Dissertations / Theses on the topic 'Anchors'
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1
Hu, Shenghua, and 胡盛华. "FRP-strengthened RC slabs anchored with FRP anchors." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47849800.
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Existing reinforced concrete (RC) structure can be strengthened upon the addition
of externally bonded high-strength light-weight fibre-reinforced polymer (FRP)
composites. An abundance of research over the last two decades has established
the effectiveness of the externally bonded FRP via extensive experimental testing.
Perhaps the most commonly occurring failure mode though is premature
debonding of the FRP and debonding generally occurs at strains well below the
strain capacity of the FRP. Debonding failures are undesirable as they are
typically brittle and represent an under-utilisation of the FRP material. A
straightforward means to prevent or at least delay debonding is by the addition of
mechanical anchors, however, research to date on anchors is extremely limited. Of
the various anchor concepts examined to date by researchers, this dissertation will
focus on anchors made from FRP which are herein referred to as FRP anchors.
The details and results of a program of research on the performance of FRP
anchors in FRP-strengthened structures are presented in this dissertation. An
extensive review of exiting literature helps establish knowledge gaps which serve
to justify the need and the scope of the research reported herein. A novel bow-tie
FRP anchor concept is then proposed and tested in smaller-scale single-shear
FRP-to-concrete joint assemblages as well as larger-scale simply-supported FRP-strengthened
RC slabs. The anchors are shown to increase the strength and slip
capacity of the joints by up to 41 % and almost 600 %, respectively, in
comparison with unanchored control joints. The anchors are then shown to
increase the load and deflection capacity of slabs by 30 % and 110 %, respectively,
above an unanchored control slab. In addition to strength, it is the ability of FRP
anchors to introduce deformability into FRP-strengthened RC slabs which is
particularly beneficial in order to produce safer structures.
An analytical model is then developed which is based on a novel quad-linear
moment-curvature response which can capture the complete load-deflection
response of the FRP-strengthened slabs anchored with FRP anchors. The
analytical modeling approach enables closed-form equations to be derived which
can then be used by design engineers to relatively easily construct load-deflections
responses and accurately predict member responses. Following the
concluding comments for the project as a whole, future research topics of
relevance are identified.published_or_final_version
Civil Engineering
Master
Master of Philosophy
2
Steele, Catherine A. "Measuring career anchors and investigating the role of career anchor congruence." Thesis, Coventry University, 2009. http://curve.coventry.ac.uk/open/items/4d808ce0-304f-08e3-36e3-c12a4460c409/1.
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This thesis empirically examines the career orientations inventory (COI) as a measure of career anchors and then, using this measure, it goes on to investigate the relationship between career anchor congruence and work related outcomes, specifically job satisfaction and organisational commitment. The psychometric properties of the 40 item COI (presented by Igbaria and Baroudi, 1993) were explored by the administration of the measure to a sample of 658 individuals from 27 organisations in the UK. Through factor analysis an eight factor structure was demonstrated in line with that proposed by Schein (1993). The factor structure was replicated with a second sample. The COI demonstrated good levels of internal consistency (.59-.83) and test retest reliability (.68-.90). Similarly it was deemed to have acceptable levels of face validity and construct validity when compared to Mantech’s (1983) Work Values Questionnaire (WVQ). An analysis of the prevalence of career anchors and the demographic differences within the current sample was undertaken. This analysis provided evidence to suggest that certain career anchors may be increasing in prevalence while others are decreasing. These findings are in line with current research on the way in which workplace changes are impacting upon careers (Baruch, 2004). Evidence was found that indicated gender differences in scores on the COI subscales. Specifically women were found to score higher on the lifestyle anchor and men to score higher on the general management anchor. Differences were also found between the age groups considered in this study in the general management, creativity, pure challenge and lifestyle anchors. Interaction effects for age and gender were found for the general management and sense of service anchors. The COI was then used to develop a commensurate measure of job career anchors. This job career anchor measure discriminated between jobs within one police organisation. The measure was then used to explore the relationship between career anchors, career anchor congruence (congruence between individual and job career anchors), job satisfaction and organisational commitment. Evidence was found to suggest that career anchors and career anchor congruence have a direct effect on job satisfaction (predicting 10% and 4% of the variance respectively). The analysis also showed support for the role of career anchor congruence as a moderator to the relationship between career anchors and job satisfaction. This thesis makes full consideration of the academic contributions and practical implications of the research presented whilst also considering its limitations. A number of suggestions for the direction of future research have been made.
3
Ljungberg, Jakob. "Pullout test of rock bolts at the Lima Hydropower station : -Assessment of the test method." Thesis, KTH, Betongbyggnad, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-192448.
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During construction of dams, rock bolts are in general installed in the interface between concrete and rock as an extra safety measure against overturning failure. These bolts are however not allowed to be taken into consideration for the stability calculations of large dams. New standards and new design criterias have increased the requirements of the safety of the old dams, leading to a need for expensive rehabilitation and strengthening. It is possible that consideration of these bolts in stability calculations may lead to money being saved. In order to do so more information about the long term strength of these bolts is needed. One way of getting this information has been the destructive testing of old dugout bolts found during reconstruction works. At the Lima hydropower station in Sweden, this kind of testing was made. The test rig used had a design where a piston pressed down on the rock around the bolt in order to pull it out. The question was raised if this could affect the failure load of the bolt. In this thesis, an attempt was made to answer this question using finite element methods. Models of a rock bolt was made in Abaqus, where one model included the piston and one where it was not. The connection between the bolt and the rock was modelled with nonlinear springs and friction, and the results were then compared between the cases and with experimental data. The results showed that the resulting force-deformation curves may be affected by the piston in cases where the dominant failure mode was adhesive failure, which would influence failure loads and deformations. Since so little was known about the properties of the rock and grout at Lima however, it is difficult to say to which extent the test rig has affected these results.
4
Bengal, Steven T. "The Impact of Implausible Anchors." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1343763460.
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Knight, Simon John. "Abstracting anchors from documents." Thesis, University of Southampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243046.
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Singh, Neena. "Biosynthesis of glycophospholipid anchors." Case Western Reserve University School of Graduate Studies / OhioLINK, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=case1054926816.
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Bill, Jinbiao Bill. "Valuation anchors and premium multiples." Thesis, Lancaster University, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.535988.
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CODARO, ROSANA SILVINA. "CAREER ANCHORS AND JOB SATISFACTION." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2015. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=25844@1.
Full textAbstract:
O presente estudo visa analisar a relação entre satisfação no trabalho e o
alinhamento do emprego do indivíduo com suas habilidades, necessidade e
valores, denominadas âncoras de carreira. Para tanto, foi realizada uma pesquisa
quantitativa, um survey baseado no Modelo de Âncoras de Carreira de Schein e
Van Maanen (2013) e na Escala de Satisfação do trabalho de Siqueira (2008), para
uma amostra não probabilística de 96 alunos de uma escola de Administração de
uma universidade privada de Rio de Janeiro. A partir da pesquisa concluímos que
não existe associação significativa entre a satisfação no trabalho e o alinhamento
com a âncora de carreira. A âncora que apresentou maior frequência,
independente do gênero do entrevistado, foi Estilo de Vida, indicando a tendência
de se buscar uma carreira que permita equilibrar a vida profissional e a vida
pessoal. Por outro lado, foi observado que participantes do sexo masculino
priorizam mais a âncora Autonomia e os de sexo feminino a de Competência
Técnica / Funcional. Por fim, também identificamos na pesquisa que os
indivíduos autônomos são mais satisfeitos que os assalariados, os de sexo
masculino estão mais satisfeitos no trabalho do que os de sexo feminino e que
existe uma associação positiva entre anos de experiência e satisfação no trabalho.The present study explores the relationship between job satisfaction and congruence between the individual s actual occupation and his talents, needs and values, namely his career anchors. For that purpose, a quantitative survey using Schein e Van Maanen s Career Anchor model (2013) and Siqueira s Job Satisfaction survey (2008) was performed for a non-probabilistic sample of 96 undergraduate and graduate students at the Business School of a private University in Rio de Janeiro. The results of that survey showed that there is no significant association between satisfaction at work and congruence with career anchor. The most frequent career anchor for both genders was Lifestyle, showing a trend towards a career that allows some balance between professional and personal life. Male participants prioritize more Autonomy and Independence, females prioritize more Technical and Functional Competence. The study showed also that self employed individuals are more satisfied than the ones employed, that among the employed individuals, men are more satisfied at work than women and that there is a significant association between years of experience and work satisfaction.
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Layton, Emily Gwilliam. "Anchors of Religious Commitment in Adolescence." BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2407.
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This study explores adolescent religious commitment using qualitative data from a religiously diverse (Jewish, Christian, and Muslim) sample of 80 adolescents from California and New England. It identifies a new construct, "anchors of religious commitment," to describe what adolescents are committing to as a part of their religious identity. Seven anchors of religious commitment are discussed: (a) religious traditions, rituals, and laws; (b) God; (c) faith traditions or denominations; (d) faith community members; (e) parents; (f) scriptures or sacred texts; and (g) religious leaders. Various forms of expression are identified within each anchor of religious commitment, with issues of relationships and authority being most common among the different anchors. The findings broaden the conceptual understanding of commitment as a relational construct and not just a behavioral or attitudinal construct. Implications for the future research on adolescent religious commitment are discussed, as well as practical implications for parents and religious leaders.
10
Jonnalagadda, Silpa P. "Standardization of test methodology: a comparison between three suture anchors." Thesis, Texas A&M University, 2005. http://hdl.handle.net/1969.1/2442.
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Suture anchors have been used successfully in many applications in orthopedics. They have been in the forefront of research in the recent years. Most of the studies, though, have focused on human suture anchors. This research concentrates on the veterinary aspect of suture anchors. Currently, there is no standardization of testing methods. One of the objectives of this research is to develop a standardized method of testing that is clinically relevant, at least for veterinary use. Another objective of this research is to compare the durability of three commercial suture anchors manufactured by Innovative Animal Products, Securos Veterinary Orthopedic Inc. and IMEXTM by comparing their pullout loads after cyclic loading. This research also aims to determine whether suture anchor failure due to eyelet cut-out or suture wear-out resulting from the sharp edges of the eyelet is the major cause of failure of bone-suture anchor-bone complexes. Cyclic loading of suture anchors during testing for durability has not been used previously even though such loading plays an important role in determining the stability of the bone-suture anchor-bone construct. The response of the construct to this type of testing followed by pullout tests has been explored in this research.
11
Richardson, Mark Damian. "Dynamically installed anchors for floating offshore structures." University of Western Australia. School of Civil and Resource Engineering, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0230.
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The gradual depletion of shallow water hydrocarbon deposits has forced the offshore oil and gas industry to develop reserves in deeper waters. Dynamically installed anchors have been proposed as a cost-effective anchoring solution for floating offshore structures in deep water environments. The rocket or torpedo shaped anchor is released from a designated drop height above the seafloor and allowed to penetrate the seabed via the kinetic energy gained during free-fall and the anchors self weight. Dynamic anchors can be deployed in any water depth and the relatively simple fabrication and installation procedures provide a significant cost saving over conventional deepwater anchoring systems. Despite use in a number of offshore applications, information regarding the geotechnical performance of dynamically installed anchors is scarce. Consequently, this research has focused on establishing an extensive test database through the modelling of the dynamic anchor installation process in the geotechnical centrifuge. The tests were aimed at assessing the embedment depth and subsequent dynamic anchor holding capacity under various loading conditions. Analytical design tools, verified against the experimental database, were developed for the prediction of the embedment depth and holding capacity.
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Olsson, Joel, and Richard Härlin. "Improvements of ground anchors for Better Shelter." Thesis, KTH, Skolan för teknikvetenskap (SCI), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-276718.
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This report is part of a bachelor’s degree project in solid mechanics at KTH, Stockholm. It is performed by two students on behalf of the social enterprise Better Shelter, which provides shelters for people displaced by war and natural disasters. The scope of the project is to expand Better Shelters product specifications by providing improvements of the shelter earth anchors. This would allow use of the shelter in areas affected by higher wind speeds and thereby help more people in need of temporary housing and shelters. The earth anchors prevent the shelter from uplifting and tilting by taking uplift forces when horizontal wind loads acts on the structure. Two wind models with wind speeds up to 36 m/s were created to find the reaction forces on the anchors resisting the wind load. The wind models were compared with each other to validate the results and find the largest reaction forces on the anchors. Simulations of the anchors were made to analyse occurring stresses due to wind loads. Redesigns of the current earth anchor were made to find improvements of the anchor shape and reduce the stresses on the anchor. Experiments were then performed to analyse the redesigned anchor shapes in practise. The redesign, calculations and computational analyses of the anchors were done using the programs SolidEdge, ANSYS and Matlab. Results showed that redesigning the anchor contact area with the anchor wire reduced the stresses on the anchors drastically. Increasing the wing size of the anchors proved to be successful for preventing anchors from being pulled out of the soil. This allows better use of the current anchor material volume. Experiments also proved that burying the anchor deeper into the soil is an effective way of increasing the resistance from being pulled out of the ground. By reducing the stresses on the anchor, more materials are available for use. This could be explored further and is a suggested as a continuation of this project. The current anchor material is aluminium, and most aluminium alloys can be used with the redesigned ball joint connection to the anchor wire even when wind forces are large.Den här rapporten är en del av ett kandidatexamensarbete inom ämnesområdet hållfasthetslära på KTH, Stockholm. Projektet är utfört av två teknologer på uppdrag av organisationen Better Shelter, som tillhandahåller tillfälliga bostäder för människor på flykt från krig och naturkatastrofer. Målet med projektet är att utöka Better Shelters produktsortiment genom förbättringar av bostadens jordankare. Sådana förbättringar möjliggör användning av bostaden i områden utsatta för högre vindbelastningar och hjälper därmed fler människor i behov av tillfälliga bostäder och skydd. Jordankaret förhindrar, tillsammans med tillhörande vajer, bostaden från att lyfta från marken genom att ta vertikala lyftande krafter när horisontell vind blåser på huset. Två vindmodeller med vindhastigheter upp till 36 m/s skapades för att beräkna reaktionskrafter uppstående på jordankarna. Vindmodellerna jämfördes för att validera resultaten och hitta de största reaktionskrafterna på ankarna. Vidare gjordes simuleringar av ankarna för att analysera uppstående spänningar på grund av vindbelastningar. Nya designer av nuvarande jordankare skapades för att hitta förbättringar av ankarets form och minimera spänningskoncentrationer på ankaret. Experiment utfördes sedan för att praktiskt analysera de nya formerna av ankaret. Nya formgivningar, beräkningar och datoranalyser gjordes med hjälp av datorprogrammen SolidEdge, ANSYS och Matlab. Resultatet av arbetet visade att ny form på kontaktytan mellan ankare och vajer minskar spänningar på ankaret kraftigt. Ökning av ankarets vingstorlek visade sig vara fördelaktigt för att förhindra ankaret från att slutas upp ur marken, vilket möjliggör optimering av ankarets materialvolym. Experiment visade också att djupare placering av jordankaret i jorden är en effektiv metod för att förbättra ankarets motstånd från att slitas upp ur marken. Genom att minimera spänningar på ankaret kan nya material användas. Detta är ett förslag på vidarearbete av projektet. Nuvarande material på jordankaret är aluminium, och med ny form på kontaktyta mellan ankare och vajer kan de flesta aluminiumlegeringar användas som material även när belastningar på ankaret är stora.
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Blanchette, Jeffrey Lee. "Pullout Strength of Epoxy Anchors Installed Underwater." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/895.
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This work presents the development of a test program and the results from the final round of testing to better understand the effect a submerged anchor installation has on the pullout strength of epoxy anchors. Two different epoxies were tested at embedment depths of two, four, and six bar diameters. These tests utilized three distinct installation procedures under dry and submerged conditions. The testing program occurred over five phases, with the final round used in analysis consisting of 24 anchor pullout tests. These tests showed that the presence of water did not have an effect on the epoxy bond when anchor holes were cleaned dry and installed underwater, but it did have a significant impact on the ability to consistently clean each anchor when it was submerged.
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Zavliaris, Konstantinos D. "Mechanical behaviour of adhesive anchors installed in concrete." Thesis, City University London, 1990. http://openaccess.city.ac.uk/7534/.
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The thesis presents the main characteristics of the mechanical behaviour of adhesive anchors installed in concrete. They are the mechanisms of failure, the relationship between applied pull-out load and slip of the anchor and the stresses and strains in each of the three components (steel-resin-concrete). The study is primarily experimental but theoretical and finite element analyses are also included. These main characteristics are dependent on the adhesion and wetting phenomena across the resin-concrete and resin-steel interfaces, and on a series of parameters relating to geometry, properties of materials and methods of installation. The principal conclusions obtained are: a) The combined mode of failure involving concrete, resin tensile and interfacial bond failure, is the most probable provided that the resin has a high adhesive strength and that the anchor diameter is larger than the minimum value necessary to prevent steel failure, which can be calculated. b) The sequence of failure in the combined mode is concrete failure in the upper part, bond failure in the remaining part of the anchor, and resin tensile fracture at the bottom of the anchor. c) The values of pull-out load normalized with respect to concrete strength can be regarded as independent of concrete strength. Therefore, a limit state design criterion for adhesive anchors in any concrete substrate can be established. d) The values of anchor displacement normalized with respect to concrete strength vary linearly with it. Based upon this, a simple mathematical function can be determined, which allows the calculation of the displacement of any adhesive anchor. This can be used as a design criterion for the limit state of serviceability of the particular system.
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Betru, Getachew. "The behaviour of model fluke anchors in sand." Thesis, Heriot-Watt University, 1995. http://hdl.handle.net/10399/1283.
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Schiavon, José Antonio. "Behaviour of helical anchors subjected to cyclic loadings." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/18/18132/tde-10072017-090437/.
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Helical anchors, used widely to resist uplift loading for a variety of applications, including in transmission towers, pipelines, offshore structures, etc., are subjected to environmental cyclic loads that influence the anchor performance and may induce fatigue failure. However, the influence of cyclic loading on helical anchor behaviour is unknown. A comprehensive evaluation of the effect of cyclic loading on the load-displacement response of single-helix anchors in sandy soils is presented here, including an interaction diagram to help designers evaluate the impact of different conditions in cyclic loadings. The experimental work of this thesis includes geotechnical centrifuge modelling and field load tests. The centrifuge model tests were carried out with reduced scale models of helical anchors in sand, at IFSTTAR (Nantes, France). The field load tests were performed on helical anchors installed in a tropical residual soil of the Experimental Site of the University of São Paulo (São Carlos, Brazil). In addition, numerical modelling was used to predict the pre- and postcyclic responses of the single-helix anchors tested in a centrifuge. The main findings of this research are: (a) helical anchor behaviour is governed by helix bearing resistance, and no loss of helix bearing capacity was observed in the range of cyclic loadings tested, (b) the degradation of shaft resistance was noticed mainly during the first 100 cycles, when the accumulation of permanent displacements is more significant, (c) an interaction diagram showing the different conditions of cyclic stability is proposed from the results of the experimental data, (d) modified values of the bearing capacity factor in tension (Nq) are suggested for the estimation of post-cyclic uplift capacity of single-helix anchors in sand, (e) the installation effect of the anchor should be taken into account in the numerical model in order to obtain reliable predictions of the helical anchor performance.As estacas helicoidais são largamente utilizadas para resistir a carregamentos de tração em uma variedade de aplicações como torres de linhas de transmissão de energia, dutos enterrados, estruturas offshore, etc. Estes tipos de estruturas são normalmente submetidos a carregamentos cíclicos que influenciam o desempenho de fundações por estacas helicoidais submetidas a esforços de tração, e podem induzir ruptura por degradação da capacidade de carga. Contudo, a influência do carregamento cíclico no comportamento das estacas helicoidais (ou ancoragens helicoidais, quando submetidas apenas a esforços de tração) é pouco conhecida. Uma avaliação abrangente do efeito de carregamentos cíclicos sobre o comportamento das ancoragens helicoidais é apresentada nesta tese, incluindo um diagrama de interação para auxiliar na avaliação do impacto de diferentes condições de carregamento cíclico. O trabalho experimental desta tese inclui modelagem em centrífuga geotécnica e ensaios de carregamento cíclico em estacas na grandeza real em campo. Os ensaios em centrífuga foram realizados com modelos reduzidos de estacas helicoidais em areia, no IFSTTAR (Nantes, França). Os ensaios de campo foram realizados em ancoragens helicoidais instaladas no solo residual tropical do Campo Experimental de Fundações da Universidade de São Paulo (São Carlos, Brasil). Além disso, modelos numéricos foram utilizados para simular os resultados do comportamento das ancoragens helicoidais ensaiadas em centrífuga nas condições pré- e pós-ciclos. Os principais resultados desta pesquisa são: (a) a capacidade de carga à tração da ancoragem helicoidal é controlada pela capacidade de carga da hélice, (b) a degradação da resistência por atrito lateral foi observada principalmente durante os primeiros 100 ciclos, período em que a acumulação dos deslocamentos permanentes é mais significante, (c) um diagrama de interação mostrando as diferentes condições de estabilidade cíclica é proposto a partir dos resultados experimentais em centrífuga, (d) valores modificados do fator de capacidade de carga em tração (Nq) são sugeridos para estimativa da capacidade pós-ciclos de ancoragens helicoidais com uma hélice em areia, (e) o efeito da instalação da ancoragem deve ser levado em consideração no modelo numérico para que se obtenha previsões confiáveis do desempenho de ancoragens helicoidais.
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Al-Mansouri, Omar. "Behavior of bonded anchors in concrete under fire." Thesis, Ecole nationale supérieure Mines-Télécom Lille Douai, 2020. http://www.theses.fr/2020MTLD0011.
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La technique des ancrages par scellement chimique consiste à sceller une tige filetée dans un trou foré dans le béton durci grâce à une résine polymère. Les principaux avantages de cette technique sont la facilité d’installation et les propriétés mécaniques élevées de la résine à température ambiante. Grâce à l’adhérence de la résine, ce type d’ancrage peut être dimensionné pour avoir des performances similaires voire supérieures de celles des autres systèmes d’ancrages (mécaniques et coulés en place). En revanche, à hautes températures, e.g. incendie, l’adhérence de la résine se dégrade rapidement menaçant la capacité de l’ancrage à supporter les charges appliquées. Cela crée un risque sur les vies et les biens dans le bâtiment. Plusieurs accidents se sont produits comme l’effondrement du Big Dig Tunnel aux USA (2006) et le tunnel Sasago au Japon (2012) qui ont montré l’importance d’avoir des méthodes d’évaluation fiables de ce type d’ancrages. L’objectif de cette thèse est d’établir une méthode d’évaluation et une méthode de dimensionnement afin d’assurer la tenue structurale des ancrages par scellement chimique en situation d’incendie. L’étude est structurée en quatre parties :i. Protocoles expérimentaux pour les essais au feu des chevilles chimiques. Des essais d’arrachements au feu ont été réalisés sur des chevilles chimiques (résine époxy). Les profils de températures le long de l’ancrage ont été déterminés expérimentalement pour différentes configurations d’essais. Ensuite, ces profils thermiques ont été exploités comme données d’entrée pour calculer la résistance des chevilles par la méthode Pinoteau (intégration des résistances). Cette étude a permis de préciser les conditions expérimentales à utiliser pour l’évaluation des chevilles chimiques au feu.ii. Proposition d’un modèle de dimensionnement basé sur des calculs thermiques en utilisant la méthode des éléments finis en 3D. Les profils de température correspondant aux différentes configurations d’un ancrage dans le bâtiment ont été calculés à l’aide des propriétés thermophysiques des matériaux Eurocode pour le béton et l’acier. La modélisation en 3D a été comparée à la modélisation en 2D plane utilisée communément dans la littérature. Les deux approches ont été comparées aux mesures expérimentales et couplées avec la méthode Pinoteau pour évaluer l’influence de la méthode de modélisation sur le résultat de l’intégration des résistances. Suite à la validation du modèle 3D, des investigations thermiques ont été conduites sur d’autres paramètres pouvant influencer les essais au feu des chevilles chimiques. Cette étude a permis de valider la méthode de calcul en 3D comme la méthode la plus représentative du problème d’une cheville chimique au feu.iii. Validation de la méthode Pinoteau pour le dimensionnement des chevilles chimiques au feu en utilisant le modèle de dimensionnement proposé précédemment. Les calculs de la résistance au feu de trois chevilles chimiques différentes ont été comparés à des essais d’arrachement. Cette étude menée sur une large gamme de tailles de chevilles a permis de valider l’utilisation de l’intégration des résistances pour le dimensionnement.iv. Etude du comportement des chevilles chimiques dans le béton fissuré à hautes températures. Une méthode d’évaluation a été développée afin de déterminer la réduction de la résistance d’adhérence liée à la fissuration du béton, à hautes températures (chauffage électrique). Des essais ont été faits sur des chevilles chimiques (résine époxy) dans le béton fissuré et non-fissuré à température ambiante et à hautes températures. La réduction de la résistance avec l’augmentation de la température a été investiguée. Cette étude a permis d’obtenir une bonne répétabilité des résultats grâce à l’augmentation du nombre d’essais et le bon contrôle du scénario thermique appliquéThe technique of bonded anchors consists of fastening a threaded rod in a drilled hole in hardened concrete by polymer adhesives. The main advantages of this technique are ease of installation and the high mechanical properties of the adhesive at ambient temperature. Due to the adherence of the adhesive resin, this type of anchors can be designed to ensure similar or even higher performances compared to other anchor systems (mechanical and cast-in). However, at high temperatures, e.g. fire situation, the adherence of the adhesive degrades rapidly. Fire decreases the adherence of the adhesive and leads to the inability of the anchor to support the fixed objects. This creates a risk on the lives and goods inside the building. Several accidents occurred like the collapse of the Big Dig Tunnel in the USA (2006) and the Sasago tunnel in Japan (2012) and highlighted the importance of having reliable evalutation methods of this type of anchors. The objective of this thesis is to establish an assessment and a design method to ensure the structural resistance of bonded anchors in fire situations. This project is structured into four main parts:i. Experimental protocols for fire tests on bonded anchors. Pull-out fire tests were conducted on bonded anchors (epoxy adhesive). Temperature profiles along the embedment depth of anchors were determined experimentally for different test configurations. Then, these temperature profiles were used as entry data to calculate the fire resistance of anchors using Pinoteau’s method (Resistance Integration Method). This study allowed to precise the experimental conditions to be adopted for fire evaluation of bonded anchors. ii. Proposition of a design model based on transient thermal calculations using finite element method in 3D. Temperature profiles were calculated using the thermophysical material properties of concrete and steel in the Eurocode. 3D modelling was compared to 2D modelling commonly used in the literature. Both approaches were compared to measurements during fire tests and coupled with Pinoteau’s method to assess their impact on the calculation of fire resistance of anchors. Following the validation of the 3D model, thermal investigations were conducted on other parameters that could influence fire tests of bonded anchors. This study allowed to validate the 3D modelling approach as the most representative of the problem of bonded anchors exposed to fire.iii. Validation of Pinoteau’s method for the design of bonded anchors under fire by using the previously proposed design model. Calculations of fire resistance of three different bonded anchor products were compared to pull-out tests. This study conducted on a wide range of anchor sizes lead to the validation of the Pinoteau’s Method for the design of bonded anchors.iv. Study of the behavior of bonded anchors in cracked concrete at high temperatures. An assessment method was developed to determine the reduction of bond strength due to cracked concrete, at high temperatures (electrical heating). Tests were conducted on bonded anchors (epoxy adhesive) in cracked and uncracked concrete, at ambient and high temperatures. The evolution of the reduction with temperature increase was investigated. This study ensured a good repeatability of test results due to the increased testing potential and the good control of the applied heating scenario
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Bylapudi, Gopi. "CORROSION OF ROCK ANCHORS IN US COAL MINES." OpenSIUC, 2010. https://opensiuc.lib.siu.edu/theses/287.
Full textAbstract:
The mining industry is a major consumer of rock bolts in the United States. Due to the high humidity in the underground mining environment, the rock bolts corrode and loose their load bearing capacity which in turn reduces the life expectancy of the ground support and, thus, creates operational difficulties and number of safety concerns [1]. Research on rock anchor corrosion has not been adequately extensive in the past and the effects of several factors in the mine atmosphere and waters are not clearly understood. One of the probable reasons for this lack of research may be attributed to the time required for gathering meaningful data that makes the study of corrosion quite challenging. In this particular work underground water samples from different mines in the Illinois coal basin were collected and the major chemical content was analyzed and used for the laboratory testing. The corrosion performance of the different commercial rock anchors was investigated by techniques such as laboratory immersion tests in five different corrosion chambers, and potentiodynamic polarization tests in simulated ground waters based on the Illinois coal basin. The experiments were conducted with simulate underground mining conditions (corrosive). The tensile strengths were measured for the selected rock anchors taken every 3 months from the salt spray corrosion chambers maintained at different pH values and temperatures. The corrosion potential (Ecorr), corrosion current (Icorr) and the corresponding corrosion rates (CR) of the selected commercial rock bolts: #5, #6, #6 epoxy coated and #7 forged head rebar steels, #6 and #7 threaded head rebar steels were measured at the solution pH values of 5 and 8 at room temperature. The open circuit potential (OCP) values of the different rock anchors were recorded in 3 selected underground coal mines (A, B & C) in the Illinois coal basin and the data compared with the laboratory electrochemical tests for analyzing the life of the rock anchors installed in the mines with respect to corrosion potential and corrosion current measured. The results of this research were statistically validated. This research will have direct consequence to the rock related safety. The results of this research indicate that certain corrosive conditions are commonly found in mines but uniform corrosion (around 0.01-0.03mm loss per year across the diameter) is generally not considered a serious issue. From this study, longer term research for long-term excavation support is recommended that could quantify the problem depending on the rock anchor used and specific strata conditions.
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Schiavon, José Antonio. "Behaviour of helical anchors subjected to cyclic loadings." Thesis, Ecole centrale de Nantes, 2016. http://www.theses.fr/2016ECDN0014/document.
Full textAbstract:
Les ancrages hélicoïdaux, largement utilisés pour résister à des efforts de traction pour une variété d’applications comme les pylônes électriques, les pipelines, les structures offshore, etc., sont soumis à des chargements cycliques qui influent sur la performance d’encrage et peuvent induire une rupture par fatigue. Cependant, l’influence des sollicitations cycliques sur le comportement d’encrage hélicoïdal est mal connue. Une évaluation approfondie de l’effet des charges cycliques sur la réponse effort – déplacement des ancrages avec une seule hélice dans les sols sableux est présentée, incluant un diagramme d’interaction pour aider à évaluer l’impact des différentes conditions de chargement cyclique. La partie expérimentale de cette thèse comprend des essais en centrifugeuse géotechnique et des essais de chargement in situ. Les essais en centrifugeuse ont été effectués sur des modèles réduits d’encrages hélicoïdaux dans du sable à l’IFSTTAR (Nantes, France). Les essais de chargement in situ ont été réalisés sur des ancrages hélicoïdaux installés dans le sol tropical résiduel du site expérimental de l’Université de Sao Paulo (Sao Carlos, Brésil). De plus la modélisation numérique a été utilisée pour prédire les réponses pré et post cycliques des ancrages d’une hélice testée en centrifugeuse. Les principales conclusions de cette recherche sont : (a) le comportement d’un ancrage hélicoïdal est régi par la capacité portante de l’hélice, et aucune perte de capacité portante d’hélice n’a été observée pour la gamme de charges cycliques testée, (b) la dégradation de la résistance par frottement latéral sur le fut a été remarquée principalement pendant les 100 premiers cycles, lorsque l’accumulation des déplacements permanents est plus importante, (c) un diagramme d’interaction montrant les différentes conditions de stabilité cyclique est proposé à partir des résultats des données expérimentales, (d) des valeurs modifiées du facteur de capacité portante (Nq) sont proposées pour l’estimation de la capacité et post-cyclique des ancrages avec une hélice dans du sable, (e) l’effet de l’installation de l’ancrage doit être pris en compte dans le modèle numérique afin d’obtenir des prédictions fiables de la performance de l’ancrage hélicoïdalHelical anchors, used widely to resist uplift loading for a variety of applications, including in transmission towers, pipelines, offshore structures, etc., are subjected to environmental cyclic loads that influence the anchor performance and may induce fatigue failure. However, the influence of cyclic loading on helical anchor behaviour is unknown. A comprehensive evaluation of the effect of cyclic loading on the load-displacement response of single-helix anchors in sandy soils is presented here, including an interaction diagram to help designers evaluate the impact of different conditions in cyclic loadings. The experimental work of this thesis includes geotechnical centrifuge modelling and field load tests. The centrifuge model tests were carried out with reduced scale models of helical anchors in sand, at IFSTTAR (Nantes, France). The field load tests were performed on hekical anchors installed in a tropical residual soil of the Experimental Site of the University of Sao Paulo (Sao Carlos, Brazil). In addition, numerical modelling was used to predict the pre- and post-cyclic responses of the single-helix anchors tested in a centrifuge. The main findings of this research are : (a) helical anchor behaviour is governed by helix bearing resistance and no loss of helix bearing capacity was observed in the range of cyclic loadings tested, (b) the degardation of shaft resistance was noticed mainly during the first 100 cycles, when the accumulation of permanent displacements is more significant, (c) an interaction diagramshowing the different conditions of cyclic stability is proposed from the results of the experimental data, (d) modified values of the bearing capacity factor in tension (Nq) are suggested for the estimation of post-cyclic uplift capacity of single-helix anchors in sand, (e) the installation effect of the anchor should be taken into account in the numerical model in order to obtain reliable predictions of the helical anchor performance
20
Krishna, Y. S. R. "Numerical Analysis Of Large Size Horizontal Strip Anchors." Thesis, Indian Institute of Science, 2000. https://etd.iisc.ac.in/handle/2005/207.
Full textAbstract:
Structures like transmission towers, tele-communication masts, dry-docks, tall chimneys, tunnels and burried pipelines under water etc are subjected to considerable uplift forces. The net effect of external loading on the foundations of these structures results in forces that try to pull the foundations out of the ground. Anchors are usually provided to resist such uplift forces.
Earlier theoretical research of anchor behavior has focused on elastic response and ultimate pullout capacity. Many investigators have proposed techniques for determining the collapse load of anchors. Essentially the approaches involve the use of limit equilibrium concepts, with some assumptions regarding the shape of the failure surface and/or the influence of the soil above the anchor. The possible effect of dilatency and initial stress state are not considered in these methods. A number of investigators have used the results of small size model anchors to understand the behavior and extrapolated the results for predicting the behavior of large sized anchors. This has lead to unsatisfactory results. It has been clearly shown by Dickin (1989) that the failure displacements and load displacement curve patterns are very different for small and large sized anchors, i.e. they are not just proportional to the size of the anchor. Critical pullout load and the load displacement behavior are required for the complete analysis of anchor foundations. Though, many theories have been proposed to predict the uplift capacity within the limits of accuracy required at engineering level, at present no simple rational method is available for computing deformations.
In the present investigation attempts have been made to analyze the load deformation behavior of large size strip anchors in sands, clays and layered soils using two-dimensional explicit finite difference program FLAG (Fast Lagrangian Analysis of Continua), well suited for geomaterials, by assuming soil to be a Mohr-Coulomb material in the case of sands and modified Cam-clay material in the case of clays.
It is now well understood that the shearing resistance of a granular soil mass is derived from two factors frictional resistance and the dilatency of the soil. So the peak friction angle can be divided in to two components critical friction angle Фcv and dilation angle Ψ. Critical friction angle is the true friction angle as a result of frictional resistance at interparticle level when the soil is shearing at constant volume. If Фcv for a given soil remains constant, the value of Ψ has to increase with the increase in initial density of soil packing. The dilatency of a soil mass gradually decreases with continued shearing from its initial high value to zero after very large shear strains, when the soil finally reaches a constant, steady volume at critical states. Correspondingly the observed friction angle Ф reduces from its peak value to Фcv at a very large strain.
In earlier days, clays used to be characterized by the strength parameters c and Ф. often, under undrained conditions, Ф would be even considered zero. But in the recent developments, it is understood that all the strength of clays is frictional. There is nothing like cohesion. The part of shear strength, which appears to be independent of normal stress, is shown to be the effect of over-consolidation and the resulting dilation. Thus although Cam-clay model uses zero cohesion for all clays, it reflects this component of strength through over-consolidation and in a more realistic way. Hence, it is appropriate to consider the pre-consolidation pressure as parameter in the analysis. More specifically, the various aspects covered in this investigation are as follows.
Chapter 1 provides the general introduction. In chapter 2, the existing literature for the analysis of anchors for both experimental and analytical investigations on the pullout capacity of anchors in homogeneous and layered soils and the load deformation behavior of anchors under pullout are briefly reviewed.
Chapter 3 deals with the features and the implementation of the two-dimensional explicit finite difference program, Fast Lagrangian Analysis of Continua (FLAC) and the constitutive modeling of soils. It discusses the background and implementation of Strain softening / hardening model. This model is based on the Mohr- Coulomb model with non-associated shear and associated tension flow rules. In this model the cohesion, friction, dilation and tensile strength may harden or soften after the onset of the plastic yield. Further the critical state concepts and implementation of the modified Cam-clay model have been discussed. Cam-clay model originally developed for clays reflects the hydrostatic pressure or density dependent hardening material response.
Chapter 4 focuses on the analysis of load deformation behavior of large size anchors in granular soils. Two-dimensional explicit finite difference program (FLAC) is used for the simulations and the soil is modeled as a Mohr-Coulomb strain softening/hardening material In this chapter a series of simulations have been carried out on large size anchor plates, with parametric variation. By analyzing these results, a generalized load deformation relationship for different sizes of anchors and different types of soil have been proposed. The results are presented in the form of influence/design charts which can be used in hand calculations to obtain an estimate of anchor capacity and deformation for a wide range of soil types and size of anchors.
Chapter 5 deals with the analysis of the drained and undrained behavior of large size horizontal strip anchors in clays using modified Cam-clay model. Earlier investigators have studied the undrained behavior of anchor plates in clays, but no studies are reported in literature for the drained behavior of anchors in clays. Further it is not clear whether, drained or undrained condition will be critical for an anchor. In this chapter the drained and undrained behavior of large size anchor plates in both normally consolidated and over-consolidated states have been made. It has been found that the undrained pullout capacity of an anchor in a soil of normally consolidated state will always be more than the drained capacity. This is contrast to the usual understanding that undrained behavior is more critical than the drained behavior.
In Chapter 6 an attempt has been made to analyze the behavior of large size anchors in two layered sands and in conditions where backfill material has a higher or lower strength than the native soil, for different shape of excavations. Soil is assumed to be a Mohr-coulomb strain softening/hardening material.
In Chapter 7 the entire investigation covered in earlier chapters has been synthesized and some specific conclusions have been highlighted.
21
Krishna, Y. S. R. "Numerical Analysis Of Large Size Horizontal Strip Anchors." Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/207.
Full textAbstract:
Structures like transmission towers, tele-communication masts, dry-docks, tall chimneys, tunnels and burried pipelines under water etc are subjected to considerable uplift forces. The net effect of external loading on the foundations of these structures results in forces that try to pull the foundations out of the ground. Anchors are usually provided to resist such uplift forces.
Earlier theoretical research of anchor behavior has focused on elastic response and ultimate pullout capacity. Many investigators have proposed techniques for determining the collapse load of anchors. Essentially the approaches involve the use of limit equilibrium concepts, with some assumptions regarding the shape of the failure surface and/or the influence of the soil above the anchor. The possible effect of dilatency and initial stress state are not considered in these methods. A number of investigators have used the results of small size model anchors to understand the behavior and extrapolated the results for predicting the behavior of large sized anchors. This has lead to unsatisfactory results. It has been clearly shown by Dickin (1989) that the failure displacements and load displacement curve patterns are very different for small and large sized anchors, i.e. they are not just proportional to the size of the anchor. Critical pullout load and the load displacement behavior are required for the complete analysis of anchor foundations. Though, many theories have been proposed to predict the uplift capacity within the limits of accuracy required at engineering level, at present no simple rational method is available for computing deformations.
In the present investigation attempts have been made to analyze the load deformation behavior of large size strip anchors in sands, clays and layered soils using two-dimensional explicit finite difference program FLAG (Fast Lagrangian Analysis of Continua), well suited for geomaterials, by assuming soil to be a Mohr-Coulomb material in the case of sands and modified Cam-clay material in the case of clays.
It is now well understood that the shearing resistance of a granular soil mass is derived from two factors frictional resistance and the dilatency of the soil. So the peak friction angle can be divided in to two components critical friction angle Фcv and dilation angle Ψ. Critical friction angle is the true friction angle as a result of frictional resistance at interparticle level when the soil is shearing at constant volume. If Фcv for a given soil remains constant, the value of Ψ has to increase with the increase in initial density of soil packing. The dilatency of a soil mass gradually decreases with continued shearing from its initial high value to zero after very large shear strains, when the soil finally reaches a constant, steady volume at critical states. Correspondingly the observed friction angle Ф reduces from its peak value to Фcv at a very large strain.
In earlier days, clays used to be characterized by the strength parameters c and Ф. often, under undrained conditions, Ф would be even considered zero. But in the recent developments, it is understood that all the strength of clays is frictional. There is nothing like cohesion. The part of shear strength, which appears to be independent of normal stress, is shown to be the effect of over-consolidation and the resulting dilation. Thus although Cam-clay model uses zero cohesion for all clays, it reflects this component of strength through over-consolidation and in a more realistic way. Hence, it is appropriate to consider the pre-consolidation pressure as parameter in the analysis. More specifically, the various aspects covered in this investigation are as follows.
Chapter 1 provides the general introduction. In chapter 2, the existing literature for the analysis of anchors for both experimental and analytical investigations on the pullout capacity of anchors in homogeneous and layered soils and the load deformation behavior of anchors under pullout are briefly reviewed.
Chapter 3 deals with the features and the implementation of the two-dimensional explicit finite difference program, Fast Lagrangian Analysis of Continua (FLAC) and the constitutive modeling of soils. It discusses the background and implementation of Strain softening / hardening model. This model is based on the Mohr- Coulomb model with non-associated shear and associated tension flow rules. In this model the cohesion, friction, dilation and tensile strength may harden or soften after the onset of the plastic yield. Further the critical state concepts and implementation of the modified Cam-clay model have been discussed. Cam-clay model originally developed for clays reflects the hydrostatic pressure or density dependent hardening material response.
Chapter 4 focuses on the analysis of load deformation behavior of large size anchors in granular soils. Two-dimensional explicit finite difference program (FLAC) is used for the simulations and the soil is modeled as a Mohr-Coulomb strain softening/hardening material In this chapter a series of simulations have been carried out on large size anchor plates, with parametric variation. By analyzing these results, a generalized load deformation relationship for different sizes of anchors and different types of soil have been proposed. The results are presented in the form of influence/design charts which can be used in hand calculations to obtain an estimate of anchor capacity and deformation for a wide range of soil types and size of anchors.
Chapter 5 deals with the analysis of the drained and undrained behavior of large size horizontal strip anchors in clays using modified Cam-clay model. Earlier investigators have studied the undrained behavior of anchor plates in clays, but no studies are reported in literature for the drained behavior of anchors in clays. Further it is not clear whether, drained or undrained condition will be critical for an anchor. In this chapter the drained and undrained behavior of large size anchor plates in both normally consolidated and over-consolidated states have been made. It has been found that the undrained pullout capacity of an anchor in a soil of normally consolidated state will always be more than the drained capacity. This is contrast to the usual understanding that undrained behavior is more critical than the drained behavior.
In Chapter 6 an attempt has been made to analyze the behavior of large size anchors in two layered sands and in conditions where backfill material has a higher or lower strength than the native soil, for different shape of excavations. Soil is assumed to be a Mohr-coulomb strain softening/hardening material.
In Chapter 7 the entire investigation covered in earlier chapters has been synthesized and some specific conclusions have been highlighted.
22
Panton, Brad. "Numerical modelling of rock anchor pullout and the influence of discrete fracture networks on the capacity of foundation tiedown anchors." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/57464.
Full textAbstract:
Numerous studies presented in this thesis have reported failure of the rock mass surrounding an anchor, as a result of applied external tensile loads (i.e. pullout loads) transferred to rock mass from the anchor and the overlying structure. Resistance to this failure mechanism is provided in design by assuming that the dead weight of a uniformly shaped inverted “cone”, with an assumed initiation point and breakout angle, provides resistance to the design loads. In some cases, a minor contribution of rock mass tensile or shear strength is considered by designers across the area of the assumed pullout cone. Strength estimates for this additional resistance are based primarily on sparse historic testing data, rock mass rating type relationships developed for other applications, and engineering judgement. However, rock mass rating systems assume that the rock mass is homogenous and isotropic, and at the scale of the anchor this assumption may not be valid since individual fractures may influence anchor stability.
As an alternative to the current foundation anchor design method, this research presents a new approach to the rock cone pullout problem using Discrete Fracture Networks (DFN) combined with numerical simulations. The simulations presented in the research investigate the influence of fractures in a synthetic rock mass on ultimate anchor strength, with the purpose of developing a method for incorporation of scale effects of jointing in anchor design.
By using numerical simulations that allow the load transfer mechanism from the anchor to the rock mass to vary with stiffness, it is contended that the failure mechanism of the rock mass under the applied loading can be considered more appropriately in anchor designs. It is also contended that some aleatory variability associated with fractures can be quantified using a DFN-based approach. Fractures are observed to have an influence on both the load distribution in the anchor as well as the ultimate resistance of the rock mass to pullout. The mapping considerations required to produce a DFN model for anchor pullout are described in this thesis and recommendations for incorporating DFN based models in anchor design are provided herein.Applied Science, Faculty of
Mining Engineering, Keevil Institute of
Graduate
23
Yang, Ming. "Undrained behavior of plate anchors subjected to general loading." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2008-12-78.
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Kim, Byoung Min. "Upper bound analysis for drag anchors in soft clay." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4887.
Full textAbstract:
This study presents an upper bound plastic limit analysis for predicting drag
anchor trajectory and load capacity. The shank and fluke of the anchor are idealized as
simple plates. The failure mechanism involves the motion of the anchor about a center
of rotation, the coordinates of which are systematically optimized to determine the
minimum load at the shackle. For a given anchor orientation, the direction of the
shackle force is varied to establish a relationship between the magnitude and direction of
the shackle load. Coupling this relationship to the Neubecker-Randolph anchor line
solution produces a unique solution for the magnitude and orientation of the shackle
force. The anchor is then advanced a small increment about the optimum center of
rotation and the process is repeated. The upper bound method (UBM) provides a
practical means to determine the trajectory of the anchor and the anchor load capacity at
any point in the trajectory. To better understand of the anchor behavior, extensive
parameter studies were carried out varying the properties of the anchor, anchor line, and
soil. The UBM show good agreement with six full-scale tests covering several different
anchor types and centrifuge model tests.
25
Merouani, Zein-Eddine. "Behaviour of anchors in sand : deterministic and probabilistic analysis /." Stockholm : Division of Soil- and Rock Mechanics, Royal Institute of Technology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4357.
Full text
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Baycan, Serhat. "Field performance of expansive anchors and piles in rock." Online version, 1996. http://bibpurl.oclc.org/web/24932.
Full text
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Nicholson, Thomas Barrett. "Molecular dissection of the functional specificity of glycophosphatidylinositol anchors." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=18463.
Full textAbstract:
Carcinoembryonic antigen (CEA) is a cell surface protein attached to the membrane by a glycophosphatidylinositol (GPI) anchor, a common modification of cell surface proteins. CEA is overexpressed in many human cancers, and plays a role in tumor progression through its ability to activate certain integrins, thereby blocking cellular differentiation, inhibiting anoikis, and disrupting normal tissue architecture. Previous work established that the CEA GPI anchor contains important and specific information directing these functions, which served as the basis for an investigation of the underlying mechanisms involved. The ability of the GPI anchor to determine protein function was examined using a chimera that consisted of the CEA GPI anchor attached to neural cell adhesion molecule (NCAM) self-adhesive external domains; this chimera, NCB, possessed CEA-like, rather than NCAM-like, functions. The CEA anchor targets the protein to specific domains on the cell surface, resulting in an association with specific signaling molecules. This targeting was employed to modify CEA function, as the presence of a protein with non-functional external domains but the same anchor led to a complete and specific loss of biological function of the CEA-like protein. GPI anchor addition is determined by a specific carboxy-terminal signal sequence, which we hypothesized contained information directing the addition of a particular GPI anchor with functional specificity. To identify this signal, chimeras were generated exchanging amino acids in this signal sequence between CEA and NCAM, a protein with different functional properties. A stretch of 6 amino acids within the signal sequence was found to be necessary and sufficient for the addition of the CEA-specific anchor. Since this region is well conserved, but not identical, in the CEA family members CC6 and CC7, we examined whether these proteins were also attached to the same GPI anchors. Surprisingly, while the anchors of these proteinL'antigène carcinoembryonnaire humain (CEA) est un membre d'une famille de protéines de surface cellulaire fixées à la membrane par un ancrage glycophosphatidylinositol (GPI), une modification commune des protéines de la membrane plasmique. CEA est surexprimé dans plusieurs cancers humains et joue un rôle dans la progression tumorale par sa capacité à activer certaines intégrines, bloquant de ce fait la différentiation cellulaire et l'anoikis, et perturbant l'architecture tissulaire normale. Plusieurs recherches antérieures ont établi que l'ancre GPI de CEA contient de l'information importante et spécifique dirigeant ces fonctions. Ces travaux ont servi de base pour l'étude biologique et moléculaire des mécanismes impliqués. Afin de démontrer les fonctions biologiques de CEA, nous avons étudié les capacités de l'ancre GPI à modifier la fonction des protéines en utilisant une protéine hybride (NCB) composée de l'ancre GPI de CEA attachée aux domaines externes auto-adhésifs de la molécule d'adhésion cellulaire neuronale (NCAM). La protéine chimérique NCB possède des fonctions similaires à CEA. L'ancre de CEA cible la protéine à des domaines spécifiques de la surface cellulaire, ce qui mène à l'association de la protéine avec des éléments de signalisation spécifiques. Ce ciblage a été utilisé pour modifier la fonction de CEA, car la présence d'une protéine dont les domaines extracellulaires sont non fonctionnels, mais dont l'ancre est la même, a causé la perte complète et spécifique des fonctions biologiques de NCB. L'ajout d'ancres GPI est déterminé par une séquence spécifique située à l'extrémité carboxyle-terminale. Nous avons présumé que cette séquence contiendrait l'information nécessaire à l'addition sélective d'une ancre GPI de fonction spécifique. Afin d'identifier ce signal, des protéines hybrides ont été produites en échangeant des acides aminés entre CEA et NCAM, deux protéines de fo
28
Ottaviani, D. "The genomic anchors of the human major histocompatibility complex." Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/16303/.
Full textAbstract:
Eukaryotic chromatin is organised into a hierarchy of topologically constrained loop structures. Matrix Attachment Regions (MARs) are genomic sequences that mediate the anchoring of chromatin to the insoluble proteinaceous fraction of the nucleus known as the nuclear matrix. Since only a few MARs have been characterised so far, their role in genomic structure and function is not well understood. The aim of this thesis is to use the human Major Histocompatibility Complex (MHC) as model region to provide novel insights into the relationship between chromatin folding mediated by MARs and gene expression. This large locus contains critical genes for immunity and is associated with more diseases than any other genomic region. Classical MHC genes are expressed in a cell type specific pattern, and can be induced by cytokines such as IFN-γ. MARs were identified across the entire MHC in uninduced fibroblasts, IFN-γ induced fibroblasts and B lymphoblastoid cells. Expression array analysis showed that these cell types exhibit different MHC expression profiles. MARs were first isolated treating nuclei with hypertonic buffers followed by nuclease digestion and then mapped by hybridizing them onto a novel tiling path array for the MHC. The suitability of this array platform to study DNA-protein interactions was verified using hybridisations of CIITA-enriched DNA and DNA enriched in H3-K9/K14 acetylation. The findings reveal that MARs are unevenly distributed across the MHC, and that they can be classified into three classes: constitutive, cell type specific and transcriptiondependent. These sequences are mainly positioned in intergenic regions and in close proximity to the MHC class boundaries, subdividing the locus into physical domains. By comparing the position of MARs in uninduced fibroblasts, IFN-γ induced fibroblasts and B lymphoblastoid cells, transcriptional activation of the MHC was found to be associated with a reconfiguration of chromatin architecture resulting from the formation of additional genomic anchors. These results suggest that the dynamic tethering of chromatin is linked to transcriptional regulation.
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Hassan, Che Ariffin Bin. "The use of flexible transverse anchors in reinforced soil." Thesis, University of Newcastle Upon Tyne, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316190.
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Weber, Jason David. "Corrosion of Rock Anchors in Illinois Coal Basin Mines." OpenSIUC, 2013. https://opensiuc.lib.siu.edu/theses/1248.
Full textAbstract:
Rock anchors are used extensively in coal mines in the United States and around the world. The conditions in many of these coal mines are conducive towards the corrosion of rock anchors. Despite this, very little research has been performed to analyze corrosion and its effects on rock anchors in US coal mines. The specific aim of this thesis is to analyze typical Illinois Coal Basin (ICB) mine parameters and their effects on corrosion. A well understood relationship between these parameters and corrosion would be useful in locating highly corrosive areas and mitigating risks associated with corrosion. To study ICB mine parameters and their effects on corrosion, three general experiment types were carried out: in situ rock anchor analysis, simulated mine environment testing and analysis, and electrochemical testing and analysis. For in situ rock anchor analysis, open circuit potential (OCP) of rock anchors in coal mines with various conditions were measured. The OCP values can be used to predict whether or not corrosion of the rock anchors has initiated, and to study relationships between mine parameters and corrosion. The readings were also used to assess the validity of experimental setups by comparing experimental OCP values to in situ mine OCP values. The OCP readings obtained were found to vary by locations within the mines indicating corrosion conditions can vary relative to location. No clear trends were found between the OCP values and moisture or rock anchor age likely indicating numerous other factors were affecting the OCP values. These other significant factors will need to be determined and measured in addition to moisture and age in order to develop clear relationships between mine parameters and OCP values. Overall, the experimental OCP values found were slightly more negative than the in situ OCP values. This may have been due to the fact that the corrosion tanks exposed the rock anchors to more moisture. It is also a possible indication that mine rock anchors were not yet significantly corroding. For simulated environments, three tanks were filled with solution made by adding chloride ions, sulfate ions, and iron ions. The concentrations were based on water samples from mines and were the same for each tank. The temperatures of each tank were set at 30°C or 50°C, and the pH levels were set at 5.5 or 9.The tanks were then loaded with thirteen different types of rock anchors. The solution compositions were monitored over time, and the rock anchors were removed at specified intervals and tested to tensile destruction. The decreasing ultimate strengths of anchors were assumed to be related to the corrosion rate. This relationship was used to study the corrosion rates of multiple rock anchor types in varying conditions. Results seemed to indicate higher temperatures caused the highest corrosion rates. Basic pH levels caused a less significant increase in corrosion. With respect to reduced visible surface corrosion, epoxy coatings were the most effective followed by the proprietary coating, and then the galvanized coating. All bolts, cable anchors, and friction bolts with no coating had significant visible corrosion relative to rock anchors with protective coatings. Cable bolts with no coating and friction bolts seemed to have had the largest decrease in strength, and this is hypothesized to be a result of having larger exposed surface areas than other rock anchor types. For electrochemical testing and analysis, potentiodynamic polarization tests were used to estimate the corrosion potential (Ecorr) and corrosion current (Icorr) of rock anchor metals in simulated mine environments. Ecorr can be used as an indication of the conditions necessary for the initiation of corrosion, and Icorr can be used to determine the rate of corrosion. The effects of pyritic sulfur from coal samples in solution, pH of solution, temperature, and the bolt grade on Ecorr and Icorr values were analyzed. No significant trends were observed between electrochemical properties and pyritic sulfur concentrations. pH, temperature, and bolt grade were also parameters that were analyzed, and of these, only temperature had a significant effect on electrochemical properties. The penetration rate increased significantly with respect to increasing temperatures. All corrosion rates in the simulated mine water were considered low according to the standard specifying corrosion rates and characteristics that was used. This research has shown mine corrosion parameters are consistent in localized areas. The results, however show additional parameters other than age and moisture must be accounted for in order to accurately predict the risk of corrosion in a given mine. Simulated mine testing results showed that corrosion prevention coatings are effective in reducing corrosion in the conditions tested. Electrochemical test showed corrosion rates were all low in the mine solutions tested. Temperature had the most significant effect on corrosion rates in both the simulated mine tests and electrochemical tests. The electrochemical tests also showed that increased temperature can only simulate increased corrosion periods up to the point that other reaction factors limit the reaction rate independent of temperature. To fully understand corrosion risks in ICB mines, additional parameters and experimental methods should be considered in order to increase the understanding of relationship between ICB mine parameters and corrosion.
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Song, Zhenhe. "Pullout behaviour of suction embedded plate anchors in clay." Thesis, Curtin University, 2008. http://hdl.handle.net/20.500.11937/2173.
Full textAbstract:
In recent years oil and gas mining has moved into increasingly deeper water in search of undeveloped fields. As water depths approach and exceed 3000 m conventional offshore foundation systems become inefficient and ineffective in stabilising platforms and floating production storage units. The trend of supporting structure design in deep water has been to install catenary and taut leg mooring systems. Consequently, many types of anchoring systems are being developed and used in order to withstand large mooring forces. The SEPLA (Suction Embedded Plate Anchor) is ideal for use in this situation. This project has employed advanced numerical techniques and centrifuge testing to study pullout behaviour of plate anchor foundations in different soil profiles and suction caisson installation effect with the aim of generating a robust framework for design. The behaviour of strip and circular plate anchors during vertical pullout in uniform and normally consolidated clays has been studied by means of small strain and large deformation finite element analyses. Both fully bonded (attached), and ‘vented’ (no suction on rear face), anchors have been considered. The current numerical results were compared with existing laboratory test data, finite element results and analytical solutions. This study showed that the ultimate pullout capacity factors (Nc) for deep embedment were 11.6 and 11.7 for smooth and rough strip anchors and 13.1 and 13.7 for smooth and rough circular anchors respectively. When the anchor base was vented, the soil stayed attached to the anchor base for deep embedment, and the pullout capacity was therefore the same as for the attached anchor. The separation depth ratio, Hs/B or Hs/D was found to increase linearly with the normalised strength ratio, su/γ'B or su/γ'D.Numerical simulation has been conducted to assess the bearing capacity for inclined pullout plate anchors. This bearing capacity analysis was performed by embedding the anchors in clay with different initial inclinations and different embedment ratios. Both the attached anchor base and vented base were evaluated. The results showed that the bearing capacities of the inclined plate anchors were associated with the inclination angles and base conditions. The separation depth of the plate anchors can be assessed by a simple equation from vertically pulled out plate anchors. Large deformation finite element analyses of plate anchor keying in clay has been performed. The effects of anchor thickness, anchor padeye eccentricity, anchor-soil interface roughness, soil shear strength, anchor submerged weight and soil disturbance have been studied with anchors in uniform or normally consolidated clays. The numerical results were compared with transparent soil test and existing centrifuge test data. The study showed that the RITSS method works well in simulating the anchor keying process. Anchor padeye eccentricity played an important role in anchor keying. A normalised anchor geometry ratio was used to estimate the loss in embedment during plate anchor’s keying. Both finite element analysis and centrifuge tests have been conducted to study the suction caisson installation effect. In finite element analysis, the soil disturbed zone varied from 3 times the caisson wall thickness to a full area inside a caisson.Centrifuge tests of suction embedded plate anchors were conducted in normally consolidated kaolin clay and transparent uniform soil. It can be concluded that the reduction in anchor capacity due to soil disturbance after suction caisson installation depends on re-consolidation time and soil sensitivity. The soil disturbance also reduced the loss of embedment during the anchor keying process.
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Song, Zhenhe. "Pullout behaviour of suction embedded plate anchors in clay." Curtin University of Technology, Dept. of Civil Engineering, 2008. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=18648.
Full textAbstract:
In recent years oil and gas mining has moved into increasingly deeper water in search of undeveloped fields. As water depths approach and exceed 3000 m conventional offshore foundation systems become inefficient and ineffective in stabilising platforms and floating production storage units. The trend of supporting structure design in deep water has been to install catenary and taut leg mooring systems. Consequently, many types of anchoring systems are being developed and used in order to withstand large mooring forces. The SEPLA (Suction Embedded Plate Anchor) is ideal for use in this situation. This project has employed advanced numerical techniques and centrifuge testing to study pullout behaviour of plate anchor foundations in different soil profiles and suction caisson installation effect with the aim of generating a robust framework for design. The behaviour of strip and circular plate anchors during vertical pullout in uniform and normally consolidated clays has been studied by means of small strain and large deformation finite element analyses. Both fully bonded (attached), and ‘vented’ (no suction on rear face), anchors have been considered. The current numerical results were compared with existing laboratory test data, finite element results and analytical solutions. This study showed that the ultimate pullout capacity factors (Nc) for deep embedment were 11.6 and 11.7 for smooth and rough strip anchors and 13.1 and 13.7 for smooth and rough circular anchors respectively. When the anchor base was vented, the soil stayed attached to the anchor base for deep embedment, and the pullout capacity was therefore the same as for the attached anchor. The separation depth ratio, Hs/B or Hs/D was found to increase linearly with the normalised strength ratio, su/γ'B or su/γ'D.Numerical simulation has been conducted to assess the bearing capacity for inclined pullout plate anchors. This bearing capacity analysis was performed by embedding the anchors in clay with different initial inclinations and different embedment ratios. Both the attached anchor base and vented base were evaluated. The results showed that the bearing capacities of the inclined plate anchors were associated with the inclination angles and base conditions. The separation depth of the plate anchors can be assessed by a simple equation from vertically pulled out plate anchors. Large deformation finite element analyses of plate anchor keying in clay has been performed. The effects of anchor thickness, anchor padeye eccentricity, anchor-soil interface roughness, soil shear strength, anchor submerged weight and soil disturbance have been studied with anchors in uniform or normally consolidated clays. The numerical results were compared with transparent soil test and existing centrifuge test data. The study showed that the RITSS method works well in simulating the anchor keying process. Anchor padeye eccentricity played an important role in anchor keying. A normalised anchor geometry ratio was used to estimate the loss in embedment during plate anchor’s keying. Both finite element analysis and centrifuge tests have been conducted to study the suction caisson installation effect. In finite element analysis, the soil disturbed zone varied from 3 times the caisson wall thickness to a full area inside a caisson.
Centrifuge tests of suction embedded plate anchors were conducted in normally consolidated kaolin clay and transparent uniform soil. It can be concluded that the reduction in anchor capacity due to soil disturbance after suction caisson installation depends on re-consolidation time and soil sensitivity. The soil disturbance also reduced the loss of embedment during the anchor keying process.
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McCredden, Mikayla. "Anchors away: The susceptibility and response to infection between native and co-introduced fishes to the alien anchor worm Lernaea cyprinacea." Thesis, McCredden, Mikayla (2016) Anchors away: The susceptibility and response to infection between native and co-introduced fishes to the alien anchor worm Lernaea cyprinacea. PhD thesis, Murdoch University, 2016. https://researchrepository.murdoch.edu.au/id/eprint/35123/.
Full textAbstract:
The introduction of alien fish species and their alien parasites pose one of the most important threats to freshwater fishes throughout the world. The south-west of Australia has a depauperate, although highly endemic freshwater fish fauna. Of the 200 native freshwater fish species in Australia 144 are exclusively confined to freshwater. In the extreme south-west there are only 11 native freshwater fish species and nine of these are endemic to the region. Six of the 11 freshwater fish species have restricted geographic ranges and four are listed as rare or likely to become extinct. In 2008, studies surveying the parasites of freshwater fishes in the South West Coast Drainage Division (SWCDD), reported the introduction of the alien parasite, Lernaea cyprinacea, into freshwater river systems in the region.
Lernaea cyprinacea, commonly known as anchor worm, is a parasitic copepod believed to have been brought in to Western Australia with the accidental release of its native host, Carassius auratus (goldfish). It is not native to Australia and, until recently, had only been reported in fish in eastern Australia. First reports of this parasite in the south-west identified it using morphological criteria from four native freshwater fishes: Galaxias occidentalis (western minnow), Nannoperca vittata (western pygmy perch), Bostockia porosa (nightfish) and Tandanus bostocki (freshwater cobbler).
The present study aimed to resolve the morphological uncertainty surrounding the taxonomy of the parasite using molecular techniques, specifically PCR and DNA sequencing, and to review the host range and geographic distribution of this invasive species within the south-west of Western Australia. A comparison of the infection success and pathogenicity of L. cyprinacea in a fish species, Nannoperca vittata (pygmy perch), that is endemic to the Southwestern Province Ichthyological, and that to the natural host, Carassius auratus (goldfish), is detailed.
Lernaea cyprinacea in south-western Australia had been morphologically identified in previous studies, but had not been identified using molecular tools. Parasite samples examined in this study typed as Lernaea cyprinacea at the 28S ribosomal RNA (rRNA) locus. Sequences were identified using Finch TV Version 1.4.0 (Geospiza Research Team 2004-2006) and checked for identity using the nucleotide database, Nucleotide BLAST (http://blast.ncbi.nlm.nih.gov).
The parasite appears to have increased its geographic range in the Southwestern Ichthyological Province; in 2008 it was reported in only one river (the Canning River), whereas in the present study it was found in another two rivers (the Murray River and Serpentine River). Lernaea cyprinacea was also found on two more host species, in addition to the four native hosts reported previously; Galaxias occidentalis (western minnow), Nannoperca vittata (western pigmy perch), Bostockia porosa (nightfish), Tandanus bostocki (freshwater cobbler), and now, Pseudogobius olorum (bluespot goby) and Leptatherina wallacei (western hardyhead). In the field, L. cyprinacea was more prevalent on native freshwater fish species than on the natural host C. auratus.
The difference in prevalence of L. cyprinacea on native fishes and C. auratus found in field studies may be due to differences in exposure to the parasite or to differences in susceptibility to infection. Laboratory experiments were used to compare the susceptibility to infection of native N. vittata and C. auratus. There was no difference found in the prevalence or intensity of infection on N. vittata or C. auratus, when they were exposed separately. In mixed communities however, a significantly greater proportion of N. vittata were infected compared to C. auratus (0.59 vs. 0.33), and the mean intensity of infection was also greater in N. vittata than in C. auratus (3.0 ± 0.3 vs. 2.2 ± 0.4).
Nannoperca vittata and C. auratus also exhibited significant differences in their behavioural reactions to infection, with putative defensive behaviours observed much more frequently in infected C. auratus than in infected N. vittata. Histologically, C. auratus had a greater pathological and inflammatory response to infection than N. vittata.
Due to the extensive and destructive effects of C. auratus on both native fishes and habitat, the control of C. auratus has become essential. Removal programs have been underway in Western Australia since 2005, however, we know very little about the effects of removal programs for C. auratus on the co-introduced parasite L. cyprinacea. In particular, it has been suggested that if goldfish are a less competent host species than native freshwater fish species, then removal may actually exacerbate the parasite problem by increasing prevalence of infection on native fishes.
This study provides no evidence that the removal of goldfish will exacerbate the problem of L. cyprinacea in river systems in south-western Australia. That being said, there is a need to expand this study to examine the comparative infectivity and pathogenicity of L. cyprinacea to other native fish species and, where possible, to monitor parasite infection rates in the field before and after goldfish control programs to ensure that there are no adverse effects from goldfish removal.
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Nilforoush, Rasoul. "Anchorage in Concrete Structures : Numerical and Experimental Evaluations of Load-Carrying Capacity of Cast-in-Place Headed Anchors and Post-Installed Adhesive Anchors." Doctoral thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-66333.
Full textAbstract:
Various anchorage systems including both cast-in-place and post-installed anchors have been developed for fastening both non-structural and structural components to concrete structures. The need for increased flexibility in the design of new structures and strengthening of existing concrete structures has led to increased use of various metallic anchors in practice. Although millions of fasteners are used each year in the construction industry around the world, knowledge of the fastening technology remains poor. In a sustainable society, buildings and structures must, from time to time, be adjusted to meet new demands. Loads on structures must, in general, be increased to comply with new demands, and the structural components and the structural connections must also be upgraded. From the structural connection point of view, the adequacy of the current fastenings for the intended increased load must be determined, and inadequate fastenings must either be replaced or upgraded. The current design models are generally believed to be conservative, although the extent of this behavior is not very clear. To address these issues, the current models must be refined to allow the design of new fastenings and also the assessment of current anchorage systems in practice. The research presented in this thesis consists of numerical and experimental studies of the load-carrying capacity of anchors in concrete structures. Two different types of anchors were studied: (I) cast-in-place headed anchors, and (II) post-installed adhesive anchors. This research focused particularly on the tensile load-carrying capacity of cast-in-place headed anchors and also on the sustained tension loading performance of post-installed adhesive anchors. The overall objective of this research was to provide knowledge for the development of improved methods of designing new fastening systems and assessing the current anchorage systems in practice. For the cast-in-place headed anchors (I), the influence of various parameters including the size of anchor head, thickness of concrete member, amount of orthogonal surface reinforcement, presence of concrete cracks, concrete compressive strength, and addition of steel fibers to concrete were studied. Among these parameters, the influence of the anchor head size, member thickness, surface reinforcement, and cracked concrete was initially evaluated via numerical analysis of headed anchors at various embedment depths. Although these parameters have considerable influence on the anchorage capacity and performance, this influence is not explicitly considered by the current design models. The numerical results showed that the tensile breakout capacity of headed anchors increases with increasing member thickness and/or increasing size of the anchor head or the use of orthogonal surface reinforcement. However, their capacity decreased considerably in cracked concrete. Based on the numerical results, the current theoretical model for the tensile breakout capacity of headed anchors was extended by incorporating several modification factors that take the influence of the investigated parameters into account. In addition, a supplementary experimental study was performed to verify the numerically obtained findings and the proposed refined model. The experimental results corresponded closely to the numerical results, both in terms of failure load and failure pattern, thereby confirming the validity of the proposed model. The validity of the model was further confirmed through experimental results reported in the literature. Additional experiments were performed to determine the influence of the concrete compressive strength and the addition of steel fiber to concrete on the anchorage capacity and performance. These experiments showed that the anchorage capacity and stiffness increase considerably with increasing concrete compressive strength, but the ductility of the anchor decreases. However, the anchorage capacity and ductility increased significantly with the addition of steel fibers to the concrete mixture. The test results also revealed that the tensile breakout capacity of headed anchors in steel fiber-reinforced concrete is significantly underestimated by the current design model. The long-term performance and creep behavior of the post-installed headed anchors (II) was evaluated from the results of long-time tests on adhesive anchors under sustained loads. In this experimental study, adhesive anchors of various sizes were subjected to various sustained load levels for up to 28 years. The anchors were also exposed to several in-service conditions including indoor temperature, variations in the outdoor temperature and humidity, wetness (i.e., water on the surface of concrete), and the presence of salt (setting accelerant) additives in the concrete. Among the tested in-service conditions, variations in the outdoor temperature and humidity had the most adverse effect on the long-term sustained loading performance of the anchors. Based on the test results, recommendations were proposed for maximum sustained load levels under various conditions. The anchors tested under indoor conditions could carry sustained loads of up to 47% of their mean ultimate short-term capacities. However, compared with these anchors, the anchors tested under outdoor conditions exhibited larger creep deformation and failure occurred at sustained loads higher than 23% of their mean ultimate short-term capacities. Salt additives in concrete and wet conditions had negligible influence on the long-term performance of the anchors, although the wet condition resulted in progressive corrosion of the steel. Based on the experimental results, the suitability of the current testing and approval provisions for qualifying adhesive anchors subjected to long-term sustained tensile loads was evaluated. The evaluations revealed that the current approval provisions are not necessarily reliable for qualifying adhesive anchors for long-term sustained loading applications. Recommendations were given for modifying the current provisions to ensure safe long-term performance of adhesive anchors under sustained loads.
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Votruba, Gregory Francis. "Iron anchors and mooring in the ancient Mediterranean (until ca. 1500 CE)." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:71d97932-c014-4e94-8305-add589758fd0.
Full textAbstract:
This dissertation examines ancient anchoring practice in the Mediterranean through ca. 1500 CE, as well as the history and technological developments of iron anchors, which are among the most important tools inherited from the ancient world. The methodology employed is holistic in synthesizing archaeological finds, textual, and iconographic evidence, and includes statistical and geographical analysis based on a substantial catalogue of ancient anchor finds. An experimental project is also included where anchor reconstructions were used in the sea and their utility tested. Mooring is one of the least studied aspects of everyday life for the people of the ancient Mediterranean. It has been elucidated that in most circumstances beaching would not have been a practical option, even for warships and the smallest cargo vessels. Rather, vessels were equipped with specialized gear for mooring off or near undeveloped shores. This included ship's boats enabling access to the shore. Lower draft vessels, particularly galleys, could approach unbuilt shores and employ mooring stakes and cables, and the ship's landing-ladder would be deployed into shallow water. Where available, however, ships would benefit from built quays which facilitated goods transport. The iron stock-anchor displays the greatest longevity of any anchoring tool, evinced as early as the 5th c. BCE, and appears to have achieved dominance over wooden types by the 3rd c. CE. From its conception the iron-stock anchor undergoes a broad range of gradual changes to its form and features. The earliest known finds take a 'V' form in the bulk-arms and gradually develop through rounded to 'T' and 'Y' forms in the Byzantine Period. The stocks evolve from removable iron types, to permanent forms entirely of wood. Reintroduction of upward-oriented arm designs from northern Europe around the 13th c. CE, and incorporation of hydraulic mechanized smithing developments, heralded a revolution of anchoring technology. Larger, stronger and more efficient anchors were being produced to standardized dimensions and quality, promoting larger ships, and ultimately resulting in novel characteristics of navigation.
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Hellrung, II James Lee. "Labels for Anchors: The Good, the Bad, and the Endpoints." TopSCHOLAR®, 2010. http://digitalcommons.wku.edu/theses/156.
Full textAbstract:
This study was designed to determine if any differences in internal consistency existed between different designs of scale anchors. The three different designs explored were properly designed scales, improperly designed scales, and endpoint only scales. Two-Hundred and thirty-five participants rated the frequency of which they performed various computer activities on a survey using one of the three different designs. Contrary to expectations, internal consistency did not differ across the three designs.
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Zhang, Huawen, and 张华文. "Influence of FRP anchors on FRP-to-concrete bonder interfaces." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hub.hku.hk/bib/B49799551.
Full textAbstract:
Existing reinforced concrete (RC) structural members such as beams, columns and joints can be strengthened and repaired with externally bonded high-strength and light-weight fibre-reinforced polymer (FRP) composites. The effectiveness of such strengthening can, however, be limited by premature debonding of the FRP at strains well below the strain capacity of the FRP. Such failures are also generally sudden and give rise to brittle member behavour. It is therefore important to prevent or even delay debonding failure in order for the FRP strengthening to be more effectively and efficiently used. Anchorage of the FRP strengthening is a logical solution and to date several different types of anchorage systems have been developed and tested. Anchors made from FRP, which are herein referred to as FRP anchors, are singled out for deeper inspection in this doctoral program of research. FRP anchors are an attractive form of anchorage as they are non-corrosive, relatively easily made by hand, and can be used in a variety of shaped RC elements ranging from beams to walls. There have been limited systematic studies though conducted on anchorage devices including FRP anchors. This knowledge gap forms the scope of the program of doctoral research reported herein.
This dissertation is concerned with investigating the ability of FRP anchors to anchor externally bonded FRP in flexural strengthening applications. This is done by investigating the influence of FRP anchors on FRP-to-concrete bonded interfaces. Following a review of relevant literature, tests on FRP-to-concrete joints anchored with FRP anchors are reported as well as tests on FRP-strengthened RC slabs anchored with FRP anchors. The joint tests are used to investigate and understand the influence of key geometric and material properties such as, but not limited to, anchor type and position as well as plate length. The optimal arrangement of FRP anchors enabled significant increases in FRP plate strain utilisation to be achieved in the joints. Two modelling approaches based on regression analysis as well as partial interaction modelling are developed for the modelling of the joint tests. In the latter method of analysis, the complete debonding process is able to be simulated. The test and modelling results of the joint specimens are then used to design anchorage schemes for application to RC slabs strengthened in flexure with externally bonded FRP plates. The slab test results show the importance of strategic FRP anchor installation for enhancing the strength, ductility and deformability of FRP-strengthened RC slabs. Future research needs are finally presented in light of the outcomes of the experimental and analytical components of the research reported herein.published_or_final_version
Civil Engineering
Doctoral
Doctor of Philosophy
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Hesar, Majid Alizadeh. "Behaviour of pile-anchors subjected to monotonic and cyclic loading." Thesis, University of Sunderland, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303764.
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Alameer, Alameer Marai. "Performance and Design of Retention Anchors in Blast Resistant Windows." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/41528.
Full textAbstract:
Windows in building façade are vulnerable to blast pressures. When subjected to blast shock waves, glass windows may suffer failures, potentially causing serious injuries and casualties to the building occupants due to the flying glass shards and other projectiles. Protective films and laminated glass are widely used to protect windows against blast loads. These techniques have proven to reduce or prevent hazards associated with glass breakage. The use of steel or strengthened aluminum frames also reduce window blast hazards associated with frame failures. However, such measures are not always sufficient to mitigate the blast hazard if window retention anchors do not have sufficient resistance to blast pressures. Research on blast resistant windows is scarce in the literature. Therefore, a comprehensive research project was undertaken to address the behaviour, analysis, and design of window retention anchors. The research program consisted of combined experimental and analytical components. Three main phases were pursued, comprising of: i) Experimental research using a shock tube as blast simulator, ii) Numerical investigation based on three-dimensional finite element method (FEM) of analysis, and iii) Non-linear dynamic analysis of window systems based on a single-degree-of-freedom (SDOF) simplification.
The experimental phase consisted of tests of 23 punched windows mounted on four different types of substrates consisting of structural steel, reinforced concrete, concrete block masonry, and stone masonry. The experimental parameters included window size and aspect ratio, glazing type, protective film thickness, substrate type, as well as the number and pattern of window retention anchors. Two levels of blast pressure-impulse combinations were used as per the recommendations of the U.S General Services Administration (GSA).The numerical phase involved FEM modelling and analysis of selected test windows. The FEM models were first validated against test results. The validated models were then employed to conduct an analytical parametric study. The parameters in this phase consisted of; substrate type, window frame rigidity, anchor fixity level in the substrate, window aspect ratio and size, anchor spacing, and blast pressure-impulse combination. The results demonstrated the significance of design parameters on window response, while also defining anchor force distribution along the window frame.
A simplified SDOF method of analysis was developed for window systems, including the effects of anchor flexibility and substrate rigidity on non-linear response. The analysis approach includes the construction of window resistance functions in pre-break and post-break phases of response, where the latter stage of response is dominated by the membrane action of protective film. The analysis leads to the computation of anchor design forces, which have been validated against anchor shear and axial tension forces recorded experimentally. The SDOF analysis is recommended for use in designing blast-resistant window retention anchors on different substrates.
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Mollahasani, Ali <1981>. "Application of Submerged Grouted Anchors in Sheet Pile Quay Walls." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6633/1/PhD_Thesis.pdf.
Full textAbstract:
Sheet pile walls are one of the oldest earth retention systems utilized in civil engineering projects. They are used for various purposes; such as excavation support system, cofferdams, cut-off walls under dams, slope stabilization, waterfront structures, and flood walls. Sheet pile walls are one of the most common types of quay walls used in port construction. The worldwide increases in utilization of large ships for transportation have created an urgent need of deepening the seabed within port areas and consequently the rehabilitation of its wharfs. Several methods can be used to increase the load-carrying capacity of sheet-piling walls. The use of additional anchored tie rods grouted into the backfill soil and arranged along the exposed wall height is one of the most practical and appropriate solutions adopted for stabilization and rehabilitation of the existing quay wall. The Ravenna Port Authority initiated a project to deepen the harbor bottom at selected wharves. An extensive parametric study through the finite element program, PLAXIS 2D, version 2012 was carried out to investigate the enhancement of using submerged grouted anchors technique on the load response of sheet-piling quay wall. The influence of grout-ties area, length of grouted body, anchor inclination and anchor location were considered and evaluated due to the effect of different system parameters. Also a comparative study was conducted by Plaxis 2D and 3D program to investigate the behavior of these sheet pile quay walls in terms of horizontal displacements induced along the sheet pile wall and ground surface settlements as well as the anchor force and calculated factor of safety. Finally, a comprehensive study was carried out by using different constitutive models to simulate the mechanical behavior of the soil to investigate the effect of these two models (Mohr-Coulomb and Hardening Soil) on the behavior of these sheet pile quay walls.
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Mollahasani, Ali <1981>. "Application of Submerged Grouted Anchors in Sheet Pile Quay Walls." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6633/.
Full textAbstract:
Sheet pile walls are one of the oldest earth retention systems utilized in civil engineering projects. They are used for various purposes; such as excavation support system, cofferdams, cut-off walls under dams, slope stabilization, waterfront structures, and flood walls. Sheet pile walls are one of the most common types of quay walls used in port construction. The worldwide increases in utilization of large ships for transportation have created an urgent need of deepening the seabed within port areas and consequently the rehabilitation of its wharfs. Several methods can be used to increase the load-carrying capacity of sheet-piling walls. The use of additional anchored tie rods grouted into the backfill soil and arranged along the exposed wall height is one of the most practical and appropriate solutions adopted for stabilization and rehabilitation of the existing quay wall. The Ravenna Port Authority initiated a project to deepen the harbor bottom at selected wharves. An extensive parametric study through the finite element program, PLAXIS 2D, version 2012 was carried out to investigate the enhancement of using submerged grouted anchors technique on the load response of sheet-piling quay wall. The influence of grout-ties area, length of grouted body, anchor inclination and anchor location were considered and evaluated due to the effect of different system parameters. Also a comparative study was conducted by Plaxis 2D and 3D program to investigate the behavior of these sheet pile quay walls in terms of horizontal displacements induced along the sheet pile wall and ground surface settlements as well as the anchor force and calculated factor of safety. Finally, a comprehensive study was carried out by using different constitutive models to simulate the mechanical behavior of the soil to investigate the effect of these two models (Mohr-Coulomb and Hardening Soil) on the behavior of these sheet pile quay walls.
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Hsiao, Hsiang-Ju, and 蕭湘如. "Effects of Number of Anchors and Anchor-Consistency on Judgment." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/12534590936109657279.
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碩士中原大學
心理學系
87
Studies have found that if an individual receives a number before a numerical judgment is made, his judgment would be influenced by the value of that number. Tversky and Kahneman (1974) named such phenomenon as “anchoring effects.” In previous anchoring studies, the researchers usually presented an anchor (i.e., a number) to the subject. The purpose of the present study is multiple-folded: (1) Whether anchoring effects are identical between single-anchor and multiple-anchor conditions? (2) How does anchor-consistency influence anchoring effects? (3) If anchor-consistency can affect anchoring effect, individual’s confidence in anchors is proposed as a mediated variable. The experiment was a 2 (anchor level: high/low) x 2 (consistency: high/low) between-subjects design (in the multiple-anchor condition), plus 2 single-anchor conditions (anchor level: high/low). The major dependent variables were the subject’s estimated value and confidence in his estimation. The results suggest that anchoring effects appear in both single- and multiple-anchor conditions. However, the anchoring effect is stronger in the multiple- than in the single-anchor condition. With multiple anchors, the anchoring effect is stronger in the high-consistent condition than in the low-consistent condition. It is interesting to find that only the number of anchors can influence the subject’s estimation-confidence. The hypothesis that anchor-confidence is the mediated variable between anchor-consistency and adjustment was not supported.
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Lin, I.-Feng, and 林一峰. "Vertically Pulled Out Behavior of Single Anchor and Dual Anchors in Gravel Formation." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/10992555996462557092.
Full textAbstract:
碩士朝陽科技大學
營建工程系碩士班
99
To evaluate the uplift behavior of single anchor and dual anchors installed in gravel formation, a series of triaxial test results were utilized to obtain the parameters of a continuous strain hardening-softening and volume dilation model named “SHASOVOD”. In conjunction with FLAC3D, a numerical study was carried out to analyze the behavior of vertically pulled out behavior of single anchor and anchor groups in gravel formation. A field test program was conducted in gravel within excavating site to verify the applicability of the numerical program. Finally, parametric studies on the factors affecting the anchorage behavior were executed. The numerical results indicate that, when overburden depth, fixed length and excavating depth which is the location of anchor head increase, the anchorage capacity also increases. Based on the development of end resistance coefficient Nq, it can be defined as a shallow anchor as overburden-diameter ratio Z/D<8.7, Z/D=8.7~17.4 of an anchor is classified to a transited anchor, Z/D>17.4 is belong to a deep anchor. The coefficient of friction K decreases with increases in both fixed length and overburden depth of an anchor in gravel formation, but increases a little bit with an increase in excavating depth. The load transfers from the top to the bottom within the anchor body; a rectangular shaped distribution of friction stress along fixed end can be found except the top and bottom of fixed end. As the horizontal spacing of a dual anchors Sh=13D, the efficiency of dual anchors is more than 90%, and the behavior of dual anchors behave like two separate anchors. Keyword: Gravel formation, End resistance coefficient, Coefficient of friction and Dual anchor
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Ou, Tai-Chuan, and 歐大銓. "Anchorage Behavior of Horizontal Underreamed Anchors and Vertical Underreamed Anchors in Sand." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/58429869751178539574.
Full textAbstract:
碩士朝陽科技大學
營建工程系碩士班
90
ABSTRACT A sand model “SHSE” and a 3D numerical software “FLAC3D” have been performed to study the anchorage behavior of horizontal and vertical underreamed anchors in sand. It was found, the anchorage capacity of horizontal anchor increases with overburden depth ratio H/D, but the influence comes from free length ratio Z/D was not evident. Although the total load, shaft friction and end bearing do not reach peak values at same anchor displacement, the total load of deep anchor reaches it peak value at same displacement almost. The peak value of end bearing of deep anchor was not found, 50%D of anchor displacement can be seen when end bearing reaches yielding value. The end resistance dominates the pullout force of anchors except a shallow anchor with Z/D=2.5 and H/D=2.5. There exists a critical depth Hcr equal to 8 which differentiates the end resistance of a shallow anchor from that a anchor with deep overburden. It can been seen from results of numerical analysis, the anchorage capacity of a horizontal anchor greater than a vertical anchor due to the effect of boundary constriction and normal stress acting on fixed length. Two translated parameters F* for shaft friction and Q* for end resistance were found between the horizontal anchor from the vertical anchor. The load transfer curve increases with pullout load proportional which is concave upward transfer from bottom to top of a shallow anchor and concave downward of a deep anchor. A uniform frictional stress distribution alone fixed end was found from the shallow anchor, but frictional stress distribution along fixed end is trapezoidal for deep anchor due to stress concentrates on the top of fixed anchor end.
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Tien, Yi-Cheng, and 田義正. "A Comparative Analysis of Tension and Seismic Tests of Chemical Adhesive Anchors and Mechanical Anchors." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/54213015196531151610.
Full textAbstract:
碩士國立屏東科技大學
土木工程系所
100
This study investigates the behaviors of chemical adhesive anchors and mechanical anchors under tension and seismic forces. The experimental parameters mainly include the concrete strength 20.6 MPa. The experimental results show in a dry environment, we implanted the M12 chemical adhesive anchors into the concrete, the maximum tension average is 47.63 KN. In the tests on effects of damp environment, the maximum tension average is 41.584 KN, which is 86% of the dry state. Subject the anchors to the sinusoidal-tension loads with 0.1Hz. The experimental results show in the simulated seismic tension tests, the results show the displacement of chemical adhesive anchors has also followed to a linear increase or decrease with the tension changes. The displacement and tension of 1/2” mechanical anchors is non-linear and displacement failure apparent. The study finds the tension in chemical adhesive anchors is stronger than in mechanical anchors. According to the results, we must consider chemical adhesive anchors impairment in the damp environment, and strengthen mechanical anchors anchorage system to increase its shock resistance.
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Lin, Hung-tsung, and 林宏聰. ""News Anchor or News Trumpery? ": A Study on the Competencies of TV News Anchors in Taiwan." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/52076586410858831303.
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Liao, Ming-Yeh, and 廖明曄. "The Mechanical Behavior of Expansion Anchors." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/88913321953186232061.
Full textAbstract:
碩士國立交通大學
土木工程學研究所
86
The expansion anchor has been used widely to affix the building envelope or annexed structure on concrete because they are easy to install. This study is to test the pullout and shear capacity of the expansion anchor which is generally used in our country. The results were compared with design codes of ACI-349 and Japan Architecture Society. The results show that when the expansion anchor fails due to pullout force, the failure model is concrete cone failure. The angle between the failure surface and horizontal surface is about 30-45 degree. The sleeve expansion anchor has better ductile behavior than the drilled-in expansion anchor when subjected to pullout force. Calculated value from design code is smaller than test data. Inadequate distance between anchors and distance to edge could decrease pullout strength of the expansion anchor. For the latter case, the failure model may become edge failure. When the expansion anchor subjected to shear force, the failure model is steel failure. Shear strength depends on the strength of steel material and test qualifications, it has little relation to concrete.
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Oliveira, Leandro Collares de. "SoundAnchoring: Personalizing music spaces with anchors." Thesis, 2013. http://hdl.handle.net/1828/4585.
Full textAbstract:
Several content-based interfaces for music collection exploration rely on Self-Organizing Maps (SOMs) to produce 2D or 3D visualizations of music spaces. In these visualizations, perceptually similar songs are clustered together. The positions of clusters containing similar songs, however, cannot be determined in advance due to particularities of the traditional SOM algorithm. In this thesis, I propose a variation on the traditional algorithm named anchoredSOM. This variation avoids changes in the positions of the aforementioned clusters. Moreover, anchoredSOM allows users to personalize the music space by choosing the locations of clusters containing per- ceptually similar tracks. This thesis introduces SoundAnchoring, an interface for music collection exploration featuring anchoredSOM. SoundAnchoring is evaluated by means of a user study. Results show that SoundAnchoring offers engaging ways to explore music collections and build playlists.Graduate
0984
0413
leandro.collares@gmail.com
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Tsai, Ying-Jie, and 蔡英傑. "Anchors in Concrete Elements Engineering Properties." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/28845405444104506408.
Full textAbstract:
碩士國立屏東科技大學
土木工程系所
101
Post-installed anchors include chemical adhesive anchors and mechanical anchors. The post-installed anchor is relatively easier than pre-installed anchor due to on-site construction requirement during installation. M12 chemical anchor, one a half inch mechanical expansion anchor bolt (drop-in anchor), and M12 mechanical screw-in Anchor (Concrete screws) were used in the study. ASTM E488-96, ASTM E1512-01, ICC AC58, ICC AC308 are the reference standards. A comparison tensile test was conducted in dry and wet conditions for the chemical anchor. Tensile test using expired chemical grout was also performed to evaluate the aging behavior of the chemical bonding agent. The tensile strength for the chemical anchor in wet condition was about 15.4% lower than the dry condition. The tensile strength for those anchors installed using expired bonding agent showed no influence. Sliding failure occurred at the interface between anchor and concrete at near 63% of its ultimate tensile strength for the test expansion anchors. The diameter of the concrete failure cones for the screw-in anchor were extended around 4 times of its installation depth which is wider than the data showed in ASTM standard. The shear strength for chemical anchor, expansion anchor bolt, and screw-in anchor was controlled by the shear strength of steel bars. Minor concrete compression failure was also observed near the edge of steel bar during the shear test of screw-in anchor. No torsion failure was observed at 200 N-m torque force for the chemical anchor and screw-in anchor. However, the average torque strength was 78 N-m for the expansion anchor. According to the ICC AC308 standard, 55% UTS tensile force was used for the creep test for the chemical anchor. No creep failure and linear creep strain curve in semi-log scale were observed for the creep tests.
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Su, Ding-fang, and 蘇定方. "Study of Load Transfer Behavior of the Horizontal Modelled Anchors Anchors in Dense Sand under Different Pull Paths." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/89787068949094703823.
Full textAbstract:
碩士國立臺灣科技大學
營建工程技術學系
81
@ 為了解摩擦型水平地錨錨碇段在不同受力型式作用下之荷重傳遞行 為,本研究乃以直徑37mm，長度170cm之鋁製模型地錨，埋置於霣降而成之 緊密砂土中進行試驗，由錨碇段上粘貼應變計所量測的試驗結果，探討拉 力式、壓力式及複合式三種受力型式模型地錨，在不同覆土深度作用下荷 重傳遞。研究結果顯示水平地錨之深淺層臨界深度可定為5∼7.5倍地錨直 徑；三種受力型式所得到之極限拉拔力相差不多，且於深層時極限拉拔力 增量不隨埋置深度增加而呈直線型增加。在相同拉拔力作用下複合式模型 地錨錨碇段剖面所承受最大荷重約為拉力式或壓力式之二分之一；荷重傳 遞行為受地錨錨碇段彈性模數與地盤彈性模數比值(E/E)所影響；錨身與 砂土間之土壓力係數K值於淺層時為上昇之趨勢，過了臨界深度後,則K值 變成下降的趨勢。 In order to study the load transfer the bond lengh, three type anchors under horizntal tensile force. Three modelled anchors were made by aluminous and were buried by rain-drop method in the dense sand. The anchor specimen shape is tube(170cm×∮37 mm). This test attempt is to investigate load transfer behavior at various overburden depth in dense sand by tensile, compressible and comound anchor respectively. The force of anchor was obtained by measuring strain of eight strain gages which were bonded on the surface of aluminous anchor. It has been found that the depth range within Z=5∼7.5D is a critical range to determine the depth coefficient for both shallow and anchors. The ultimate loads of three medelled anchors were found were approximate to be equal. The unltimate load nonlineary increases with buried depth. In order to investigate the load transfer, the eight corresponding forces of eight strain gages were calculated. It is found that the maximum force of compound anchor is about 50% of the other two type anchors under the same overburden pressure. The load transfer is effected by the elastic module ratio between anchor and ground, Ea/Eg. The earth pressure coefficient, k, on the anchor shaft increases with buried depth shallow anchor, and K decreases for deep anchro if the depth is deeper than critical range.