume que as ligações viga-coluna são rígidas ou flexíveis. As ligações rígidas, onde não ocorre nenhuma rotação entre os membros conectados, transferem não só momento fletor, mas também força cortante e força normal. Por outro lado, as ligações flexíveis são caracterizadas pela liberdade de rotação entre os membros conectados impedindo a transmissão de momento fletor. Desconsiderando- se estes fatos, sabe-se que a grande maioria das ligações não possuem este comportamento idealizado. De fato, a maioria das ligações transfere algum momento fletor com um nível de rotação associado. Estas ligações são chamadas semi-rígidas e seu dimensionamento deve ser executado de acordo com este comportamento estrutural real. Porém, algumas ligações viga-coluna estão sujeitas a uma combinação de momento fletor e esforço axial. O nível de esforço axial pode ser significativo, principalmente em ligações de pórticos metálicos com vigas inclinadas, em pórticos não-contraventados ou em pórticos com pavimentos incompletos. As normas atuais de dimensionamento de ligações estruturais em aço não consideram a presença de esforço axial (tração e/ou compressão) nas ligações. Uma limitação empírica de 5 por cento da resistência plástica da viga é a única condição imposta no Eurocode 3. O objetivo deste trabalho é descrever alguns resultados experimentais e numéricos para estender a filosofia do método das componentes para ligações com ações combinadas de momento fletor e esforço axial. Para se cumprir este objetivo, quinze ensaios foram realizados e um modelo mecânico é apresentado para ser usado na avaliação das propriedades da ligação: resistência à flexão, rigidez inicial e capacidade de rotação.
Traditionally, the steel portal frame design assumes that beam-to-column joints are rigid or pinned. Rigid joints, where no relative rotations occur between the connected members, transfer not only substantial bending moments, but also shear and axial forces. On the other extreme, pinned joints, are characterised by almost free rotation movement between the connected elements that prevents the transmission of bending moments. Despite these facts, it is largely recognised that the great majority of joints does not exhibit such idealised behaviour. In fact, many joints transfer some bending moments associated with rotations. These joints are called semi-rigid, and their design should be performed according to their real structural behaviour. However, some steel beam-to-column joints are often subjected to a combination of bending and axial forces. The level of axial forces in the joint may be significant, typical of pitched-roof portal frames, sway frames or frames with incomplete floors. Current standard for steel joints do not take into account the presence of axial forces (tension and/or compression) in the joints. A single empirical limitation of 5 percent of the beam s plastic axial capacity is the only enforced provision in Annex J of Eurocode 3. The objective of the present work is to describe some experimental and numerical results to extend the philosophy of the component method to deal with the combined action of bending and axial forces. To fulfil this objective a set of sixteen specimens were performed and a mechanical model was developed to be used in the evaluation of the joint properties: bending moment resistance, initial stiffness and rotation capacity.
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Scott-Emuakpor, Onome Ejaro. "Development of a novel energy-based method for multi-axial fatigue strength assessment." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1196280356.
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Doruk, Koray. "Fiber Reinforced Polymer Confined Rc Circular Columns Subjected To Axial Load And Bending Moment." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607474/index.pdf.
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Fiber reinforced polymers (FRPs) have gained increasing popularity in upgrades of reinforced structural elements due to high strength to weight ratio and ease of application. In this study, the effectiveness of the carbon reinforced polymer wrapping (CFRP) on ductility and strength of circular reinforced concrete columns, made of low strength concrete, is presented. Four circular reinforced columns with similar dimensions, longitudinal and confining steel reinforcement were tested under combined axial load and bending moment. Three specimens were strengthened with CFRP and the results were compared with the control specimen. The main parameter of the experimental study was selected as the level of eccentricity. First of all, the strain profiles of FRPs in the circumferential direction were observed and the confining stress distributions were examined. Then, an axial stress-strain model for FRP confined concrete with a transition from softening to hardening response for different confinement ratios is proposed. The proposed model was verified by comparing the model estimations with the test results obtained from this study and results reported by other researches. In addition, a parametric study was presented to obtain a simple equation to estimate curvature ductility of FRP confined circular columns.
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Ping, Hsin-Chih. "Coupled axial and bending vibrations of a uniform beam-column with an oblique crack /." Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/7076.
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Jadid, Mansour Nasser. "The application of neural network techniques to the analysis of reinforced concrete beam-column joints subjected to axial load and bi-axial bending." Thesis, University of Edinburgh, 1994. http://hdl.handle.net/1842/14160.
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The application of neural networks in the form of parameter predictions to the behaviour and strength of beam-column joints under axial load and biaxial bending has been studied. Computation algorithms in the form of numerical analysis were performed on the beam-column joints to simulate the existing experimental data. A systematic approach was provided by implementing neural networks in the form of prediction by backpropagation algorithms. The objective of this study was to demonstrate a concept and methodology, rather than to build a full-scale knowledge-based system model, by incorporating most of the fundamental aspects of a neural network to solve the complex non-linear mapping of a beam-column joint. In general, it should be possible to identify certain parameters and allow the neural network to develop the model, thus accounting for the observed behaviour without relying on a particular algorithm but depending entirely on the manipulation of numerical data. The aim of this study was to view available experimental data on beam-column joint parameters from different angles and establish a concept and methodology that would provide rapid and economic benefits to experimental research. The focus of this study is to reconstruct previous experimental work by evaluating several parameters and establish valid mathematical relationships based on neural networks which are in agreement with relationships based on the experimental results. The computational methodology considered for the analysis of the beam-column joints has been formulated by adopting three stages to establish a procedure to implement the concept and methodology proposed. The procedure is demonstrated by the evaluation of the ultimate flexural strength of the reinforced concrete members, the moment-curvature relationship and the shear strength of the beam-column joint.
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Van, Toen Carolyn Yvonne. "Biomechanics of cervical spine and spinal cord injury under combined axial compression and lateral bending loading." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/45728.
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Cervical spine and spinal cord injuries are significant health concerns. Although lateral
forces are present during real-world head-first impacts, there is a lack of information about
combined lateral bending moments with axial compression. The general aim of this research
was to evaluate the effects of lateral bending in dynamic axial compression of the cervical
spine on kinetics, kinematics, canal occlusions, and injuries of the cervical spine and this
required the development of novel loading and measurement apparatus. We experienced
technical challenges in experimentally producing lateral bending moments requiring novel
loading methods. Also, as acoustic emission (AE) signals could provide more objective
estimates of the timing of injuries produced experimentally, these techniques were developed
for use in the spine.
In Study 1, techniques were developed to measure the time of injury of isolated spinal
components using AE signals. Injuries to human cadaver vertebral bodies resulted in AE
signals with higher amplitudes and frequencies than those from ligamentum flavum
specimens.
Study 2 presented a theoretical and experimental evaluation of the effects of test
configuration on bending moments during eccentric axial compression. Design
recommendations were provided that allowed us to apply appropriate bending moments in
the subsequent studies.
In Studies 3, 4, and 5 dynamic axial compression forces with lateral eccentricities were
applied to human cadaver cervical spine segments and AE signals were used to detect the
time of injury. High lateral eccentricities resulted in lower peak axial forces, inferior
displacements, and canal occlusions and greater peak ipsilateral bending moments, bending
rotations, displacements, and spinal flexibilities in lateral bending and axial rotation
compared to low eccentricity impacts. Also, low and high lateral eccentricities produced
primarily hard and soft tissue injuries, respectively. In this three-vertebra model, AE signals
from injuries to endplates and/or vertebral bodies had higher amplitudes and frequencies than
those from injuries to the intertransverse ligament and/or facet capsule.
The effects of lateral bending in dynamic axial compression on injury mechanisms of the
cervical spine and the injury detection techniques demonstrated in this thesis may potentially
assist in the development and improvement of injury prevention and treatment strategies.
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ENCISO, ROXANA OLARTE. "BEHAVIOR OF SLENDER HIGH STRENGTH CONCRETE COLUMNS SUBJECTED TO AXIAL LOAD AND BENDING ABOUT ONE AXIS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2010. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=16425@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOEste trabalho apresenta um estudo experimental do comportamento de pilares esbeltos de alta resistência submetidos à flexão composta reta. Foram ensaiados oito pilares divididos em duas séries, sendo uma série com concreto de 40 MPa e a outra com concreto de 80 MPa aos vinte e oito dias. Todos os pilares tinham seção transversal de 15x25 cm e altura de 300 cm. Em cada série, a variável foi a taxa de armadura longitudinal que assumiu quatro valores diferentes. O objetivo foi verificar os valores da excentricidade de segunda ordem que devem ser considerados no dimensionamento de pilares esbeltos de concreto de alta resistência. Os resultados dos ensaios foram comparados com os resultados teóricos obtidos pelos modelos da curvatura aproximada e da rigidez aproximada que constam na NBR6118:2003. Essa comparação mostrou uma boa concordância entre os resultados experimentais e teóricos.
This work presents an experimental study of the behavior of slender high strength concrete columns under uniaxial eccentric compression loads. Eight columns were tested, divided into two series, one series with concrete of 40 MPa and the other with concrete of 80 MPa at twenty eight days. All columns had a cross-section of 15x25 cm and height of 300 cm. In each series, the variable was the longitudinal reinforcement ratio which assumed four different values. The objective was to verify the values of the eccentricity of second order that should be taken into account in the design of slender high strength concrete columns. The experimental results were compared with theoretical results obtained by the models of the approximated curvature and approximated stiffnes methods prescribed in the NBR6118:2003 code. This comparison showed a good agreement between the experimental and theoretical results.
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Lau, J. C. K. "The strength of masonry walls and columns of geometric cross section subjected to axial load and bending." Thesis, University of Manchester, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.705159.
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Voinier, Steven. "Passive Stiffness Characteristics of the Scoliotic Lumbar Torso in Trunk Flexion, Extension, Lateral bending, and Axial Rotation." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/52241.
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As the average American age increases, there is a need to study the spine biomechanics of adults with scoliosis. Most studies examining the mechanics of scoliosis have focused on in vitro testing or computer simulations, but in vivo testing of the mechanical response of a scoliotic spine has not yet been reported. The purpose of this study was to quantitatively define the passive stiffness properties of the in vivo scoliotic spine in three principle anatomical motions and identify differences relative to healthy controls.
Scoliotic (n=14) and control (n=17) participants with no history of spondylolisthesis, spinal fracture, or spinal surgery participated in three different tests (torso lateral side bending, torso axial rotation, and torso flexion/extension) that isolated mobility to the in vivo lumbar spine. Scoliotic individuals with Cobb angles ranging 15-75 degrees were accepted. Applied torque was measured using a uni-directional load cell, and inertial measurement units (IMU) recorded angular displacement of the upper torso relative to the pelvis and lower extremities. Torque-rotational displacement data were fit using a double sigmoid function, resulting in excellent overall fit (R2 > 0.901). The neutral zone (NZ) width, or the range of motion where there is minimal internal resistance, was then calculated. Stiffnesses within the NZ and outside of the NZ were also calculated. Stiffness asymmetries were also computed within each trial. These parameters were statistically compared between factor of population and within factor of direction.
There was an interaction effect between populations when comparing axial twist NZ width and lateral bend NZ width. The lateral bend NZ width magnitude was significantly smaller in scoliotic patients. NZ stiffness in the all three directions was greater in the scoliotic population. There was no significant difference in asymmetrical stiffness between populations.
The present study is the first investigation to quantify the in vivo neutral zone and related mechanics of the scoliotic lumbar spine. Future research is needed to determine if the measured lumbar spine mechanical characteristics can help explain progression of scoliosis and complement scoliosis classification systems.Master of Science
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Walters, Martin. "The effects of wall inertia and axial bending on instabilities in flow through an elastic-walled tube." Thesis, University of East Anglia, 2016. https://ueaeprints.uea.ac.uk/58536/.
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In certain parameter regimes, steady flow through flexible tubes is unstable to self-excited oscillations. Whittaker et al. (2010, Proc. Roy. Soc. A 466) solved an asymptotic model for the onset of self-excited oscillations in a long, thin-walled,flexible tube clamped between two rigid tubes, with a large axial tension. This work neglected effects such as wall inertia, axial bending, and in-plane shear forces. Whittaker (2015, IMA J. Appl. Math.) reintroduced in-plane shearing and found a shear-relaxation boundary layer at the tube ends. In this thesis,wall inertia and axial bending are reintroduced into these models. In Chapter 2, wall inertia terms are added to the governing equations for the wall mechanics, and a new ‘tube law’ describing the wall motion is derived. Combining this with a description of the fluid mechanics, the effect of wall inertia on the oscillations is quantified. Wall inertia is found to be a destabilising effect. In Chapters 3–7, axial bending is reintroduced allowing ‘clamped’ boundaryconditions to be satisfied at the tube ends. Three different regimes dependent on the dimensionless length and wall thickness of the tube are found. Chapters 4–5 concentrate on the two regimes where the shear layer found by Whittaker (2015) must be considered. An axial bending boundary layer that induces higher-order corrections to the shear layer and bulk solution is found in these regimes. In Chapters 6–7, a final regime is considered where the shear layer no longer needs consideration, but a new model for the wall mechanics is needed. Deriving and solving a linearised 2D model for bending a semi-infinite block under tension, corresponding to a 2D cross-section of the tube wall, a new transverse shear-relaxation layer is found. This boundary layer allows clamped boundary conditions to be satisfied and induces higher-order corrections to the bulk solution.
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Bairán, García Jesús Miguel. "A non-linear coupled model for the analysis of reinforced concrete sections under bending, shear, torsion and axial forces." Doctoral thesis, Universitat Politècnica de Catalunya, 2005. http://hdl.handle.net/10803/6177.
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La mayoría de las estructuras de hormigón armado se someten a solicitaciones combinadas de esfuerzos axiles, flexión, cortante y torsión. La fisuración del hormigón, plastificación de las armaduras y otros efectos no-lineales hacen que las secciones transversales de estos elementos presenten un comportamiento anisótropo que deriva en el acoplamiento de los esfuerzos normales y tangenciales. Es decir, esfuerzos normales o momentos flectores pueden producir deformaciones de corte y vice versa. Aunque en algunas ocaciones, esta interacción es considerada de forma simplificada en el dimensionamiento de estructuras, hasta el momento no se ha realizado un análisis profundo de los efectos acoplados en secciones de forma arbitraria bajo cargas 3D generales utilizando modelos de fibras.El objetivo principal de esta tesis es generalizar el análisis de secciones de hormigón armado mediante fibras, de forma que se pueda reproducir la res-puesta no-lineal acoplada frente a esfuerzos normales y tangenciales bajo solicitaciones tridimensionales generales. De igual forma, se pretende obtener, para los esfuerzos cortantes y torsión, la misma capacidad de representación de geometrías y combinación de materiales que ofrecen los modelos de fibras para esfuerzos de flexo-compresión.
La primera problemática estriba en representar adecuadamente la cinemática de la sección transversal. Con la excepción de las deformaciones normales contenidas en el plano de la sección, no existe una teoría cinemática que a priori pueda dar la distribución del resto de deformaciones o tensiones en la sección, sin dejar de satisfacer las condiciones de equilibrio interno o continuidad entre las fibras que componen la misma.
Por otra parte, para materiales anisótropos, como el hormigón fisurado, en general todos los esfuerzos internos pueden estar acoplados. Además, es preciso considerar la distorsión de la sección transversal para satisfacer el equilibrio entre fibras.
El problema se aborda de forma general, considerando una sección de forma y materiales cualesquiera. Se parte del problema diferencial de equilibrio de un sólido con el que se ha podido deducir un sistema de equilibrio entre fibras (equilibrio a nivel sección). Se puede demostrar que éste es complementario al problema estándar de vigas. El sistema complementario permite recuperar información tridimensional que normalmente se pierde al resolver un problema de vigas.
Posteriormente, se propone una solución interna del problema complementario, en la que el alabeo y la distorsión de la sección quedan expresados como una función de las deformaciones generalizadas de una viga: deformaciones axil y cortantes, curvaturas de flexión y torsión. No son necesarios grados de libertad adicionales a nivel estructura ni hipótesis a-priori sobre la forma de los campos de deformación o tensión interna.
A partir de la formulación teórica, se desarrolla un modelo de elementos finitos plano de la sección transversal. El modelo está preparado para servir como respuesta constitutiva de cualquier tipo de elemento viga en sus puntos de integración. %Se evita así la necesidad de realizar un modelo de elementos sólidos de toda la barra para estudiar la respuesta frente a una combinación general de esfuerzos normales y tangenciales.
Se implementan una serie de modelos constitutivos para distintos materiales. En particular, se implementa un modelo constitutivo triaxial para hormigón fisurado, considerando la anisotropía inducida por la fisuración e incluyendo la superficie de rotura según un criterio multiaxial.
La formulación seccional es validada mediante varios casos de estudio teóricos y experimentales. La respuesta no-lineal acoplada bajo diversas combinaciones de esfuerzos normales y tangenciales es reproducida con precisión, lo cual queda patente tanto en las curvas esfuerzo-deformación obtenidas como en las matrices de rigidez seccionales.
Finalmente, se recopilan las conclusiones derivadas de la presente investigación y se
ofren recomendaciones para futuros trabajos.
Most RC structures are subjected to combined normal and tangential forces, such as bending, axial load, shear and torsion. Concrete cracking, steel yielding and other material nonlinearities produce an anisotropic sectional response that results in a coupling between the effects of normal and shear forces, i.e. normal force or bending moments may produce shear strains and vice versa. Although this interaction is sometimes taken into account, in a simplified manner, in the design of RC structures, a deep analysis of the coupling effects of RC sections using fiber models has not yet been made for arbitrary shape sections under general 3D loading.
The main objective of this thesis is to generalize the fiber-like sectional analysis of reinforced concrete elements, to make it capable of considering the coupled non-linear response under tangential and normal internal forces, from a general 3D loading.
Similarly, it is desired to obtain, for torque and shear forces, the same capacity and versatility in reproducing complex geometry and materials combination that fiber-like sectional representations offers for bending and stretching.
The first problematic lies in finding a proper representation of the section's kinematics under such general loading. Except for in-plane normal strains, there is no single kinematical theory capable of a-priori representing the correct distribution of the others strains or stresses satisfying, at the same time, inter-fiber equilibrium and continuity. On the other hand, for rather anisotropic materials, such as cracked concrete, all internal forces are, in general, coupled. It is also required that distortion is allowed for the section's kinematics in order to guarantee satisfaction of internal equilibrium.
The problem is dealt in a general form considering arbitrary shaped sections and any material behaviour. Starting from the differential equilibrium of a solid, an inter-fiber equilibrium system (equilibrium at the sectional level) was deduced. This system, which is complementary to the standard equilibrium problem of a beam-column, allows to recuperate information of the three-dimensional problem that is generally lost when solving a beam problem.
Further, a solution of the equilibrium at the sectional level is proposed in which the section's warping and distortion are posed as a function of the generalized beam-column strains (axial and shear strains, bending and torsion curvatures). No additional degrees of freedom are required at the structural level nor a-priori hypotheses on the distribution of the internal strains or stresses.
After the theoretical formulation, a planar finite element model for cross-sectional analysis is developed. The model can be used as a constitutive law for general beam column elements at their integration points.
A series of constitutive models have been implemented for several materials. In particular, a triaxial constitutive model for cracked concrete is implemented considering crackinduced anisotropy and a multiaxial failure criterion.
The sectional formulation is validated by means of various theoretical and experimental case studies. Non-linear coupled response under normal and tangential internal forces is reproduced with accuracy, as can be seen both in the predicted internal force-strain curves and in the sectional stiffness matrixes.
Finally, the conclusions drawn from the current research are summarized and
recomendations for future works are given.
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Engström, Anders, and Toma Sumbasacu. "The length effect on Norway spruce boards : An investigation on indicating properties based on axial dynamic and edgewise bending MOEs." Thesis, Linnéuniversitetet, Institutionen för byggteknik (BY), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-49099.
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When using timber for construction purposes it is important to know its strength. One way to do this is by sorting the boards into strength classes that are defined by European standards. A commonly used method for strength grading is based on dynamic excitation in the longitudinal direction of the board to obtain an average dynamic longitudinal modulus of elasticity (MOE). This in turn correlates with the bending strength of the board in such a way that it can be used as an indicating property (IP) to bending strength. The use of MOE as an IP has proven to give the highest coefficient of determination (R2) to both bending and tensile strength in boards. Through the research described in this thesis, one might find that both reducing the length of a board to half its initial length and by removing the part containing the lowest local MOE in edgewise bending provided similar results, the axial dynamic MOE remaining within a 1% tolerance whereas the lowest IP based on local MOE in edgewise bending increased by 6–7%.
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Shope, Ronald L. "Response of Wide Flange Steel Columns Subjected to Constant Axial Load and Lateral Blast Load." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/29521.
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The response of wide flange steel columns subjected to constant axial loads and lateral blast loads was examined. The finite element program ABAQUS was used to model W8x40 sections with different slendernesses and boundary conditions. For the response calculations, a constant axial force was first applied to the column and the equilibrium state was determined. Next, a short duration, lateral blast load was applied and the response time history was calculated. Changes in displacement time histories and plastic hinge formations resulting from varying the axial load were examined. The cases studied include single-span and two-span columns. In addition to ideal boundary conditions, columns with linear elastic, rotational supports were also studied. Non-uniform blast loads were considered. Major axis, minor axis, and biaxial bending were investigated. The effects of strain rate and residual stresses were examined. The results for each column configuration are presented as a set of curves showing the critical blast impulse versus axial load. The critical blast impulse is defined as the impulse that either causes the column to collapse or to exceed the limiting deflection criterion.
A major goal of this effort was to develop simplified design and analysis methods. To accomplish this, two single-degree-of-freedom approaches that include the effects of the axial load were derived. The first uses a bilinear resistance function that is similar to the one used for beam analysis. This approach provides a rough estimate of the critical impulse and is suitable only for preliminary design or quick vulnerability calculations. The second approach uses a nonlinear resistance function that accounts for the gradual yielding that occurs during the dynamic response. This approach can be easily implemented in a simple computer program or spreadsheet and provides close agreement with the results from the finite element method.Ph. D.
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Schmitt, Bernardo. "Ensaio biomecânico para determinação do diâmetro de barra conectora de polimetilmetacrilato em fixador esquelético externo tipo Ia: no úmero de suínos." Universidade Federal de Santa Maria, 2014. http://repositorio.ufsm.br/handle/1/10211.
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Conselho Nacional de Desenvolvimento Científico e TecnológicoWhile seemingly inert appearance, bones are highly dynamic structures, which promote formation, resorption, repair and maintenance of homeostasis. Fractures in bones occur when the load applied to a specific bone region exceeds its resilience. The use of external skeletal fixator (ESF) is a method of fairly common internal stabilization, in which connector bars polymethylmethacrylate (PMMA) are used without criterion in diameter. In these cases, it can break if it gets too thin or too heavy and uncomfortable when bulky. The aim of this study was to test biomechanical through axial compression and bending, considering different connector bar diameter PMMA correlated to bone diameter for use to type Ia ESF. For this, it was collected 24 swine humerus to make measurements of length, diameter, circumference and testing biomechanical. After the bars confected with 1.5 times the average diameter of the bone (group I), the same diameter bone (group II) and 0.5 times the diameter of the bone (group III). The results obtained, it was observed that the connector bars in group II were more resistant than the bones in the compression test. In the bending test, the bones resisted flexion strength when compared to group III. The group II was 4.3 times more resistant than Group III in the same mechanical test. The results allow a direction for making bars PMMA considering bone diameter as a reference.
Apesar do seu aspeto aparentemente inerte, os ossos são estruturas altamente dinâmicas, envolvidas em constante formação, reabsorção, reparação e manutenção da homeostasia. As fraturas ocorrem quando a carga aplicada sobre determinada região do tecido ósseo supera sua capacidade de resistência. A utilização de fixadores esqueléticos externos (FEE) é método de estabilização interna bastante frequente, no qual podem ser utilizadas barras conectoras de polimetilmetacrilato (PMMA) sem preocupação com o diâmetro. Tais barras podem quebrar se ficarem muito delgadas ou tornarem-se desconfortáveis quando volumosas e pesadas. O objetivo deste trabalho foi testar, por meio de ensaio biomecânico de compressão axial e flexão, qual é o diâmetro mais adequado para a barra conectora de PMMA, correlacionado as dimensões da barra com o diâmetro ósseo para FEE tipo Ia. Para tanto, coletaram-se 24 úmeros suínos para a realização de medidas de comprimento, diâmetro, circunferência e os ensaios biomecânicos. Após, confeccionaram-se barras de 1,5 vezes a média do diâmetro ósseo (grupo I), do mesmo diâmetro (grupo II) e 0,5 vez o diâmetro ósseo (grupo III). Com os resultados obtidos ao comparar os valores dos ossos com os dos grupos II e III, verificou-se que as barras conectoras do grupo II mostraram-se mais resistente do que o tecido ósseo no ensaio de compressão. No ensaio de flexão, o osso foi mais resistente à força de flexão quando comparados ao grupo III. O grupo II foi 4,3 vezes mais resistente do que o grupo III nesse mesmo ensaio. O grupo I apresentou secagem incompleta, onde seu comportamento não foi similar com o restante dos grupos, por isso, não participou da estatística do trabalho. Os resultados permitem um direcionamento para confecção de barras de PMMA do mesmo diâmetro ósseo, sendo suficiente para sustentar sem quebrar um FEE tipo Ia.
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Borges, Ana Cláudia Leão. "Análise de pilares esbeltos de concreto armado solicitados a flexo-compressão oblíqua." Universidade de São Paulo, 1999. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-06122017-144257/.
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Como conseqüência do atual desenvolvimento tecnológico dos materiais aço e concreto, várias pesquisas têm surgido com vistas a um melhor aproveitamento da capacidade desses dois materiais, exigindo um maior conhecimento sobre o comportamento dos elementos, inclusive sobre sua vulnerabilidade a estados limites últimos. Sendo a instabilidade um estado limite último possível de ocorrer em configurações de equilíbrio de peças de concreto armado submetidas a determinadas solicitações normais, seu estudo torna-se fundamental para que seja possível propor soluções estruturais seguras e economicamente viáveis. Este trabalho apresenta a análise de alguns aspectos que interferem no estudo da estabilidade de pilares esbeltos de concreto armado, através de uma abordagem envolvendo aspectos teóricos, como também aspectos práticos oriundos da resolução de exemplos. O estudo é feito com base nos métodos geral e do equilíbrio, com os processos exato e do pilar padrão, através de um software (SISTEMA FLEXOR), desenvolvido por CADAMURO Jr. (1997). O objetivo é testar a viabilidade desses métodos a fim de propor soluções e, com isso, tornar mais amplo e acessível o uso de pilares esbeltos de concreto armado, incentivando a adoção de projetos mais arrojados sem subutilização dos materiais.As a consequence of the actual technological development of the materials steel and concrete, many researches have come up with proposal of better use of these two materials capacity, demanding a bigger knowledge about the behaviour of the elements, included your vulnerability to ultimate limit states. Being the instability a possible ultimate limit state of reinforced concrete columns equilibrium configuration, this study has been fundamental to make possible to propose safe and economically reasonable structural solutions. This work presents the analysis of some aspects that interfere in the study of slender reinforced concrete columns stability, through an approach involving theoretical and practical aspects derived from numerical solutions. The scheme is based in the General and Equilibrium Methods with the Exact Process and Model Column Method, through a software (SISTEMA FLEXOR) developed by CADAMURO Jr. (1997). The objective is to testify the practicability of these methods, to propose solutions and to render wider and more practical the use of slender reinforced concrete columns, stimulating the adoption of projects bolders without underutilisation of the materials.
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Williams, Zachary. "Krouse Fatigue for Metals with Elevated Mean Stress." Ohio University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1597075964521893.
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Thilakarathna, Herath Mudiyanselage Indika. "Vulnerability assessment of reinforced concrete columns subjected to vehicular impacts." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/43693/1/Herath_Thilakarathna_Thesis.pdf.
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Columns are one of the key load bearing elements that are highly susceptible to vehicle impacts. The resulting severe damages to columns may leads to failures of the supporting structure that are catastrophic in nature. However, the columns in existing structures are seldom designed for impact due to inadequacies of design guidelines. The impact behaviour of columns designed for gravity loads and actions other than impact is, therefore, of an interest.
A comprehensive investigation is conducted on reinforced concrete column with a particular focus on investigating the vulnerability of the exposed columns and to implement mitigation techniques under low to medium velocity car and truck impacts. The investigation is based on non-linear explicit computer simulations of impacted columns followed by a comprehensive validation process. The impact is simulated using force pulses generated from full scale vehicle impact tests. A material model capable of simulating triaxial loading conditions is used in the analyses. Circular columns adequate in capacity for five to twenty story buildings, designed according to Australian standards are considered in the investigation. The crucial parameters associated with the routine column designs and the different load combinations applied at the serviceability stage on the typical columns are considered in detail.
Axially loaded columns are examined at the initial stage and the investigation is extended to analyse the impact behaviour under single axis bending and biaxial bending. The impact capacity reduction under varying axial loads is also investigated. Effects of the various load combinations are quantified and residual capacity of the impacted columns based on the status of the damage and mitigation techniques are also presented. In addition, the contribution of the individual parameter to the failure load is scrutinized and analytical equations are developed to identify the critical impulses in terms of the geometrical and material properties of the impacted column. In particular, an innovative technique was developed and introduced to improve the accuracy of the equations where the other techniques are failed due to the shape of the error distribution.
Above all, the equations can be used to quantify the critical impulse for three consecutive points (load combinations) located on the interaction diagram for one particular column. Consequently, linear interpolation can be used to quantify the critical impulse for the loading points that are located in-between on the interaction diagram. Having provided a known force and impulse pair for an average impact duration, this method can be extended to assess the vulnerability of columns for a general vehicle population based on an analytical method that can be used to quantify the critical peak forces under different impact durations. Therefore the contribution of this research is not only limited to produce simplified yet rational design guidelines and equations, but also provides a comprehensive solution to quantify the impact capacity while delivering new insight to the scientific community for dealing with impacts.
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Ma, Jiayao. "Thin-walled tubes with pre-folded origami patterns as energy absorption devices." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:7502b18d-674d-4eff-bbc4-e649aa4d7f42.
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This dissertation is concerned with a type of energy absorption device made of thin-walled tubes. The tubes will undergo plastic deformation when subjected to an impact loading, and therefore absorb kinetic energy. It has been found that, if the surface of a tube is pre-folded according to an origami pattern, the failure mode of the tube can be altered, leading to a noticeable increase in energy absorption while at the same time, reducing the force needed to initiate plastic deformation within the tube. The main work is presented in four parts. First of all, an experimental study of a type of previously reported thin-walled square tube with pre-manufactured pyramid patterns on the surface has been conducted. Quasi-static axial crushing tests show that the octagonal mode, although numerically proven to be efficient in terms of energy absorption, cannot be consistently triggered. Secondly, a new type of thin-walled tubular energy absorption device, known as the origami tube, which has origami pattern pre-fabricated on the surface, has been studied. A family of origami patterns has been designed for tubes with different profiles. The performances of a series of origami tubes with various configurations subjected to quasi-static axial crushing have been investigated numerically. It is found that a new failure mode, referred to as the complete diamond mode, can be triggered, and both over 50% increase in the mean crushing force and about 30% reduction in the peak force can be achieved in a single tube design in comparison with those of a conventional square tube with identical surface area and wall thickness. A theoretical study of the axial crushing of square origami tubes has been conducted and a mathematical formula has been derived to calculate the mean crushing force. Comparison between theoretical prediction and numerical results shows a good agreement. Quasi-static axial crushing experiments on several square origami tube samples have been carried out. The results show that the complete diamond mode is formed in the samples and both peak force reduction and mean crushing force increase are attained. Thirdly, a new type of curved thin-walled beam with pre-manufactured origami pattern on the surface, known as the origami beam, has been designed and analyzed. A numerical study of a series of origami beams with a variety of configurations subjected to quasi-static lateral bending has been conducted. The results show that two new failure modes, namely, the longitudinal folding mode and the mixed mode, can be induced, and both reduced peak force and increased energy absorption are achieved. Finally, a number of automobile frontal bumpers, which have the origami tube and the origami beam as key components, have been designed and analyzed. Three impact tests have been conducted on each bumper. The numerical results show that both types of origami structures can perform well in realistic loading scenarios, leading to improved energy absorption of the bumpers.
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Jämting, Åsa. "Mechanical properties of thin sol-gel films." Thesis, Queensland University of Technology, 1999. https://eprints.qut.edu.au/36085/6/A%CC%8Asa%20J%C3%A4mting_Digitised%20Thesis.pdf.
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This thesis presents a study of the mechanical properties of thin films. The main aim was to determine the properties of sol-gel derived coatings. These films are used in a range of different applications and are known to be quite porous. Very little work has been carried out in this area and in order to study the mechanical properties of sol-gel films, some of the work was carried out on magnetron sputtered metal coatings in order to validate the techniques developed in this work.
The main part of the work has concentrated on the development of various bending techniques to study the elastic modulus of the thin films, including both a small scale three-point bending, as well as a novel bi-axial bending technique based on a disk resting on three supporting balls. The bending techniques involve a load being applied to the sample being tested and the bending response to this force being recorded. These experiments were carried out using an ultra micro indentation system with very sensitive force and depth recording capabilities. By analysing the result of these forces and deflections using existing theories of elasticity, the elastic modulus may be determined. In addition to the bi-axial bending study, a finite element analysis of the stress distribution in a disk during bending was carried out.
The results from the bi-axial bending tests of the magnetron sputtered films was confirmed by ultra micro indentation tests, giving information of the hardness and elastic modulus of the films.
It was found that while the three point bending method gave acceptable results for uncoated steel substrates, it was very susceptible to slight deformations of the substrate. Improvements were made by more careful preparation of the substrates in order to avoid deformation. However the technique still failed to give reasonable results for coated specimens. In contrast, biaxial bending gave very reliable results even for very thin films and this technique was also found to be useful for determination of the properties of sol-gel coatings.
In addition, an ultra micro indentation study of the hardness and elastic modulus of sol-gel films was conducted. This study included conventionally fired films as well as films ion implanted in a range of doses. The indentation tests showed that for implantation of H+ ions at doses exceeding 3x1016 ions/cm2, the mechanical properties closely resembled those of films that were conventionally fired to 450°C.
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Nunes, Pedro Carlos da Lomba. "Análise Paramétrica de Ligações com Placa de Extremidade em Estruturas de Aço Submetidas a Momento Fletor e Força Axial." Universidade do Estado do Rio de Janeiro, 2006. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=424.
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Fundação Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de JaneiroUsualmente, o projeto de pórticos em estruturas de aço assume que as ligações viga-coluna são rígidas ou flexíveis. As ligações rígidas, onde não ocorre nenhuma rotação entre os membros conectados, transferem não só momento fletor, mas também força cortante e força normal. Por outro lado, as ligações flexíveis são caracterizadas pela liberdade de rotação entre os membros conectados impedindo a transmissão de momento fletor. Sabe-se que a grande maioria das ligações não possuem este comportamento idealizado. Na realidade, a maioria das ligações transfere algum momento fletor com um nível de rotação associado. Estas ligações são denominadas semi-rígidas e seu dimensionamento deve ser executado de acordo com este comportamento estrutural. Contudo, algumas ligações viga-coluna estão sujeitas a uma combinação de momento fletor (M) e força axial (N). O nível de esforço normal pode ser significativo, principalmente em ligações de pórticos metálicos com vigas inclinadas, em pórticos não- contraventados ou em pórticos com pavimentos incompletos. As normas atuais de dimensionamento de ligações estruturais em aço não consideram a presença de esforço normal (tração e/ou compressão) nas ligações. Uma limitação empírica de 5% da resistência plástica da viga é a única condição imposta no Eurocode 3. O objetivo deste trabalho é realizar uma análise paramétrica de dois tipos de ligações aparafusadas para se avaliar a influência de combinações M/N no comportamento global destas ligações. Para se cumprir este objetivo, os resultados experimentais de quinze ensaios realizados por Lima [1] são comparados com os resultados obtidos através de um modelo analítico proposto por Cerfontaine [2], [3].
Traditionally, the steel portal frame design assumes that beam-to-column joints are rigidor pinned. Rigid joints, where no relative rotations occur between the connected members, transfer not only substantial bending moments, but also shear and axial forces. On the other extreme, pinned joints, are characterised by almost free rotation movement between the connected elements that prevents the transmission of bending moments. Despite these facts, it is largely recognised that the great majority of joints does not exhibit such idealised behaviour. In fact, many joints transfer some bending moments with associated rotations. These joints are called semi-rigid, and their design should be performed according to their real structural behaviour. However, some steel beam-to-column joints are often subjected to a combination of bending (M) and axial forces (N). The level of axial forces in the joint may be significant, typical of pitched-roof portal frames, sway frames or frames with incomplete floors. Current standard for steel joints do not take into account the presence of axial forces (tension and/or compression) in the joints. A single empirical limitation of 5% of the beams plastic axial capacity is the only enforced provision in Eurocode 3. The objective of the present work is to perform a parametrical analysis of two bolted joints types in order to evaluate the influence of M/N combinations in the joints global response. To fulfil this objective, the experimental results obtained by Lima [1] are compared to the analytical results using the Cerfontaine analytical model [2], [3].
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Mercier, Charlotte. "Développement d’un modèle de stabilité des barres à section tubulaire comprimées fléchies sensibles aux effets du second ordre." Thesis, Université de Lorraine, 2019. http://www.theses.fr/2019LORR0113/document.
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Cette thèse s’inscrit dans une démarche d’amélioration des connaissances des instabilités des éléments comprimés et fléchis sensibles aux effets du second ordre. Il s’agit de traiter la prise en compte des imperfections initiales dans l’analyse de la structure et d’adapter les critères actuels de vérification pour les structures tubulaires de type échafaudage. Les formulations existantes, proposées dans la littérature et les codes de calculs, sont souvent issues d’hypothèses, et conduisent à des incohérences entre les critères de vérification en section, et les critères de vérification en instabilité. L’approche développée traite l’interaction entre la résistance en section et les phénomènes d’instabilités, et inclut l’influence des imperfections initiales. Ces effets seront, dans la mesure du possible, découplés. À ce titre, une méthode a été conçue pour permettre la définition des imperfections initiales d’une structure, de manière à être la plus précise possible. Cette méthode, basée sur la définition d’une imperfection unique, d’allure identique à la déformée critique du mode de flambement prépondérant, est une méthode précise, entièrement définie permettant de tenir compte des caractéristiques géométriques, des caractéristiques mécaniques intrinsèques, des conditions aux limites et de la forme du chargement, dans la définition de l’imperfection initiale unique d’une structure. Une campagne d’essai a été réalisée en collaboration avec le SFECE, visant à analyser le comportement expérimental au flambement de sections tubulaires formées à froid. Des essais de flambement sur des échelles d’échafaudage, provenant de divers fournisseurs européens, ont été effectués. Une étude statistique des résultats expérimentaux a permis de mettre en évidence que le facteur d’imperfection actuellement défini pour les sections tubulaires formées à froid est bien trop pénalisant à l’égard des sections usitées dans le domaine des échafaudages. Afin de répondre à la problématique, de nouveaux critères de vérification en instabilité ont également été établis en utilisant une approche similaire à celle d’Ayrton-Perry. Ces nouveaux critères permettent de s’affranchir de la modélisation des imperfections initiales tout en offrant une estimation sûre et précise du facteur de sollicitation d’une structure. Des études comparatives ont été menées de manière à s’assurer de la sécurité des formulations proposées par rapport aux critères de vérification en section de la norme actuelleThis thesis is part of an effort to improve knowledge of the instabilities of beam-columns sensitive to second-order effects. The works deal with the means to take into account the initial imperfections in the structural analysis and to adapt the current verification criteria for tubular section structures, such as scaffold structures. The existing formulations, proposed in the literature and calculation codes, are often based on hypotheses, and thus lead to inconsistencies between, on the one hand, the verification criteria in section, and on the other hand, the verification criteria in instability. The developed approach takes into account the interaction between section resistance and instability phenomena, and includes the influence of initial imperfections (initial defect of aplomb, lack of straightness, residual stresses). As far as possible, these effects will be decoupled. As such, a method has been developed to allow the definition of initial imperfections of a structure, to be as accurate as possible. This method, based on the definition of a single imperfection, identical in appearance to the shape of the predominant critical buckling mode, is a precise, fully defined method to take into account the geometric characteristics, intrinsic mechanical characteristics, limits and the form of loading, in the definition of the initial imperfections of a structure. A test campaign was carried out in collaboration with the French Syndicate of Scaffolding, Formwork and Shoring (SFECE), aiming to analyze the experimental behavior of buckling of cold-formed tubular sections. Nine buckling tests on scaffold ladders, from various European suppliers, have been carried out. A statistical study of the experimental results has made it possible to highlight that the imperfection factor currently defined for the cold-formed tubular sections is far too penalizing for the sections used in the field of scaffolds. In order to respond to the problem, new instability criteria have also been established using a similar approach to that of Ayrton-Perry. These new criteria make it possible to free ourselves from the modeling of initial imperfections while offering a safe and accurate estimate of the stress factor of a structure. A comparative study was conducted in order to ensure the safety of the proposed formulations as regards the section verification criteria of the NF EN 1993-1-1 current standard
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Silva, Leonardo Martins e. "Programa computacional para análise e verificação de seções de concreto armado e protendido com flexão oblíqua composta." Universidade Federal de São Carlos, 2015. https://repositorio.ufscar.br/handle/ufscar/4707.
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In this paper, a free analysis program is presented for the verification of ultimate and serviceability limit states of reinforced or prestressed concrete sections with polygonal shape submitted to axial forces and biaxial bending. In addition, the program also calculates the bending-axial force-curvature relation (M, N, 1 / r) of the sections, which can be used in further analysis, for example, the general method for calculating pillars. For this is used the object-oriented programming, so that this work can be resumed and amended, providing technical material for future work in the same line, therefore provides that the calculation routines along with the program. The programming lines and routines includes explanations of its operation to encourage its further use as part of other programs. The data entry is presented as a form and the program enables the exchange of data, both input and output via text type files. The criteria adopted follows the brazilian standard ABNT NBR 6118: 2014, which compared to the previous version features suggestions for concrete with superior characteristic strength higher than 50 MPa. The structure of the routines is presented so that criteria of other standards, or updates of the same Brazilian standard referenced, can be easily implemented. Some validation examples for the program are presented in different situations and finally commented and listed some other extensions which can be made.
No presente trabalho, apresenta-se um programa livre e gratuito de análises e verificações de estados-limite último e de serviço de seções de concreto armado e protendido com forma poligonal submetidas à flexão composta oblíqua. Além disso, o programa calcula também a relação momento-normal-curvatura (M, N, 1/r) das seções, que pode ser usada em outras análises, como por exemplo, o método geral para o cálculo de pilares. Para isso se usa a programação orientada ao objeto, a fim de que o presente trabalho possa ser retomado e alterado, dando subsídio técnico para trabalhos futuros da mesma linha, por esse motivo fornece-se as rotinas de cálculo juntamente ao programa. As linhas e rotinas de cálculo constam com explicações de seu funcionamento para incentivar seu uso posterior como parte de outros programas. A entrada dos dados é feita de forma de formulário e o programa permite a troca de dados, tanto de entrada como de saída através de arquivos do tipo texto. Os critérios adotados seguem a norma brasileira ABNT NBR 6118:2014, que em relação à versão anterior apresenta sugestões para concretos com resistência superior a 50 MPa. A estrutura das rotinas é apresentada de maneira que critérios de outras normas, ou ainda atualizações da mesma norma brasileira referenciada, possam ser facilmente implementadas. Apresenta-se vários exemplos de validação do programa em diversas situações e finalmente comentadas e listadas as ampliações que podem ser feitas.
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Malakoski, Joice. "Pilares esbeltos de concreto armado com seção variável." Universidade de São Paulo, 1998. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-22022018-152222/.
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São descritas as recomendações da Norma Brasileira NBR-6118/1978 e do Código Modelo do Comité Euro-internacional du Béton CEB-1990 para a verificação da estabilidade de pilares esbeltos de concreto armado com seção variável submetidos à flexão normal composta, empregando-se a teoria do método geral. Para a obtenção dos momentos de segunda ordem são descritos os métodos de Engesser-Vianello e da integração numérica das curvaturas das seções transversais ao longo do pilar. Para a determinação do momento fletor absorvido pelas seções em função da curvatura proveniente da flexão do pilar sob a ação de uma força normal, desenvolvem-se as expressões para seções retangulares e circulares (cheias e vazadas) com base nas relações de tensão-deformação dos materiais segundo a norma e o código supracitados. Apresenta-se também um programa para microcomputador, elaborado em linguagem PASCAL, destinado à verificação da estabilidade de pilares com opção de adoção dos critérios da NBR-6118/1978 ou do CEB-1190. Não foram abordados os efeitos decorrentes de vibrações, fazendo-se apenas a descrição dos métodos de consideração dos efeitos decorrentes da deformação lenta.The recommendations of Brazilian Code NBR-6118/1978 and Comité Euro-Internacional du Béton Model Code CEB-1990 are described, for stability verification of concrete slender columns with variable cross sections, subjected to axial load and bending moment, using the exact method. To obtain the second order bending moments, the Engesser-Vianello method and the numeric integration of the cross section curvatures along the longitudinal axial of column method are described. To obtain of bending moment supported by the cross sections due to curvature resultant of the column flexure under axialload, expressions for rectangular and circular (full and hollow) cross sections are developed, using stress-strain relations for materials proposed by model codes above mentioned. It\'s also presented a software written in PASCAL language for microcomputer and destined to column stability verification, with option to adopt the NBR-6118/1978 or CEB-1990 model code recommendations. Effects due to vibrations were nor included. Methods to take in account creep effects were described.
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Miotto, José Luiz. "Avaliação dos critérios de dimensionamento para peças comprimidas e flexocomprimidas de madeira." Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-03052005-150420/.
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A recente revisão da NBR 7190/97 culminou em avanços inegáveis no projeto das estruturas de madeira. As excentricidades acidentais, amplificação das excentricidades e efeitos da fluência incidem diferentemente no cálculo das peças curtas, medianamente esbeltas ou esbeltas, estabelecendo descontinuidades nos diagramas de esforços de projeto em função da esbeltez das barras comprimidas ou flexocomprimidas. Associando-se a outras particularidades, como a complexidade de algumas de suas expressões, esse modelo tem sido alvo freqüente de críticas. Neste trabalho são avaliados os critérios propostos para a verificação da estabilidade de peças de madeira serrada, nas solicitações de compressão e flexo-compressão, pelos documentos normativos: alemão, australiano, canadense, europeu e norte-americanos. Essas recomendações são confrontadas com as da norma brasileira, comparando-se a objetividade dos métodos e os resultados alcançados. A proposição da AF&PA/ASCE 16-95/96 para o dimensionamento das peças comprimidas demonstra grande praticidade e continuidade nos diagramas Nd x 'lâmbda', evitando as críticas que se conectam aos critérios da norma brasileira. Por outro lado, as prescrições dessa mesma norma para as peças flexocomprimidas embasadas em argumentos teóricos convincentes evitam as deficiências constatadas nas propostas da norma brasileira, concordando com os propósitos de sugestão para uma necessária reformulação normativaThe recent revision of NBR 7190/97 culminated in undeniable progresses in the project of the timber structures. The accidental eccentricities, amplification of the eccentricities and the creep effects happen differently in calculation of the short members, the middling slenders or the slenders ones, establishing discontinuities in the diagrams of the design forces in function of slenderness of the members in compression and in combined bending and axial compression. Being associated to other particularities, as the complexity of some of its equations, that model has been often criticized. In this work, the proposed criteria for the verification of the stability of sawed timber members in compression and in combined bending and axial compression are appraised for the following normative documents: german, australian, canadian, european and north americans. Those recommendations are confronted with the brazilian code ones, comparing the objectivity of the methods and the gained results. The proposition of AF&PA/ASCE 16-95/96 for the compressed members design demonstrates great practicality and continuity in the diagrams of Nd x 'lâmbda', avoiding the critics that are connected to the criteria of the brazilian code. On the other hand, the prescriptions of that same code for the members in combined bending and axial compression based in convincing theoretical arguments avoid the deficiencies verified in the proposal of the brazilian code, agreeing with the purposes for suggestion in a necessary normative reformation
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Stehno, Pavel. "Statické řešení novostavby administrativní budovy." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226958.
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In this master’s thesis I study statical solution of new office building. The load – bearing elements are appraised according to ultimate limit state. Structural analysis contains of dimensioning ceiling plate with ribs, the most stressed support column and footing. There will be applied computer simulation to finding out values of internal forces. The solution is checked by simple method of replacement frames. The main purpose of this thesis consists of elaboration structural analysis, drawing up the technical report and creation design documents of load – bearing elements.
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Лазарєв, Іван Вікторович, Иван Викторович Лазарев, and Ivan V. Lazariev. "Розробка та вдосконалення методів розрахунку міцності елементів конструкції силових трансформаторів." Thesis, Запорізький національний технічний університет, 2016. http://eir.zntu.edu.ua/handle/123456789/887.
Full textAbstract:
Лазарєв, І.В. Розробка та вдосконалення методів розрахунку міцності елементів конструкції силових трансформаторів [Текст]: дис. … канд. техн. наук: 01.02.04 /Лазарєв Іван Вікторович. – Запоріжжя, 2016. – 243 с.UK: Створено узагальнені методи визначення критичних напружень радіальної стійкості та розрахунку на міцність при дії радіальних і осьових сил гнучкого кругового кільця круглого та прямокутного з заокругленнями кутів перерізу, яке моделює провідники обмоток трансформаторів. Визначено осьові зусилля в деформівних елементах механічної системи, утвореної двома простими осциляторами з розташованими на одній осі безінерційними пружинами і твердими тілами, звязаними паралельними стержнями, на які діють відмінні у часі зосереджені аперіодичні осьові сили, що виникають при коротких замиканнях в обмотках різних фаз трансформатора, розміщених на одному стрижні магнітної системи. Розроблено методи визначення осьових зусиль в деформівних компонентах складної механічної системи, яку утворіють обмотки та конструкція їх пресування, при дії сил, що виникають у процесі виготовлення, транспортування, та експлуатації трансформаторів. EN: Transformer winding conductors were simulated by a flexible circular ring with round and rectangular (filleted and non-filleted) cross-section. For such a ring there were created generalised methods for determining critical stresses of radial stability and for strength analysis under the action of radial an axial forces. There were determined axial internal forces in deformable elements of the mechanical system comprising two simple oscillators with inertialess springs and rigid bodies located on the same axis and connected by parallel rods with the latter being loaded by concentrated aperiodic axial forces that change in time by distinct time functions and originate in windings of different transformer phases installed on the same magnetic system leg. There were developed methods for determining axial internal forces in deformable components of a complex mechanical system comprising windings and their clamping structure under the action of forces occurring in the process of transformer manufacture, shipment and in service. RU: Разработаны обобщенные методы определения критических напряжений радиальной устойчивости и расчета прочности при действии радиальных и осевых сил гибкого кругового кольца круглого и прямоугольного с закруглениями углов сечения, которое моделирует проводники обмоток трансформаторов. Определены осевые усилия в деформируемых элементах механической системы, образованной двумя простыми осцилляторами с расположенными на одной оси безынерционными пружинами и твердыми телами, связанными параллельными стержнями, на которые действуют сосредоточенные апериодические осевые силы, которые изменяются во времени по различающимся функциям, и возникают в обмотках разных фаз трансформатора, расположенных на одном стержне магнитной системы. Разработаны методы определения осевых усилий в деформируемых компонентах сложной механической системы, которую образуют обмотки и конструкция для их прессовки, при действии сил, которые возникают в процессе изготовления, транспортирования и эксплуатации трансформаторов.
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CHAN, FU-CHIEH, and 詹富傑. "Seismic behavior of steel reinforced concrete columns subjected to axial load and bi-axial bending." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/24214364015380944232.
Full textAbstract:
碩士國立中央大學
土木工程研究所
92
ABSTRACT This study investigated the seismic performance of 24 composite columns composed of H-steel and reinforced concrete. Major parameters studied included the sectional strength ratios and the magnitudes of biaxial bending. It was found from test results that member performance was governed by the strength of reinforced concrete when they were loaded in the section’s weak axis. It was also observed that the performance of member with weak axis bending decreased when the section’s steel strength increased. Test results suggested that the strength ratio between the section’s strong and weak directions be adequately adjusted so that high member performance could be achieved. It is proposed in this study that the ratio be set to 2.2 and 2.5.
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陳璽字. "Concrete infilled steel columns subjected to axial load and bending moment." Thesis, 1992. http://ndltd.ncl.edu.tw/handle/79171040185599712906.
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Lin, Yie-Ming, and 林益民. "Behavior of Reinforced Concrete Columns under Combined Biaxial Bending and Axial Force." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/39690352268326788806.
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Cheng, Tzu-Chung, and 鄭子仲. "Simultaneous Measurement of Bending Curvature and Axial Stress Using Fiber Bragg Grating Sensors." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/95929429443805820037.
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碩士逢甲大學
電機工程所
97
In this thesis, simultaneous measurement of bending curvature and axial stress using fiber Bragg grating sensors is presented. The side-polishing technique was used to produce FBG sensors with different polishing lengths and thicknesses. The experimental configurations were used the cantilever beam for measuring the bending curvature range of 0 - 6 m-1 and simply supported beam for measuring curvature range of 31 - 71 m-1. The length of fiber Bragg gratings was 20 mm and the polished residual thickness was from 55.95 to 93.94 �慆. The curvature sensitivity of 0.739 nm/m-1 was obtained by using D-shaped FBG sensor with 50 mm polishing length and a cantilever beam configuration. Finally, the sensing sensitivities of both curvature and axial stress measurements have been improved and demonstrated by changing the mounted method. The bending curvature sensitivity was 1.341 nm/m-1 for the curvature range from 0 to 6 m-1, and the stress sensitivity was 27.90 nm/GPa for the measuring range from 0 to 0.208 GPa.
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Weilung, Sun, and 孫維隆. "Experimental Behavior of Stiffened Concrete Filled Tube under Combined Axial and Bending Loads." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/80210011147062856303.
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Lin, Chih-chong, and 林志聰. "Lateral-Torsional Buckling Analysis of Elastic Beam under Axial Force and Bending Moment." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/32223107805407364581.
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碩士國立交通大學
機械工程系
89
In this study, a consistent co-rotational formulation of second order beam theory is employed for the nonlinear lateral-torsional buckling analysis of three-dimensional elastic Euler beam under axial force and bending moment. The beam structure is divided into several segments, called beam element for convenience. A set of element coordinate system is constructed at the current configuration of the deformed beam element. The deformations, equilibrium equations, and constitutive equations of the beam element are defined in the element coordinates. The principle of virtual work and the consistent second order linearization of the fully geometrically nonlinear beam theory are used to derive the equilibrium equations and constitutive equation of the beam element. The governing equations for primary equilibrium path for beam under axial force and uniform bending moment is derived using equilibrium equations and constitutive equation of the second order beam theory. The exact solution of the primary path is solved using an analytical and numerical combined method. To derive the governing equations for laternal-torsional buckling analysis, disturbing nodal displacement and rotation vectors are applied to the primary path of beam elements. Then element coordinates corresponding to this disturbance can be constructed, and element nodal rotation parameters defined in this element coordinates can be determined in terms of the disturbing nodal displacement and rotation vectors. The governing equations for laternal-torsional buckling analysis are derived in this element coordinates by using the first order linearization. A power series solution method is used to solve the buckling moment for spatial beams under axial force and different types of end moment to demonstrate the accuracy and effectiveness of the proposed method. Numerical examples are studied to investigate the effect of compressive force on the buckling moment of spatial beams.
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Hsu, Hung-Yi, and 徐宏一. "Measurement of Axial Stress and Bending Curvature by Side-Polished Fiber Grating Sensors." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/71960631459378546852.
Full textAbstract:
碩士逢甲大學
電機工程所
98
To enhance the sensing sensitivity of fiber gratings, we used the side-polished technique to remove parts of cladding to reduce the thickness of fiber. The long-period and short-period fiber gratings have different response characteristics and sensitivities for the bending curvature and axial stress. Therefore, we can manufacture various types of fiber sensors based on the side-polished technique. In this research, we make long-period and short-period fiber gratings sensing elements with different polishing thicknesses based on fiber gratings writing and side-polished techniques. These sensing elements can be used to measure the axial stress and the cantilever bending curvature. The grating length and the effective polishing length are 2 centimeters. The sensing range and sensitivity are 0−124.73 MPa and 0.020 nm/MPa for axial stress and 0−0.066 m-1 and 16.95 nm/ m-1 for cantilever bending curvature, respectively. We presented a novel structure combined with long-period and short-period fiber gratings. This sensing structure used for measuring multi-parameters such as axial stress, cantilever’s bending curvature and bending directions.
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Young, Y. S., and 楊育碩. "Mechanical Ratchetting of a Stepped Beam under Steady Axial Tension and Cyclic Bending." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/59811028001197578677.
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Chung, Youngjin. "Buckling of composite conical shells under combined axial compression, external pressure, and bending." Thesis, 2001. http://library1.njit.edu/etd/fromwebvoyage.cfm?id=njit-etd2001-099.
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chen, Hsin-pu, and 陳信甫. "Numerical Analysis of Thin-Walled Composite Box Beam under Combined Bending and Axial Force." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/35885609329526607577.
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碩士國立成功大學
土木工程學系碩博士班
97
A nonlinear failure mode had been used for studying and predicting material failure under the condition of thin-walled composite box beam and subjected to combined bending and axial force. This nonlinear failure mode including three parts: first, the nonlinear constitutive law of material before failure; second, the mixed failure criterion to predict the time of failure; third, the analysis of post failure mode. The simulation of nonlinear mode before failure for the thin-walled composite box beam is assumed that lamina is plastic-elastic in axial and transverse directions, and using constant shear parameter in in-plane. The mixed failure criterion, combining the excellence of Tsai-Wu theory and maximum stress theory, had been used for judge failure timing. During analyzing of post failure mode for the thin-walled composite box beam, the brittle failure mode had been adopted in axial, shear and transverse direction. The result of the nonlinear failure mode will compare with the experimental data of thin-walled composite box beam subjected to bending to verify the mode in this study correct. Finally, using the models in this study discuss the thin-walled composite box beam under the different length, section size, order of laminates, and bending-axial forces to apply in engineering.
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Tsai, Hung-Yu, and 蔡宏裕. "Study on Interaction Behaviors of RC Columns Excited by Axial Force and Biaxial Bending." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/6u9jpa.
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碩士國立臺北科技大學
土木與防災研究所
95
This thesis proposed a set of visualized operation system for the analysis on interaction behaviors of RC columns excited by axial force and biaxial bending. Incorporating with equilibrium and compatibility condition, the constitutive law of concrete proposed by Kawashima et. al. as well as the elastoplastic model of reinforcement was taken into account mechanically. By necessary comparisons, a good consistency can be found between the analysis results and the results obtained by conventional load contour method. To testify the accuracy and validity of the proposed approach, twenty-six reported results of bidirection-eccentry tests of RC columns were adopted for necessary investigation. It shows that this study can provide an acceptable result and might benefit the paractial design efforts for structural engineers.
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Ali, Usman. "Numerical Modeling of Failure in Magnesium Alloys under Axial Compression and Bending for Crashworthiness Applications." Thesis, 2012. http://hdl.handle.net/10012/6511.
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Numerical modeling of failure was performed for magnesium alloys with circular and square cross-sections under axial compression. The failure criterion was employed using material model 124, where failure was simulated using the element deletion method. LS-DYNA material model 124 (MAT_124) was calibrated using stress-strain curves in compression and tension. This approach, combined with MAT_124, captures the material asymmetry. Comparisons with experiments showed that the failure criterion accurately predicted the stress-strain behavior during axial compression tests of the round tubes of magnesium alloy, AZ31. A parametric study was also performed to investigate the effects of various phenomena on simulated results. Numerical modeling of square magnesium tubes during bending was also simulated for extruded magnesium alloys AZ31, AM30 and AM60. The failure criterion, based on element erosion, was used in these models to simulate fracture for all three alloys. Comparisons with experiments, for all three alloys, showed that the proposed numerical model accurately predicted the force-displacement curves during bending. Engineering strain at failure was found from the tensile test curves for the three magnesium alloys (AZ31, AM30 and AM60). Simulations were done to predict local strain at the necking region at this engineering strain. The necking strain was incorporated in the failure criterion, which considerably improved results for the bending simulations. Numerical modeling of slow and fast axial compression tests were also performed for AM30, AM60 and AZ31 magnesium tubes with square cross-section. Comparisons with experiments, for all three alloys, showed that the proposed numerical model accurately predicted the force-displacement curves during quasi-static and high-speed crush tests. Furthermore, the predicted fracture locations and patterns were in good agreement with experimental observations. Finally, new failure criteria was employed to improve the crashworthiness behavior of magnesium alloys by several tube design variations. Magnesium tubes cladded with aluminum and magnesium tubes with alternating strips of aluminum were simulated. Magnesium tubes with thinned sections and spirals were also simulated. Results showed that most of the design modifications increased the crashworthiness of magnesium alloys tubes.
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Tsai, Shih-Heng, and 蔡世桓. "Nonlinear Analysis of Double-Skin Concrete Filled Tube Subject to Axial Compression and Bending Moment." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/86723765577269248263.
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碩士國立成功大學
土木工程學系碩博士班
94
This paper use ABAQUS software to analyse the Double-Skin Concrete Filled Tubes (DS-CFT) that subject to axial compression and bending moment, then compare the analysis results with experimental data of national earthquake center. By the way, we can find the Fl, K3, and K4 of a DS-DFT subject to such loads, understand the benefit that concrete can produce in DS-CFT so, and calculate the experience formulas used for material parameters. By the result analysing, we can find that the specimen under pure bending can’t let the concrete keep its compressive resistibility because of lacking the axial compression, therefore the strength of such specimen is less than others, but DS-CFT can still offer a certain Fl that is much stronger than CFT. Besides, we find the experience formula and K2 of CFT are not suitable for DS-CFT specimens, K2 value of CFT will lead to a strain that is too large. so this paper repeated trying for many times, induct new values of K2, and find out the suitable material parameters and experience formulas again.
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Hsieh, Wu-Teng, and 謝武燈. "On Draw Bending Process of a Metal Tube in Small Bend Radius with Axial Load." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/31743402312239187610.
Full textAbstract:
碩士國立中興大學
機械工程學系
93
Nowadays, becoming lighter and smaller is an important direction for product design. Metal tubes which are broadly used to transport the materials and energy should therefore diminish their application volume without any weakening their function and losing the safety. For this reason metal tubes bent into small radius becomes more and more significant. However, in processing metal tubes into small bend radius, some defects will exist, such as hollows on them or thinning on their outer walls. These defects might lose the function of metal tubes. Thus this research attempts to modify the draw bending process which is mostly applied in the industry to bend the metal tube into small radius, so that the defects might be eliminated. A test platform with a stroke controllable mandrel and a mechanism pushing metal tube in the axial direction was setup. The mandrel positioning, axial loading, and bending speed as well as lubricant status are therefore investigated experimentally in this research. The experiment results show that there is no significant difference found between various bending speeds. Regarding lubrication on the tube inner wall, a stick slip phenomenon can be found during tube bending, if no lubricant is applied. By positioning the mandrel firstly deeper beyond the bend center and then moving back during the bending process to its normal position, the hollowing on the tube can be reduced. However, if the mandrel moves deeper during the bending process from its normal position, the wall thickness can be conversely thinned. An axial loading imposed on the tube bending process can reduce the flattening of the bent tube. Superposing an axial loading on the tube bent with a mandrel can induce an excellent cross-section of the bent metal tube. The results obtained in this research regarding the mandrel positioning and the imposed axial loading can be offered for tube bending application industry to improve the tube bending process particularly into small bend radius.
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JIAO, XIAN-QI, and 焦先齊. "The influence of axial pressure on the coupled bending-torsion vibration of a rotating bladezeng." Thesis, 1992. http://ndltd.ncl.edu.tw/handle/65074334639215497893.
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Hsu, Shuo-Hsiu, and 許碩修. "Lateral-Torsional Buckling Analysis of Bisymmetric Thin-Walled Beam under Axial Force and Nonuniform Bending Moment." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/49196229549752184772.
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碩士國立交通大學
機械工程系
90
In the study, the nonlinear lateral-torsional buckling analysis of bisymmetric thin-walled beam under axial force and nonuniform bending moment is investigated. The beam element developed in reference [1] is employed here. In reference [1], the co-rotational formulation, the virtual displacement method and the consistent second order linearization of geometric beam theory are used. An incremental-iterative method based on the Newton-Raphson method combined with constant arc length of incremental displacement vector is employed for the solution of nonlinear equilibrium equations. The zero value of the tangent stiffness matrix determinant of the structure is used as the criterion of the buckling state. A bisection method of the arc length is used to find the buckling load. The nonlinear lateral-torsional buckling moment and post buckling behavior of beams with different sections, lengths, and boundary conditions under axial force and nonuniform bending momen is investigated. The accuracy of results of the linear buckling analysis given in the literature is examined.
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Lin, Yan-Xing, and 林彥興. "Delamination Growth Experiment and Analysis of Composite Laminates under Axial Compression、Transverse Loading and Pure Bending." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/36391501931458111322.
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HUANG, MING-HUI, and 黃明輝. "Elasto-plastic analysis of thin-walled tubes and beam subjected to steady axial load and cyclic bending." Thesis, 1991. http://ndltd.ncl.edu.tw/handle/72356379149993705403.
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Haremza, Cécile. "Robustness of open car parks under localised fire." Doctoral thesis, 2015. http://hdl.handle.net/10316/27324.
Full textAbstract:
Tese de doutoramento em Construção Metálica e Mista apresentada à Faculdade de Ciências e Tecnologia da Universidade de CoimbraO número crescente de carros a circularem na Europa nas últimas décadas, bem como o aumento de grandes centros comerciais, aeroportos e estações ferroviárias, aumentou consideravelmente o número de parques de estacionamento abertos. Uma maneira fácil e de baixo custo para a construção é a utilização de uma estrutura mista aço-betão. Em situação de incêndio, a combustão generalizada (flash-over) é improvável de ocorrer nesses espaços abertos, e devem ser considerados incêndios localizados. Um incêndio localizado, que se desenvolve num parque de estacionamento misto sem protecção contra incêndio, conduz ao aquecimento dos elementos estruturais mais próximos do incêndio: ligações, vigas e colunas. O colapso de uma coluna sujeita a incêndio localizado provoca grandes deslocamentos verticais nos andares superiores. Para atingir um equilíbrio nesta configuração deformada, e assim evitar o colapso progressivo do edifício, desenvolvem-se forças de membrana nas lajes e nas vigas. Portanto, durante este evento, as ligações viga-coluna estão sujeitas a sequências particulares de carregamento, envolvendo principalmente momentos flectores e esforços axiais. Essas ligações devem resistir à nova distribuição de esforços e ter ductilidade suficiente para poder sustentar grandes rotações, sem rupturas. Para tal, a estrutura deve ser dimensionada tendo em conta a robustez necessária para este evento acidental. O trabalho de investigação apresentado nesta tese está inserido no projecto Europeu RFCS ROBUSTFIRE, e no projecto Nacional IMPACTFIRE. As diversas fases deste trabalho estão relacionadas com um caso de estudo que envolve uma configuração estrutural de um edifício típico de parque de estacionamento aberto. O cenário considerado é o colapso de uma coluna devido a um incêndio localizado (combustão de veículos), e são consideradas as restrições axiais devidas à estrutura não afectada pelo incêndio. Este trabalho tem como principal objectivo o estudo detalhado do comportamento de uma ligação mista aço-betão viga-coluna com placa de extremidade, aquecida pelo incêndio localizado, quando está sujeita a momentos flectores e esforços axiais variáveis. Numa fase inicial, realiza-se uma revisão das regras práticas actuais, e o estado da arte sobre a concepção e avaliação de parques de estacionamento abertos sujeitos a um incêndio localizado. Em seguida, a investigação centra-se em estudos experimentais, numéricos e analíticos: i) Realizam-se sete ensaios experimentais em ligações mistas aço-betão viga-pilar sob diferentes combinações de momentos flectores e esforços axiais, considerando não só condições isotérmicas, mas também um cenário de temperatura transitória. ii) Desenvolvem-se modelos numéricos 3D detalhados da ligação mista, de forma a reproduzir os ensaios experimentais. iii) Finalmente, é estudado a influência de alguns parâmetros que afectam a robustez deste tipo de edifícios (tais como temperatura, vão da viga, tamanho da ligação, etc....), usando os modelos numéricos desenvolvidos e um procedimento analítico existente na bibliografia.
The growing number of cars in Europe during the last decades, as well as the amount of large shopping centres, airports and railway stations, have considerably increased the number of open car park buildings. An easy and low cost way for the construction of these open car park buildings is to use a composite steel-concrete structure. Under fire situation, flash-over is unlikely to occur in these opened compartments and localised fires should be considered. When a localised fire develops in an unprotected steel composite car park, it leads to the heating of some of the nearby structural elements: connections, beams and columns. The loss of a column under localised fire induces large vertical displacements in the above floors. To reach equilibrium in the deformed configuration and avoid progressive collapse of the building, membrane forces in the slabs, and catenary forces in beam elements should develop. So, during the event, the beam-to-column connections are subject to particular load sequences mainly involving bending moments and axial forces. These connections are also required to have sufficient ductility in order to sustain large rotations without brittle damages. Therefore, sufficient robustness should be provided to the structure at the design stage. The research work presented in this thesis is based on the European RFCS ROBUSTFIRE project, and the National IMPACTFIRE project. The various stages of this work are related to a case study involving a structural configuration that represents a typical open car park building. The considered scenario is the loss of a column due to a localised fire (burning cars), and the strong restraints to the beams provided by part of the building not directly affected by this accident are taken into account. The behaviour of steel-concrete composite beam-to-column joints in open car park buildings under column loss scenario, due to fire, is investigated in detail. The main objective is to provide a detailed analysis of the heated joint behaviour subject to variable bending moments and axial loads when the column fails. First, a review of current practice and state of the art in the design and assessment of open car parks subject to localised fire is performed. Then the investigation is based on experimental, numerical and analytical results: i) Seven experimental tests are performed on composite steel-concrete beam-to-column joints under different combinations of bending moments and axial forces, considering isothermal conditions, and also one transient temperature scenario. ii) Detailed 3D numerical models of the heated joint are developed to reproduce the experimental tests. iii) Finally, the influence of some parameters that affect the robustness of this type of building (such as temperature, beam span, joint size, etc.…) are studied using the developed numerical models and an existing analytical procedure.