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1
Karsu, Burak. "The load deformation response of single bolt connections." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-01242009-063304/.
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Molloy, Patrick Donal. "The load-deformation characteristics of steel-concrete sandwich construction." Thesis, Queen's University Belfast, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317463.
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MOROTE, CARLOS HUGO SOTO. "STABILITY AND DEFORMATION OF SOIL SLOPES UNDER SEISMIC LOAD." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2006. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=9532@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO<br>O comportamento sísmico de taludes tem sido um tópico de
grande
interesse da engenharia geotécnica nos últimos 40 anos.
Durante este período, a
prática da engenharia nesta área evoluiu do emprego de
técnicas elementares para
procedimentos numéricos bastante complexos. A abordagem
mais simples é a
análise pseudo-estática na qual o carregamento do
terremoto é simulado por uma
aceleração horizontal estática equivalente atuando na
massa de solo deslizante,
utilizando-se um procedimento de equilíbrio limite
(método
das fatias),
geralmente conservativo. O parâmetro que descreve o
comportamento dinâmico
do solo é referido como coeficiente sísmico k, e sua
seleção depende fortemente
da experiência e normas técnicas locais, porque não há
maneira simples e segura
de se escolher um valor adequado. O segundo procedimento
é
conhecido como
método de Newmark, que envolve o cálculo de uma
aceleração
de escoamento,
definida como a força inercial necessária para o fator
de
segurança atingir 1 em
uma análise pseudo-estática pelo método de equilíbrio
limite. O procedimento
então usa os registros de aceleração do terremoto de
projeto e o integra
duplamente no tempo para calcular os deslocamentos
permanentes acumulados.
O terceiro método é referido como análise de Makdisi-
Seed,
que procura definir a
estabilidade sísmica do talude em termos de
deslocamentos
aceitáveis em vez de
um fator de segurança tradicional através de uma versão
modificada do método de
Newmark. Esta técnica apresenta uma maneira racional de
calcular uma
aceleração de escoamento média, necessária para produzir
um valor do coeficiente
de segurança do talude igual a 1. Gráficos específicos
foram também
desenvolvidos para estimativa dos deslocamentos
permanentes, tendo sido
bastante aplicados em aterros rodoviários, barragens e
aterros sanitários.
Finalmente, o mais sofisticado método para análise de
estabilidade sísmica de
taludes é conhecido como análise dinâmica, que
normalmente
incorpora modelos
de elementos finitos e relações tensão x deformação
complexas numa tentativa de obter melhores
representações
para o comportamento mecânico de taludes sob
cargas cíclicas Os resultados destas análises podem
incluir a história no tempo dos
deslocamentos e tensões, bem como das freqüências
naturais, efeitos de
amortecimento, etc. Este trabalho apresenta uma
comparação
entre os métodos
mencionados anteriormente, analisando o comportamento
sísmico dos taludes da
estrutura de contenção dos resíduos de lixiviação de
minério de urânio, na Bahia,
e dos taludes do bota-fora sul da mina de cobre
Toquepala,
situada no Peru.<br>The seismic stability of slopes has been a topic of
considerable interest in
geotechnical engineering for the past 40 years. During
that period, the state of
practice has moved from simples techniques to more
complicated numerical
procedures. The simplest approach is the pseudo-static
analysis in which the
earthquake load is simulated by an equivalent static
horizontal acceleration
acting on the mass of the landslide, according to a
generally conservative limit
equilibrium analysis. The ground motion parameter used in
a pseudo-static
analysis is referred to as the seismic coefficient k, and
its selection has relied
heavily on engineering judgment and local code
requirements because there is no
simple method for determining an appropriate value. The
second main procedure
is known as the Newmark displacement analysis which
involves the calculation of
the yield acceleration, defined as the inertial force
required to cause the static
factor of safety to reach 1 from the traditional limit
equilibrium slope stability
analysis. The procedure then uses a design earthquake
strong-motion record which
is numerically integrated twice for the amplitude of the
acceleration above the
yield acceleration to calculate the cumulative
displacements. These displacements
are then evaluated in light of the slope material
properties and the requirements of
the proposed development. The third method is referred to
as the Makdisi-Seed
analysis sought to define seismic embankment stability in
terms of acceptable
deformation instead of conventional factors of safety,
using a modified Newmark
analysis. Their method presents a rational means to
determine yield acceleration,
or the average acceleration required to produce a factor
of safety of unity. Design
curves were developed to estimate the permanent earthquake-
induced
deformations of embankments, which have since been applied
to sanitary landfill and highway embankments. Finally, the
most sophisticated method for seismic
slope stability calculations is known as the dynamic
analysis, which normally
incorporates a finite element model and a rather complex
stress-strain behavior for
geological materials in an attempt to obtain a better
representation of the behavior
of soils under cyclic loading. The results of the analysis
can include a time
history of displacements and stresses, as well as natural
frequencies, effects of
damping, etc. This work presents a comparison of the
results obtained by the
aforementioned approaches, considering the seismic
behavior of the slopes of an
uranium lixiviation pad situated in Bahia, Brazil, and the
South embankment of
the waste landfill of the Toquepala Mine, Peru.
4
Jakobsen, Bo. "In-situ studies of bulk deformation structures : static properties under load and dynamics during deformation /." Roskilde : Roskilde University, Department of Science, Systems and Models & Center for Fundamental Research, Metal Structures in Four Dimensions Materials Research Department, Risø National Laboratory, 2006. http://hdl.handle.net/1800/3059.
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McLaughlin, Kirsten Kathleen. "TEM diffraction analysis of the deformation underneath low load indentations." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613392.
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Goudie, K. "Experimental study of the gross deformation of tubular beams." Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380143.
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McMahon, Brendan. "Deformation mechanisms beneath shallow foundations." Thesis, University of Cambridge, 2013. https://www.repository.cam.ac.uk/handle/1810/244367.
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Shallow foundations can provide the most economical solution for supporting small-scale structures. The design approach is quite simple considering the ultimate bearing capacity and working-load settlement. Research has shown that settlement calculations, determined using a linear-elastic approach, usually govern the design but this approach is inappropriate because soil is highly non-linear, even at small strains. The result is that signifi cant discrepancies are observed between predicted and actual settlements. This uncertainty has seen the development of settlement-based approaches such as Mobilisable Strength Design (MSD). MSD uses an assumed undrained mechanism and accounts for soil non-linearity by scaling a triaxial stress-strain curve to make direct predictions of footing load-settlement behaviour. Centrifuge experiments were conducted to investigate the mechanisms governing the settlement of shallow circular foundations on clay and saturated sand models. Clay model tests were performed on soft or rm kaolin beds, depending on its pre-consolidation. Sand model tests were performed on relatively loose Hostun sand saturated with methyl-cellulose to slow consolidation. One-dimensional actuators were developed to apply footing loads through dead-weight or pneumatic loading. A Perspex window in the centrifuge package allowed digital images to be captured of a central cross-section, during and after footing loading. These were used to deduce soil displacements by Particle Image Velocimetry which were consistent with footing settlements measured directly. Deformation mechanisms are presented for undrained penetration, consolidation due to transient flow, as measured by pore pressure transducers, and creep. A technique was developed for discriminating consolidation settlements from the varying rates of short and long-term creep of clay models. Using MSD, a method for predicting the undrained penetration of a spread foundation on clay was proposed, using database results alone, which then provided estimates of creep and consolidation settlements that follow. The importance of the undrained penetration necessitated further investigation by using the observed undrained mechanism as the basis of an ellipsoidal cavity expansion model. An upper-bound energy approach was used to determine the load-settlement behaviour of circular shallow foundations on linear-elastic and non-linear clays, with yield defined using the von Mises' yield criterion. Linear-elastic soil results were consistent with those obtained from nite element analyses. The non-linear model, as described by a power-law, showed good agreement with both centrifuge experiment results and some real case histories. The single design curve developed through this model for normalised footing pressure and settlement could be used by practising engineers based on existing soil correlations or site investigations.
8
Friedman, Ross Aaron. "The dehydration of pharmaceutical hydrates under mechanical load." Diss., University of Iowa, 2014. https://ir.uiowa.edu/etd/3224.
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Nearly one-third of all pharmaceutical substances on the market are able to sorb water into their crystal lattices to form hydrates, which can often compromise stability during processing and/or storage[1]. The tendency of a hydrate to lose its water of crystallization during the manufacturing process of tablet compression is of particular concern to formulation scientists. The amount of water freed as a function of increasing compaction pressure can be explained by the mobility of water within the compact. The mobility of water is determined by the size and shape of the crystal lattice, the numbers and strengths of the hydrogen bonds, and the presence of high-energy sites of disorder[2]. Due to their differing crystal structures, theophylline monohydrate (THM), citric acid monohydrate (CAM), theophylline-water-citric acid cocrystal hydrate (CATHP hydrate), and dicalcium phosphate dihydrate (DCPD) make for interesting model systems to examine the dehydration under mechanical load.
The thermal dehydration of both powders and tablets was carried out via thermal gravimetric analysis (TGA). By comparing the temperatures required to start removal of water loss from the powder to that of the tablet, the average amount of water of crystallization that is freed by the compaction process may be quantified. The average amount of water freed by the compaction process results from a competition between the mechanically-induced disorder of the crystal structure that increases the molecular mobility of water within the tablets, and the trapping of water within the interparticulate void spaces at high compaction pressures.
The compressibilities, compactabilities, and tabletabilities of the materials were calculated as a function of increasing compaction pressure. The consolidation of the powder bed under pressure was modeled by out-of-die Heckel Analysis which demonstrated the ease of deformation of the model compounds. XRD was utilized to show the decrease in overall order of the crystal lattice as a result of compression as well as anisotropy within the tablets. Crystallographic approaches were utilized to demonstrate the compactness of the crystal structure, and how it affects water mobility.
Relaxation pulse experiments (T1, T2) utilizing solid-state NMR were used to directly probe the mobilities of the water molecules within the crystal lattice of THM. The results from T1 and T2 relaxation experiments directly measure the change in molecular mobility of water within the tablets as a function of compaction pressure. This provided independent verification of the trends in molecular mobility and average water freed as a function of compaction pressure observed during TGA dehydration. Raman spectroscopy was used to indirectly measure the polarizability and vibrational motions of THM, and these results corroborate those obtained from ssNMR and TGA dehydration experiments. Overall, this work highlights the potential impact that tablet compression can have on API hydrate stability.
1. Hilfiker R (editor). 2006. Polymorphism in the Pharmaceutical Industry. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co, KGaA.
2. Byrn SR, Pfeiffer RR, Stowell JG. 1999. Solid-state chemistry of drugs. SSCI, Inc.
9
O'Brien, Patrick Emmet. "Characterizing the Load-Deformation Behavior of Steel Deck Diaphragms using Past Test Data." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/78679.
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Recent research has identified that current code level seismic demands used for diaphragm design are considerably lower than demands in real structures during a seismic event. However, historical data has shown that steel deck diaphragms, common to steel framed buildings, perform exceptionally well during earthquake events. A new alternative diaphragm design procedure in ASCE 7-16 increases diaphragm seismic demand to better represent expected demands. The resulting elastic design forces from this method are reduced by a diaphragm design force reduction factor, Rs, to account for the ductility of the diaphragm system. Currently, there exist no provisions for Rs factors for steel deck diaphragms. This research was therefore initiated to understand inelastic steel deck diaphragm behavior and calculate Rs factors.
A review of the literature showed that a large number of experimental programs have been performed to obtain the in-plane load-deformation behavior of steel deck diaphragms. To unify review of these diaphragm tests and their relevant results, a database of over 750 tested specimens was created. A subset of 108 specimens with post-peak, inelastic behavior was identified for the characterization of diaphragm behavior and ductility. A new recommended method for predicting shear strength and stiffness for steel deck diaphragms with structural concrete fill is proposed along with an appropriate resistance factor. Diaphragm system level ductility and overstrength are estimated based on subassemblage test results and Rs factors are then calculated based on these parameters. The effects of certain variables such as deck thickness and fastener spacing on diaphragm ductility are explored.<br>Master of Science
10
Colin, Julie Anne. "Deformation History and Load Sequence Effects on Cumulative Fatigue Damage and Life Predictions." University of Toledo / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1260390033.
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Colin, Julie. "Deformation history and load sequence effects on cumulative fatigue damage and life predictions /." Connect to full text in OhioLINK ETD Center, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=toledo1260390033.
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Gibb, John Michael. "Evaluation of resistance to permanent deformation in the design of bituminous paving mixtures." Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318643.
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Ssemakula, Hamzah. "Manufacturihng of heavy rings and large copper canisters by plastic deformation." Doctoral thesis, KTH, Production Engineering, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3682.
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<p>Plastic deformation processes transform material fromas-received state to products meeting certain requirements inproperties, microstructure and shape. To achieve thistransformation, the relationship between material response andprocess conditions should be understood. This is usuallycomplicated by the complex conditions describing the actualprocess. Numerous techniques including empirical, physical,analytical and numerical can be employed.</p><p>In this thesis, numerical technique supported by lab- andfull-scale experiments has been employed to analyse the formingparameters. The first part of the thesis is focused on the useof such parameters to predict occurrence of material poresduring manufacturing of bearing rings. The second part dealswith the influence of forming parameters on the grain sizeduring fabrication of large copper canisters for encapsulationof nuclear waste. The primary task has been to study with thehelp of commercial FE-codes the magnitude and distribution offorming parameters such as accumulated effective strain,temperature, instantaneous hydrostatic pressure and materialflow at different stages of the forming process. In the firstpart, two types of ring manufacturing routes, which result inpore free and pore loaded rings are studied and compared.Material elements located in different areas of the workpiecehave been traced throughout the process. Results of theaccumulated strain and instant hydrostatic pressure have beenanalysed and presented in pressure-strain space. Itsassumed that high hydrostatic pressures together with higheffective strains are favourable for pore closure. Area of theworkpiece with unfavourable parameters have been identified andcompared with ultrasonic test results. Good agreement has beenobtained. Based on the results of this analysis, a new conceptfor avoiding pores in manufacturing of yet heavier rings hasbeen presented. The concept proposes a lighter upsetting in theinitial stage of the process and a more efficient piercingwhich results in higher hydrostatic pressure and bigger andbetter distributed effective strain.</p><p>In the second part of the thesis, the influence of formingparameters such as effective strain and temperature on thefinal grain size of the product has been studied in laboratoryscale. As-cast billets of cylindrical shape were extruded atdifferent temperatures and reductions. It has been shown thatthe grain size in the final product should be small in order toenable ultrasonic tests and to guarantee resistance towardscreep and corrosion. Simulations for different materialelements located at different distances from the axis ofsymmetry of the initial cylindrical workpiece have been carriedout. In this way, the parameters describing the deformationhistory of the elements have been determined as functions oftime. Experimentally obtained pre- and post deformation grainsize in the corresponding locations of the material weredetermined. Its concluded that low temperature coupledwith high effective strain are conducive for obtaining a smallgrain size. Based on the beneficial conditions for extrusion ofcopper, a more detailed FE-analysis of a full-scale industrialprocess is carried out. A coarse-grained cast ingot of purecopper is heated and by upset forging formed into a cylinder,which is then punched into a hollow blank for subsequentextrusion. The blank is extruded over a mandrel through a45-degree semi-angle die. Accumulated effective strain andtemperatureas functions of the tubular wall thickness havebeen studied at five different locations along the tubularaxis. Forming load requirement as function of tool displacementfor each stage of the process has been determined. Strain andtemperature levels obtained have been related to the grain sizeinterval obtained in the earlier work. It has been concludedthat the levels reached are within the interval that ensures asmall grain size. A similar analysis has been carried out forforging of large copper lids and bottoms. Die designmodifications to improve the grain size in the lid and tooptimise the forging process with respect to forging load andmaterial yield have been proposed. A method requiring a smallforging load for fabrication of the lids has been analysed</p><p><b>Keywords:</b><i>Pores; grain size; low forging load; effective strain;temperature; hydrostatic pressure; extrusion; forging;canister; lid; rings</i></p>
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Albrecht, Felix. "Numerical modeling and simulation of the deformation of wood under an applied indentation load." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-231914.
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Borges, RÃmulo Luiz. "Permanent deformation in asphalt mixtures from viscoplastic shift model and triaxial repeated load test." Universidade Federal do CearÃ, 2014. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=13192.
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FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico<br>Permanent deformation or rutting is a major distress in asphalt pavements. To predict permanent
deformation of asphalt mixtures the dynamic creep test is often used in laboratory, with the
result presented in terms of the so called flow number. However, for this work it was performed
the triaxial repeated permanent deformation load test, a confined test that better represents field
conditions. The models that incorporate the flow number do not represent the main zone of the
dynamic creep test result, denoted secondary region, in which the permanent deformation rate
of growth is constant. In this work the Shift Model was used, which is a viscoplastic model that
accesses the permanent deformation from the superposition principles, i.e., time-temperature
superposition and time-stress superposition. Thus, the asphalt mixtures were tested under
different loading conditions, temperature, load time and rest period, in order to assess three
parameters of the test: parameter C, which indicates where the secondary region begins
(parameter that governs the primary region of the test); the parameter α (alpha) is the slope of
the secondary region; and the parameter B represents the level of permanent deformation of the
secondary region. The results show that the TRLPD test is more severe than the conventional
dynamic creep test. Nevertheless, the use of TRLPD test represents an advance in the
understanding of the behavior of asphalt mixtures with respect to rutting performance, and has
the advantage of allowing the use of results in computational simulations.<br>A deformaÃÃo permanente à um dos principais defeitos em pavimentos asfÃlticos. Para prever
esta falha em revestimentos, por meio de ensaios laboratoriais, Ã frequentemente utilizado o
ensaio de creep dinÃmico cujo resultado final à apresentado em termos do chamado flow
number. No entanto, para este trabalho foi realizado o triaxial repeated load permanent
deformation (TRLPD) test, que à um ensaio sob condiÃÃes de confinamento, a fim de melhor
se aproximar das condiÃÃes encontradas em campo. Os modelos que incorporam o flow number
nÃo representam a principal regiÃo de ensaio de creep dinÃmico, denominada regiÃo secundÃria,
na qual o incremento de deformaÃÃo permanente cresce em valor constante. No presente
trabalho utilizou-se o Shift Model, o qual à um modelo viscoplÃstico que avalia a deformaÃÃo
permanente a partir da superposiÃÃo dos efeitos tempo-temperatura e tempo-tensÃo. Dessa
forma, as misturas asfÃlticas foram testadas sob diferentes condiÃÃes de carregamento,
temperatura, tempo de aplicaÃÃo de carga e perÃodo de repouso. Foram avaliados trÃs
parÃmetros do ensaio em questÃo: o parÃmetro C, que fornece os dados de onde a regiÃo
secundÃria se inicia (parÃmetro que governa a regiÃo primÃria do ensaio); o parÃmetro α (alfa),
que à o aclive da regiÃo secundÃria; e o parÃmetro B, que representa o nÃvel de deformaÃÃo
permanente da regiÃo secundÃria. Os resultados obtidos mostram que o ensaio TRLPD Ã mais
severo do que o ensaio convencional de creep dinÃmico, porÃm considera-se que a utilizaÃÃo
de ensaios confinados representa um avanÃo para o entendimento do comportamento das
misturas asfÃlticas quanto à resistÃncia à deformaÃÃo permanente das mesmas, e este traz a
vantagem de poder ser usado em simulaÃÃes computacionais.
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Zhalehjoo, Negin. "Characterisation of the deformation behaviour of unbound granular materials using repeated load triaxial testing." Thesis, Federation University of Australia, 2018. http://researchonline.federation.edu.au/vital/access/HandleResolver/1959.17/166953.
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Unbound Granular Materials (UGMs) are used in the base/subbase layers of flexible pavements for the majority of roads around the world. The deterioration of pavements increases with the increase of traffic loadings. To ensure the long-term performance and serviceability of pavement structures through a realistic design, the precise evaluation and comprehensive characterisation of the resilient and permanent deformation behaviour of pavement materials are essential. The present PhD study aims to investigate the characterisation of the resilient and permanent deformation behaviour of four road base UGMs sourced from quarries in Victoria, Australia, using Repeated Load Triaxial (RLT) testing. The triaxial system used in this study is instrumented with four axial deformation measurement transducers to achieve highly precise measurements and to evaluate the effect of instrumentation on the resilient modulus of UGMs. The resilient Poisson’s ratio of the studied UGMs is also determined using a radial Hall-Effect transducer. Moreover, a series of permanent deformation tests is performed to precisely characterise the axial and radial permanent deformation behaviour of UGMs and investigate the factors that may significantly influence the accumulated axial and radial permanent deformations. Finally, three permanent deformation models incorporated with a time-hardening procedure are employed to predict the magnitude of permanent strain for multiple stress levels of the RLT test. The predictions using the employed models are then compared against the measured values to evaluate the suitability of the models and to identify the model that best predicts the strain accumulation behaviour of the tested UGMs. While this study focuses on the resilient and permanent deformation behaviour of four Victorian UGMs under repeated loading, the knowledge generated from this comprehensive investigation will contribute towards the global development of more reliable methods for evaluating the long-term performance of pavement structures and minimising road maintenance and repair costs.<br>Doctor of Philosophy
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Lodhi, Muhammad S. "RESPONSE ESTIMATION OF REINFORCED CONCRETE COLUMNS SUBJECTED TO LATERAL LOADS." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1269631164.
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Juchnevičius, Žilvinas. "Deformation and strength of a cyclically bent threaded connection." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2012. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2012~D_20120206_165453-81433.
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Industry equipment such as pressure vessels, mining equipment, heat exchang-ers, steam generators and other structures are provided with bolted closures for the purpose of in-service inspection and maintenance of internal components. Threaded connections often experience variable cyclic loads due to temperature, inner pressure and variation in the deformation of connection fittings. Often, studs and screws are not only affected by an axial load, but also by bending moments.
More sophisticated high-cycle and low-cycle durability calculation meth-odologies have been already developed for threaded connections experiencing cyclic axial loads, and in these methodologies the distribution of axial load among turns is assessed quantitatively. The quantitative data of load distribu-tion in the thread enables a more accurate assessment of the influence of the constructional design particularities (connection length, material, nut and turn’s form) and the deformation stages of the connection element.
These durability calculation methodologies are not applied for threaded connections that are cyclically bent, as the analytical models that are suitable for practical application in the load distribution of the turns have not been cre-ated for bent threaded connections. In this field, no models have been created to be calculated by the BE method.
As the threaded connection is a complex node consisting of deformed el-ements, the load distribution among turns is influenced by the... [to full text]<br>Srieginės jungtys dažnai patiria ciklinių lenkimo apkrovų dėl temperatū-ros, vidaus slėgio ir jungiamųjų detalių deformacijų kitimo. Srieginėms jung-tims, kurios patiria ašinių ciklinių apkrovų jau yra sukurtos modernesnės daugiaciklio ir mažaciklio ilgaamžiškumo skaičiavimo metodikos, kuriomis detaliai kiekybiškai įvertinamas ašinės apkrovos pasiskirstymas tarp vijų. Ap-krovos pasiskirstymo sriegyje kiekybiniai duomenys leidžia detaliau ir tiksliau įvertinti konstrukcijos ypatumų (jungties ilgio, medžiagos, veržlės ir vijų for-mos) ir jungties elementų deformavimo stadijų įtaką. Tokios ilgaamžiškumo skaičiavimo metodikos cikliškai lenkiamoms srieginėms jungtims netaikomos, nes lenkiamoms srieginėms jungtims nėra sukurtų apkrovos pasiskirstymo vijose analitinių modelių, tinkamų praktiniam naudojimui. Šioje srityje taip pat nėra sukurtų ir modelių, kurie skaičiuojami baigtinių elementų metodu. Kadangi srieginė jungtis yra kompleksinis mazgas, kurį sudaro deformuo-jami elementai, tai apkrovos pasiskirstymą tarp vijų lemia jungties elementų deformacijų ir poslinkių suderinamumas. Matematiškai aprašant jungties de-formuotą būvį, reikalingi teoriniai ir eksperimentiniai duomenys, kurie atspin-dėtų jungties elementų deformavimo specifinius ypatumus, pasireiškiančius veikiant lenkimui. Disertacijoje siekiama sukurti cikliškai lenkiamų srieginių jungčių apkro-vos pasiskirstymo sriegyje skaičiavimo metodą ir pritaikyti jį mažacikliam ilga-amžiškumui skaičiuoti.
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Srithar, Thillaikanagasabai. "Stress, deformation and flow analysis of oil sand masses under applied load and temperature changes." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/28067.
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Stress and temperature changes in oil sand masses associated with oil recovery can give rise to stability and deformation problems. An analytical formulation is developed to analyze such kind of problems and incorporated in the finite element program 'CONOIL II’.
Oil sand is a multiphase material, which can be analyzed as an equivalent two phase material; solid grains saturated with a single fluid phase, having an equivalent compressibility. The equivalent compressibility is obtained by combining the concepts of unsaturated soils with the gas laws and the gas-liquid interaction effects. Classical approach, as used in thermal elasticity is not appropriate to analyze the temperature induced effects, unless the time steps are made very small. A better formulation is presented, which involves introducing additional terms in the stress-strain relation and in the flow continuity equation, to account for temperature induced effects. The new approach reduces the oscillations predicted by the classical approach and leads to more realistic results.
The analytical equations for the coupled stress, deformation and flow problems have been solved by finite element analysis. The finite element formulation involves nonlinear variations of stress-strain response, compressibility and flow, and is performed in an incremental manner. The developed finite element program has been verified by comparing its results with the closed form solutions and laboratory data. Then, the program has been applied to predict the responses associated with an oil recovery scheme. Such kind of analyses are important in the rational design of oil recovery schemes in oil sands.<br>Applied Science, Faculty of<br>Civil Engineering, Department of<br>Graduate
20
Neuman, Tomáš. "Přívěs pro přepravu formulového vozu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229871.
Full textAbstract:
This thesis deals with the conceptual design of a trailer for transportation of Formula car SAE and experimental vehicle Formula Ford. The design of the trailer is presented in the thesis in accordance with the legislation of the Czech Republic. The trailer dimensioning is desinged in view of the anticipated loads. The main task of the thesis is the strength test of the designed trailer.
21
Rahman, Mohammad Shafiqur. "Characterising the Deformation Behaviour of Unbound Granular Materials in Pavement Structures." Doctoral thesis, KTH, Väg- och banteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-162277.
Full textAbstract:
Unbound granular materials (UGMs) used in the base and sub-base layers of flexible pavements play a significant role in the overall performance of the structure. Proper understanding and characterization of the deformation behaviour of UGMs in pavement structures are, therefore, vital for the design and maintenance of flexible pavements. In this study, the resilient deformation (RD) and the permanent deformation (PD) behaviour of UGMs were investigated for the better understanding and improved modelling of these deformation characteristics. The study is based on a series of repeated-load triaxial (RLT) tests carried out on several UGMs commonly used in pavement structures. Here, the influences of stress level and moisture content - two of the most significant factors affecting the deformation behaviour of UGMs - were analysed. The effects of the grain size distribution and the degree of compaction were also considered. The study on the RD behaviour indicated that the resilient stiffness (MR)of UGMs increases with the increased bulk stress level, which can be satisfactorily described by the k-θ model. Moisture was found to negatively impact the MR as long as the deformation was mostly resilient with a negligible amount of accumulated PD. Analysis of the influence of moisture on the parameters k1 and k2 of the k-θ model showed that k1 decreases with increased moisture and k2 is relatively insensitive to moisture. Based on these observations, a simple model was developed for the impact of moisture on MR. The performance of this model was comparable to an existing moisture dependent MR model. In contrast, it was further observed that at the later stages of the RLT tests, after a relatively large number of load applications, the MR increased with increased moisture up to the optimum moisture content. This occurred when the RD was accompanied by a significant amount of PD. Further investigation suggested that moisture aided the post-compaction (PC) and possible particle rearrangement that resulted in the increased PD and increased MR. In this case k1 decreased, whereas k2 increased, with increased moisture. The existing MR-moisture model did not work for this behaviour. This suggests that the effect of PC on MRshould be considered in modelling. However, although not explored in this study, it may be possible to simulate this effect of increase in MR with increased moisture due to PC using the proposed model if k2 is expressed as a function of moisture. The PD characteristics of UGMs were investigated based on the multistage (MS) RLT test. In contrast with the single stage (SS) RLT test, the MS RLT test accounts for the effect of stress history and enables a comprehensive study of the material behaviour under cyclic stresses of various magnitudes. Since the existing PD models cannot be directly applied for the MS loading procedure, a general formulation based on the time hardening concept was derived that can be used to extend the models for the MS loading conditions. Based on this formulation, some of the current models were calibrated and their performance in predicting the PD behaviour in MS RLT tests was compared. The investigation regarding the impact of moisture on PD showed that moisture significantly increases the accumulation of PD. Generally, materials with finer grading showed more sensitivity to moisture with regards to both PD and RD. To characterize the impact of moisture, moisture sensitivity of different grain size distributions and the impact of the degree of compaction on PD with reduced effort, a simple model was proposed. Unlike some of the well-performing existing models, this model can be calibrated using a single MS RLT test without requiring any separate static failure triaxial tests. This model was validated using the MS RLT test data with satisfactory results. The sensitivity of the parameters of this model was studied with respect to moisture content, degree of compaction and grain size distribution. Some reasonable trends for the sensitivity of the parameters to these influential factors were obtained, which suggests that these may be further developed to incorporate into the model.<br><p>QC 20150325</p>
22
Raziq, Noor. "GPS structural deformation monitoring : the mid-height problem /." Connect to thesis, 2008. http://repository.unimelb.edu.au/10187/3340.
Full textAbstract:
GPS has been used to monitor engineering structures for a number of reasons. One important reason for monitoring high rise buildings (and other engineering structures) is their safety assessment in events of extreme loading, such as earthquakes and storms. Decisions must be made as soon as possible, whether to allow re-occupation of such buildings, or to assess them for further damage. The time required to reach such decisions is cost-critical, both for the building owner or manager and for the agency doing the assessment. Peak inter-storey drift ratio and detection of permanent damage are some of the damage assessment parameters recommended by assessment agencies. Traditionally, accelerometers have been used to monitor these parameters. Accelerometers measure accelerations which are double-integrated to get displacements. These double integrated displacements are then used for computing the inter-storey drift ratios and locating permanent damage. Displacements obtained by double-integration and inter-storey drift ratios by subtraction of these displacements, are often erroneous and unreliable and direct measurement of displacement is preferred. Direct measurement of displacement is required at a number of points along the height of the building. For example, for computing inter-storey drift ratios, measurements of displacement at both the floor level and roof level are required. Such points on buildings and other engineering structures of vertical profile are termed as mid-height points in this thesis. While GPS has been used for deformation monitoring of engineering structures and to assist in damage assessment during and after extreme loading events, its use has been limited to roof top installations.<br>This research is an attempt to measure displacements at mid-height locations of engineering structures of vertical profile using GPS. (For complete abstract open document).
23
NAKAMURA, Hikaru, Naoshi UEDA, Minoru KUNIEDA, and Ahmed KAMAL. "ASSESSMENT OF STRENGTHENING EFFECT ON RC BEAMS WITH UHP-SHCC." 日本コンクリート工学会, 2008. http://hdl.handle.net/2237/20917.
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24
Dareeju, Biyanvilage. "Performance evaluation of unsaturated rail track foundations under cyclic moving wheel load." Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/102697/4/Biyanvilage%2520Sampath%2520Sri%2520Sameera_Dareeju_Thesis.pdf.
Full textAbstract:
This thesis developed an alternative laboratory element testing method to evaluate the response of the unsaturated soils of rail track foundations under repeated moving wheel loadings. The novel laboratory testing method is more capable of producing the realistic strength-deformation characteristics of the unsaturated soils with the effects of principal stress axis rotation (PSAR), which can be used to redesign the conservative rail track guidelines.
25
de, Falco Paolino. "Mechanisms of deformation and energy dissipation in antler and arthropod cuticle with bio-inspired investigations." Thesis, Queen Mary, University of London, 2018. http://qmro.qmul.ac.uk/xmlui/handle/123456789/54050.
Full textAbstract:
Bio-composite hierarchical materials have attracted the interest of the academic community operating in the field of bio-inspired materials for their outstanding mechanical properties achieved via lightweight structural designs. Antler and mantis shrimp's cuticle are extreme examples of materials naturally optimised to resist impacts and bear dynamic loading. Firstly, a class of finite-element fibril models was developed to explain the origin of heterogeneous fibrillar deformation and hysteresis from the nanostructure of antler. Results were compared to synchrotron X-ray data and demonstrated that the key structural motif enabling a match to experimental data is an axially staggered arrangement of stiff mineralised collagen fibrils coupled with weak, damageable interfibrillar interfaces. Secondly, the cuticle of the crustacean Odontodactylus scyllarus, known as peacock mantis shrimp, was investigated. At the nanoscale it consists of mineralised chitin fibres and calcified protein matrix, which form plywood layers at the microscale. Lamination theory was used to calculate fibrillar deformation and reorientation and, in addition, an analytical formulation was used to decouple in-plane fibre reorientation from diffraction intensity changes induced by 3D lamellae tilting. This animal also attracted my attention for using its hammer-like appendages to attack and destroy the shells of prey with a sequence of two strikes. Inspired by this double impact strategy, I performed a set of parametric finite-element simulations of single, double and triple mechanical hits, to compute the damage energy of the target. My results reveal that the crustacean attack strategy has the most damaging effect among the double impact cases, and lead me to hypothesise, that optimal damaging dynamics exists, depending on the sequence of consecutive impacts and on their time separation values. These new insights may provide useful indications for the design of bio-inspired materials for high load-bearing applications.
26
Armaleh, Sonia Hanna 1956. "ANALYSIS OF SINGLE AND GROUP PILES IN COHESIONLESS SOILS (BEARING CAPACITY, FINITE ELEMENT METHOD, LOAD-DEFORMATION, VERTICAL LOADING, SPACING)." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/291192.
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27
Frost, Matthew W. "The performance of pavement foundations during construction." Thesis, Loughborough University, 2000. https://dspace.lboro.ac.uk/2134/11152.
Full textAbstract:
There is an impetus in the UK to move away from empirical pavement foundation design and the current method specification, towards an analytical design approach. For an analytical design approach to be adopted, the required performance properties of stiffness and resistance to permanent deformation of the foundation materials (sub grade and capping) need to be measured, both in the laboratory for design and in the field in order to ensure compliance. This thesis studies the influence of the sub grade on the constructability and performance of a series of full-scale pavement foundations. This has been achieved by measuring the performance parameters of several sub grade materials in the laboratory, using repeated load triaxial testing. These data have been compared to comparable data collected in situ using dynamic stiffness measuring devices during the construction of trial pavement foundations. The performance of the trial foundations has been measured during the placement and compaction of the different foundation materials, and again after their subsequent trafficking. The testing demonstrates the stress dependency of the foundation materials. The laboratory testing shows that the sub grade permanent deformation under cyclic loading (used to simulate construction operations) becomes unstable at a deviator stress of half the deviator stress at failure (0.5qmax)· The stiffness at this applied stress and above is shown to be approaching a consistent value. This indicates that large changes in the stiffness of inversely stress dependent fine grained soils occur below the deviator stress at which the permanent deformation becomes unstable. Significant variability of data has been found in the performance parameters measured (both in the laboratory and in the field) for samples of subgrade collected from small areas of the same site. However comparable patterns of stress dependency have been observed between measured laboratory and field performance using the different apparatus. The resistance to permanent deformation is shown to be a more critical design load case for construction than the need for adequate stiffness of support required to compact the foundation layers. The performance of a composite road foundation is shown to be material and site specific, and this will have important implications for design and site compliance testing.
28
Muturi, Christopher. "Characterization of viscoelastic properties of an epoxy composite and simulation of time dependent deformation of an annulus seal under load." Thesis, KTH, Hållfasthetslära (Inst.), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-176400.
Full textAbstract:
A new sealing stand-alone tool, i.e. CannSeal to produce a barrier packer or zonal isolation in oil/gas wells has been developed by a Norwegian company (AGR CannSeal AS). The tool allows injection of a fluid into the annulus between the production casing and the surroundings in an oil/gas well. After injection the fluid will solidify and form an annulus solid plug which will prevent/reduce axial flow in the annulus volume. During operation and testing of well integrity the plug may be subjected to high pressure gradients, e.g. 250 bar. AGR CannSeal has developed epoxy formulations for different applications for use with the CannSeal tool. After curing the epoxy will form a solid, or more specifically a cross-linked polymer. Since the epoxy plug may be exposed to large differential pressure for long times it is of great interest to study the viscoelastic properties and estimate the severity of the time dependent deformation (creep) by FEA simulations, considering the load scenarios expected in an oil or gas well. An annulus shaped epoxy plug intended for use as a barrier seal at 70°C was manufactured by injection of an epoxy formulation at 70°C and 150 bar hydrostatic pressure into the annulus of two steel tubings (5 1/2" and 9 5/8") on top of a defect packer. Curing was interrupted after 3 weeks well beyond the Gel point. Test specimens were prepared and subjected for post-curing at 120°C for 2 days after which extensive material testing at 70°C was performed, i.e. tensile testing, relaxation testing, creep testing and compression testing. The degree of curing (conversion) was estimated to be 67 % and the glass transition to about 80°C by means of DMA, DSC and HFC. Different material models were evaluated of which the Generalized Maxwell model, which assumes linear viscoelastic properties, was found to adequately describe all experimental results. The model parameters were determined by means of the method of Non-linear least squares. FEA simulations were made using the model selected and the parameters determined. Two load cases, one simulating the most sever predicted load scenario of an epoxy plug and the second simulating loading under ideal circumstances were evaluated. The simulations predicted that the most severe load case of the epoxy plug would have a safety factor of approximately 1.8 - 2,3 before reaching the estimated fracture strain, after one year of exposure to a differential pressure of 250 bar.<br>Ett nytt sorts verktyg kallat CannSeal har utvecklats av ett norskt bolag (AGR CannSeal AS)för att skapa barriärpackningar och zon-isolation inom olje- och gasbrunnar. Verktyget tillåter injicering av en reaktiv vätska mellan produktionsröret och omgivande underlag i en olje-/gasbrunn. Efter injicering stelnar vätskan och formar en solid annulär epoxitätning som förhindrar eller minskar axiella flöden i utrymmet. Under användning och testning av brunnintegriteten kan tätningen utsättas för höga tryckgradienter som kan uppgå till 250 bar. AGR CannSeal har utvecklat ett flertal olika epoxiformuleringar avsedda för olika typer av applikationer, som injiceras med CannSeal. Efter härdning kommer epoxin att forma en solid eller mer specifikt en tvärbunden polymer, en så kallad härdplast. Eftersom epoxitätningen är utsatt för höga tryckgradienter under långa perioder är det av stort intresse att undersöka de viskoelastiska egenskaperna och utgående från FEA simuleringar, simulera graden av tidsberoende deformation (krypdeformation) vid lastfall uppskattade att inträffa under applikation. Ett annulärt formad epoxitätning avsedd till användning som barriärpackning vid 70oC, tillverkades via en inmatning av en epoxiformel vid 150 Bar hydrostatiskt tryck. Tätningen placerades mellan två stålrör (5 1/2" och 9 5/8"), befinnande ovanpå en redan befintlig defekt barriärspackning. Härdningen var avbruten efter 3 veckors tid och därför även långt efter uppnådd gelpunkt. Provstavar förberedes och utsattes för en efterhärdning vid 120oC under 2 dagars tid, efterföljt av omfattande mekaniskprovning vid 70oC. Provningen bestod av dragprov, relaxationsprov, krypprov samt kompressionsprov. Graden av härdning uppskattades till 67 % och en glasomvanlingstemperatur på cirka 80oC, uppskattningen utfördes med hjälp av DMA-, DSC- samt HFC-provning. Olika materialmodeller evaluerades varav den Generaliserade Maxwell modellen valdes. Modellen ansätter linjära viskoelastiska egenskaper som passade bra med avseende på experimentella resultat. Modellens parametrar kalibrerades med hjälp av en olinjär-minstakvadratmetod. Två typer av lastfall med FEA simuleringarna utfördes sedan med den definierade materialmodellen. Ena lastfallet skulle representera belastning under värst uppskattade förhållanden var den andra skulle modellera belastning under ideala förhållanden, i en olje-/gasbrunn. Simuleringarna visade att vid värsta förhållanden, under 1års belastning av 250 bar differentialtryck, skulle epoxitätningen ha en säkerhetsfaktor mellan 1.8 - 2,3 innan den estimerade brottöjningen är uppnådd.
29
Paik, Kwang Jun. "Simulation of fluid-structure interaction for surface ships with linear/nonlinear deformations." Diss., University of Iowa, 2010. https://ir.uiowa.edu/etd/569.
Full textAbstract:
The present research develops a numerical fluid-structure interaction (FSI) code based on CFDShip-Iowa version 4, a general-purpose URANS/DES overset fluid solver. Linear and nonlinear FSI methods are developed to compute structural responses on surface ships or marine structures. The modal superposition transient analysis and the nonlinear FEM structure solver are used for small and large deformation FSI problems, respectively.
The gluing method is applied to transfer the forces and displacements on non-matching grids for fluid and structure domains. The linear FEM solver is applied to deform the boundary layer grid with large deformation in the fluid domain, while the deformation is ignored in small deformation problems. Deformation of an interior point in the boundary layer grid is obtained using linear interpolation in both linear and nonlinear deformation problems.
The S175 containership is studied in regular waves as an application example for the linear problem. Heave and pitch responses are compared with the experiments, showing good agreement. Time histories of vertical bending moment (VBM) are calculated using rigid model, one-way coupling, and two-way coupling approaches. The elastic models are able to capture the ringing of the VBM induced by slamming, while the rigid model shows a peak at the moment of slamming without further fluctuations. The two-way coupling method shows the effects of hull deformation on the amplitude and phase of VBM as well as the accelerations of heave and pitch.
For the nonlinear deformation problem three sloshing tanks with an elastic bar clamped to its bottom or top are simulated and compared with the experiments and other numerical simulation results. The present simulation results show reasonable agreement with the experiments for bar deformation and free surface elevation. A secondary wave on the free surface is creadted by the vorticity generated from the free surface. The effect of the bar on the sloshing impact is studied comparing dynamic pressure acting on the tank wall without bar, with an elatic bar, and with a rigid bar.
30
Штефан, Т. О., та О. В. Величко. "Вплив способів закріплення стійок для перевезення важких вантажів на міцність конструкції". Thesis, Сумський державний університет, 2014. http://essuir.sumdu.edu.ua/handle/123456789/39286.
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Babadopulos, Lucas Feitosa de Albuquerque Lima. "A Contribution to couple aging to hot mix asphalt (HMA) mechanical characterization under load-induced damage." reponame:Repositório Institucional da UFC, 2014. http://www.repositorio.ufc.br/handle/riufc/11164.
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BABADOPULOS, L. F. A. L. A Contribution to couple aging to hot mix asphalt (HMA) mechanical characterization under load-induced damage. 2014. 139 f. Dissertação (Mestrado em Engenharia de Transportes) – Centro de Tecnologia, Universidade Federal do Ceará, Fortaleza, 2014.<br>Submitted by Marlene Sousa (mmarlene@ufc.br) on 2015-03-17T12:56:14Z
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Previous issue date: 2014-06-26<br>Although aging simulation in binder is performed through RTFO and PAV tests, n
o
considerations of
asphalt
mixture
aging are
made
in regular laboratory characterization.
T
he
present work is focused in
incorporating aging
to
the
modeling of the
mechanical behavior of
hot
mix asphalt (HMA) during
load
-
induced
damage. This is
accomplished
by
combining
existing models
and the adaptation of mixture aging procedures
.
The aging model
used
is
based on the evolution of an internal state v
ariable,
associated to oxygen availability,
aging
temperature a
nd
four
material parameters. The
se parameters are related to aging
susceptibility
, reaction kinetics
and
dependency on aging history and on aging temperature.
The model allows to establish
relation
ship
s
between different aging processes. Results at
four
aging states
(using two different temperatures)
we
re
analyzed
and
the aging model parameters
w
ere estimated.
Capturing aging dependency on temperature constitutes a contribution of the
presen
t work with respect to
previous
results
reported
in the literature
.
T
he aging model
is
coupled to viscoplasticity and damage, comparing
the
behavior observed at
the
different aging
states.
Concerning
the
damage models, t
his thesis
used
mechanical models de
rived from
Schapery's work potential theory
to model fatigue behavior
.
T
he Simplified Viscoelastic
Continuum Damage
(S
-
VECD)
model
was
selected
.
U
nconfined dynamic creep tests were
used to
evaluate the effect of
aging in the mixture resistance to permanent
deformation.
In
addition to
the
state
-
of
-
the
-
art modeling of HMA,
the
characterization
methods
currently in
use in Brazil (tensile strength, resilient modulus and
controlled force indirect tensile
fatigue
tests)
were
also
conducted
.
T
he
possibility to sim
ulate the material behavior
for
various
loading conditions
constitutes a
n advantage
of the state
-
of
-
the
-
art model
over
the state
-
of
-
the
practice method
for fatigue characterization, used primarily
to
rank mixtures.
It was
concluded that, depending on pavem
ent conditions and layer geometry, aging not necessarily
affects
negatively
the
fatigue behavior, while certainly improving
the
permanent deformation
characteristics.
That happens de
s
pite the fact that aging produces less damage tolerant
materials, i.e., m
aterials that fail for less evolved damage states.
T
he framework (
testing
and
analysis) for damage characterization of asphalt mixtures was implemented
and it is expected
to contribute to further developments
in aging modeling of asphalt mixtures<br>Apesar de simulação de envelhecimento ser realizada em ligantes asfálticos através dos ensaios de RTFOT e PAV, nenhuma consideração sobre envelhecimento de misturas é feita na caracterização laboratorial comum. O presente trabalho se concentra na incorporação do envelhecimento na modelagem do comportamento mecânico de concretos asfálticos (CA) para carregamentos que induzem dano. Isto é feito através da combinação de modelos e da adaptação de procedimentos de envelhecimento existentes. O modelo de envelhecimento utilizado se baseia na evolução de uma variável interna de estado e é associado à disponibilidade de oxigênio, à temperatura e a quatro parâmetros materiais. Estes parâmetros são relacionados à susceptibilidade ao envelhecimento, à cinética de reação e à dependência sobre o histórico e sobre a temperatura de envelhecimento. O modelo permite estabelecer relações entre diferentes processos de envelhecimento. Resultados em quatro estados de envelhecimento (em duas temperaturas diferentes) foram analisados, e os parâmetros do modelo estimados. Capturar a dependência do processo quanto à temperatura constitui uma contribuição do trabalho quanto a resultados da literatura. O modelo de envelhecimento é acoplado à resposta viscoplástica e ao dano, comparando-se o comportamento nos diferentes estados. Quanto aos modelos de dano, esta dissertação trata dos derivados da teoria do potencial de trabalho de Schapery para análise da fadiga. O modelo simplificado de dano contínuo em meio viscoelástico (S-VECD) foi selecionado. Ensaios de Creep Dinâmico não confinado foram utilizados para avaliar o efeito do envelhecimento na resistência à deformação permanente. Além da modelagem mecânica do comportamento do CA usando modelos do Estado da Arte, também foram executados métodos de caracterização em uso no Brasil (resistência à tração, módulo de resiliência e ensaios de fadiga por compressão diametral). A possibilidade de se simular a resposta do material em várias condições de carga constitui uma vantagem do método do Estado da Arte sobre o do Estado da Prática, usado principalmente para comparar misturas. Concluiu-se que, dependendo das condições do pavimento e da geometria das camadas, o envelhecimento não necessariamente diminui a resistência à fadiga, embora certamente melhore a resistência à deformação permanente. Isso acontece apesar de o envelhecimento produzir materiais menos tolerantes ao dano, i.e., materiais que rompem para estados de dano menos evoluídos. O procedimento para a caracterização do dano em misturas asfálticas foi implementado e espera-se ter contribuído para um maior desenvolvimento da modelagem de misturas quanto ao envelhecimento.
32
Woldemikael, Biruk Worku. "Effects of cracking of coupling beams onhigh rise towers subjected to wind load." Thesis, KTH, Betongbyggnad, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-290589.
Full textAbstract:
In high rise towers, reinforced concrete elevator shafts with coupling beams are extensively used as a principal structural element to resist lateral loads. The lateral load resistance of the tower is dominantly dependent on the stiffness of the load-bearing walls, and coupling beams connecting them. In an interest to study the reduction in the stiffness of high rise tower due to cracking in the coupling beams, variability in the reinforcement content, concrete grade and the effect of joint flexibility at the beam-wall intersection, this master thesis presents the analytical and finite element approaches to determine the equivalent height of the concrete coupling beams and the overall global stability of the high-rise tower. A comprehensive parametric study on 240 combinations of reinforced concrete coupling beams and 48 models of the global tower has been carried out to backtrack the effective stiffness of the RC coupling beams from the load-deflection curve. As a result, the stiffness and the equivalent height of coupling beams are computed and plotted as a function of the concretegrade, reinforcement content and aspect ratio. Additionally, the tip deflections of the towers for both the cracked & reinforced and un-reinforced & un-cracked models are also plotted as functions of the concrete grade, reinforcement content and aspect ratio.The obtained results show that the stiffness ratio and the ratio of the equivalent height to the normal height increase with the increase in the longitudinal reinforcement ratio and aspectratio but decrease with an increase in the concrete grade for both analytical and finite element methods. The tip deflection of tower is not significantly affected by an increase in the reinforcement content of slender coupling beams and vice versa for both the analytical and the finite element method. Independently of the slenderness of the composing coupling beams, the stiffness increases significantly with an increase in the concrete grade. These results show a good picture on how to choose the equivalent height in the model with no reinforcement. So, the developed diagram will be a more practical method for the designer of awhole building at the early stage design. Thick coupling beams need to be reinforced to reach the gross section’s stiffness while slender sections will have a higher stiffness with reinforcement. This would help the designer to find a more rational model without reinforcement. Using Hans Petersson’s analytical method, regarding the joint flexibility at the beam wall intersection, to exploit the full capacity of a concrete coupling beam section, the stiffness should be reduced. For global models, independently of the slenderness of the composing coupling beams, the stiffness increases significantly with an increase in the concrete grade.<br>I höghus används hisschakt av armerad betong tillsammans med kopplingsbalkar i stor utsträckning som främsta konstruktionselement för att motstå horisontella laster. Tornets horisontella bärförmåga är beroende av analytiska studier och studier med finita element metoden styvheten hos de bärande väggarna, och kopplingsbalkarna som förbinder dem. För att studera minskningen av styvheten i höghustorn på grund av sprickbildning i kopplingsbalkar, variationen i armeringsmängden, betongkvaliteten och effekten av ledflexibilitet vid balk-vägg-knutpunkten, presenterar detta examensarbete kopplingsbalkarnas effektiva styvhet och höghusets globala stabilitet. En omfattande parametrisk studie på 240 olika kombinationer av armerade kopplingsbalkar och 32 modeller av ett höghus har genomförts för att härleda den effektiva styvheten i de armerade kopplingsbalkarna från last-deformationskurvan. Som ett resultat beräknas styvheten och den ekvivalenta höjden av kopplingsbalkarna och plottas som funktion av betongkvaliteten och armeringsmängden. Dessutom modelleras höghuset för både spruckna & armerade kopplingsbalkar samt oarmerade & ospruckna kopplingsbalkar för att erhålla utböjningen av höghusets topp. Resultatet plottas som funktion av betongkvaliteten och armeringsmängden. De erhållna resultaten visar att styvhetsförhållandet och förhållandet mellan ekvivalent höjd till normal höjd ökar med mer längsgående armering och tvärsnittsförhållandet men minskar med en ökning av betongkvaliteten för både den analytiska och finita elementmetoden. Utböjningen av höghusets topp påverkas inte nämnbart av en ökning av armeringsmängden i de slanka kopplingsbalkarna och vice versa för både den analytiska och finita elementmetoden. Oberoende av slankheten av kopplingsbalkarna ökar styvheten betydligt med en ökning av betongkvaliteten. Dessa resultat visar en bra bild på hur man väljer ekvivalent höjd i modellen utan armering. Därmed kommer det framtagna diagrammet vara en mer praktisk metod för att i ett tidigt skede konstruera en hel byggnad. Tjocka kopplingsbalkar måste armeras för att nå tvärsnittets styvhet medan smala tvärsnitt kommer att ha en högre styvhet med armering. Detta skulle hjälpa konstruktören att hitta en mer rationell modell utan armering. Med hjälp av Hans Peterssons analytiska metod, angående ledflexibiliteten vid balk-väggknutpunkten, bör styvheten minskas för att utnyttja den fulla kapaciteten hos en betongkopplingsbalk. För globala modeller, oberoende av de slanka kopplingsbalkarna, ökar styvheten betydligt med en ökning av betongkvaliteten.
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Sartori, Julian [Verfasser], Martin S. [Gutachter] Fischer, Hartmut [Gutachter] Witte, and Tobias [Gutachter] Siebert. "The fibrous structure of the Achilles tendon enthesis in mice and its deformation under load / Julian Sartori ; Gutachter: Martin S. Fischer, Hartmut Witte, Tobias Siebert." Jena : Friedrich-Schiller-Universität Jena, 2020. http://d-nb.info/1227444443/34.
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Casalena, Lee. "Multimodal Nanoscale Characterization of Transformation and Deformation Mechanisms in Several Nickel Titanium Based Shape Memory Alloys." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1499568013015563.
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Pezeshky, Payam. "Distortional Static and Buckling Analysis of Wide Flange Steel Beams." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36074.
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Existing design provisions in design standards and conventional analysis methods for structural steel members are based on the simplifying kinematic Vlasov assumption that neglects cross-sectional distortional effects. While the non-distortional assumption can lead to reasonable predictions of beam static response and buckling strength in common situations, past work has shown the inadequacy of such assumption in a number of situations where it may lead to over-predicting the strength of the members. The present study thus develops a series of generalized theories/solutions for the static analysis and buckling analysis of steel members with wide flange cross-sections that capture distortional effects of the web. Rather than adopting the classical Vlasov assumption that postulates the cross-section to move and rotate in its own plane as a rigid disk, the present theories assume the web to be flexible in the plane of the cross-section and thus able to bend laterally, while both flanges to move as rigid plates within the plane of the cross-section to be treated as Euler-Bernouilli beams. The theories capture shear deformation effects in the web, as well as local and global warping effects.
Based on the principle of minimum potential energy, a distortional theory is developed for the static analysis of wide flange steel beams with mono-symmetric cross-sections. The theory leads to two systems of differential equations of equilibrium. The first system consists of three coupled equilibrium differential equations that characterize the longitudinal-transverse response of the beam and the second system involves four coupled equilibrium differential equations of equilibrium and characterizes the lateral-torsional response of the beam. Closed form solutions are developed for both systems for general loading. Based on the kinematics of the new theory, two distortional finite elements are then developed. In the first element, linear and cubic Hermitian polynomials are employed to interpolate displacement fields while in the second element, the closed-form solutions developed are adopted to formulate special shape functions. For longitudinal-transverse response the elements consist of two nodes with four degree of freedom per node for longitudinal-transverse response and for lateral-torsional response, the elements consist of two nodes with eight degrees of freedom per node. The solution is able to predict the distortional deformation and stresses in a manner similar to shell solutions while keeping the modeling and computational effort to a minimum.
Applications of the new beam theory include (1) providing new insights on the response of steel beams under torsion whereby the top and bottom flanges may exhibit different angles of twist, (2) capturing the response of steel beams with a single restrained flange as may be the case when a concrete slab provides lateral and/or torsional restraint to the top flange of a steel beam, and (3) modelling the beneficial effect of transverse stiffeners in reducing distortional effects in the web.
The second part of the study develops a unified lateral torsional buckling finite element formulation for the analysis of beams with wide flange doubly symmetric cross-sections. The solution captures several non-conventional features. These include the softening effect due to web distortion, the stiffening effect induced by pre-buckling deformations, the pre-buckling nonlinear interaction between strong axis moments and axial forces, the contribution of pre-buckling shear deformation effects within the plane of the web, the destabilizing effects due to transverse loads being offset from the shear centre, and the presence of transverse stiffeners on web distortion. Within the framework of the present theory, it is possible to evoke or suppress any combination of the features and thus isolate the individual contribution of each effect or quantify the combined contributions of multiple effects on the member lateral torsional capacity. The new solution is then applied to investigate the influence of the ratios of beam span-to-depth, flange width-to-thickness, web height-to-thickness, and flange width-to-web height on the lateral torsional buckling strength of simply supported beams and cantilevers. Comparisons with conventional lateral torsional buckling solutions that omit distortional and pre-buckling effects quantify the influence of distortional and/or pre-buckling deformation effects. The theory is also used to investigate the influence of P-delta effects of beam-columns subjected to transverse and axial forces on their lateral torsional buckling resistance. The theory is used to investigate the load height effect relative to the shear centre. Comparisons are made with load height effects as predicted by non-distortional buckling theories. The solution is adopted to quantify the beneficial effect of transverse stiffeners in controlling/suppressing web distortion in beams and increasing their buckling resistance.
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Seyis, Onder. "Development Of An Algorithm For Material Selection." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606020/index.pdf.
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Material selection is one of the major points that should be taken into account seriously in the engineering design stage. Each material has various properties such as mechanical, thermal, electrical, physical, environmental, optical and biological properties. However, it is a well known fact that only a limited number of design engineers have a thorough knowledge on all these properties of a specific material, which is planned to be used in the manufacturing of the product. Therefore, the design engineer should be guided in selecting the most suitable material. In the scope of this thesis, the aim was to develop an algorithm and a software package for material selection to help the design engineer in his decision making process. In the program, since steel is a widely used material in industry, it was selected as a material class among whole engineering materials, and a database covering all the necessary properties of various steels was constructed. These properties include chemical, mechanical, thermal, electrical and physical properties for steels. The database developed by using Microsoft Access also contains steels of 29 different steel standards and can be updated if the user wants. The software package was developed for Windows environment by using Microsoft Visual Basic 6.0. In the program, steels can be searched for the list of suitable steels by entering application areas and properties such as chemical component, yield strength, heat capacity and electrical resistance. In addition to this, lists of steels can be created by selecting the appropriate name of the steel standards. Force and load calculations for various deformation processes such as forging, rolling, extrusion and drawing can also be carried out in the relevant modules within the program.
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Samarakkody, Dilrukshie. "Differential axial shortening in high rise buildings with concrete filled tube columns." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/96417/1/Dilrukshie%20Induprabha_Samarakkody%20Arachchilage_Thesis.pdf.
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This research developed and applied a comprehensive technique to evaluate the Differential Axial Shortenings (DASs) in composite high rise buildings. The findings of this research will help to reduce the adverse effects of DASs and facilitate safer designs of buildings. A method, based on the vibration characteristics of the building, to update the initial predictions during the service stage of the building has also been developed and applied.
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Teklemariam, Daniel Mekonnen, and Bennie Hamunzala. "Design of Thick Concrete Beams : Using Non-Linear FEM." Thesis, KTH, Bro- och stålbyggnad, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-189141.
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The experimental studies performed on the behaviour of very thick concrete beams subjected to static loads have revealed that the shear mechanisms play an important role in the overall response and failure behaviour. The aim of this thesis is to recommend suitable design methods for thick concrete beams subjected to off-centre static concentrated load according Eurocode 2 by using non-linear finite element analysis (NLFEA). To achieve this task, Abaqus/Explicit has been used by employing constitutive material models to capture the material non-linearity and stiffness degradation of concrete. Concrete damaged plasticity model and perfect plasticity model has been used for concrete and steel respectively. Three dilation angles (30º, 38º and 45º) and fracture energy from FIB 1990 (76 N/m) and FIB 2010 (142 N/m) has been used to investigate their influence on the finite element model. The dilation angle of 38º and FIB 2010 fracture energy was adopted as the suitable choice that reasonably matched with the experimental results. In verifying and calibrating the finite element model, the experimental results of the thick reinforced concrete beam conducted by the American Concrete Institute have been used. Three design approaches in the ultimate and serviceability limit state according to Eurocode 2 recommendations have been used namely; the beam method, strut and tie method and shell element method. Using the reinforcement detailing of the hand calculations of beam method and strut and tie method and linear finite element analysis of shell element method, non-linear finite element models have been pre-processed and analysed in Abaqus/Explicit. During the post-processing, the results have been interpreted and compared between the three design methods. The results under consideration are hand-calculated load at 0.3 mm crack width, FE-load at 0.3 mm crack width, amount of reinforcement and FE-failure load. The comparison of the results between the three design approaches (beam method, strut and tie method and shell element method) indicates that strut and tie method is better design approach, because it is relatively economic with regards to the quantity of reinforcement bars, has the higher load capacity and has a higher load at crack width of 0.3 mm crack width.<br>De experimentella studier som utförts på tjocka betongbalkar som utsätts för statisk last har visat att skjuvning spelar en viktig roll i brottmekanismen. Syftet med detta examensarbete är att rekommendera lämpliga dimensioneringsmetoder för tjock betongbalkar utsatt for statisk koncentrerad last enligt Eurokod 2 med hjälp av ickelinjära finita element metod. Abaqus/Explicit användes genom att utnyttja konstitutiva materialmodeller för att fånga materialens icke-linjäritet och minskad styvhet. Tre dilatationsvinklar (30°, 38° och 45°) och två brottenergi från FIB 1990 (76 N/m) och FIB 2010 (142 N/m) tillämpas för att kontrollera deras inverkan på FE-modellerna. Dilatationsvinkel med 38° och FIB 2010 med högre brottenergi valdes i de icke-linjära finita elementanalyserna. Kontroll av FE-modellerna är baserad på ”American Concret Institutes” experimentella resultat på de tjocka betongbalkarna. Handberäkningar av tjocka betongbalkar har utförts i brott- och bruksgränstillstånd med tre dimensioneringsmetoder i Eurokod 2 nämligen balk metoden, fackverksmetoden och linjära-FE skalelementmetoden. Jämförelse har gjorts för de olika dimensioneringsmetoderna, genom att använda de armeringsdetaljer av handberäkningar i de verifierade och kalibrerade icke linjära FE-modellerna i Abaqus/Explicit. Resultaten i fråga är last för 0.3 mm handberäknad sprikvidd, FE-last för 0.3 mm sprikvidd, armeringsmängd och FE-brottlast. Jämförelse av resultaten mellan de tre dimensioneringsmetoder (balkmetod, fackverksmetod och skalelementmetod) visar att fackverksmetod är bättre design metod, eftersom det är relativt ekonomiskt med avseende på armeringsmängd, har högre lastkapacitet och last på 0.3 mm sprickvidd.
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Menegotto, Mauro Leandro. "Previsão da curva tensão-recalque de ensaios de placa em solo não saturado." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/18/18132/tde-23062008-143454/.
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Apresenta-se um método para a previsão da curva tensão-recalque a ser obtida em provas de carga em placa circular, instalada a diferentes profundidades e com vários diâmetros, para diversos níveis de sucção em solo não saturado. Também é proposto um procedimento para correção dos recalques medidos em ensaio com carregamento do tipo rápido, para a obtenção dos correspondentes recalques estabilizados de um ensaio lento. A previsão realizada apresenta resultados bastante próximos dos obtidos em provas de carga, verificando-se assim a aplicabilidade do método proposto para reproduzir o comportamento do sistema solo-placa neste tipo de solo. Além disso, este trabalho apresenta um estudo do módulo de deformabilidade a partir de ensaios de campo e de laboratório, para o solo do campo experimental de fundações da EESC/USP, aplicando conceitos da mecânica dos solos não saturados. Em campo, o módulo de deformabilidade foi obtido por meio de provas de carga em placa circular com e sem inundação prévia do solo. Em laboratório, o módulo foi obtido a partir de ensaios de compressão confinada e triaxiais, ambos com sucção controlada. Observou-se que a sucção matricial tem grande influência no módulo de deformabilidade do solo.<br>This thesis presents a method for prediction the stress-settlement curve to be obtained in circular plate load tests, at different depths and with several diameters, to differents suction levels on unsaturated soil. A procedure is also proposed for correction the settlement measured with a quick maintained load (QML) tests to obtain the stabilized settlement in a slow maintained load (SML) tests. This prediction presents quite results of the real measured stress-settlement curve through load tests, thus verifying the applicability of the proposed method to reproduce the behavior the soil-plate system in this soil. Besides, this work presents a study of the deformation modulus using field and laboratory tests, to the soil of the foundations experimental field of EESC/USP, applying concepts of the unsaturated soil mechanics. In field, the deformation modulus was obtained by means of circular plate load tests with and without previous soaking of the soil. In laboratory, the modulus was obtained using confined compression and triaxial tests, both with controlled suction. It was observed that the matric suction has great influence in the soil deformation modulus.
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Rivera, Rojas Alfonso Jose. "Lateral response of stiff column-supported shallow foundations." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/100795.
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The mechanisms that control the lateral response of stiff column-supported shallow foundations, resulting from the application of horizontal load on shallow foundations supported by stiff columns, are uncertain. Stiff columns constructed in soft clayey soil have been used to support retaining walls and in such cases, the lateral thrust applied behind these geotechnical structures is a source of horizontal loading. For seismic events, stiff columns constructed in soft clayey soil have been used to support shallow foundations subjected to horizontal load coming from the upper structure of buildings. Due to its practical applications, it has become important to understand the consequences of subjecting a shallow foundation supported by stiff columns to horizontal load by identifying the factors that control the lateral response of such systems.
A series of centrifuge tests were carried out to examine the lateral response of stiff column-supported shallow foundations. The experimental trends suggested that the thickness of the coarse-granular mattress placed above the soil-column composite, called the Load Transfer Platform (LTP), controlled the lateral capacity and the overall lateral response of these systems. A numerical study using the finite element method confirmed the experimental trends. A parametric analysis was conducted with the purpose of investigating the influence of different geometry-based and material-based variables in the lateral response of these systems. The results of the parametric analysis further confirmed the importance of the thickness of the LTP in controlling the lateral response. The parametric results also emphasized the contribution of other variables to this lateral response, and these variables included the undrained shear strength of the soft clayey soil around the stiff columns, the stiff column diameter, and the spacing of the stiff columns after they are constructed in the soft clayey soil.<br>Doctor of Philosophy
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Jing, Peng. "Etude de l'effet des fines et de la teneur en eau sur le comportement hydromécanique des matériaux granulaires." Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAD008/document.
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Les matériaux granulaires sont souvent utilisés dans les chaussées à faible trafic, pour la réalisation des couches d'assise non liées. L'objectif de la thèse est une meilleure compréhension du comportement hydromécanique des matériaux granulaires insaturés sous charge répétée en tenant compte des différents effets couplés: teneur en eau et teneur en fines. Une série d'essais triaxiaux à chargements répétés (TCR) est réalisée avec les différents échantillons de sable de Missillac remodelés à différentes teneurs en eau et en fines pour caractériser les comportements de déformation permanent et résilient. En outre, les courbes de rétention sont obtenues par des essais de succion. Puis, sur la base des résultats expérimentaux, les modèles de déformations permanentes et réversibles existants sont améliorés pour prendre en compte les teneurs en fines et en eau variables. Finalement, le comportement de l'état limite du sable Missillac est estimé avec les effets des teneurs en fines et en eau<br>Granular materials are often used in low traffic pavement structures as unbound granular base and sub-base layers. The objective of this context is a better understanding of hydromechanical behaviour (deformation behaviour mainly) of the unsaturated granular materials under repeated loading taking into account the various coupled effects: water content and fine content. A series of RLTTs are conducted with the different remolded Missillac sand samples at different water contents and fine contents to characterize the permanent and resilient deformation behaviour. Besides, the soil water retention curves (SWRCs) are obtained by suction measurement. Then, based on the experimental results, the existing permanent and resilient deformation models are improved to accommodate to the changeable fine content and water content. In the end, the shakedown behaviour of Missillac sand is estimated with the effects of fine content and water content
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Alachaher, Abderrahim. "Abd : une nouvelle loi de comportement incrémentalement non linéaire et applications par la méthode des éléments finis." Université Joseph Fourier (Grenoble), 1994. http://www.theses.fr/1994GRE10136.
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Ce memoire presente une etude locale et numerique du comportement mecanique des geomateriaux. La premiere partie de ce memoire presente une synthese de quelques modeles utilises dans le cadre de la description du comportement des sols. Quelques aspects lies aux schemas d'integration et au temps de calcul ont ete degages. Ensuite, nous presentons une nouvelle loi de comportement incrementalement non-lineaire de type interpolation denommee abd, caracterisee par le sens de son ecriture qui permet d'exprimer directement la reponse incrementale si la sollicitation incrementale est completement definie en termes de deformations incrementales. Nous avons valide ce nouveau modele au niveau global et incremental de la sollicitation. Nous avons montre les performances du modele en le comparant au modele incremental de darve et aux essais experimentaux. Quelques problemes inherents a la stabilite des chemins de reponse sont discutes a la fin de cette partie. La seconde partie vise a integrer le nouveau modele dans un code de calcul par elements finis sic. Un algorithme de controle et d'adaptation de l'etape de chargement en temps reel est presente. Enfin, nous presentons diverses modelisations numeriques d'essais pressiometriques. Une analyse detaillee des chemins locaux est abordee, et nous comparons aussi nos resultats avec ceux obtenus avec le code gefdyn et avec les essais experimentaux
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Parry, A. R. "The deformation of hard materials under point loads." Thesis, University of Exeter, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259813.
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Suits, Chris Allen. "DEFORMATION OF BEARING PADS WHILE UNDER SERVICE LOADS." OpenSIUC, 2013. https://opensiuc.lib.siu.edu/theses/1167.
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Bearing pads undergo deformation while under service loads of any bridge. The pad translates the load to the support structure, and allows for movement of the superstructure. The deformation of bearing pads is an important element to consider when designing both the super and sub structures of the bridge. The Federal Highway Administration provides a guide for the design of steel brigdes, and Step 6 of this guide covers the design of bearing pads. The purpose of this study is to analyze the deformation of bearing pads using a finite element analysis software. This study will analyze two separate models, one ignoring the steel plates in a bearing pad and ignoring friction, while the other will take into account the steel plates as well as friction during the analysis. Once the linear analysis is run the models that are built can be compared with the FHWA design examples to compare and verify the results. This will facilitate the possible improvement of current design examples and allow for a more realistic result for designers to use. This study also looks at the internal testing results provided by a bearing pad manufacturing company. These internal results will provide a real world model for the linear analysis models to be compared to as well. Once all factors are taken into account, the validity of the current standards can be evaluated.
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Widarda, Dina Rubiana. "Longitudinal forces in continuously welded rails due to nonlinear track-bridge interaction for loading sequences." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1238081328011-05497.
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The use of continuously welded rails (CWR) governs the longitudinal stress caused by seasonal temperature changes, bending of supporting structure and braking/accelerating due to passing trains. Those three loads have been regulated in Eurocode1 and accomplished by the national codes like DIN Fb-101 in Germany. An additional loading case identified and treated in this thesis is the load due to a change of the coupling stiffness in longitudinal direction between the track and bridge. This additional load occurs as a consequence of the employment of a nonlinear stiffness law which increases the restoring force by a factor of 3 when the situation of the track changes from ‘unloaded’ to ‘loaded’ due to a passing train. This particular phenomenon has not been mentioned in the codes so far though it is a natural consequence of fundamental conditions in those codes. For CWR the longitudinal coupling between the rail and bridge plays an important role. This coupling interface is created either by a ballast, for a ballasted track, or by a fastening system in the case of slab track. The deformation state of the coupling interface characterizes the behaviour of the system, whether elastic or plastic. Therefore, the nonlinear behaviour is valid for the system. To accommodate the nonlinear nature, a sequential loading analysis is used, taking into account the loading history. As the change situation due to a passing train happens in a short time, the influence of the mass acceleration should be taken into account in the system’s equilibrium. This aspect is investigated by treating the dynamic load as an impulse-like load. However, a realistic load needs some time to affect the whole bridge, thus the continuous change of stiffness is used to simulate the dynamic analysis. There is a lack of information on determining the value of coupling stiffness in longitudinal direction caused by a passing train. Therefore, it is important to evaluate the coupling stiffness from field measurements in order to find reliable values. The implementation of the load onto several typical bridges shows that the change of the coupling stiffness increases the stresses and it should not be neglected. The evaluation of the load due to a change of the coupling stiffness accompanied by bending of the supporting structure gives satisfactory results by using the static analysis only. Thus, a dynamic analysis can be avoided. Multiple cycles of passing trains occurring after seasonal temperature change indicate a significant increase of elastic parts along the track-bridge coupling interface and a decrease in stresses in the rails. Thus the danger of deterioration is reduced significantly<br>Die Verwendung von durchgehend geschweißten Schienen auf Brücken führt zu zusätzlichen Längsspannungen infolge der Lastfälle jahreszeitliche Temperaturänderung, Brückendurchbiegung und Bremsen/Anfahren. Diese drei Lasten sind durch den Eurocode 1 vorgegeben und in die nationale deutsche Norm DIN Fb-101 integriert. In dieser Arbeit wird erstmals ein weiterer Lastfall identifiziert und behandelt, der durch den Wechsel der Koppelsteifigkeit in Längsrichtung zwischen Gleis und Tragwerk bei der Zugüberfahrt begründet wird. Dieser Lastfall wird hier mit „Ruck“ bezeichnet und ist eine zwangsläufige Konsequenz des nichtlinearen Längsverschiebewiderstandes, wie er im EC 1 und im DIN Fb-101 vorgegeben ist. Dennoch wurden die Auswirkungen auf das Systemverhalten bisher nicht untersucht. Bei einem Wechsel vom unbelasteten Gleis zum belasteten Gleis während einer Zugüberfahrt erhöht sich zum Beispiel der Längsverschiebewiderstand für ein Schottergleis um den Faktor 3! Die dadurch bedingte Veränderung des Zusammenwirkens zwischen Gleis und Tragwerk führt zu einer Veränderung des Systemzustandes und damit zu veränderten Schienenspannungen. Für durchgehend geschweißte Schienen spielt die Längskopplung zwischen Schiene und Brücke eine wesentliche Rolle. Beim Schottergleis wird sie dargestellt durch die Einbettung des Gleisrostes im Schotterbett im Zusammenwirken mit der Schienenbefestigung. Bei der festen Fahrbahn durch das Befestigungssystem. Für kleine Deformationen ist die Koppelsteifigkeit proportional zur Relativverschiebung zwischen Gleis und Brücke. Darüberhinaus geht das linear elastische Verhalten in ein quasi plastisches Verhalten mit konstanter Koppelkraft über. Folgerichtig ist die Behandlung einer Lastenfolge nur in inkrementeller Weise unter Einbeziehung der Verformungsgeschichte mechanisch korrekt. Die Lastfälle Bremsen/Anfahren, Brückendurchbiegung und Ruck ereignen sich nur während der Zugüberfahrt; also in relativ kurzer Zeit, dann allerdings mit einem erheblichen Lastgradienten. Somit stellt sich die Frage nach dem Einfluss der Massenbeschleunigungen, die in dieser Arbeit geklärt wird. Die im Fachbericht genanntenWerte für den Längsverschiebewiderstand des belasteten Gleises basieren auf einer relativ geringen Datenmenge. Aus diesem Grund werden die Messdaten einer umfangreichen Feldmessung mit Zugüberfahrten zu Aussagen über den Längsverschiebewiederstand herangezogen und die Problematik derartiger Messungen beleuchtet. Die unterschiedlichen Modellierungen des Lastfalls „Ruck“, einmal rein statisch und zum anderen dynamisch, ergeben übereinstimmende Schienenlängsspannungen für die statische und die kontinuierliche dynamische Variante. Somit kann auf die aufwändige dynamische Analyse verzichtet werden. Mehrere Zyklen von Zugüberfahrten im Anschluss an eine jahreszeitliche Temperaturänderung bewirken einen signifikanten Abbau der Durchrutschbereiche, also eine Erhöhung der elastischen Abschnitte in der Koppelfuge zwischen Bauwerk und Gleis verbunden mit einer Abnahme der Schienendruckspannungen. Somit hilft dieser Effekt dem System, der jahreszeitlichen Temperaturänderung zu widerstehen
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Beaude, Nicolas. "Etude théorique et expérimentale du comportement élasto-plastique et de la localisation de la déformation dans les monocristaux." Paris 13, 1988. http://www.theses.fr/1988PA132005.
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Etude experimentale sur des monocristaux en superalliage à base de nickel soumis à des essais à chaud d'écrouissage cyclique à basse fréquence. Observation d'un phénomene d'instabilité plastique accompagné de la formation de lignes de glissement cristallographiques sur le fut de l'éprouvette. Modélisation du comportement élasto-plastique par une généralisation de la loi de schmid. L'extension de la loi de normalite permet de déterminer la direction de l'écoulement plastique et les systèmes actifs du glissement octaédrique. C'est la bifurcation locale de cette loi de comportement qui rend compte de l'instabilite observée
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Bendaas, Mohamed. "Analyse et conception des structures textiles tendues." Grenoble INPG, 1994. http://www.theses.fr/1994INPG0121.
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Les structures textiles tendues sont generalement considerees comme instables. Leur instabilite depend de l'etat de contraintes dans la structure avant application des charges externes. De ce fait, un interet particulier est accorde a l'etude de l'equilibre de ces structures avant et apres application des chargements climatiques. Ce travail est divise en deux parties: ? dans la premiere partie, differents aspects de l'equivalence entre la membrane et un reseau de cables sont abordes. Une extension de la methode des densites de force est etablie pour tenir compte de la membrane orthotrope. La methode des densites de force adoptee pour la definition de formes spatiales conduit a l'obtention de structures en equilibre sans calcul des deformations elastiques. Les formes mises a plat sont rectifiees selon les caracteristiques mecaniques du materiau. Une nouvelle methode est proposee pour determiner les decoupes initiales (rectifiees). Le modele developpe est lineaire et se limite au traitement des structures dites a contraintes isotropes. ? la deuxieme partie est consacree a l'etude du comportement non lineaire des toiles tendues soumises a des sollicitations quelconques. Etant donne la faible rigidite en flexion des toiles techniques, la structure spatiale de forme gauche est representee par un modele membranaire. Les calculs elements finis sont effectues dans le domaine des zones en compression. Une nouvelle technique est proposee afin d'ameliorer la vitesse de convergence du processus iteratif pour les structures initialement non-precontraintes (hypostatiques)
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Yun, Xiaoyou 1965. "Geomechanical behaviour of biaxially loaded rock." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=115913.
Full textAbstract:
The stress state at the boundary of any underground mine opening is that of plane stress. This planar state of stress can be simulated in laboratory by subjecting a cubic rock specimen to a biaxial loading condition. Thus, research on the behaviour of biaxially loaded rock is important for better understanding of the stability of mining fronts such as crown pillar skin, drift face or shaft floor.<br>The objective of this research is to study the geomechanical behaviour of biaxially loaded rock. Three rock types were selected, namely limestone, granite and sandstone.<br>The laboratory work was conducted using a newly developed, 500-tonne biaxial loading frame, that is equipped with a servo-controlled load and displacement system. Recently patented in China, the new biaxial loading frame is spatially symmetric and equally rigid in both directions. Steel brush platens and solid platens with and without MoS2 were developed to help examine the end friction effect on biaxial strength. It is found that the biaxial strength can decrease up to 26.7% with the increase of cubic specimen size from 75 mm to 150 mm. The biaxial strength increases by 29.3% with the increase of loading rate from 1 MPa/s to 10 MPa/s, for granite. The biaxial strength of granite specimen decreases by nearly 6% when either solid platens with MoS 2 lubricant or brush platens are used. A comparison of the sigma 1-sigma2 failure envelopes reveals that the shape of the envelope and the location of the peak biaxial strength are dependent on the rock type.<br>Varying intensities of rock spalling generally initiate at the free faces of the specimen when sigma1 and sigma2 exceed sigma c/2. Ultimate failure occurs in the form of an out-of-plane shear failure, which splits the rock specimen into two or more wedges.<br>It is shown that both Mohr-Coulomb and Hoek-Brown criteria underestimate the biaxial strength of the rock. The Drucker-Prager failure criterion appears to provide poor correlation with experimental results. A new empirical biaxial rock failure criterion for intact rock is derived and another, accounting for rock mass characteristics through the Geological Strength Index (GSI), is then proposed.
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ZHOU, XIAO-WEI. "Contribution au comportement dynamique des materiaux metalliques : etude experimentale de l'alliage al-li en torsion et en compression, simulation numerique du processus de penetration a grande vitesse." Nantes, 1988. http://www.theses.fr/1988NANT2014.
Full textAbstract:
Etude experimentale sur les alliages al-li soumis a des essais de traction et de compression pour des vitesses de deformation comprises entre 10**(-4) et 310**(3) s**(-1) et de 10**(-3) a 210**(3) s**(-1) respectivement. Auparavant ces alliages ont ete traites thermiquement. Analyse de la sensibilite a la vitesse de deformation. Influence du mecanisme d'activation thermique sur le processus de deformation. Determination du mode de rupture. Analyse des facies de rupture pour les echantillons deformes en traction et de la formation des cellules de dislocation dans ceux deformes en compression. Simulation numerique du processus de penetration a grande vitesse d'une cible mince par un projectile circulaire en utilisant un modele de fluide elasto-plastique. Comparaison avec des resultats experimentaux
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Navrátil, Petr. "Objekt pro sportovní účely." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-226045.
Full textAbstract:
The theme of this diploma thesis is design and check load-carrying steel structure of building for sport purposes in two variants. Building is situated in Holešov town. Primary emphasis is placed on purpose of this building and on her integration to the given locality. The steel structure is created by two objels, main (hall) and side part (admin. part). Both of this building have common east wall. Plan dimension of hall part is 40 on 40m and the highest point of this part is 15,9m height above ground. Admin. part is greated like frame with columns in 8x8m grid and 8m height. Overall height of this part is 8m. For analisys of internal forces was constructed spatial bar model which was used for an optimization of partial bars for both limit states. The cladding will be made by system of Kingspan panels.