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Brown, Adrian D. "The use of carbon fibre reinforced cement as tensile reinforcement for concrete structural elements." Thesis, University of Bath, 1987. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287533.
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Russell, Darren. "Finite element analysis of embankments on soft ground incorporating reinforcement and drains." Thesis, University of Sheffield, 1992. http://etheses.whiterose.ac.uk/1853/.
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The objectives of the research were threefold. Firstly, to improve .the numerical modelling capability for reinforced embankments constructed over soft compressible soils containing vertical drains. Secondly, to demonstrate the ability to model accurately such embankments. Finally, to develop simplified procedures to be used in the design of embankments over soft soils. The modifications to the finite element program, CRISP, included the incorporation of three additional elements: modelling the reinforcement, the soil/reinforcement interface and the vertical drains. The facility to vary permeability with stress level was also implemented. A technique for modelling the consolidation of soil containing vertical drains in plane strain finite element analyses was developed and validated. The modified program was validated in three ways. Firstly, each element was used to analyse simple problems so that the correct formulation was ensured. Secondly, a series of analyses was carried out of problems for which analytical solutions were available; these problems involved collapse of undrained sub soils and consolidation around a single vertical drain. Thirdly, an analysis of a case history of an embankment constructed over a normally consolidated clay, improved with vertical drains, was performed. Based on the results of the previous finite element analyses, and an additional analysis of an idealized two-stage constructed embankment, simple design procedures have been proposed. Firstly, a method for the design of single stage embankments and, secondly, a method for the calculation of subsoil strength increases in multi-stage construction, which can be used in conjucntion with limit equilibrium analyses. It is concluded that the finite element method is a useful technique for the analysis of reinforced embankments over soft soils containing vertical drains.
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Sundberg, Lars Andreas. "Analysis of welded reinforcements on a boom mower : A structural and modal analysis of reinforcement properties on a industrial boom mower." Thesis, Umeå universitet, Institutionen för tillämpad fysik och elektronik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-148593.
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Road safety is a complicated issue that affects most world economies due to its negative socioeconomic impact. Road safety programs include different programs that cover different areas for minimizing the effects of these impacts. One of these programs focuses road safety against invasion of wildlife into traffic roads. Most economies that heavily include these particular programs, such as Sweden, rely on specific machinery and techniques for clearing road shoulders that allows driver to foresee any possible danger or road invasion in good time. The most common piece of machinery used for covering this type of activity is known as a boom mower. Boom mowers can be pictured as giant lawnmowers that are attached into a long boom crane from wheel loaders or excavators, so they can clear invading vegetation from the road shoulders. Boom mowers suffer from heavy wear due to their dimensions, weight and operating speed which it requires companies to pay extra attention to their construction and choice of materials. Cranab Slagkraft is a Swedish company that has been specialized for providing high quality boom mowers for the last 30 yearsfor clearing vegetation on the Swedish roads. But, despite their higher quality products, these boo mowers are often expensive and complicated to manufacture. For this reason, Cranab has requested a study to minimize the manufacturing burden in order to simplify its production and diminish cost. This research study focuses on the latest components addition into the boom mower construction to assess their performance. For this research, the researcher will put to test the reinforcements of the boom mower’s model SH150 and see what their performance against harmonic vibrations and structural strength against local stresses are. The research follows two complementary analysis. First, a modal analysis on the boom mower’s main structure for evaluating resonance levels at an operating frequency. Second, a structural analysis with idealized conditions at operating speed to determine construction stress resilience. The results in this research reveals that the modal analysis rejects the viability of one group of reinforcements and confirms the implications of the other one. Also, the results reveal that the complicated geometry requires advanced software for providing more conclusive results. In addition, the boom mower’s own geometry and choice of material might play a role in adjusting the harmonic resonance and adjusting the boom mower’s mechanical properties. The latter conclusion should be considered as a theme of study for future research in this same field.Trafiksäkerhet är ett komplicerat ärende som påverkar de flesta världsekonomier på grund av dess negativa socioekonomiska inverkan. I trafiksäkerhetsprogrammen ingår olika program som täcker olika områden för att minimera de socioekonomiska effekterna. Ett av dessa program koncentrerar sig på trafiksäkerhet mot invasion av vilda djur på motorbanor. De flesta världsekonomiers system som omfattar dessa trafiksäkerhetsprogram, till exempel Sverige, är beroende av specifika maskiner och tekniker för röjning av vägarna som gör det möjligt för föraren att i god tid ska kunna förutse eventuell fara eller vilt som kommer in på vägen. Den vanligaste maskinen som används för röjning av vägar kallas kättingröjare. Kättingröjaren kan liknas vid gigantiska gräsklippare som är fastsatta på en grävmaskin, hjullastare och/eller väghyvel så att de kan rensa bort gräs från vägkanten. Kättingröjare lider av kraftigt slitage på grund av deras dimensioner, vikt och driftshastighet. Det kräver att tillverkaren uppmärksammar konstruktionen och materialvalet till kättingröjaren. Cranab Slagkraft är ett svenskt företag som under de senaste 30 åren har specialiserat sig på att leverera högkvalitativa kättingröjare. Kättingröjarna är ofta dyra och komplicerade att tillverka. Av den anledningen har Cranab begärt en studie för att förenkla produktionen och minska tillverkningskostnaderna. Den här studien koncentrerar sig på det senaste komponenttillägget i kättingröjarens konstruktion för att bedöma deras prestanda. I den här studien testas flera förstärkningar i kättingröjarens modell SH150 för att undersöka deras prestanda mot harmonisk vibration och strukturell hållfasthet mot lokala spänningar. I studien ingår två kompletterande analyser. Först görs en modalanalys på kättingröjarens huvudstruktur för utvärdering av resonansnivåer vid driftsfrekvensen. Sedan görs en strukturell analys med idealiserat tillstånd vid driftshastigheten för att bestämma spänningsmotståndet. I resultatet beskrivs en grupp av förstärkningar som inte har någon påverkan för kättingröjarens harmoniska vibration och spänningsmotstånd och en andra grupp som visar påverkan. Även resultaten visar att den komplicerade geometrin kräver avancerad mjukvara för att ge mer avgörande resultat. Dessutom kan kättingröjarens egen geometri och materialval ha påverkan vid justering av dess harmoniska resonans och mekaniska egenskaper. Den senare slutsatsen bör betraktas som ett begrepp för framtida studier inom samma område.
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Reyes, Ordoñez Murray Olaf, and Argomedo Yuliana Vanessa Alegre. "Análisis estructural de la iglesia de San Pedro de Carabayllo – Lima / Perú." Bachelor's thesis, Universidad Ricardo Palma, 2015. http://cybertesis.urp.edu.pe/handle/urp/1343.
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La presente investigación trata sobre “El análisis estructural de la Iglesia San Pedro de Carabayllo” considerada el monumento histórico más antiguo de Lima Norte.
Este trabajo se desarrolló con el objetivo de determinar su análisis estructural; utilizando un modelo matemático de acuerdo al método de elementos finitos, determinando los valores numéricos de los esfuerzos y sus desplazamientos.
Esta tesis es una investigación aplicada, cuantitativa de diseño descriptivo y de tipo explicativo, no experimental, transversal y prospectivo.
Se concluye que la estructura no cumple con los desplazamientos mínimos según norma sismo resistente y que falla al someterla a cargas de sismo, planteándonos de esta manera alternativas de reforzamiento para la estructura; evitando así afectar la autenticad de los materiales de la estructura.
This research is about “Structural analysis of the San Pedro Church of Carabayllo " considered the oldest historic monument in North Lima.
This work was developed with the aim of determining their structural analysis; using a mathematical model according to the finite element method, determining the numerical values of forces and movements.
This thesis is an applied research, quantitative descriptive and explanatory design type, not experimental, transversal and prospective.
It is concluded that the structure does not meet the minimum standard displacement as earthquake resistant and fails when subjected to earthquake loads , by posing this alternative way of reinforcement for the structure ; thus avoiding authenticate affect the structure material.
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Baingo, Darek. "A Framework for Stochastic Finite Element Analysis of Reinforced Concrete Beams Affected by Reinforcement Corrosion." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23063.
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Corrosion of reinforcing bars is the major cause of deterioration of reinforced concrete (RC) structures in North America, Europe, the Middle East, and many coastal regions around the world. This deterioration leads to a loss of serviceability and functionality and ultimately affects the structural safety. The objective of this research is to formulate and implement a general stochastic finite element analysis (SFEA) framework for the time-dependent reliability analysis of RC beams with corroding flexural reinforcement. The framework is based on the integration of nonlinear finite element and reliability analyses through an iterative response surface methodology (RSM). Corrosion-induced damage is modelled through the combined effects of gradual loss of the cross-sectional area of the steel reinforcement and the reduction bond between steel and concrete for increasing levels of corrosion. Uncertainties in corrosion rate, material properties, and imposed actions are modelled as random variables. Effective implementation of the framework is achieved by the coupling of commercial finite element and reliability software. Application of the software is demonstrated through a case study of a simply-supported RC girder with tension reinforcement subjected to the effects of uniform (general) corrosion, in which two limit states are considered: (i) a deflection serviceability limit state and (ii) flexural strength ultimate limit state. The results of the case study show that general corrosion leads to a very significant decrease in the reliability of the RC beam both in terms of flexural strength and maximum deflections. The loss of strength and serviceability was shown to be predominantly caused by the loss of bond strength, whereas the gradual reduction of the cross-sectional area of tension reinforcement was found to be insignificant. The load-deflection response is also significantly affected by the deterioration of bond strength (flexural strength and stiffness). The probability of failure at the end of service life, due to the effects of uniform corrosion-induced degradation, is observed to be approximately an order of magnitude higher than in the absence of corrosion. Furthermore, the results suggest that flexural resistance of corroded RC beams is controlled by the anchorage (bond) of the bars and not by the yielding of fully bonded tensile reinforcement at failure. This is significant since the end regions can be severely corroded due to chloride, moisture, and oxygen access at connections and expansion joints. The research strongly suggests that bond damage must be considered in the assessment of the time-dependent reliability of RC beams subjected to general corrosion.
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Fawwaz, Maha, and Adnan Hanna. "Structural behavior of notched glulam beams reinforced by means of plywood and FRP." Thesis, Linnéuniversitetet, Institutionen för teknik, TEK, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-19479.
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Nowadays, timber is widely used in construction industry thanks to its availability and good properties. The use of solid (sawn) timber is not always proper since it is only available up to certain dimensions. Therefore, the so-called Engineered WoodProducts (EWPs) have been introduced to cope with the different design needs of structures. The Glued laminated Timber (glulam) is a type of EWPs that consists of smallsections of timber laminates glued together to form beams and columns. Glulam can be manufactured in almost any size and shape; it can also be tapered or notched. However, notching a beam at its end leads to a stress concentration at the re-entrantcorner of the notch due to the sudden change in the notched beam’s cross section. The concentration of shear and tensile stresses perpendicular to the grain can lead to a catastrophic brittle failure caused by the crack propagation from the notch corner. Crack opening due to tensile stresses perpendicular to grain is the most common failure at the notch corner and it is always taken into design consideration. However,shear component is usually exists and must be also considered in design to guarantee the safety of the structure. Currently, only the normal forces perpendicular to the beam’s axis are considered in the design of the reinforcement in design handbooks. The aim of this thesis was to study the structural behavior of notched glulam beams reinforced by adhered plywood panels and FRP. The carrying capacity of the notched glulam beams at their ends is the main subject of this thesis. In addition, a review of the notched beams design, reinforcements, and analysis theories are included. Experimental series of three point bending tests with notched glulam beams withdifferent configurations of reinforcement was carried out in lab. Deformations and forces were measured both with conventional techniques and with contact-free measurement systems - ARAMIS. On the other hand, a simple model of two dimensional plane stress element has been created of the unreinforced notchedbeam in ABAQUS. The normal and shear stresses were calculated for a horizontalpath of 100 mm in length starting from the notch tip. Afterwards, the mean stresseswere determined for the same path and have been used in calculations. The Mean Stress Approach has been adopted in the hand calculations to calculate the crack length and the failure load according to the ABAQUS model. Accordingly, the failure load was about 40 kN for the unreinforced beams. Also, Eurocode 5 has been used to calculate the failure load which gave a value of 20.2 kN for the unreinforced beams. The average maximum applied load in tests was 30 kN for the unreinforced beams while it reached about two and a half times this value for the CF-reinforced and the plywood-reinforced beams.Tack vare sina goda egenskaper används trä i byggnadskonstruktioner i allt storeomfattning. Konstruktionsvirke (sågade trävaror) kan dock inte alltid användas pågrund av de begränsade dimensioner som finns tillgängliga. På grund av bl a dettahar ett flertal så kallade engineer wood products (EWP) utvecklats. Limträ är en typav EWP som består av sammanlimmade lameller som bygger upp tvärsnitt i balkareller pelare. Limträ kan tillverkas i nästan godtycklig storlek och form och kan enkeltförses med t ex urtag. Vid urtag i balkändar nära upplag uppstår högaspänningskoncentrationer vid urtagets horn på grund av geometrin. Koncentrationenav normalspänningar och skjuvspänningar kan leda till plötsligt brott på grund avsprickpropagering från urtagets hörn, något som måste tas hänsyn till viddimensionering. Dagens dimensioneringsmetoder är baserade på att man tar hänsyntill enbart normalspänningarna vinkelrät fiberriktningen.Målet med detta arbete har varit att studera beteendet hos limträbalkar med urtag vidupplag som förstärkts med fiberarmering eller plywood. Huvudmålet har varit attbestämma balkarnas bärförmåga, vilket skett genom att genomföra försök med olikakonfigurationer vad gäller förstärkningsmaterial och dess utformning. Vidare harolika dimensioneringsmetoder från litteraturen studerats.Kraft och förskjutning under provningarna uppmättes dels med traditionellamätmetoder, men deformationerna mättes även med beröringsfri metod, ARAMIS.En enkel tvådimensionell finit elementmodell skapades och analyserades i ABAQUSför analys av oförstärkt balk. Normalspänningar och skjuvspänningar beräknades ochmedelspänningarna längs en på förhand definierad sträcka beräknades.Medelspänningskriteriet användes sedan för att uppskatta balkens bärförmåga.Enligt FE-beräkningarna uppskattades bärförmågan för de oförstärkta balkarna till ca40 kN. Provningarna gav ett medelvärde på balkarnas bärförmåga på ca 30 kN,medan de förstärkta balkarna hade en 2,5 gånger högre bärförmåga. Skillnadenmellan FE-beräkningarna och provningarna kan förklaras med den osäkerhet somfinns vad gäller det aktuella trämaterialets egenskaper.Beräkningar enligt Eurokod 5 gav en karakteristisk bärförmåga på 20,2 kN.
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Anampa, Vilcas Oscar Alonso, and Carranza Lucia Isabel Loyola. "Evaluación estructural del Museo de Sitio Bodega y Quadra ante un evento sísmico severo." Bachelor's thesis, Universidad Ricardo Palma, 2015. http://cybertesis.urp.edu.pe/handle/urp/1346.
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El Museo de Sitio Bodega y Quadra es el primer museo de sitio del Centro Histórico que muestra detalles del estilo de vida en la Lima antigua. Declarada Patrimonio Cultural Inmueble Colonial por el INC, actual Ministerio de Cultura; es por ello que consideramos importante realizar la evaluación estructural del mismo ante un evento sísmico severo. Dicha evaluación se ha realizado mediante el programa “VisualFEA”, el cual se basa en la teoría de los elementos finitos, además se ha respetado la norma de diseño peruana y las consideraciones necesarias por ser, la estructura en estudio, un monumento histórico. La presente es una investigación aplicada, cuantitativa, explicativa y descriptiva; de diseño no experimental, transversal y prospectivo. Se concluye que la estructura no cumple los desplazamientos mínimos, según norma, al someterla al sismo severo; por lo que se procede a plantear la propuesta de reforzamiento estructural haciendo uso de las técnicas de reconstrucción local y refuerzo externo, evitando afectar la integridad y la autenticidad de los materiales por tratarse de un patrimonio cultural.
The museum of site Bodega y Quadra is the first museum of the historic center which shows the old´s life style of lima citizen. It was named Cultural Heritage Colonial Property by the Ministerio de la Cultura; because of that reason we considered important to realize the structural assessment of this museum to prevent any problem in case of a severe earthquake. This thesis has been done using the “VisualFEA” software which is based on the theory of the finite elements, besides it has been considered the Peruvian regulation of design and the properly considerations since it is a Heritage Property. This is an applied, quantitative, descriptive and explanatory research; design not experimental, transversal and prospective. Concludes that the structure does not meet minimum displacement, as a rule, when subjected to sever earthquake; so it proceeds to raise the proposed structural reinforcement using the local reconstruction technique and external reinforcement, preventing affect the integrity and authenticity of the materials because it is a historical monument.
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Gowripalan, N. "Reinforcement of concrete elements with modified polymers." Thesis, University of Leeds, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378032.
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Haji, Oussama. "Modèles de comportement de structures textiles : développement, identification, implémentation." Thesis, Orléans, 2018. http://www.theses.fr/2018ORLE3007.
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Les renforts fibreux subissent des mécanismes de déformations complexes lors du procédé de fabrication des pièces composites. Par conséquent, des défauts se produisent à différentes échelles du renfort qui peuvent affecter drastiquement la qualité de la pièce finale. Afin d’améliorer celle-ci, il serait judicieux de prévoir la faisabilité des pièces composite par la modélisation et la simulation du procédé de mise en forme. Cette tâche nécessite d’établir, tout d’abord, une loi de comportement du renfort fibreux par le biais de la modélisation du comportement des mèches, qui dépend lui-même du comportement des fibres et des interactions entre elles. D’où l’intérêt de commencer par l’étude d’un milieu fibreux modèle à l’échelle de la fibre. La présente étude s’inscrit dans cette approche en ayant comme objectif de développer un milieu modèle basé sur une géométrie réaliste d’un réseau de fibres faiblement enchevêtrées et quasiment unidirectionnelles. À l’issue de ce travail, deux éléments clés sont présentés : (i) des outils automatisés de reconstruction de la microstructure des milieux fibreux à partir des images de la tomographie à rayons X, jusqu’à son modèle CAO. (ii) une stratégie de simulation fiable,nourrie par des essais expérimentaux de compaction effectués sur un milieu fibreux modèle de 40 fibres de polyester. En utilisant ces outils, des simulations de compaction confinée, sur la même microstructure que celle de l’échantillon réel, ont été effectuées sur Abaqus®. Les fibres ont été modélisées par des éléments poutres 3D en prenant en compte le frottement entre elles. Un modèle numérique de contact, basé sur la loi de Hertz, est utilisé également. La confrontation des résultats numériques avec ceux des expériences montre une cohérence très encourageante qui permet de valider le modèle numérique d’une part, et de tester d’autres trajets de chargement en augmentant le nombre de fibres d’autre partThe fibrous textile undergoes different mechanical loads, which induce strains and damage to the fabric at different scales. As a result, the mechanical properties of the final parts are drastically impacted. It is therefore essential topredict the feasibility of composite parts by the modelization and the simulation of the fabric preforming process.This task requires an appropriate mechanical behaviour of the fibrous textile. This behaviour is mainly a structural effect that depends essentially on the yarn interlacing and secondly on the yarn behaviour. Each yarn is composedof thousands of fibers; therefore, the objective of the present thesis is to establish a reliable numerical model ofslightly entangled and quasi-parallel fibers. The present work presents mainly: (i) a realistic representation of the fiber network geometry and (ii) a reliable simulation strategy to model the main phenomena at the fiber scale. To feed this approach, compaction tests were conducted on fiber network specimens of 40 polyester fibres. The experiments were combined with X-ray tomography image analysis. Using these tools, simulations of confined compaction on the same microstructure of the used specimen were performed on Abaqus®/Explicit. Beam finite elements were chosen to model the fibers and optimise the calculation cost. The normal contact behaviour between the fibers were was accurately modelled using the contact stiffness scaling and referring to Hertz contact model. The simulation strategy has been validated by comparing the mechanical response of the compaction experiment with the numerical one. The proposed model offers encouraging results in accordance with the real compaction test. More loading trajectories will be performed on a bundle of hundreds of fibers to gather more information on the microscopic scale (fiber scale), and then formulate a mechanical behaviour at the mesoscopic scale (yarn scale)
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Tabatabai, Seyed Mohammad Reza. "Finite element-based elasto-plastic optimum reinforcement dimensioning of spatial concrete panel structures /." Basel ; Boston ; Berlin : Birkhäuser, 1996. http://e-collection.ethbib.ethz.ch/show?type=incoll&nr=815.
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Schiøler, Tyge. "Multi-stable structural elements." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615076.
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Wickholm, Kristina. "Structural elements in native celluloses /." Stockholm, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3095.
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Elliott, Kenny B. "Structural modification utilizing beam elements." Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/53876.
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This study presents a concept that provides a structural dynamicist the ability to analyze the effects of making sophisticated (beam-type) structural changes to a structural system whose modal database is known. The modification technique combines the Dual Modal Space Modification Method (DMSM) and the Transfer-Matrix Method to institute general beam modifications. The DMSM method is employed to implement the beamtype modification, while the transfer-matrix method is used to formulate the modification element. The use of transfer-matrix methods provides the ability to model virtually any beam modification a designer might consider in terms of the two points being connected without the loss of any dynamic information between the points. The result is a modification scheme which is both flexible and universal.
Two numerical examples are considered. One example demonstrated the performance of the modification scheme in instituting a severe structural change. The second example demonstrated a change to a complex structure. In both cases, continuum beams were used as modification elements. The results of these two examples show that the modification scheme provides very promising results, providing an adequate modal database was used. Modal truncation was determined to be the primary source of error.Ph. D.
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Hachouf, Kamel. "Geotextile soil reinforcement in retaining walls." Thesis, Queen Mary, University of London, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283366.
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Reis, Jonathan M. "Structural Concrete Design with High-Strength Steel Reinforcement." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1277124990.
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Du, Yingang. "Effect of reinforcement corrosion on structural concrete ductility." Thesis, University of Birmingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368516.
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This thesis presents the experimental and analytical results to investigate the effect of corrosion on the mechanical properties of reinforcing bars and concrete beams, with particular reference to their ductility. In the experimental works, specimens were electrochemically corroded, before they were loaded to failure. In the finite element analysis, the corrosion of reinforcement was modelled as either internal pressure or radial expansion around corroded bars. The study indicates that the amount of corrosion to cause cracking at the bar and concrete surfaces almost linearly increased with the bar diameter and ratio of cover to diameter, respectively. No matter whether concrete cover c increased or bar distance S decreased, once the ratio of S / c became less than 2.5, corrosion cracks first propagated internally between the bars and caused delamination. Although corrosion did not alter the shape of force-extension curves substantially, it decreased bar strength and, especially, ductility greatly. Furthermore, although the reductions of strengths were identical, the ductility of bars corroded in concrete decreased more rapidly than that of bare corroded bars. Corrosion decreased beam strength and altered its ductility and failure mode. When the cracking of compressive concrete or the reduction of tensile bar area dominated beam response, corrosion increased beam ductility and caused a beam to fail in a less brittle and even ductile manner. When the deterioration of bond strength or the reduction of steel ductility controlled beam behaviour, however, corrosion decreased beam ductility and led the beam to fail in a less ductile and even brittle manner. There is a concern regarding the ductility of reinforcing bars and under-reinforced beams if the amount of corrosion exceeds 100/0, since bar ultimate strain decreased below the minimum requirements prescribed in the Model Code 90 for situations requiring high ductility.
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Lai, Katharine 1977. "Use of structural steel diagonal reinforcement in coupling beams." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=79240.
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Coupling beams are a key structural element for resisting seismic loading because of their energy dissipating capabilities and high ductilities. In coupling beams with short span-to-depth ratios, diagonal reinforcement is used to provide the amount of ductility required. Because of the large amount of steel congestion within traditionally reinforced diagonally reinforced coupling beams, however, alternative reinforcement layouts are desired to simplify their construction. Two specimens were constructed and tested under reversed cyclic loading. The results were then compared to previous experimental results to evaluate the viability of these construction techniques. One specimen contained No. 20 diagonal bars placed in a symmetrical arrangement and confined with closely spaced headed reinforcing bars in place of hoops. The second specimen used diagonal reinforcement constructed using structural steel elements that were anchored in the shear wall elements with shear studs. For comparison, the structural steel elements used in the design of the second specimen were chosen to match the yield force of the diagonal reinforcement of the first specimen.The hysteretic responses of the two specimens showed that the specimen containing the structural steel diagonal reinforcement had a higher ductility and was able to dissipate more energy than those using headed reinforcing bars or traditional hoops. This indicates that the use of structural steel is a viable alternative for the diagonal reinforcement of coupling beams. In addition, these results also demonstrated that the use of headed reinforcing bars as confinement for diagonal reinforcement is similar to, and therefore a feasible replacement for, diagonal reinforcement confined with closely spaced hoops.
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Alam, Parvez. "The reinforcement of timber for structural applications and repair." Thesis, University of Bath, 2004. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409885.
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Nakayama, Hiroaki. "Modelling interfaces between sand and structural elements." Thesis, University of Bristol, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440276.
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Ross, Jonathan E. "Peptidomimetic foldamers of β-secondary structural elements." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:a44b48d0-59fa-4f28-abac-7b66b6391d6c.
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Foldamers have the potential to be the synthetic equivalent of Nature's macromolecules; man-made oligomers that use a range of non-covalent interactions to fold into well defined structures. Chapter 1 introduces the challenges laid down by Gellman to chemists in creating foldamers; i) to design new polymers that reliably display interesting folding properties; ii) to be able to include novel and unnatural functional groups; and iii) make them easy to synthesise. Each of the foldamers made in this thesis will be evaluated against these challenges. Chapter 2 develops a mimic of the linear β-strand, based on alternating pyridyl/urea units, with the conformation enforced by dipolar repulsion. Conformational bias is demonstrated in the solution phase by computational and NMR studies, and in the solid phase by X-ray crystallography. The concept is extended to the inclusion of hydrophilic residues and conformation is maintained in a polar protic solvent. Chapter 3 describes the design and synthesis of a three- and four-stranded β-sheet mimic templated by the diphenylacetylene motif. The folding is enforced by a hydrogen bonding network demonstrated via extensive solution phase studies and X-ray crystallography. Chapter 4 explores the scope of this new architecture. The meander is successfully elongated to seven strands, and the structure shown to be amenable to the inclusion of D-amino acids and hydrophilic residues. The foldamer is therefore shown to meet all of Gellman's criteria. Chapter 5 uses the diphenylacetylene motif to study the factors involved in the formation of β-sheets, specifically the effect of side-chain identity on hydrogen bond strength. The difference in strengths is shown to be minimal, suggesting that β-sheet propensity is due to the energy changes in forming the extended conformation rather than forces between strands.
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Zdanowicz, Katarzyna [Verfasser]. "Chemical Prestressing of Thin Concrete Elements with Carbon Textile Reinforcement / Katarzyna Zdanowicz." Hannover : Gottfried Wilhelm Leibniz Universität, 2021. http://d-nb.info/1234148285/34.
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Samadian, Fariborz. "Investigation of shear reinforcement for reinforced concrete flat slabs." Thesis, University of Westminster, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362692.
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Døssland, Åse Lyslo. "Fibre Reinforcement in Load Carrying Concrete Structures : Laboratory and Field Investigations compared with Theory and Finite Element Analysis." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for konstruksjonsteknikk, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-2289.
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Fibre reinforcement can provide an alternative to conventional steel bars in order to improve the efficiency and working conditions on construction sites and in the prefabrication industry. Through the fibres ability to bridge cracks they improve the structural behaviour of the concrete by increased shear, moment and punching resistance, increased dowel effect, reduced crack spacing and crack widths, increased flexural stiffness and increased ductility in compression. A main reason for limited use of FRC in load-carrying structures seems to be the lack of accepted design guidelines. The principal aim of this research project is to improve the current knowledge of the mechanical and structural behaviour of fibre reinforced concrete, focusing on practical applications. An experimental study is carried out where the following parameters are investigated: fibre volume, fibre length, steel versus synthetic fibres, size effect, influence of conventional reinforcement, self compacting versus vibrator compacted concrete, casting process and type of structural element. Most of the test series were evaluated through calculations and finite element analysis (FEA) and compared with available design rules. Generally the agreement was good, both with discrete and smeared crack approach. This shows that FEA is an appropriate tool to determine the contribution of fibres to the load bearing capacity. Moreover, the results of the test series implied that the theoretical framework that exists today describes the behaviour of fibre reinforced structures relatively well, and that the design rules which are developed is satisfactory.
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O'Sullivan, Donald Quinn 1970. "Structural elements with mathematically defined surfaces for enhanced structural and acoustic performance." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8664.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.Includes bibliographical references (p. 205-209).
Two design methods are explored to reduce vibration, minimize unwanted acoustic noise, and increase stiffness in structures. The first design approach is to create nearly isotropic panels with increased stiffness using two-dimensional curvature. These quasi-isotropic designs can be used in lieu of typical panel reinforcements, and can provide an inexpensive alternative to honeycomb sandwich designs. The second approach is to design panels formed into the shape of a mode shape to reduce detrimental modal dynamics. The effects of combining the two-dimensionally curved designs with constrained layer damping is also investigated. Further, it is also the goal of this research that these panels can be inexpensively manufactured with current manufacturing methods (e.g. stamping, rolling, thermoforming, etc.), resulting in a more effective structural element that does not require significant extra cost or weight. Initial analysis was performed using geometric modeling and finite element analysis. Experimental analysis involved both static and dynamic system identification. The experimental results indicate that quasi-isotropic designs can be accomplished with two-dimensional curvature.
(cont.) These quasi-isotropic designs increase the stiffness of a panel and raise the natural frequency by a factor of 2 (compared to a flat panel of the same mass). Although the quasi-isotropic designs have no acoustic benefit, they were shown to be effective replacements as honeycomb cores. The mode-shaped designs demonstrated the unique quality of simultaneously reducing vibration and acoustic noise over a broad frequency range (50-10,000 Hz). The mode-shaped panels demonstrated a factor of 3 increase in the natural frequency, a ten-fold reduction in dynamic deflection displacements, and a 3 to 4 dB RMS reduction in the radiation index over a broad frequency range.
by Donald Quinn O'Sullivan.
Ph.D.
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Navarro, Bridget I. (Bridget Isabela). "The effect of reinforcement on loadbearing capacity of structural glass." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/66844.
Full textAbstract:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 49-50).
The transparent property of glass makes it a favored choice of material in the design of structures because it maximizes light and creates an illusion of larger spaces. However, it is a very brittle, making it difficult to use as a common building material. Laminated glass significantly improves the strength through a layer of resin called polyvinyl butyral (PVB). Laminated glass is typically used for buildings in which human impact is vulnerable, such as hurricane prone areas or important government buildings. However, laminated glass still lacks the residual loadbearing capacity that one would find in reinforced steel, for instance. Residual loadbearing capacity is important to ensure the safety and reliability of glass as a structural material. This thesis will provide an overview of the common glass treatments, fixings, structural systems, and design methods used today. Additionally, two research studies investigating the effects of reinforced glass will be examined. Finally, the author will provide a simulation of a three-layer laminated glass stair tread with an applied design load. The simulation compares the stresses and displacements of the unreinforced glass tread with a glass tread reinforced with a 4 mm thick steel plate. The results from the simulation are inconclusive. However, experimental results from the two research studies show promise for the use of reinforcement in glass to improve load bearing capacity.
by Bridget I. Navarro.
M.Eng.
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Amin, Mahmoud Samy Mohamed Fahmy. "Boron Nitride Nanotubes (Bnnts) For Thermal Management And Structural Reinforcement." W&M ScholarWorks, 2020. https://scholarworks.wm.edu/etd/1593091980.
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Boron nitride nanotubes (BNNTs) are a fascinating material that has a lot of potential applications due to its outstanding physical and chemical properties. BNNTs synthesized using different high- and low-temperature methods, unfortunately, contain 30-70% impurities. To maximize the potential of BNNTs, new characterization techniques and purification methods are needed, especially with respect to industrial applications. Research groups have used different characterization techniques to monitor the synthesis and purity of BNNTs. Quantitative and qualitative characterization of the tubes for quality or purity control has not been previously described in the literature. In this work, we created a comprehensive set of thermogravimetric and spectroscopic analysis techniques to detect and quantify the different types of BNNT impunities. Based on our thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy results, we demonstrated that it is possible to monitor the presence of boron, boron oxide, and boron nitride impurities quantitatively in BNNTs and to verify their removal after purification. Although there are several reported purification methods in the literature, none of them succeeded in purifying BNNTs from boron nitride (BN) impurities without damaging the tubes and resulting in a low yield. Here we introduce a non-aggressive, non-destructive, high-yield purification method using heptane at the moderate temperature T=90 °C. Our method effectively removes ≥99.8% of the hexagonal boron nitride (h-BN) and a significant amount of other BN impurities. This is a substantial advancement over all previously reported methods that rely on more aggressive treatments. Field emission scanning electron microscope (FESEM) and transmission electron microscopy (TEM) images, as well as X-ray diffraction, Raman, and FTIR spectra, were used to support our purification results. The latter three spectroscopic techniques characterize a macroscopic region of the sample and are thus more representative than imaging selected areas using electron microscopy. Finally, we studied the effect of the BNNT loading and composite morphology - networked versus dispersed BNNTs - on the composite's thermal and structural properties. BNNT composites at different loadings showed that the thermal conductivity sharply increases with the increase in the BNNT loading. Loading polystyrene with 18% BNNTs increased the thermal conductivity by a factor of three. The thermal conductivity in the radial direction was higher than the axial direction for all composites. The difference in thermal conductivity between the radial and the axial direction is believed to be due to the hot-pressing step introducing radial tube orientation and alignment. Regarding the tensile properties of the BNNT composites, the Young's modulus was increased 50-105% at 5%-7.5% loadings compared to the neat polystyrene, and tensile strength increased by around 40%. Higher loadings led to more brittle composites. Impregnation of the BNNT network with polystyrene led to better mechanical properties than BNNT dispersion. The FESEM images showed favorable wetting of the tubes by polystyrene and a good matrix/tubes load transfer.
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Zhu, Jian. "The stabilities of RNA and DNA structural elements." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/25194.
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Hoang, Lee. "Genetic and biochemical analysis of structural ribosomal elements /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2006. http://uclibs.org/PID/11984.
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Magnusson, Johan. "Structural concrete elements subjected to air blast loading." Licentiate thesis, Stockholm : Byggvetenskap, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4441.
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Su, Meini, and 蘇玫妮. "Behaviour and design of aluminium alloy structural elements." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206728.
Full textAbstract:
Aluminium alloys are nonlinear metallic materials with continuous stress-strain curves that are not well represented by the simplified elastic, perfectly plastic material model used in most existing design specifications. The aims of this study are to develop a more efficient design method for aluminium alloy structures by rationally exploiting strain hardening. The key components of this study include laboratory testing, numerical modelling and development of design guidance for aluminium alloy structures.
As part of the present study, the experimental programme included tests on 11 stub columns, 40 simply supported beams, 46 continuous beams and corresponding tensile coupon tests. Numerical investigations of aluminium alloy simply supported beams and continuous beams were also conducted. The validated finite element models were used for extensive parametric studies, generating 96 results for beams under three-point bending, 96 under four-point bending and 210 for continuous beams. The experiments and numerical simulations have shown the following key features of the inelastic behaviour of aluminium alloy structural elements: (1) the significance of strain hardening, indicated by the ultimate stress over the yield stress, could be up to 50%; (2) non-slender section capacities could be generally up to 40% higher than the yield limits in compression, and 50% greater than the plastic moments in bending; (3) the experimental and numerical ultimate loads of continuous beams on non-slender sections go beyond the calculated loads corresponding to the occurrence of the first hinge by more than 10%.
Previous experimental data on aluminium alloy stub columns and simply supported beams were also collected. These collected test data were used together with the newly generated experimental and numerical results obtained from this study, totalling about 900 data, to assess the design predictions of the American, Australian/New Zealand and European specifications. On average, the existing design methods under-estimated the capacity of aluminium alloy stub columns by around 15%~22%, simply supported beams by around 18%~40% and continuous beams by around 27% ~ 50%. Existing section classification limits in Eurocode 9 (2007) were also assessed, and while they were found to be safe, some improved limits were proposed.
The combined experimental and numerical results were used to develop and calibrate a new design method, termed the continuous strength method (CSM). Two key components of the CSM – a base curve and a bi-linear material model for aluminium alloys have been proposed in this study. Global plastic analysis allowing for moment redistribution has also been adopted in the CSM. Unlike current practices, the CSM has the merits of adopting the continuous treatment for the cross-section deformation response, rationally exploiting the available capacity beyond the yield limit and reasonably allowing for redistributing the internal forces.
The capacity predictions of aluminium alloy structural members have been improved by more than 30% using the CSM. Reliability analyses have also been performed to assess the reliability level of different design methods according to the American Institute of Steel Construction (2010) and European Standard EN1990 (2002) approaches. The CSM has been shown to be safe, efficient and consistent for aluminium alloy structural members.published_or_final_version
Civil Engineering
Doctoral
Doctor of Philosophy
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Li, Qingming. "Dynamic inelastic response and failure of structural elements." Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266315.
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The dynamic shear response and failure of structural elements under transverse impact loads are studied in the present work. The dynamic shear response is one of the important response modes in structural elements under transverse impact loads, which may lead to various shear failures depending on the loading rates and intensities. Transverse shear localization phenomena, which are represented by a shear hinge, have been observed in several structural elements when subjected to transverse dynamic loading and are studied in this thesis. The features of a stationary shear hinge are illustrated using a rigid, perfectly plastic simplification. The dimensions of a shear hinge for several structural elements are estimated both theoretically and numerically. It is shown that there exists a fixed shear hinge length for a given two-dimensional structural element. The length of a shear hinge is determined by its bending and shearing properties which can be obtained from a quasi-static analysis. When the shear hinge length has been determined, the conventional rigid-plastic method can be used to calculate the shear strain and shear strain rate within the shear hinge during the shear response phase. These theoretical results are employed to model Menkes and Opat' s beam problem to find two possible failure mechanisms, i.e., ductile shear failure and adiabatic shear failure and the associated transition conditions. A double-shear beam(DSB) subjected to a transverse projectile impact is studied experimentally and numerically in order to provide a more fundamental understanding on the features of structural failure in a localised shear zone. Both ductile tensile failure and adiabatic shear banding failure are found in the shear notch section. An analytical model and FEM simulation are developed to predict the DSB response and failures. The theoretical background of the strain energy density failure criterion is discussed and verified in this problem. Among the failure criteria examined in the current study, the strain energy density failure criterion is observed to give reasonable predictions for the failure initiation.
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Starbuck, Jonathan. "Structural studies of compounds containing p-block elements." Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340162.
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Brevus, Vitaly. "Analysis of structural elements' integrity after thermomechanical loading." Thesis, Clermont-Ferrand 2, 2014. http://www.theses.fr/2014CLF22443.
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Cette thèse a été réalisée en cotutelle entre l'Université Technique Nationale Ivan Pul'uj de Ternopil (TNTU, Ukraine) et l’Université Blaise Pascal (Clermont-Ferrand, France). Les travaux ont été effectués au sein de l'Institut Pascal de l’Université Blaise Pascal - Clermont II, de l’IFMA et du CNRS, dans le thème scientifique Matériaux actifs et intelligents, modélisation multi-échelle de l'axe Mécanique, Matériaux et Structures, et au sein de l'Institut Français de Mécanique Avancée. La thèse présentée appartient au domaine scientifique de la mécanique de la rupture et la science des matériaux. L'objectif de la thèse est de développer la méthodologie analytique et expérimentale pour la durée de vie résiduelle des collecteurs du surchauffeur dans les centrales thermiques, en tenant compte des caractéristiques de fonctionnement de chargement thermomécanique. La prédiction de la durée de vie est une tâche cruciale pour un fonctionnement continu des éléments structuraux très chargés et fait partie d'un problème plus large, couvert dans la recherche de la résistance et la durabilité des éléments structurels à haute température dans les équipements d'énergie générateur. Le mémoire décrit l'influence de la température de fonctionnement sur la vitesse de propagation des fissures de fatigue et micromécanismes de rupture dans le matériau du collecteur de surchauffeurThis thesis was performed under the cotutelle agreement between Ternopil Ivan Pul’uj National Technical University (TNTU, Ukraine) and Blaise Pascal University (Clermont Ferrand, France). The thesis was carried out within Pascal Institute of the Blaise Pascal University - Clermont II, the IFMA and the CNRS, in the Scientific Theme “Active and Smart Materials and Multiscale Modeling” of the Mechanics, Materials and Structures Department, and within the French Institute for Advanced Mechanics. The presented thesis belongs to the scientific field of fracture mechanics and material science. The aim of the thesis is to develop the analytical and experimental methodology for the residual lifetime estimation of the superheater collectors at thermal power stations (TPS), taking into account the operational features of thermomechanical loading. Prediction of lifetime is crucial task for continuous operation of heavy loaded structural elements and is a part of a broader problem, covered in the research of the strength and durability of high temperature structural elements in power-generating equipment. The thesis describes the influence of operating temperature on the fatigue crack growth rate and fracture micromechanisms in the material of the superheater collector
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Drazin, Paul Luke. "Modeling and Analysis of Elements in Structural Mechanics." Thesis, University of California, Berkeley, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10276506.
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The focus of this work is to advance the theoretical and modeling techniques for the fields of hybrid simulation and multi-slider friction pendulum systems (MSFPs). Hybrid Simulation is a simulation technique involving the integration of a physical system and a computational system with the use of actuators and sensors. This method has a strong foundation in the experimental mechanics community where it has been used for many years. The hybrid simulation experiments are performed with the assumption of an accurate result as long as the main causes of error are reduced. However, the theoretical background on hybrid testing needs to be developed in order validate these findings using this technique. To achieve this objective, a model for hybrid simulation is developed and applied to three test cases: an Euler-Bernoulli beam, a nonlinear damped, driven pendulum, and a boom crane structure. Due to the complex dynamics that these three test cases exhibit, L2 norms, Lyapunov exponents, and Lyapunov dimensions, as well as correlation exponents were utilized to analyze the error in hybrid simulation tests. From these three test cases it was found that hybrid simulations are highly dependent on the natural frequencies of the dynamical system as well as how and where the hybrid split is located. Thus, proper care must be taken when conducting a hybrid experiment in order to guarantee reliable results.
Multi-stage friction pendulum systems (MSFPs), such as the triple friction pendulum (TFP), are currently being developed as seismic isolators. However, all current analytical models are inadequate in modeling many facets of these devices. Either the model can only handle uni-directional ground motions while incorporating the kinetics of the TFP system, or the model ignores the kinetics and can handle bi-directional motion. And in all cases, the model is linearized to simplify the equations. The second part of this dissertation presents an all-in-one model that incorporates the full nonlinear kinetics of the TFP system, while allowing for bi-directional ground motion. In this way, the model presented here is the most complete single model currently available. It was found that the non-linear model can more accurately predict the experimental results for large displacements due to the nonlinear kinematics used to describe the system. The model is also able to successfully predict the experimental results for bi-directional ground motions.
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Su, Meini. "Behaviour and design of aluminium alloy structural elements." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/25588.
Full textAbstract:
Aluminium alloys are nonlinear metallic materials with continuous stress-strain curves that are not well represented by the simplified elastic, perfectly plastic material model used in most existing design specifications. The aims of this study are to develop a more efficient design method for aluminium alloy structures by rationally exploiting strain hardening. The key components of this study include laboratory testing, numerical modelling and development of design guidance for aluminium alloy structures. As part of the present study, the experimental programme included tests on 11 stub columns, 40 simply supported beams, 46 continuous beams and corresponding tensile coupon tests. Numerical investigations of aluminium alloy simply supported beams and continuous beams were also conducted. The validated finite element models were used for extensive parametric studies, generating 96 results for beams under three-point bending, 96 under four-point bending and 210 for continuous beams. The experiments and numerical simulations have shown the following key features of the inelastic behaviour of aluminium alloy structural elements: (1) the significance of strain hardening, indicated by the ultimate stress over the yield stress, could be up to 50%; (2) non-slender section capacities could be generally up to 40% higher than the yield limits in compression, and 50% greater than the plastic moments in bending; (3) the experimental and numerical ultimate loads of continuous beams on non-slender sections go beyond the calculated loads corresponding to the occurrence of the first hinge by more than 10%. Previous experimental data on aluminium alloy stub columns and simply supported beams were also collected. These collected test data were used together with the newly generated experimental and numerical results obtained from this study, totalling about 900 data, to assess the design predictions of the American, Australian/New Zealand and European specifications. On average, the existing design methods under-estimated the capacity of aluminium alloy stub columns by around 15%~22%, simply supported beams by around 18%~40% and continuous beams by around 27% ~ 50%. Existing section classification limits in Eurocode 9 (2007) were also assessed, and while they were found to be safe, some improved limits were proposed. The combined experimental and numerical results were used to develop and calibrate a new design method, termed the continuous strength method (CSM). Two key components of the CSM - a base curve and a bi-linear material model for aluminium alloys have been proposed in this study. Global plastic analysis allowing for moment redistribution has also been adopted in the CSM. Unlike current practices, the CSM has the merits of adopting the continuous treatment for the cross-section deformation response, rationally exploiting the available capacity beyond the yield limit and reasonably allowing for redistributing the internal forces. The capacity predictions of aluminium alloy structural members have been improved by more than 30% using the CSM. Reliability analyses have also been performed to assess the reliability level of different design methods according to the American Institute of Steel Construction (2010) and European Standard EN1990 (2002) approaches. The CSM has been shown to be safe, efficient and consistent for aluminium alloy structural members.
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Schach, Rainer, and Manuel Hentschel. "Grundlagen für die Nutzwertanalyse für Verstärkungen aus textilbewehrtem Beton." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1244049476991-75979.
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Im Rahmen des Transferprojektes sollen baubetriebliche Rahmenbedingungen und Kennwerte, die zur Beurteilung der wirtschaftlichen Anwendung des Verfahrens geeignet sind, erarbeitet werden. Untersucht werden soll die Applikation von textilbewehrtem Beton im Bereich der Sanierung und Verstärkung von großflächigen Betonbauteilen. Generell können Bauaufgaben in sehr vielen Fällen durch verschiedene Bauverfahren realisiert werden, die sich regelmäßig hinsichtlich der Kosten, der benötigten Bauzeit aber auch hinsichtlich der gelieferten Qualität und des Einflusses auf die Umwelt unterscheiden. Aus baubetrieblicher Sicht wird traditionell über den kalkulatorischen Verfahrensvergleich jenes Verfahren ermittelt, mit dem die Realisierung am wirtschaftlichsten ausgeführt werden kann. Falls qualitative Kriterien beim Verfahrensvergleich mit berücksichtigt werden sollen, stehen verschiedene Methoden zur Auswahl. Der Begriff Nutzwertanalyse wird häufig als Synonym für diese nichtmonetären Bewertungsverfahren verwendet. In diesem Sinne ist auch der Titel des Beitrages zu verstehen. Die Grundlage bilden die baubetrieblichen Rahmenbedingungen, welche im Rahmen dieses Forschungsprojektes bestimmt werden. Hierzu zählen unter anderem die Entwicklung einer Trockenmischung des zu verwendenden Betons aus der bisher verwendeten Standardrezeptur der TU Dresden und geeigneter Maschinen für die Applikation des textilbewehrten Betons.
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Kostova, Kaloyana Zdravkova. "Design and constructability of fabric-formed concrete elements reinforced with FRP materials." Thesis, University of Bath, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.707574.
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Concrete has many advantages as a low cost and sustainable material. However, more than 5% of the planet’s total carbon emissions are associated with the production of cement, which, in fact, is predominantly due to the large volume of concrete used worldwide. It is known that traditionally designed concrete structures typically use more material than structurally required and, therefore, an important question is whether material demand can be reduced through structural optimisation. A major drawback from optimised design, however, is the cost and complexity of producing conventional rigid moulds. Fabric formwork is emerging as a new method for construction, gaining popularity among architects and engineers for the opportunity to build unique forms and to shape concrete elements efficiently. Porous fabrics, acting as controlled permeability formwork, also have proven effect on the durability characteristics of concrete. While fabric formwork has a profound potential to change the appearance of concrete structures, the shapes cast in fabrics are not defined in advance and have been often created unintentionally. The design of load-bearing reinforced concrete structures, however, requires accurate form-prediction and construction methods for securing steel reinforcement inside flexible fabrics, which presents a number of constructability challenges. For example, cover formers cannot be used to ensure adequate thickness of protective cover, inevitably affecting the acceptance of such structures in practice. This research has demonstrated that non-corrodable FRP reinforcement can be incorporated more easily than steel bars in fabric-formed concrete due to its light weight and flexibility, while it is possible to ensure ductility of such structures through confinement of concrete using FRP helices. A novel splayed anchorage system has been developed to provide end anchorage for optimised sections where standard bends or hooks cannot fit. This work also provides an experimentally verified methodology and guidance for the design and optimisation of fabric-formed elements.
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Lokits, Jeremy Craig. "Structural Reinforcement Layout and Sizing Optimization of a Composite Advanced Sail." MSSTATE, 2006. http://sun.library.msstate.edu/ETD-db/theses/available/etd-04162006-162337/.
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Structural reinforcement layout optimization can be a very useful tool in the preliminary stages of design. In this research, sizing optimization techniques are used to generate results very similar to traditional layout optimization techniques with advantages in composite modeling and available strength and stability responses. Both linear and nonlinear sizing-to-design variable relationships are applied to a composite advanced sail design problem with high and low-complexity finite element models. An alternate methodology based on fractional-factorial-design and response surface modeling is also presented with promising results for finding the globally optimum reinforcement layout design. The stiffener layouts obtained from the different approaches are used to define an improved stiffener layout for sizing optimization for minimum weight. A weight savings of more than 19% is obtained over a baseline model using these methodologies.
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Ward, Elizabeth L. "Analytical Evaluation of Structural Concrete Members with High-Strength Steel Reinforcement." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1235402100.
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Jacobs, Colin D. "An investigation of soil nail reinforcement using a large direct shearbox." Thesis, Cardiff University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318686.
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Abid, Saddek. "Analysis of shear wall coupling beams with two types of reinforcement." Thesis, Heriot-Watt University, 1994. http://hdl.handle.net/10399/757.
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Rafeeqi, Sahibzada Farooq Ahmed. "Flexural behaviour of reinforced concrete beams strengthened by external unbonded reinforcement." Thesis, Heriot-Watt University, 2000. http://hdl.handle.net/10399/1163.
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Darwish, I. Y. S. "Steel fibre-reinforced concrete elements in shear." Thesis, Bucks New University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375129.
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Carolin, Anders. "Carbon fibre reinforced polymers for strengthening of structural elements." Doctoral thesis, Luleå, 2003. http://epubl.luth.se/1402-1544/2003/018.
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Horsburgh, Lynne. "Structural studies of complexes of some S-block elements." Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318708.
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OLIVEIRA, ADENILSON COSTA DE. "A DYNAMIC INTERACTION MODEL OF TRACK RAILWAY STRUCTURAL ELEMENTS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2006. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=9498@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOREm uma ferrovia, o veículo interage dinamicamente com a superestrutura (trilhos, palmilha e dormentes) e a subestrutura (lastro, sublastro e sub- base). O conforto dos passageiros, a vibração no solo e a freqüência dos trabalhos, de manutenção tanto dos veículos como também dos trilhos são determinadas considerando-se que todos os elementos estruturais interagem entre si. A resposta de cada componente estrutural é sensível µa pressão do eixo da roda no trilho, µas irregularidades na superfície do trilho e µa velo- cidade do trem, que está relacionada com à velocidade crítica na ferrovia (velocidade da fase mínima com que as ondas se propagam no trilho e no dormente). No projeto de uma nova ferrovia, como também na própria ava- liação das condições de trabalho de ferrovias existentes, todos os aspectos brevemente mencionados acima têm que ser levados em conta em um modelo matemático. A interação trilho-palmilha-dormente-lastro é representada por um modelo unidimensional em que os trilhos são representados por vigas de Timoshenko, assim como os dormentes; o lastro é representado por uma fundação elástica com amortecimento viscoso. A interação local entre tri- lho e dormente é simulada utilizando um elemento de treliça com rigidez e amortecimento. As propriedades mecânicas de cada componente da ferro- via são na maioria dos casos desconhecidas, principalmente as propriedades do lastro. Para cada elemento, são desenvolvidas as equações de equilíbrio entre esforços e deslocamentos. As equações de equilíbrio global são dadas por um desenvolvimento em série das matrizes de massa, rigidez e amorte- cimento em função de uma freqüência circular de vibração. O interesse final é a resposta transiente no domínio do tempo, obtida utilizando técnicas de superposição modal. Por fim, são propostos três modelos globais para a ferrovia, obtidos considerando algumas modificações no dormente.
In a railway, the vehicle interacts dynamically with a track superstructure (rails, rail pad and sleepers) and sub-structure (ballast, sub-ballast, sub- grade). Passengers' comfort, environmental loading (ground vibration) and frequency of maintenance works of vehicles as well as of the track are deter- mined by the way all the structural elements interact. The response of each single structural component is sensitive to the wheel-axle pressure on the track, the effects of joint in un welded rails, the unevenness of wheel and rail, and the train speed as referred to the track critical velocity (minimum phase velocity of bending waves propagating in the track rails, supported by the ballast). An important issue is for example how the ballast will be affected when old, soft, timber sleepers and replaced by much, stiffer, pres- tressed concrete elements, and how newly introduced irregularities propa- gate along the track, among uncountable mathematical model possibilities, the presents a rail-pad-sleeper-ballast model mainly based on an assemble of Timoshenko beam elements (for the rail) including, in case of the sle- epers, elastic foundation (for the ballast) and viscous damping. The local interaction of the rail-pad-sleeper set is simulated with a bar element that includes damping. The dissertation reports on the numerical model, which relies on exact, dynamic beam and truss elements derived on a variational basis for the frequency-domain analysis. The model enable the assessment of the vibration characteristics of a rail track, the inverse evaluation of se- veral mechanical properties of the structural components and eventually, if everything goes well, the assessment of a dynamic behavior of the rail track actual service load. Theoretical basis for transient analysis is the advanced mode superposition technique. Finally, are proposed three global models for the railway, obtained considering some modifications in the sleeper.
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Stanic, Andjelka. "Solution methods for failure analysis of massive structural elements." Thesis, Compiègne, 2017. http://www.theses.fr/2017COMP2383/document.
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Objectifs de la thèse : l’analyse à rupture de structure de type solides et membranes et la modélisation de la rupture quasi-fragile par la méthode des éléments finis à forte discontinuité en cas de solide 2D. Dans ce travail, la méthode de continuation avec une équation de contrainte quadratique est présentée sous sa forme linéarisée. En présence de ruptures locales, la méthode de continuation standard peut échouer. Afin d’améliorer la performance de cette méthode, nous proposons de nouvelles versions plus sophistiquées qui prennent en compte les ruptures locales des matériaux. D’une part, une version est basée sur une équation supplémentaire adaptative imposant une limitation. Cette version est considérée relativement satisfaisante pour les matériaux adoucissants. D’autres versions sont basées sur le contrôle de la dissipation incrémentale pour les matériaux inélastiques. Plusieurs formulations d’éléments finis à forte discontinuité sont présentées en détails pour l’analyse de rupture quasi-fragile. Les approximations discrètes du champ de déplacement sont basées sur des éléments quadrilatéraux isoparamétriques ou des éléments quadrilatéraux enrichis par la méthode des modes incompatibles. Afin de décrire la formation d’une fissure ainsi que son ouverture, la cinématique de l’élément est enrichie par quatre modes de séparation et des paramètres cinématiques. On a également proposé un nouvel algorithme de repérage de fissure pour l’évaluation de la propagation de la fissure à travers le maillage. Plusieurs exemples numériques sont réalisés afin de montrer la performance de l’élément quadrilatéral à forte discontinuité ainsi que l’algorithme de repérage de fissure proposéThe thesis studies: the methods for failure analysis of solids and structures, and the embedded strong discontinuity finite elements for modelling material failures in quasi brittle 2d solids. As for the failure analysis, the consistently linearized path-following method with quadratic constraint equation is first presented and studied in detail. The derived path-following method can be applied in the nonlinear finite element analysis of solids and structures in order to compute a highly nonlinear solution path. However, when analysing the nonlinear problems with the localized material failures (i.e. materialsoftening), standard path-following methods can fail. For this reason we derived new versions of the pathfollowing method, with other constraint functions, more suited for problems that take into account localized material failures. One version is based on adaptive one-degree-of-freedom constraint equation, which proved to be relatively successful in analysing problems with the material softening that are modelled by the embedded-discontinuity finite elements. The other versions are based on controlling incremental plastic dissipation or plastic work in an inelastic structure. The dissipation due to crack opening and propagation, computed by e.g. embedded discontinuity finite elements, is taken into account. The advantages and disadvantages of the presented path-following methods with different constraint equations are discussed and illustrated on a set of numerical examples. As for the modelling material failures in quasi brittle 2d solids (e.g. concrete), several embedded strong discontinuity finite element formulations are derived and studied. The considered formulations are based either on: (a) classical displacement-based isoparametric quadrilateral finite element or (b) on quadrilateral finite element enhanced with incompatible displacements. In order to describe a crack formation and opening, the element kinematics is enhanced by four basic separation modes and related kinematic parameters. The interpolation functions that describe enhanced kinematics have a jump in displacements along the crack. Two possibilities were studied for deriving the operators in the local equilibrium equations that are responsible for relating the bulk stresses with the tractions in the crack. For the crack embedment, the major-principle-stress criterion was used, which is suitable for the quasi brittle materials. The normal and tangential cohesion tractions in the crack are described by two uncoupled, nonassociative damage-softening constitutive relations. A new crack tracing algorithm is proposed for computation of crack propagation through the mesh. It allows for crack formation in several elements in a single solution increment. Results of a set of numerical examples are provided in order to assess the performance of derived embedded strong discontinuity quadrilateral finite element formulations, the crack tracing algorithm, and the solution methods
Doktorska disertacija obravnava: (i) metode za porušno analizo trdnih teles in konstrukcij, ter (ii) končne elemente z vgrajeno močno nezveznostjo za modeliranje materialne porušitve v kvazi krhkih 2d trdnih telesih. Za porušno analizo smo najprej preučili konsistentno linearizirano metodo sledenja ravnotežne poti skvadratno vezno enačbo (metoda krožnega loka). Metoda omogoča izračun analize nelinearnih modelov, ki imajo izrazito nelinearno ravnotežno pot. Kljub temu standardne metode sledenja poti lahko odpovedo,kadar analiziramo nelinearne probleme z lokalizirano materialno porušitvijo (mehčanje materiala). Zatosmo izpeljali nove različice metode sledenja poti z drugimi veznimi enačbami, ki so bolj primerne zaprobleme z lokalizirano porušitvijo materiala. Ena različica temelji na adaptivni vezni enačbi, pri katerivodimo izbrano prostostno stopnjo. Izkazalo se je, da je metoda relativno uspešna pri analizi problemov zmaterialnim mehčanjem, ki so modelirani s končnimi elementi z vgrajeno nezveznostjo. Druge različicetemeljijo na kontroli plastične disipacije ali plastičnega dela v neelastičnem trdnem telesu ali konstrukciji.Upoštevana je tudi disipacija zaradi širjenja razpok v elementih z vgrajeno nezveznostjo. Prednosti inslabosti predstavljenih metod sledenja ravnotežnih poti z različnimi veznimi enačbami so predstavljeni naštevilnih numeričnih primerih. Za modeliranje porušitve materiala v kvazi krhkih 2d trdnih telesih (npr. betonskih) smo izpeljali različne formulacije končnih elementov z vgrajeno močno nezveznostjo v pomikih. Obravnavane formulacije temeljijo bodisi (a) na klasičnem izoparametričnem štirikotnem končnem elementu bodisi (b) na štirikotnem končnem elementu, ki je izboljšan z nekompatibilnimi oblikami za pomike. Nastanek in širjenje razpoke opišemo tako, da kinematiko v elementu dopolnimo s štirimi osnovnimi oblikami širjenja razpoke in pripadajočimi kinematičnimi parametri. Interpolacijske funkcije, ki opisujejo izboljšano kinematiko, zajemajo skoke v pomikih vzdolž razpoke. Obravnavali smo dva načina izpeljave operatorjev, ki nastopajo v lokalni ravnotežni enačbi in povezujejo napetosti v končnem elementu z napetostmi na vgrajeni nezveznosti. Kriterij za vstavitev nezveznosti (razpoke) temelji na kriteriju največje glavne napetosti in je primeren za krhke materiale. Normalne in tangentne kohezijske napetosti v razpoki opišemo z dvema nepovezanima, poškodbenima konstitutivnima zakonoma za mehčanje. Predlagamo novi algoritem za sledenje razpoki za izračun širjenja razpoke v mreži končnih elementov. Algoritem omogoča formacijo razpok v več končnih elementih v enem obtežnem koraku. Izračunali smo številne numerične primere, da bi ocenili delovanje izpeljanih formulacij štirikotnih končnih elementov z vgrajeno nezveznostjo in algoritma za sledenje razpoki kot tudi delovanje metod sledenja ravnotežnih poti
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Mahony, Luke T. School of Mining UNSW. "Development of a laboratory facility for testing shear performance of installed rock reinforcement elements." Awarded by:University of New South Wales. School of Mining, 2006. http://handle.unsw.edu.au/1959.4/25700.
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Rock reinforcing elements provide a significant proportion of their ground control capability through offering resistance to shear movement of adjacent rock masses or blocks. This potential shear movement may take the form of sliding on horizontal bedding planes leading to strata bending; or block displacement along other geological structures such as joints or similar discontinuities. Much has been reported about this type of behaviour of rock bolts and other tendons, in theoretical concepts. However, there is a shortage of quality data available on the exact nature of this mechanism for shear resistance, and the role played by parameters such as pre-tensioning. A clearer understanding of the nature and significance of this type of behaviour has major implications for rock reinforcing materials and installation design. This thesis, which was supported by the Australian Coal Research Program (ACARP) describes the design, construction and commissioning of a laboratory testing facility at the School of Mining Engineering, University of New South Wales (UNSW), Australia and a subsequent testing program. The single failure plane design adopted in the test rig has been successful in allowing shear loading to be directly applied to fully installed rockbolts. Rockbolts were installed into an offset concrete rockmass, which consisted of two separate concrete samples that created a smooth shear plane surface. The reinforced samples were subjected to an applied shear load and critical parameters such as load and shear displacement were recorded. Influencing parameters such as concrete strength and applied pre-tension were altered and recorded to determine their effects on the overall shear performance of the sample. The failure mode of the rockbolts was also examined. The results indicate that a relative stronger rockmass material caused the rockbolt to fail within a lower shear displacement compared to a relatively weaker material. Also, a pre-tensioned rockbolt tended to resist shear displacement at least initially, until high shear loads developed. This phenomena is beneficial to ground support as less movement would tend to maintain integral strength of the rockmass. The use of strain-gauged rockbolts indicated as would be expected that the shear loading arrangement induced a compressive axial loading that tended to dissipate with distance from the shear surface.
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Chang, O. V. "Boundary elements applied to three dimensional elastodynamic problems." Thesis, University of Southampton, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373572.
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Nyaoro, Dalmas Lucas. "Analysis of soil-structure interaction by finite elements." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/8675.
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