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Whitcomb, Richard W. "Quantitative ultrasonic evaluation of concrete." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/19004.
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Blum, Frank. "A focused, two dimensional, air-coupled ultrasonic array for non-contact generation." Thesis, Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04072004-180005/unrestricted/blum%5Ffrank%5F200312%5Fms.pdf.
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Mong, Seng Ming. "Non-destructive evaluation with ultrasonic pulse velocity (UPV) in concrete structure." access abstract and table of contents access full-text, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21175032a.pdf.
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Thesis (M.Sc.)--City University of Hong Kong, 2005.At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Sept. 4, 2006) Includes bibliographical references.
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Lau, Connie K. Y. "Non-destructive evaluation with ultrasonic pulse velocity (UPV) in concrete structure." access abstract and table of contents access full-text, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21174441a.pdf.
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Thesis (M.Sc.)--City University of Hong Kong, 2005.At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Sept. 1, 2006) Includes bibliographical references.
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In, Chi-Won. "Defect characterization in heterogeneous civil materials using ultrasound." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47545.
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Asphalt and Portland cement concrete constitutes a significant portion of the total infrastructure all over the world. It has been reported that much of this concrete infrastructure is now approaching or has already passed its original design life. Thus it is critical to be able to quantitatively assess the condition of these concrete components. In order to rehabilitate or repair the civil infrastructure, nondestructive evaluation (NDE) techniques have been of great interest for infrastructure management agencies. However concrete components present several specific NDE challenges that must be addressed. . Concrete naturally exhibits large scale heterogeneous microstructure with a great deal of local material property variability, For this reasons, many conventional NDE techniques that work well for steel and other homogeneous materials cannot be applied to concrete; concrete is unable to transmit high frequencies, as the heterogeneity of the concrete causes signals of smaller wavelengths or wavelengths equal to the nominal aggregate size to be scattered and severely attenuated. Nevertheless, progress has been made towards accurate and reliable in-place NDE of concrete structures and materials, for example impact echo, ultrasonic pulse velocity method, and the ultrasonic wave transmission method. However, the detection of smaller sized defects or remote defects that are located away from the testing location still pose problems. In addition, the large size and potential limited access conditions of civil structures raise additional challenges. To overcome the limitations of current NDE techniques for concrete, this research considers two different types of ultrasonic waves (coherent and incoherent wave) to quantitatively characterize and monitor defects in heterogeneous concrete materials. The global objective of this research is to determine the feasibility and applicability of using these ultrasonic waves as a global, rapid, reliable, and non-biased technique for the routine screening of defects or monitoring of concrete structures and materials. Three different problems are considered: 1) characterization of segregation in asphaltic concrete, 2) crack depth determination in pier cap of concrete bridge structure, and 3) monitoring of self-healing process in cement-based concrete.
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Chan, Denny Yuk. "Structural integrity assessment of cantilevered type concrete structures by instrumented impact hammer (IIH) technique & ultrasonic pulse velocity (UPV) technique." access abstract and table of contents access full-text, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21174088a.pdf.
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Thesis (M.Sc.)--City University of Hong Kong, 2005.At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Aug. 31, 2006) Includes bibliographical references.
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Schempp, Fabian. "Fully non-contact, air-coupled generation and detection of ultrasound in concrete for nondestructive testing." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50396.
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It is well known that liquid coupling agents, which are commonly used in conventional ultrasonic testing to couple an ultrasonic transducer to a solid specimen, cause a number of problems including inconsistency in results and slowness of the inspection. This is especially true when the specimen surface is rough, such as those in field concrete structures; here the solution involves time-consuming surface preparation to polish every single point of inspection, making it impractical to inspect field structures with conventional, contact methods. To address this issue, this thesis proposes a new, fully non-contact, air-coupled measurement setup in the mid to high ultrasonic frequencies (50-150 kHz). This advanced setup and measurement technique is evaluated by calculating the signal to noise ratio for different numbers of signal averages. In addition, the effect of the lift-off distance of the transducer over the sample is also investigated. Ultrasonic waves are generated and detected in this frequency range with a sufficiently high signal to noise ratio (SNR), which enables performing a fast scan with a small number of signal averages. Using this setup, phase velocity and attenuation of Rayleigh surface waves in a concrete specimen are first measured. Then, the air coupled ultrasound technique is used to detect dicontinuities such as cracks at a concrete joint and reinforcement bars in a concrete block. Also, the capability of the proposed technique for measuring depths of surface-breaking cracks using air-coupled generated Rayleigh waves is demonstrated. Since this measurement setup directly generates Rayleigh waves, most of the disadvantages in the techniques based on the impact-echo method can be avoided and thus data processing is much simpler than that in the impact-echo based techniques. The results of the measurements show that this setup is highly promising and a big advancement towards the rapid ultrasonic nondestructive testing on large-scale field concrete structures.
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Arne, Kevin C. "Crack depth measurement in reinforced concrete using ultrasonic techniques." Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51914.
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Concrete is the most widely used construction material in the world, so the assessment of damage in concrete is critical from the point of view of both safety and cost. Of particular interest are macro cracks that extend through the concrete cover of the reinforcement, which can potentially expose the reinforcement to corrosive elements. The high density of scatterers such as aggregate and voids in concrete makes quantitative imaging with coherent ultrasound difficult. As an alternative, this research focuses on diffuse energy based ultrasonic methods rather than coherent ultrasonic methods for crack depth assessment. Two types of ultrasonic measurements were made on real cracks formed under four point bending: one that focuses on time of flight measurements from an impactor; while the other uses the arrival time of maximum energy in a diffuse field excited by an impulsive load from a transducer. Each of these ultrasonic techniques is used to interrogate a macro crack in a concrete beam, and the results are compared to determine their accuracy and robustness. The actual crack depth is determined using direct surface measurements and a destructive dye-injected approach with drilled cores. The results suggest that the diffusion method, using a maximum energy approach, more accurately estimates the crack than visual inspection and impact echo methods, which overestimate the depth.
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Punurai, Wonsiri. "Cement-based materials' characterization using ultrasonic attenuation." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-04042006-171125/.
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Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2006.Dr. Jennifer Michaels, Committee Member ; Dr. Jacek Jarzynski, Committee Member ; Dr. Jianmin Qu, Committee Member ; Dr. Laurence J. Jacobs, Committee Chair ; Dr. Kimberly E. Kurtis, Committee Co-Chair.
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Deroo, Frederik. "Damage detection in concrete using diffuse ultrasound measurements and an effective medium theory for wave propagation in multi-phase materials." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31801.
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Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2010.Committee Chair: Laurence J. Jacobs; Committee Member: Jianmin Qu; Committee Member: Jin-Yeon Kim. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Chitti, Abhishek. "ASSESS MATERIAL PROPERTIES OF CONCRETE USING COMBINED NDT METHODS." OpenSIUC, 2019. https://opensiuc.lib.siu.edu/theses/2490.
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The aim of this research is to assess the material properties of concrete like modulus of elasticity, compressive strength, and Poisson’s ratio using various nondestructive Testing (NDT) methods like Ultrasonic Pulse Velocity (UPV) and Rebound Hammer (RH). Assessment of material properties of concrete is very important as they are used for structural design process. Various NDT methods are applied to ensure the quality of concrete specimens but they can also be used to find material properties. UPV is a NDT method which is used to test the internal condition of the concrete specimen. RH is a surface hardness testing method and can be used to test the homogeneity of the specimen. For this study, several batches of concrete samples with three different design strengths of 6000 psi, 8000 psi, and 12000 psi were casted. Modulus of elasticity and Poisson’s ratio were calculated from UPV P-wave and S-wave velocities. A Nomogram was developed by combining the longitudinal ultrasonic pulse velocities, rebound numbers, and compressive strengths measured from UPV, RH, and compressive strength tests respectively. This combined NDT correlation curve (Nomogram) can be used to estimate compressive strength of concrete if UPV and rebound values are known. The accuracy of these NDT methods were determined by comparing estimated strength to the actual strength. Furthermore, the effect of moisture content on UPV and rebound values was reviewed and also studied dynamic modulus of elasticity and its relation with static modulus of elasticity of the concrete was investigated for better understanding.
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Salles, Lucio Salles de. "Short continuously reinforced concrete pavement design recommendations based on non-destructive ultrasonic data and stress simulation." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3138/tde-20102017-082704/.
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Four sections of continuously reinforced concrete pavement (CRCP) were constructed at the University of São Paulo campus in order to introduce this kind of pavement structure to Brazil\'s technical transportation community. Sections were designed as 50 m long concrete slab, short in comparison to traditional CRCP, in order to simulate bus stops and terminals - locations of critical interest for public infrastructure. The thesis presented herein concludes this research project initiated in 2010. As the initial goal of this study was the development of coherent, reliable and intuitive design recommendations for the use of CRCP technology in Brazil, a profound understating of its structural and performance peculiarities was needed. For that, the cracking process of the experimental CRCP sections was recorded over a span of seven years. Due to the sections\' short length and lack of anchorage, the experimental \"short\" CRCP presented a cracking behavior quite different than traditional CRCP. There were much less visible cracks than expected. To address this issue, a novel technology in ultrasonic non-destructive testing of concrete structures was applied. Through ultrasonic signal interpretation it was possible to discover several incipient non-visible cracks within the slabs - many of these became apparent on the slab surface in later crack surveys - and to characterize visible and non-visible cracks regarding crack depth. The updated crack map with non-visible cracks showed similarities with traditional CRCP. Additionally, the ultrasonic data analysis provided important information on thickness variation, reinforcement location and concrete condition that were applied in theoretical simulations (finite element software) of the short CRCP. Simulations were attempted considering different slab geometries, firstly with transverse cracks as joints with high load transfer efficiency (LTE) and secondly with a continuous slab without cracks or joints. The latter simulation was more accurate reaching a shift factor between field and simulated stresses in the order of 0.7 to 1.0. Deflection data and LTE analysis from cracks and panels in between cracks further attested the slab continuous behavior, which contradicts current CRCP design models and performance predictors. Furthermore, critical traffic and environmental loading conditions concerning Brazil\'s climate and bus traffic characteristics were investigated and related using a selected fatigue model resulting in design recommendations in a chart format for the short CRCP aimed at long-term projects for over 20 years of operation. The design chart was successfully applied to investigate three failures presented by the experimental short CRCP due to thickness deficiencies pointed out by the ultrasonic testing.Quatro seções de pavimento de concreto continuamente armado (PCCA) foram construídas no campus da Universidade de São Paulo, com o objetivo de introduzir esta estrutura, de reconhecido sucesso internacional, à comunidade técnica de engenharia de transportes brasileira. As seções foram projetadas com uma placa de concreto de 50 m de extensão, curta em comparação ao PCCA tradicional, com a finalidade de simular paradas e terminais de ônibus - locais de grande interesse para a infraestrutura pública. A tese aqui apresentada conclui este projeto de pesquisa iniciado em 2010. Como o objetivo inicial deste estudo foi o desenvolvimento de recomendações de projeto coerentes, confiáveis e intuitivas para a utilização do PCCA no Brasil, foi necessário um profundo entendimento de suas peculiaridades estruturais e de desempenho. Para isso, o processo de fissuração das secções experimentais foi acompanhado durante sete anos. Devido à curta extensão e falta de ancoragem das seções, o PCCA \"curto\" apresentou um padrão de fissuração diferente do PCCA tradicional com muito menos fissuras visíveis na superfície do que o esperado. Para abordar esta questão, uma nova tecnologia ultrassônica para ensaios não destrutivos de estruturas de concreto foi aplicada. Pela interpretação do sinal de ultrassom, foi possível descobrir várias fissuras incipientes (não visíveis) dentro das placas - muitas dessas foram observadas na superfície da placa em levantamentos de fissuras posteriores - e caracterizar fissuras visíveis e não-visíveis quanto à profundidade da fissura. O mapa de fissuração atualizado com fissuras não visíveis mostrou semelhanças com PCCA tradicional. Além disso, a análise dos dados de ultrassom forneceu informações importantes sobre a variação da espessura, localização da armadura longitudinal e condição do concreto, que foram aplicados em simulações teóricas (software de elementos finitos) do PCCA curto. Simulações foram propostas considerando diferentes geometrias, primeiramente com fissuras transversais como juntas com alta eficiência de transferência de carga (LTE) e posteriormente com uma placa contínua, sem fissuras ou juntas. Esta última simulação foi mais precisa alcançando um fator de conversão entre tensões de campo e simuladas na ordem de 0,7 a 1,0. Dados de deflexão e análise de LTE em fissuras e placas entre fissuras atestaram novamente o comportamento contínuo das placas, o que vai em contradição com os modelos atuais de dimensionamento e de previsão de desempenho para o PCCA. Ademais, o tráfego crítico e condições de carga ambiental correspondentes ao clima e tráfego de ônibus típicos brasileiros foram investigados e relacionados usando um modelo de fadiga resultando em recomendações de projeto para o PCCA de curta extensão sendo direcionado para projetos de longo prazo para mais de 20 anos de operação. O gráfico de projeto foi aplicado com sucesso para investigar três falhas apresentadas pelo PCCA curto experimental devido a deficiências de espessura apontadas pelo teste ultrassônico.
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Yu, Ting. "Modélisation de la propagation des ondes ultrasonores dans le béton pour l'amélioration du diagnostic des structures de génie civil." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0210/document.
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Les Essais Non Destructifs (END) par ultrasons permettent de caractériser le béton, sans le dégrader en raison de leurs liens avec ses propriétés mécaniques et sa composition. Cependant, les signaux mesurés résultant de diffusions successives et multiples des ondes sont complexes à analyser. Afin d’optimiser les techniques ultrasonores, il est nécessaire de mieux comprendre les interactions onde-matière dans ce type de milieu et de modéliser au mieux les phénomènes associés. Afin d’aller au-delà des limites des modèles analytiques d’homogénéisation, dans ce travail de thèse un modèle numérique bidimensionnel décrivant la propagation d’ondes ultrasonores dans un milieu hétérogène, adapté au béton, est construit dans le logiciel SPECFEM2D. Ce modèle est comparé à des modèles analytiques, et validé expérimentalement à l’aide d’un milieu synthétique à forte hétérogénéité en comparant les deux paramètres effectifs cohérents : vitesse de phase et atténuation. Il permet également de prendre en compte la viscoélasticité du mortier par l’intermédiaire d’un facteur de qualité. Celui-ci est déterminé à partir des mesures effectuées pour une série de mortiers étudiés.L’outil numérique complet peut être utilisé à plusieurs fins: d’une part, la réalisation d’études afin d’évaluer l’influence de certains paramètres sur la propagation d’onde (la forme et la distribution des granulats), et d’autre part, la simulation des configurations de mesure mises en œuvre sur structure afin de les optimiser en fonction des paramètres qui interviennent, en particulier la fréquence des ondes. Cette meilleure maîtrise des mesures permettra de conduire à terme à l’amélioration du diagnosticUltrasonic non-destructive testing (NDT) is used to characterize concrete, without degrading it, because of its relationship to its mechanical properties and composition. However, the measured signals resulting from successive diffusions and thus from multiple scattering are therefore complex to analyze. In order to optimize ultrasonic techniques, it is thus necessary to better understand the wave-material interactions in this type of medium and to better model the associated phenomena. In order to go beyond the limits of analytical homogenization models, in this thesis a two-dimensional numerical model describing the propagation of ultrasonic waves in a heterogeneous medium, adapted to concrete, is built in the SPECFEM2D software package. This model is compared to analytical models, and validated experimentally using a synthetic medium with high heterogeneity by comparing the two effective parameters of coherent waves: phase velocity and attenuation. This numerical model also makes it possible to take into account the viscoelasticity of the mortar by means of a quality factor. This quality factor is determined from measurements made for a series of mortars that we study. The complete set of numerical tools developed in this work can be used for several purposes: firstly, to carry out studies to evaluate the influence of certain parameters on wave propagation (the shape and distribution of aggregates), and secondly, the simulation of the measurement configurations implemented for a structure in order to optimize them in terms of the parameters involved, in particular the wave frequency. This better control of the measures will ultimately lead to better diagnosis
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Mikulec, Jan. "Nedestruktivní zjišťování vlastností betonu předpjatých nosníků." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-227019.
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The masers’s thesis is about the methods of non-destructive testing and about determining the properties of prestressed concrete. The first part pursues an introduction on the prestressed concrete, its essence and material properties. The next section describes the non-destructive diagnostic methods used in the practical part – the ultrasound impulse method, the resonance method and the rebound hardness test method. There are described destructive tests on the specimens for the calculation of the calibration. This is followed by a practical part, which describes the item tested - truss, its manufacturing, storage, and perform the test. Then search value are calculated from the test results and results are compared according to various procedures specified in the standards. The last section is devoted to the calculation of camber truss and loss of preload.
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Wasserbauer, Jaromír. "Mechanické vlastnosti mikrostrukturních komponent anorganických materiálů." Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2013. http://www.nusl.cz/ntk/nusl-233368.
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Disertační práce se zabývá studiem strukturních a mechanických vlastností anorganických materiálů. Cílem je nalezení jednotlivých fází ve zkoumaném materiálu a hlavně lokalizace (mechanicky) nejslabšího místa, jeho ovlivnění a následně výroba materiálu o lepších mechanických vlastnostech. Z důvodu velkého množství použitých metod je základní teorie vložena vždy na začátku příslušné kapitoly. Taktéž z důvodu značného množství výsledků jsou na konci kapitol uvedeny dílčí závěry. Práce je rozdělena na tři části, kdy první se zabývá seznámením s možnostmi modelování mikro-mechanických vlastností a provedením experimentů umožňujících posouzení rozsahu platnosti některého modelu. V druhé části je provedeno shrnutí současných možností indentačních zkoušek pro měření mechanických vlastností strukturních složek betonu a praktické zvládnutí metodiky vhodné k užití pro výzkum materiálů zkoumaných domovským pracovištěm. V třetí části je navržena metoda identifikace nejslabších článků struktury anorganických pojiv a její ověření na konkrétním materiálu zkoumaném na domovském pracovišti. V této dizertační práci jsou použity tyto metody: kalorimetrie, ultrazvukové testování, jednoosá pevnost v tlaku, nanoindentace, korelativní mikroskopie a rastrovací elektronová mikroskopie s energiově disperzním spektrometrem. Dílčími výsledky jsou kompletní charakterizace cementových materiálů, upřesnění stávajících poznatků a nalezení optimálního postupu pro charakterizaci. Hlavním výsledkem je inovativní přístup vedoucí k pozitivnímu ovlivnění materiálu.
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Kozáček, Vojtěch. "Experimentální stanovení závislosti parametrů NDT a pevnosti v tlaku betonu." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2020. http://www.nusl.cz/ntk/nusl-409957.
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The diploma thesis deals with non-destructive testing of concrete as well as with the relationship between determined parameters and the compressive strength of concrete. The thesis is mainly focused on the ultrasonic pulse velocity method and the rebound hammer test. The experimental part of the thesis describes non-destructive tests performed on concrete blocks. The compressive strength was tested on the drill cores taken from the concrete blocks. The aim of this thesis is to find regression models of the relationship between the compressive strength and non-destructive parameters, and the subsequent analysis of the results.
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Morelli, Roberto. "Resistivity testing of concrete." Thesis, University of Edinburgh, 1985. http://hdl.handle.net/1842/15425.
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Banthia, Nemkumar P. "Impact resistance of concrete." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26956.
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During its service life, a structure may be subjected to various environmental and loading conditions. However, in general, the properties determined under one set of conditions may not be used to determine the behaviour of the material under a different set of conditions. For example, it is well known that concrete is a strain rate sensitive material; therefore, its properties determined under conventional static loading cannot be used to predict the performance of concrete subjected to high strain rates. The problem is serious because these high strain rate loadings are associated with large amounts of energy imparted to the structure in a very short period of time, and concrete is a brittle material. Since the strain rate sensitivity of concrete prohibits the use of its statically determined properties in assessing its behaviour under dynamic conditions, high strain rate tests are required.
Impact tests were carried out on about 500 concrete beams. An instrumented drop weight impact machine was used. The instrumentation included strain gauges mounted in the striking end of the hammer (called 'the tup'), and also in one of the support anvils. In addition, three accelerometers were mounted along the length of the beam in order to obtain the beam response, and also to enable the inertial correction to the observed tup load to be made. Two different concrete mixes, normal strength with a compressive strength of 42 MPa, and high strength with a compressive strength of 82 MPa, were tested. The effect of two types of fibres, high modulus steel, and low modulus fibrillated polypropylene, in enhancing concrete properties was investigated. In addition, tests were also conducted on beams with conventional reinforcement. Hammer drop heights ranging from 0.15m to 2.30m were used. Static tests were conducted on companion specimens for a direct comparison with the dynamic results.
In general, it was found that concrete is a very stain rate sensitive material. Both the peak bending loads and the fracture energies were higher under dynamic conditions than under static conditions. Fibres, particularly the steel fibres, were found to significantly increase the ductility and the impact resistance of the composite. High strength concrete made with microsilica, in certain circumstances, was found to behave in a far more brittle manner than normal strength concrete.
High speed photography (at 10,000 frames per second) was used to study the propagation of cracks under impact loading. In general, the crack velocities were found to be far lower than the theoretical crack velocities. The presence of reinforcement, either in the form of fibres, or of continuous bars was found to reduce the crack velocity. A model was proposed based on a time step integration technique to evaluate the response of a beam subjected to an external impact pulse. The model was capable of predicting not only the experimentally observed non-linear behaviour of concrete under impact loading, but also the more pronounced brittle behaviour of high strength concrete.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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Gudmarsson, Anders. "Resonance Testing of Asphalt Concrete." Doctoral thesis, KTH, Väg- och banteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-155906.
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This thesis present novel non-destructive laboratory test methods to characterize asphalt concrete. The testing is based on frequency response measurements of specimens where resonance frequencies play a key role to derive material properties such as the complex modulus and complex Poisson’s ratio. These material properties are directly related to pavement quality and used in thickness design of pavements. Since conventional cyclic loading is expensive, time consuming and complicated to perform, there has been a growing interest to apply resonance and ultrasonic testing to estimate the material properties of asphalt concrete. Most of these applications have been based on analytical approximations which are limited to characterizing the complex modulus at one frequency per temperature. This is a significant limitation due to the strong frequency dependency of asphalt concrete. In this thesis, numerical methods are applied to develop a methodology based on modal testing of laboratory samples to characterize material properties over a wide frequency and temperature range (i.e. a master curve). The resonance frequency measurements are performed by exciting the specimens using an impact hammer and through a non-contact approach using a speaker. An accelerometer is used to measure the resulting vibration of the specimen. The material properties can be derived from these measurements since resonance frequencies of a solid are a function of the stiffness, mass, dimensions and boundary conditions. The methodology based on modal testing to characterize the material properties has been developed through the work presented in paper I and II, compared to conventional cyclic loading in paper III and IV and used to observe deviations from isotropic linear viscoelastic behavior in paper V. In paper VI, detailed measurements of resonance frequencies have been performed to study the possibility to detect damage and potential healing of asphalt concrete. The resonance testing are performed at low strain levels (~10^-7) which gives a direct link to surface wave testing of pavements in the field. This enables non-destructive quality control of pavements, since the field measurements are performed at approximately the same frequency range and strain level.QC 20141117
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Gudmarsson, Anders. "Laboratory Seismic Testing of Asphalt Concrete." Licentiate thesis, KTH, Väg- och banteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-104236.
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Nondestructive laboratory seismic testing to characterize the complex modulus and Poisson’s ratio of asphalt concrete is presented in this thesis. These material properties are directly related to pavement quality and the dynamic Young’s modulus is used in thickness design of pavements. Existing standard laboratory methods to measure the complex modulus are expensive, time consuming, not truly nondestructive and cannot be directly linked to nondestructive field measurements. This link is important to enable future quality control and quality assurance of pavements based on the dynamic modulus.Therefore, there is a need for a more detailed and accurate laboratory test method that is faster, more economic and can increase the understanding and knowledge of the behavior of asphalt concrete. Furthermore, it should be able to be linked to nondestructive field measurements for improved quality control and quality assurance of pavements. Seismic testing can be performed by using ultrasonic measurements, where the speed of sound propagating through a material with known dimensions is measured. Seismic testing can also be used to measure the resonance frequencies of an object. Due to any excitation, a solid resonates when the frequency of the applied force matches the natural frequencies of the object. In this thesis, resonance frequency measurements have been performed at several different temperatures by applying a load impulse to a specimen while measuring its dynamic response. The measured resonance frequencies and the measured frequency response functions have been used to evaluate the complex modulus and Poisson’s ratio of asphalt concrete specimens. Master curves describing the complex modulus as a function of temperature and loading frequency have been determined through these measurements.The proposed seismic method includes measurements that are significantly faster, easier to perform, less expensive and more repeatable than the conventional test methods. However, the material properties are characterized at a higher frequency range compared to the standard laboratory methods, and for lower strain levels (~10-7) compared to the strain levels caused by the traffic in the pavement materials. Importantly, the laboratory seismic test method can be linked together with nondestructive field measurements of pavements due to that the material is subjected to approximately the same loading frequency and strain level in both the field and laboratory measurements. This allows for a future nondestructive quality control and quality assurance of new and old pavement constructions.QC 20121120
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Hedlund, Nadja. "Non-Destructive Testing Of Concrete Bridges." Thesis, Luleå tekniska universitet, Byggkonstruktion och brand, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-81923.
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Non-destructive testing is of great value in cases where a structure's future is investigated to find out what the best measure is. It is not always the best solution to demolish and build new. Many structures can be repaired and function several more years. In this thesis the main goal is to investigate some different non-destructive techniques and learn more about difficulties and strengths. The test subjects will be a cast T-beam in a laboratory environment as well as a case study of a railway bridge in Abisko. The different testing equipment being used in this thesis is a covermeter, a rebound hammer and ultrasonic pulse velocity. For both the T-beam and the bridge the results are overall very good. The covermeter is proven to be both easy to use and very reliable and the ultrasonic pulse velocity was more to learn about and more difficult but is giving very good results as well. Conclusions after the thesis project is that it requires a lot of experience of the user and time to make non-destructive testing useful and competitive in the society. Getting all the pieces together it is a powerful tool that hopefully is a sustainable asset in the future, regarding both economic and environmental issues.
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Bukenya, Patrick. "Ambient vibration testing of concrete dams." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10178.
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In this thesis, seven techniques namely; rational fractional polynomial, complex exponential, frequency domain decomposition (FDD) based techniques which include; frequency domain decomposition (FDD), enhanced frequency domain decomposition (EFDD), curve fitting frequency domain decomposition (CFDD) and stochastic subspace identification (SSI) methods namely; unweighted principal component (UPC), principal component (PC) and canonical variant analysis (CVA)) have been applied to data from ambient vibration testing of two concrete dams namely; Roode Elsberg and Kouga dams.
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Kapanpour, Mehrdad. "Superplasticizers in concrete." Thesis, Kansas State University, 1985. http://hdl.handle.net/2097/9856.
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Procházka, David. "Vytvoření předpokladů pro hodnocení vlastností vysokopevnostních betonů s využitím nedestruktivních metod zkoušení." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-233795.
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High-strength concrete (HSC) belongs in the recent years to frequently used types of concrete. It allows realization of static challenging structures and also shows due to its dense structure greater durability especially against aggressive media. Currently HSC construction realization abroad is not exceptional. It’s using in the Czech Republic is still limited. When realized, then in a small scale in civil engineering works. The realization of high-strength concrete structures is closely related with the concrete construction quality verification. Good efficiency of the quality control methods can provide non-destructive testing methods (NDT), especially when investigating strength of concrete built in structure. A lack on relevant data for non-destructive testing of HSC in technical and normative rules is to be considered as a significant deficiency. Evident for HSC generally is the lack in literature on deeper analysis of the factors affecting their non-destructive testing, as well a meaningful methodology or practically usable calibration relationships. HSC differs from ordinary concrete not only by used components, but also by more compact structure with different strength – elastic characteristics. Considering these differences, HSC strength prediction can not be performed by using calibration relationships developed for ordinary concrete. Moreover, the question is to what extent the current knowledge of the NDT results influencing factors can be considered as valid. The paper presents findings on the effects of the key factors affecting the measurement results of Schmidt hardness method and ultrasonic pulse method, including recommendations for the practical application of these methods. The problematic of static vs. dynamic modulus of elasticity was also solved. Calibration equations for predicting the compressive strength of HSC from the non-destructive testing parameter were elaborated, showing high cohesion among variables and practically usability.
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Parsons, Adrian. "Seismic exploration techniques applied to ultrasonic imaging within concrete." Thesis, University of Liverpool, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368818.
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Chai, Hsi-Wen. "Design and testing of self-compacting concrete." Thesis, University College London (University of London), 1998. http://discovery.ucl.ac.uk/1317644/.
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Self-compacting concrete (SCC) can flow into place and compact under its own weight into a uniform void free mass even in areas of congested reinforcement. The research reported in this thesis examined the production of SCC with readily available UK materials, with the overall aims of evaluating test methods and establishing a suitable mix design procedure. There have been significant recent developments and applications of SCC in several countries, notably Japan. A literature survey gave an understanding of the advantages and properties of SCC, test methods and the range of constituent materials and their relative proportions for its successful production. A range of SCC mixes can be produced with the common features of a lower aggregate content than conventional concrete and the use of superplasticizers. Most mixes also contained one or more of pulverized fuel ash, ground granulated blast furnace slag and an inert powder filler. A four stage experimental programme was carried out: *tests on pastes to assess the effect of the types and proportions of the powders and superplasticizers on the rheology. *tests on mortars to determine suitable dosage of superplasticizers for high fluidity, low segregation and low loss of workability with time after mixing. Flow spread and funnel tests were used. *tests on fresh concrete to enable suitable types and quantities of coarse aggregate to be combined with these mortars to produce SCC. Fluidity and viscosity were measured using slump flow and V-funnel tests, and passing ability using L- and U-type tests. Two-point workability tests were also carried out, and a novel way of assessing segregation resistance was developed. *tests on hardened concrete to determine compressive strength, bond to reinforcement and drying shrinkage. A mix design procedure, based on a method suggested by Japanese workers, has been developed. This includes optimisation of the mix with a linear optimisation tool from a commercial spreadsheet package.
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Buchner, Susanne. "Full scale testing of prestressed concrete structures." Thesis, University of Surrey, 1989. http://epubs.surrey.ac.uk/804425/.
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Mahawish, Ali Hassan. "Axisymmetric compression testing of concrete by nitrogen." Thesis, Cardiff University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316326.
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Mitchell, Andrew Douglass. "Shear friction behavior of high-strength concrete." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/19274.
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Loedolff, Matthys Johannes. "The behaviour of reinforced concrete cantilever columns under lateral impact load." Thesis, Stellenbosch : Stellenbosch University, 1989. http://hdl.handle.net/10019.1/67104.
Full textAbstract:
Microreproduction of original thesis.Thesis (PhD)--Stellenbosch University, 1990.
Some digitised pages may appear illegible due to the condition of the original microfiche copy.
ENGLISH ABSTRACT: see item for full text
AFRIKAANSE OPSOMMING: sien item vir volteks.
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Schurr, Dennis Patrick. "Monitoring damage in concrete using diffuse ultrasonic coda wave interferometry." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37237.
Full textAbstract:
The prevalence of concrete and cement-based materials in the civil infrastructure
plus the risk of failure makes structural health monitoring an important issue in the
understanding of the complete life cycle of civil structures. Correspondingly, the
field of nondestructive evaluation (NDE) has been maturing and now concentrates
on the detection of flaws and defects, as well as material damage in early stages of
degradation.
This defect detection is typically usually done by looking at the impulse response
of the medium in question such as a cement-based material. The impulse response
of a solid can be used to image a complex medium. Classically, the waveform is
obtained by an active setup: an ultrasonic signal is generated at one location and
recorded at another location. The waveform obtained from imaging can be used to
quantitatively characterize the medium, for example by calculating the material's
diffusivity coefficient or dissipation rate.
In recent years, a different monitoring technique has been developed in seismology
to measure the velocity of different kinds of waves, the Coda Wave Interferometry
(CWI). In this CWI technique, the main focus is given to the late part of the recorded
waveform, the coda. CWI is now successfully used in seismology and acoustics.
In the current research, CWI is applied on concrete in different damage states
to develop basic knowledge of the behavior of the wave velocity, and how it can be
used to characterize cement-based materials. By comparing two impulse responses,
the relative velocity change between the two impulse responses is used to characterize
damage. Because of the stress-dependency of the velocity change, the calculations can also be used to directly calculate the Murnaghan's and Lam´e's coefficients. The
newer technique of CWI is applied - the Stretching Technique (ST) [27]. The first goal
of this research is to establish the viability of using CWI in cement-based materials.
Next, we use the ST in the application of stress as we compress concrete samples for
the detection of thermal damage, ASR-damage and mechanical softening.
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Vu, Quang Anh. "Evaluation du béton d'enrobage par acoustique non linéaire et ondes de surface." Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4712/document.
Full textAbstract:
Cette thèse s’inscrit dans le contexte des contrôles non destructifs du béton par ultrasons. Nous focalisons notre étude sur les mesures en acoustique non linéaire qui permettent d’ausculter le béton à l’échelle mésoscopique où les ondes interagissent avec les microfissures et le réseau de porosité. Les paramètres associés sont connus comme étant beaucoup plus sensibles que ceux issus des mesures linéaires. Le béton est un matériau hétérogène et complexe, ce qui présente un comportement fortement non linéaire croissant avec l’état endommagé.Nous développons dans cette thèse un type de mesure non linéaire : Dynamic Acousto-Elastic Testing (DAET). Cette technique fondée sur le principe d’une excitation dynamique du matériau, utilise les ondes ultrasonores pour suivre la variation du comportement élastique en fonction de l’amplitude d’excitation. Nous focalisons notre étude sur le problème du béton d’enrobage qui tient un rôle essentiel dans la durée de vie d’une structure de génie civil. Nous étudions l’interaction des mesures non linéaires par DAET avec les ondes de Rayleigh qui se propagent dans le béton d’enrobage. Nous montrons la sensibilité importante de l’évolution de paramètres non linéaires en fonction de l’endommagement thermique et de la carbonatation.Par la suite, nous proposons une nouvelle méthodologie de la mesure DAET, dans laquelle la vibration transitoire est générée par un impact et les ondes sont générées en continue. Nous présentons différentes applications de la méthode proposée, incluant le cas des éprouvettes de grandes dimensions. Cette approche ouvre de larges possibilités de transposer les mesures pour une application sur siteThis thesis is related to the field of nondestructive evaluation of concrete by ultrasound. We focus our study on nonlinear acoustic-based measurements that allow the concrete auscultation at mesoscopic scale where waves interact with microcracks and porosity network. The nonlinear parameters are known to be much more sensitive than those from linear measurements. Concrete is a heterogeneous and complex material. Its behavior is highly nonlinear with increasing damaged state.We develop in this thesis a type of nonlinear measurement: Dynamic Acousto-Elastic Testing (DAET). This technique is based on the principle of a dynamic excitation of the material, using ultrasounds to follow the variation of the elastic behavior depending on the excitation amplitude. We focus our study on the problem of concrete cover which holds a key role in the life of a civil engineering structure. We study the interaction of the DAET measurement with the Rayleigh waves which propagate in the concrete cover. We show the high sensitivity evolution of non-linear parameters in function of thermal damage and carbonation.Subsequently, we propose a new methodology of DAET measurement, in which the transient vibration is generated by an impact and ultrasounds are generated continuously. We present different applications of the proposed method including the case of large specimens. This approach opens broad possibilities of transposing measurements for on-site application
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Reutlinger, Christopher George. "Direct pull-out capacity and transfer length of 06-inch diameter prestressing strand in high-performance concrete." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/19026.
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Meyer, Karl F. "Transfer and development length of 06-inch diameter prestressing strand in high strength lightweight concrete." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/20727.
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Long, Robert. "Improvement of ultrasonic apparatus for the routine inspection of concrete." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343846.
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Jurado, Monica C. "Quantifying anistropy in asphalt concrete pavements using an ultrasonic method." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2008. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Azar, Lawrence 1973. "Ultrasonic phased arrays of the condition assessment of concrete structures." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/50432.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1998.Vita.
Includes bibliographical references (leaves 107-112).
by Lawrence Azar.
S.M.
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Azzawi, Mostfa Al. "Investigations on FRP-Concrete Bond." Scholar Commons, 2018. http://scholarcommons.usf.edu/etd/7116.
Full textAbstract:
This dissertation presents findings from three separate investigations, a laboratory study and two field studies that evaluated the durability of the Fiber Reinforced Polymer (FRP)-concrete bond. The laboratory study explored the role of porosity on CFRP-concrete bond following immersion in warm water. Two disparate field studies measured residual bond after 20 years outdoor exposure of FRP repairs of full-size masonry walls and after 12 years for partially submerged piles supporting the Friendship Trail Bridge, Tampa Bay.
The ACI 440 code requires the same surface preparation for all externally bonded FRP concrete repairs. This disregards the role of porosity that is a function of the water / cementitious (w/c) ratio. Concretes with high w/c ratios are low strength concretes, have large voids and a more elaborate capillary pore network compared to low w/c, high strength concretes. Epoxies will therefore penetrate deeper into high porosity concretes. As a result, the performance of low strength, high porosity concrete under moisture exposure can be anticipated to be superior. The laboratory study was intended to determine whether this hypothesis was correct or not.
Three different concrete mixes with water / cementitious ratios of 0.73, 0.44 and 0.25 representing high, medium and low porosities were used for the study. The corresponding target compressive strengths were 2,500 psi, 5,000 psi and 7,500 psi respectively. A total of eighteen, 9 in. x 9 in. x 2.5 in. thick slabs, three for each concrete porosity were tested. Slabs were allowed to cure for over 90 days before surfaces were lightly sand blasted to provide the required concrete surface profile (CSP 3). Specimens were then pre-conditioned in an oven for 48 hours to ensure uniform drying.
Concrete porosity was characterized using mercury porosimetry, SEM, 3D surface scanning and images obtained using a portable microscope. Two commercially available CFRP materials were bonded to the oven-dried prepared slab surfaces and the epoxy allowed to cure at room temperature for 4 weeks. Twelve FRP bonded slabs were completely submerged in potable water at 30 oC (86 oF) as part of the aging program. The six remaining slabs were used for establishing baseline bond values through destructive pull-off tests. The twelve exposed slabs were similarly tested following 15 weeks of exposure.
Results showed minimal degradation in the high porosity, low strength concrete but over 20% reduction in the low porosity, higher strength concrete. Analysis of the failure plane indicated that the lower porosity of the high strength concrete had limited the depth to which the epoxy could penetrate. This was confirmed from magnified images of the bond line taken using a microscope and from a careful assessment of the failure mode. Findings also suggest that the CSP 3 surface profile (light sand blasting) may be adequate for lower strength concrete but not so for higher strength concrete. For applications where FRP concrete repairs of higher strength concrete are permanently or intermittently exposed to moisture, alternative surface preparation may be needed to allow epoxy to penetrate deeper into the concrete substrate. The viscosity of the resin hitherto not considered may be a critical parameter.
In 1995, two full-scale concrete masonry walls were repaired using three horizontally aligned 20 in. (508 mm) wide uni-directional carbon fiber sheets using different commercially available epoxies. Twenty years later the CFRP-CMU bond was determined through selective pull-off tests that were preceded by detailed non-destructive evaluation. Results showed that despite superficial damage to the top epoxy coating and debonding along masonry joints, the residual CFRP-CMU bond was largely unaffected by prolonged exposure to Florida’s harsh environment.
Therein, 99% of samples exhibited in cohesive failure of the CMU or mortar. Pull-off strength was poorer at mortar joints but because the CFRP was well bonded to the masonry surface, its impact on structural performance of the repair was expected to be minimal. Overall, the repairs proved to be durable with both epoxy systems performing well.
The Friendship Trail Bridge linking St. Petersburg to Tampa FL was demolished in 2016. This was the site of three disparate demonstration projects in which 13 corroding reinforced concrete piles were repaired using fiber reinforced polymer (FRP) in 2003-04, 2006, and 2008. The repairs were undertaken using combinations of carbon and glass fiber, pre-preg and wet layup, epoxy and polyurethane resin, and were installed using either shrink wrap or pressure bagging. Residual FRP-concrete bond was evaluated after up to 12 years of exposure through 120 pull-off tests conducted on 10 representative repaired piles. Results showed a wide variation in the measured pull-off strength depending on the type of resin, the number of FRP layers, the prevailing conditions at the time the epoxy was mixed and the method of installation. Epoxy-based systems were found to be sensitive to ambient conditions at installation. Pressure bagging improved performance. The highest residual bond was recorded in pressure bagged piles repaired in 2008. The findings suggest that in marine environments epoxy-based systems installed using pressure bagging can lead to durable repairs.
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Kgoboko, Kobamelo. "Collapse behaviour of non-ductile partially prestressed concrete bridge girders." Title page, contents and summary only, 1987. http://web4.library.adelaide.edu.au/theses/09EN/09enk445.pdf.
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Ng, Yu-ting Ivan, and 吳汝鋌. "Performance and robustness of self-consolidating concrete." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B4088790X.
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Palumbo, Nicolino. "Accelerated corrosion testing of steel reinforcement in concrete." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60681.
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In the last few decades, there has been an increasing worldwide problem of deterioration of reinforced concrete structures, caused primarily by the corrosion of the steel reinforcement embedded within the concrete. Several factors can influence the corrosion process in different types of inservice structures. This thesis reviews the basic principles of the reinforcement corrosion. Various protection and rehabilitation schemes that can be undertaken in the repair of deteriorated concrete structures are presented. In particular, three specific types of structures in the Montreal region which have undergone rehabilitation are presented as typical case studies. Additionally, major research work done in the area of reinforcement corrosion over the last twenty years is reviewed.This thesis reports the results of an experimental research program carried out at McGill University dealing with accelerated electrochemical corrosion testing of reinforced concrete. The main objective of this study is to determine the importance and influence of the depth of the concrete cover thickness on the rate of corrosion of steel reinforcement and thereby, on the resistance of concrete. Appropriate conclusions and recommendations regarding the construction variables affecting the corrosion process are brought forth.
These conclusions and recommendations can be summarized.
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Syropoulou, Stella. "AC Impedance Testing of Surface Treatments on Concrete." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511869.
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Katab, Anwar Othman. "The testing of repair techniques for concrete structures." Thesis, University of Sunderland, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.290443.
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Kaděrová, Jana. "Multi-filament yarns testing for textile-reinforced concrete." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2012. http://www.nusl.cz/ntk/nusl-225556.
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The scope of the presented master thesis was the experimental study of multi-filament yarns made of AR-glass and used for textile-reinforced concrete. The behavior under the tensile loading was investigated by laboratory tests. A high number of yarn specimens (over 300) of six different lengths (from 1 cm to 74 cm) was tested to obtain statistically significant data which were subsequently corrected and statistically processed. The numerical model of the multi-filament bundle was studied and applied for prediction of the yarn performance and for later results interpretation. The model of n parallel filaments describes the behavior of a bundle with varying parameters representing different sources of disorder of the response and provides the qualitative information about the influence of their randomization on the overall bundle response. The aim of the carried experiment was to validate the model presumptions and to identify the model parameters to fit the real load-displacement curves. Unfortunately, due to unsuccessful correction of measured displacements devalued by additional non-linear contribution of the unstiff experiment device the load-displacement diagrams were not applicable to model parameters identification. The statistical evaluation was carried only for the maximal load values and the effect of the specimen size (length) on its strength was demonstrated. The size effect curve did not exclude the existence of spatial correlation of material mechanical properties modifying the classical statistical Weibull theory.
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Kizito, Nicholas Magera. "Predicting and testing the tensile relaxation of concrete." Master's thesis, University of Cape Town, 2013. http://hdl.handle.net/11427/5036.
Full textAbstract:
Includes abstract.Includes bibliographical references.
Tensile relaxation is an important property in structural concrete members such as concrete overlays and patch repairs under sustained imposed restraint. Tensile relaxation helps in reducing tensile stresses in concrete which leads to mitigation of cracking in restrained concrete members. Normally, it is assumed that tensile relaxation is influenced in a similar way by the same parameters that influence creep despite potential differences between the two. Moreover, relaxation is predicted from functions that link it to creep. Whereas it is easy to find published literature on creep of concrete, little can be found on the relaxation behaviour of concrete. More research is therefore needed to understand the factors that influence relaxation and its prediction. This study aimed at comparing the influence of selected factors on creep and relaxation to establish a correlation if any between the two. The parameters investigated include: w/c ratio, age of loading, initial stress-strength ratio and aggregate content. Tensile relaxation tests are difficult to perform and hence prediction models are often relied upon to predict relaxation. Two simplified approximate methods are suggested in the fib Model Code to obtain the relaxation function from the creep function. The Age Adjusted Effective Modulus method (AAEM) given in the MC2010 and the Approximate Relaxation Function (ARF) in MC90-93 are mentioned. Values from the two were compared with experimental relaxation results to verify their accuracy in predicting the relaxation potential of selected concretes. Results show that tensile relaxation of concrete, similar to creep is affected by parameters such as w/c ratio, age of loading and aggregate content. It is observed that the magnitude of tensile relaxation, with other factors held constant, was found to reduce with a reduction in w/c ratio, increase in age and increase in aggregate content. The initial stress-strength ratio does not seem to have a significant influence on relaxation. However, an increase in the initial stress leads to a small and un- proportional increase in relaxation. The use of models linking the creep function and relaxation function to predict low-age relaxation is probably valid. Although both the AAEM and ARF methods yield fairly good predictions of relaxation, the simplicity of the AAEM makes it a better option.
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Lahlouh, El-hachemi. "Compressive membrane action in concrete silos." Thesis, University of Bristol, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280887.
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Ng, Ah Book. "Physical models in fire study of concrete structures." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=64055.
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Gaber, Ahmed Yaseen 1962. "Pore-water pressure debonding of asphaltic concrete." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277077.
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The report presents an evaluation of a modification to an asphalt-debonding test procedure when used with a water debonding apparatus developed at the University of Arizona, the Pore-Water Pressure Debonding Device. The method being modified is that outlined by Jimenez in his report "Testing for Debonding of Asphalt from Aggregates". A regular test specimen, 4 inches in diameter by 2½ inches high, is water-saturated at 122°F and subjected to repeated pore-water pressure varying from 5 to 30 psi. The above factors are kept constant and the following ones are varied: air void content, stress frequency, stress repetition, stress duration and testing temperature. Test results of the modified testing procedure demonstrated the following trend: the higher the value of any of the aforementioned test variables, i.e., the void content, stress frequency, stress repetition, or stress duration, or any combination of these variables, the greater the loss of the mix resistance to stripping.
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Barrus, Natasha Christine. "Sensitivity of Resistivity Measurements on Concrete Bridge Decks to Operator-Controlled and Concrete Material Variables." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3203.
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The objectives of this research were to investigate the sensitivity of two-prong and fourprong resistivity measurements to certain operator-controlled variables and to conduct a direct comparison of the sensitivity of two-prong and four-prong resistivity measurements to certain concrete material variables. Four full-factorial experiments were designed for this research. In the experimentation on operator-controlled variables with two-prong resistivity testing, main effects that are both statistically significant and practically important include hole depth and surface water. In the experimentation on operator-controlled variables with four-prong resistivity testing, probe position, surface water, and prong spacing are all neither statistically significant nor practically important. This high degree of unexplained variation may be of concern to practitioners. In the experimentation on concrete material variables with two-prong and four-prong resistivity testing, main effects that are both statistically significant and practically important include chloride concentration and temperature, both of which exhibit inverse relationships with resistivity. These research findings support several important recommendations for resistivity testing. Operators of the two-prong resistivity device should use an accurately positioned drill stop to ensure that the prepared holes are consistently the correct depth, and they should expect to obtain different values depending on the presence of surface water on the deck surface. Operators considering use of the four-prong resistivity device should not expect the measurements to be sensitive to probe position with respect to rebar, presence of surface water, or prong spacing for conditions similar to those investigated in this research. Operators interested in monitoring resistivity values over time to ascertain material changes in a bridge deck should develop protocols for measuring concrete temperature in the field and subsequently normalizing resistivity measurements to a standard temperature.
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Jafar, Ali, and Mohan Maharjan. "Understandability of General Versus Concrete Test Cases." Thesis, Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-4358.
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One possibility to automate more of software testing is to have developers write more general test cases. Given a general (parameterized test case), that holds in many situations, software can generate many different test instances and execute them automatically. Thus, even though the developers write fewer and smaller tests they can test more. However, it is not clear what other effects the use of generalized test cases has. One hypothesis is that “More general test cases are harder to understand than concrete ones and thus would lead to overall tests that are harder to understand”. Software understandability can be defined as the system that is written by one person is easy to read and understand by another person easily without any resistance. However, software understandability is hard to measure because understandability depends on the cognitive behavior of human. Software understandability assists in software reusability and software maintainability.