Dissertations / Theses on the topic 'Pullout test'

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.

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.

A review of literature and standards revealed no standardized process exists for the evaluation or characterization of wind uplift resistance of Adhesive Applied Roofing Systems (AARS). It was determined that a pullout test method -- a test in which the adhered components of roofing samples were subjected to tensile loading until failure -- could be used to quantify wind uplift performance. From the literature study, critical variables were extracted. Among these were the pullout rate, the specimen size and the specimen attachment condition. After conducting a series of extensive pullout tests, data showed that the optimum pullout rate was 6.35mm/min. Additional tests showed that a specimen size of 300 mm x 450 mm with all flutes fastened provided the experimentally consistent data. Based on the investigation outlined above, the present study drafted a standard test method for the determination of the pullout resistance of adhesively applied roofing components. This contribution is being presented to the Canadian Standards Association (CSA) and American Society of Testing Materials (ASTM) for adoption of a standardized test method. The present study also implemented the standardized test procedure to characterize the pullout behaviour of a variety of different configurations. Over 400 specimens were constructed varying the deck type (steel & concrete), insulation facer (paper and acrylic facer) and coverboard (fiberboard and asphalt core board). Experimental results showed that the use of steel deck, paper faced polyisocyanurate, and asphalt core board yielded optimum pullout resistance. Alternative adhesion patterns were also tested and showed a maximum reduction of 60% from the optimized adhesion pattern.

Geosynthetics, or manmade materials used in soils engineering, have successfully been used as base reinforcement of pavements for over 40 years. Use of geosynthetics can result in cost savings by allowing the aggregate base layer to be reduced in thickness and/or the service life of the pavement to be extended. Design methods for this type of reinforcement have typically been developed by individual manufacturers for specific products. These methods are not widely used by state transportation agencies because 1) they are proprietary, 2) they are empirically based, and 3) they lack compatibility with the current national trend towards mechanistic-empirical pavement design procedures. This project was initiated to develop testing methods to determine one of the critical material properties needed for mechanistic-empirical base-reinforced pavement design, namely, the resilient interface shear stiffness. This property describes the interaction, in particular the shear stiffness, between the geosynthetic and the surrounding aggregate. This new test protocol closely mimics vehicular load patterns, resulting in design parameters pertinent to the use of the geosynthetics to reinforce the base course. A study was conducted to evaluate the repeatability of these tests and to develop a standardized test method. Specific parameters under investigation include load pulse and rest period duration, embedment length of the geosynthetic, and differences in results using different soils and types of geosynthetics. Some parameters seemed to have little effect on values of resilient interface shear stiffness, while others vastly impacted the results. Load pulse and rest period durations did not affect output results significantly. Maintaining a constant confinement or shear stress during the test duration produced higher repeatability and correlated well to the adapted resilient modulus equation. Three-aperture length tests on polyester geogrid also correlated well with this equation, however repeatability was moderately low. Polypropylene geogrid and a woven geotextile confined in Ottawa sand displayed low correlation to this equation. During testing, very small displacements occur, and therefore, every effort should be made to ensure that these measurements are accurate and not skewed by electrical noise and interference.

The compressive strength of mortar is typically determined using the American Societyfor Testing and Materials (ASTM) standard method using 2 inch cubes which are compressed tillfailure. There is however a disparity between the compressive strengths of mortar cubes, and insitumortar. This disparity is a result of the differences in thickness, aspect ratio, curingconditions, water content, and confinement between mortar cubes and mortar joints. While thesedifferences lead to mortar joints being stronger than mortar cubes, a relationship between theirstrengths is desired.Two less-common mortar strength tests were used to determine more accurately thecompressive strength of in-situ mortar. The results of both tests were compared to the results ofASTM standard compressive testing with mortars of the same water content. The first was theDouble Punch test which involves the use of two metal punches that compress either side of athin mortar sample till failure. The Double Punch test is more difficult to perform than theASTM standard compression test, but was useful because it simulates the confinement that insitumortar will experience. The Double Punch test was also used with mortar specimens ofvarying thickness to determine a relationship between specimen thickness and compressivestrength. The second test used was the Helix Pullout test. This test is performed by insertingmetal helical screws into a mortar joint, and pulling from the joint while restricting rotation. Themaximum load used to extract the Helix is recorded as the Pullout Load, and is used to find thecompressive strength by use of a calibration curve. This test was used on a masonry wall paneland mortar cubes were also made with the same mortar for compressive testing.The tested mortar exhibited decreased compressive strength with increased water content.The mortar also decreased in strength with increasing specimen thickness. Mortar joints wereshown to be significantly stronger than mortar cubes based on factors of specimen thickness andconfinement by an average factor of at least 2.40. Although results are affected by punchdiameter, the Double Punch test was shown to be a consistent and reliable means of estimatingmortar compressive strength. The Helix Pullout test exhibited wide variation, and wasdetermined to be primarily useful for qualitative comparison as opposed to quantitativedetermination of strength.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
The adoption of the soil nailing technique in the project of slope stability once or excavations it is being more and more frequent. This with it is reguire a larger number of studies about the estimate of the the pullout resistance (qs) in function of parameters of field tests for the most varied types of Brazilian soils.The objective of this research was to propose correlations for the qs resistence in function of field tests, and also to compare the results also found in the pullout test with dear in existent formulations. The study was accomplished in a slope of young gneissic residual soil, Viçosa - MG.In the field test they occurred the standard penetration test (SPT), Menard pressuremeter test (PMT), Marchetti dilatometer test (DMT) and pullout test in twelve nails, only made with no injection procedures. The assembly of the pullout test system was different from the proposal for other authors and it was shown effective.The qs values obtained in the pullout tests and the correlations found for each nails were compared using appropriate statistics for each analysis. The parameters of the field test used in the proposed correlations Nspt, PL, and P0, were certain for the average of your magnitudes along the nails. The pullout resistance found for each nails and the parameters obtained in the field tests they were plotted in dispersion graphs us which lineal and no-lineal regressions were applied in the intention of to evaluate which mathematical model was adapted better to each proposition. For the correlation qs x Nspt the logarithmic model presented larger correlation coefficient (R2) and significance (p <0,05), in the relationship qs x p0 the quadratic form obtained larger R2, however the behavior of the curve was not suitable with the one of the soil, being accomplished the option by the logarithmic model that was highly significant (p <0,01). The correlation qs X PL didn't show any statistically significant and the choice of the format of the lineal curve was based on the behavior of the soil, same not presenting the largest value of R2. In the case to to the proposed correlations it s possible to conclude that they can be used as initial estimate of project being indispensable the execution of pullout tests to prove the safety with relationship to the values of adopted qs.
A adoção da técnica de solo grampeado no projeto de contenção de taludes ou escavações vem sendo cada vez mais freqüente, com isto se faz necessário um maior numero de estudos sobre a estimativa da resistência ao arrancamento (qs) em função de parâmetros de ensaios de campo para os mais variados tipos de solos brasileiros. O objetivo desta pesquisa foi propor correlações para a estimativa de qs em função de ensaios de campo, e também comparar os valores encontrados nos ensaios de arrancamento com estimados em formulações existentes. O estudo foi realizado em um talude de solo residual jovem de origem gnáissica, Viçosa MG. No campo efetuaram-se os ensaios de penetração (SPT), sondagem pressiometrica de Ménard (PMT), sondagem dilatometrica de Marchetti (DMT) e ensaios de arrancamento em 12 grampos, confeccionados somente com a bainha. A montagem do sistema de arrancamento foi diferente da proposta por outros autores e se mostrou eficaz. Os valores de qs obtidos nos ensaios de arrancamento e os encontrados pelas correlações existentes para cada grampo foram comparados através de estatísticas adequadas para cada análise. Os parâmetros dos ensaios de campo utilizados nas correlações propostas Nspt, PL, e p0, foram determinados pela média de suas magnitudes ao longo dos grampos. As resistências ao arrancamento encontrada para cada grampo e os parâmetros obtidos nos ensaios de campo foram plotados em gráficos de dispersão nos quais se aplicaram regressões lineares e não-lineares no intuito de avaliar qual modelo matemático se adequou melhor a cada proposição. Para a correlação qs x Nspt o modelo logarítmico apresentou maior coeficiente de correlação (R2) e significância estatística (p<0,05), na relação qs x p0 a forma quadrática obteve maior R2, porém o comportamento da curva não foi condizente com o do solo, sendo realizada a opção pelo modelo logarítmico que se mostrou altamente significante (p<0,01). Já a correlação qs X PL não apresentou nenhum modelo estatisticamente significante e a escolha do formato da curva linear foi baseada no comportamento do solo, mesmo não apresentando o maior valor de R2. Quanto às correlações propostas conclui-se que podem ser utilizadas como estimativa inicial de projeto sendo imprescindível a execução de ensaios de arrancamento para comprovar a segurança quanto aos valores de qs adotados.

Master of Science
Department of Civil Engineering
Robert J. Peterman
An experimental testing program was conducted at Kansas State University (KSU) to test the bond characteristics of various 5.32-mm-diameter steel wires and smaller diameter (less than 0.5 in.) strands used in prestressed concrete railroad ties. A total of 13 wires and six strands produced by seven different steel manufacturers were used during this testing. Since no wire bond pullout test currently exists, one was developed and its validity tested. This un-tensioned pullout test could serve as a quality control test similar to the standard test for strand bond (ASTM A1081) that has been developed for pretensioned strands. This strand test is currently not verified for strands less than 0.5-in. in diameter, so the procedure was also scrutinized using strands common in the concrete railroad tie industry. Some of the wires and strands contained surface indentations. It is generally accepted that indentations in the reinforcements improve the bond between the steel and concrete. To further complicate the issue, reinforcements with different surface conditions (rust, oils, lubricants) are allowed to be used in the concrete ties which further affects the bond quality of the reinforcements. However, no standardized indentation patterns (shape, size, depth of indent, etc.) or surface conditions (degree of rusting, amount of surface lubricants, etc.) are utilized by all wire and strand manufacturers. Thus, the corresponding bond behavior of these different reinforcements when placed in various concrete mixtures, in terms of average transfer lengths and typical variations, is essentially unknown. The purpose of this testing program was to develop (in the case of wires) or verify/develop (in the case of strands) a pullout testing procedure predictive of the reinforcement’s bond performance in a prestressed application. The test should be relatively inexpensive, demonstrably repeatable, and easily reproducible. Results from the un-tensioned pullout tests were compared to transfer length measurements from accompanying pretensioned concrete prisms in the lab. Additionally, pullout tests and transfer length measurements were obtained at an actual concrete railroad tie manufacturing plant. The obtained data was compared to the lab data and analyzed to further understand the relationship between un-tensioned pullout tests and pretensioned concrete members.

Doctor of Philosophy
Department of Civil Engineering
Kyle A. Riding
ASTM recently adopted the Standard Test Method for Evaluating Bond of Seven-Wire Steel Prestressing Strand as ASTM A1081, a pull-out test procedure developed for verifying the ability of steel strands to bond to cementitious materials prior to their use as tensile reinforcement in prestressed concrete sections. The required by ASTM International precision and bias statement has not been developed for this test method. In addition, a minimum threshold value that will ensure only adequately bonding strand sources will be accepted has not yet been applied to ASTM A1081. The test method was developed after findings that prestressing steel strand sources of identical type and grade vary significantly as far as their bonding capacity. Bond is a crucial aspect of the prestressing force being transferred into the concrete, and insufficient bonding action can result in the prestressed concrete section lacking in capacity to sustain the loads that it was designed for. After an initial survey of the pull-out strength of North American Strand in mortar, three strands of differing pull-out strengths were selected for inclusion in further testing. A precision and bias statement for ASTM A1081 was developed by first performing ruggedness testing to determine how the results are affected by allowable variations in methods and materials, and followed by an inter-laboratory study to determine the reproducibility of the test method. Once the precision and bias statement for the standard test method was developed, the same strand sources were tested for their performance in concrete beams. Statistical analysis of the flexural beam testing data and correlation with the prestressing strand sources’ ASTM A1081 test results was performed, and the industry was provided with minimum acceptance criteria for prestressing strand tested by ASTM A1081, along with recommendations regarding the standard test method and aspects of prestressed concrete design.

Os materiais utilizados nas osteossínteses passam constantemente por avanços tecnológicos. Um dos mais recentes dispositivos é a chamada placa bloqueada, suas principais indicações são fraturas com alto grau de cominução, fraturas que não exigem uma redução anatômica, ossos osteopenicos, por exemplo, acometidos pela osteoporose, entre outras. Atualmente novos modelos de placas com bloqueio estão sendo desenvolvidos, onde a interface do parafuso e a placa são feito pela deformação do orifício, com a vantagem da instalação do parafuso em diversos ângulos. O presente projeto tem por objetivo estudar comparativamente a diferença entre os dois tipos de interface parafuso placa, como também realizar teste de quatro pontos comparando o sistema novo de bloqueio com o sistema convencional de bloqueio. Realizamos ensaios de arrancamento com sistema convencional de bloqueio (Synthes) e com o novo sistema de bloqueio (PAX) em parafusos 2,0mm; 2,4mm; 2,7mm e 3,5mm. Em todos os grupos testados o sistema convencional de bloqueio foi mais resistente e apresentou diferença significativa estatisticamente, teste de Mann- Witney (p< 0,05). Os valores de P obtidos foram: sistema 2.0mm p = 0,008; sistema 2.4 mm p= 0,008; sistema 2.7 mm p= 0,016; sistema 3.5 mm p= 0,008. No teste de 4 pontos utilizamos 20 placas da marca Synthes (sistema convencional de bloqueio) e 20 da marca PAX (novo sistema de bloqueio) e o sistema convencional de bloqueio se mostrou novamente mais resistente com diferença significativa. Os valores de P obtidos foram: sistema 2.0mm p = 0,008; sistema 2.4 mm p= 0,008; sistema 2.7 mm p= 0,008; sistema 3.5 mm p= 0,008. Conclui-se que o sistema convencional de bloqueio se mostrou mais resistente tanto no teste de arrancamento quanto no teste de flexão de quatro pontos.
The materials used in osteosynthesis constantly technological advances. One of the most recent devices is called the locking plate, its main indications are fractures with a high degree of comminution, fractures which do not require anatomical reduction, osteopenic bones, for example, affected by osteoporosis, among others. Currently new locking plate designs are being developed, where the screw interface and the plate are made by deformation of the hole, with the installation of the advantage screw at various angles. This study aims to compared the difference between the two types of interface screw - plate but also perform four-point test comparing the new locking system with the conventional system lock. Pullout tests conducted with conventional locking system (Synthes) and the new locking system (PAX) by screws 2.0mm; 2.4mm; 2.7mm and 3.5mm. In all groups tested the conventional system of blockade was stronger and showed a statistically significant difference, Mann-Witney test (p <0.05). P values were obtained: System 2.0mm P = 0.008; system 2.4 mm p = 0.008; System 2.7 mm p = 0.016; system 3.5 mm p = 0.008. In test points 4 used 20 Synthes plate mark (conventional blocking system) and 20 brand PAX (new locking system), the conventional locking system again showed a significant difference resistant. P values were obtained: System 2.0mm P = 0.008; system 2.4 mm p = 0.008; system 2.7 mm p = 0.008; system 3.5 mm p = 0.008. It follows that the conventional locking system has proved much more resistant peel test as in the four point bending test.

This research presents the results on an experimental investigation to identify the significant factors influencing horizontal cracking in continuously reinforced concrete pavements (CRCP). An in-depth analysis of the microstructure, morphological characteristics of the interfacial transition zone (ITZ) and the observation of cracking using the environmental scanning electron microscope (ESEM) was done. Characterization of oxides using Fourier transform infrared spectroscopy (FTIR) and electron dispersive x-ray spectroscopy (EDS) was also performed. Water to cement ratio (w/c) and rebar temperature had a significant influence on the rebar-concrete bond strength. The 28-day shear strength measurements showed an increase in rebar-concrete bond strength as the water to cement ratio (w/c) was reduced from 0.50 to 0.40. There was a reduction in the peak pullout load as the temperature increased from 14oF to 252oF for the corroded and non-corroded rebar experiments. The corroded rebar pullout test results showed a 20-50 % reduction in bond strength compared to the non-corroded rebars. FTIR measurements indicated a presence of lepidocrocrite (γ -FeOOH) and maghemite (γ -Fe2O3) on the ITZ. ESEM images showed the existence of microcracks as early as three days after casting with the bridging of these cracks between coarse aggregate locations in the interfacial zone propagating through the mortar.

Avaliou-se experimentalmente o comportamento da resistência ao cisalhamento de interface em reforços unidirecionais utilizados em estruturas de contenção. Para tal, foram realizados ensaios de arrancamento em fitas metálicas, utilizadas para soluções em terra armada e chumbadores, para soluções em solo grampeado. Os ensaios, em campo e laboratório, permitiram constatar a pouca influência do diâmetro dos chumbadores no valor da resistência ao cisalhamento de interface (qs). Ainda em relação aos chumbadores, os resultados mostraram que o volume de calda de cimento para preenchimento da cavidade escavada está diretamente associado ao ganho de qs. Os ensaios em fitas metálicas, em obras executados com solos finos, mostraram que o seu uso requer um estudo mais detalhado do seu comportamento, visto que os parâmetros sugeridos pela NBR 9286/86 não condiz com os resultados experimentais desta pesquisa.
This study evaluated experimentally the behavior of interface shear strength in unidirectional reinforcements used in reinforced soil structures. Pullout tests were carried out on reinforcements used in reinforced earth and soil nailing techniques. Nail diameter has little influence on interface shear strength (qs), according to field and laboratory tests. Additionally, increasing grout volume in nail cavity was directly linked to gain of qs. Tests on reinforced earth reinforcements using fine-grained soils showed that the results do not match with the suggestion of NBR 9286/86.

Este trabalho apresenta resultados de ensaios de arrancamento de geogrelha, obtidos com a utilização de equipamento de dimensões reduzidas. A força de arrancamento foi aplicada por uma máquina universal com capacidade máxima de 30kN, dotada de instrumentação que permitiu registrar a força de arrancamento e o deslocamento da geogrelha em relação ao solo envolvente. Além disto, o ensaio foi instrumentado com uma célula de tensão total instalada no nível da inclusão. A grande vantagem deste equipamento é o pequeno volume de solo utilizado, resultando em um ensaio mais rápido e econômico, proporcionando um controle maior do teor de umidade e do grau de compactação do solo. Considerando que uma grande parte do estado de São Paulo é coberto por solos de granulometria fina, esse equipamento passa a ser uma excelente alternativa para obtenção dos parâmetros de ensaios de arrancamento necessários ao desenvolvimento de projetos em solo reforçado. Para averiguar a possibilidade de uso do ensaio de pequeno porte, nestas condições, para substituir uso das caixas de grandes dimensões foram inicialmente realizadas comparações, através do coeficiente de interação, entre os resultados obtidos através desses dois tipos de ensaios. Os resultados obtidos mostraram que, para as condições de ensaio empregadas utilizando solos com 100% passando na peneira de abertura 2mm e geogrelhas de abertura de malha aproximadamente de 20mm, a resposta do equipamento, se comparada à de ensaios de grandes dimensões, foi excelente. Isto permitiu que se procedesse a uma ampla análise paramétrica, de cunho experimental, em que se variou a velocidade de ensaio, a tensão confinante, as dimensões das amostras de geogrelha, o tipo de solo e a geogrelha, com o intuído de cobrir diferentes situações possíveis de se encontrar nos projetos de engenharia. O trabalho apresenta os principais resultados desta análise
This work presents results of geogrid pullout tests conducted using small scale equipment. The pullout load was applied using a universal load frame, with a maximum capacity of 30kN, capable of recording the pullout load and front displacement. In addition, the test was instrumented with an earth pressure cell installed at the level of the geogrid inclusion. The primary advantage of this equipment is the small volume of soil used in test preparation, resulting in reduced testing time, greater control of the water content and degree of compaction, and significant reduction in overall testing costs. Furthermore, a significant area of the state of Sao Paulo in Brazil is covered by fine grained soils which could be tested according to its pullout behavior using the proposed equipment. To investigate the feasibility of the small scale test facility, comparisons were made between the coefficient of interaction obtained from tests of small and large dimensions. The results show that for the tested materials there were no differences between pull out parameters from both equipment. Additionally it was investigated the effects of testing speed, confining pressure, sample dimensions, and soil and geogrid materials. Results of these tests are presented and discussed

COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
A utilização de pneus usados é uma técnica interessante para reforço de solos, sob o aspecto ambiental. Os pneus usados constituem uma matéria-prima abundante e de custo reduzido. A técnica de utilização de pneus em obras geotécnicas vem sendo difundida no Brasil desde meados dos anos 90, com a construção do muro experimental de solopneus da PUC-Rio, em colaboração com a Fundação Geo-Rio e a Universidade de Ottawa (Canadá). O presente trabalho tem por objetivo apresentar a metodologia para avaliação da resistência ao arrancamento de malhas de pneus. Os pneus podem ser dispostos em um plano horizontal e amarrados entre si, formando uma malha de reforço. Podem ser utilizados pneus inteiros ou com uma das bandas laterais cortadas. A sobrecarga atuando no reforço provém do confinamento provocado pela altura do aterro de solo, construído sobre a malha de pneus. Os ensaios de arrancamento dos pneus no campo utilizaram uma estrutura metálica de reação, atirantada, a qual foi desenvolvida especificamente para o programa experimental sobre reforço de solos. Os resultados permitiram idealizar um mecanismo de ruptura envolvido no processo de arrancamento das malhas de pneus, bem como a verificação das características de resistência e deformabilidade deste tipo de reforço.
The use of scrap tires as soil reinforcement is an environmentally interesting technique. Scrap tires are an abundant and low cost waste material. The technique for using tires in geotechnical construction is becoming popular in Brazil since the construction of an experimental gravity wall made with soil and tires in 1995. This wall was part of a research project by carried out by PUC-Rio in collaboration with Geo-Rio and University of Ottawa. The objective of this work is to present a methodology to evaluate the pull-out behaviour of tire meshes. The tires can be placed in a horizontal plane and tied with rope or wire, forming a reinforcement mesh. The surcharge on these meshes comes from the confinement due to the height of a soil embankment built on the mesh. Field pull-out tests were performed on these reinforcement meshes, using a metallic reaction structure, which was developed specifically for this experimental research. The results allowed the idealization of a shearing mechanism based on the pull-out of tire meshes, as well as the verification of the strength and deformability characteristics of the reinforcement.

CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
A utilização de inclusões passivas para reforços de solos, comumente conhecida como solo grampeado, vem tendo aceitação crescente no meio geotécnico, em especial no sudeste do Brasil. Porém, esta técnica carece de estudos mais detalhados, em particular sobre a resistência ao arrancamento [qs] e sobre a influência de parâmetros tais como o tempo de cura da calda de cimento, o número de injeções, a lavagem do furo e o tipo de solo. Assim, nesta pesquisa, estudou-se o comportamento tensão- deformação-resistência de grampos sob solicitação de arrancamento, em função do método de instalação. Foram considerados grampos com e sem pré- lavagem do furo, com uma ou duas injeções de nata de cimento, com três ou dez dias de cura. Os grampos foram executados em solo residual (maduro ou jovem) e em rocha alterada de gnaisse na cidade de Niterói, RJ. Esta pesquisa apresenta uma metodologia de instrumentação de grampos. O monitoramento das deformações dos strain gages distribuídos ao longo do comprimento dos grampos forneceu ferramentas para se analisar os mecanismos de distribuição de carga e deformação dos grampos. Esta pesquisa propõe ainda uma metodologia a ser adotada em ensaios de arrancamento de grampos, enfocando-se os detalhes executivos. Alguns dos grampos ensaiados foram exumados e os resultados são apresentados, destacando-se os aspectos da superfície de arrancamento, a uniformidade do diâmetro, a presença de fissuras no grampo, e a litologia dos materiais encontrados ao longo do comprimento do grampo. Uma das principais conclusões é a de que o arrancamento de grampos re-injetados (bainha + 1 injeção) executados em solo residual maduro forneceu resistência ao arrancamento em média 37% superior à do grampo com 1 injeção (bainha).
The use of passive inclusions for soil reinforcement, commonly known as soil nail, has experienced an increasing acceptance in the geothecnical projects, especially in the southeast of Brazil. However, this technique still lacks more detailed studies regarding the influence of different installation methods on the pullout resistance [qs]. This research was focused on the study of stress-strainstrength behavior of nails under pullout loading, under different installation procedures. A comprehensive series of pullout tests was carried out on nails installed in holes with and without pre-washing procedures, with one or two consecutive pre-injection steps os cement mortar and with curing time of three or ten days. Test nails were installed in residual gneissic soils with different degrees of weathering along a profile in the same slope in the city of Niterói, Brazil. This methodology developed for the instrumentation of test nails is described in detail. Several strain gages were installed on the nails, for monitoring the strain distribution along the length of the nails. Some of the tested nails were exhumed and observed in detail. This investigation reveals the aspects of the soil-nail interface, with special attention to the uniformity in diameter to the presence of fissures along the nail, and the litology of materials found along the length of the nail. One of the main findings of this experimental investigation is that the re-injection of nails in residual soil resulted in an average increase of 37% of the pullout resistance qs as compared to usual nails with no re-injection procedures. This research concludes with a proposal for a standard methodology to be adopted in nail´s pullout tests.

Ces dernières années, les matériaux composites à matrices minérales ont suscité un grand intérêt dans le domaine du génie civil, en raison de leurs multiples avantages tels que la grande résistance en traction, le comportement pseudo-ductile, la facilité de mise en oeuvre, la nontoxicité et la compatibilité aux substrats. Toutefois, l’efficacité de ces composites est souvent limitée du fait de la faible adhérence du renfort avec la matrice. Cela est du à la faible pénétration des particules de la matrice entre les filaments internes du fil, ce qui entraine une rupture prématurée du matériau. Ce travail a pour but d’améliorer l’adhérence fil-matrice par pré-imprégnation du renfort, afin d’optimiser le comportement mécanique des composites. Deux méthodes de pré-imprégnation ont été utilisées : pré-imprégnation classique par voie humide et pré-imprégnation par voie sèche. Cette dernière se base sur l’application d’un champ électrostatique alternatif permettant la pénétration de la poudre au sein du renfort. La première méthode a déjà été utilisée dans la littérature et a permis d’améliorer les propriétés mécaniques du composite. Cependant, son utilisation reste limitée aux éléments préfabriqués simples contrairement à la deuxième méthode qui peut être appliquée pour réaliser des éléments de construction de grande taille, ou bien pour le renforcement et la réparation des structures in situ. La présente étude s’appuie sur une analyse multi-échelles permettant d’aborder le problème d’adhérence à l’échelle d’interface (fil-matrice) et à l’échelle du composite (fil-matrice et textile-matrice). Tout d’abord, des essais d’arrachement ont été conduits sur des fils de verre enrobés dans une matrice ettringitique. Huit configurations ont été étudiées afin d’évaluer l’effet du processus de pré-imprégnation et le type des matériaux de pré-imprégnation à sec. Il en sort que le comportement d’arrachement est amélioré par pré-imprégnation du fil par voie humide et sèche mais, précisons que par voie sèche, l’amélioration est significative seulement dans le cas d’utilisation de poudre de particules très fines. Une modélisation numérique de l’essai d’arrachement a été également réalisée afin d’identifier les propriétés d’interface fil-matrice. En se basant sur ces résultats, une étude expérimentale et numérique du comportement en traction des composites fil-matrice a été ensuite réalisée. Cinq configurations ont été retenues, après avoir écarté les prétraitements de fil ayant eu un effet néfaste sur l’adhérence fil-matrice. Il s’est avéré que les deux procédés contribuent à une augmentation significative des propriétés mécaniques du composite. De plus, un modèle numérique 3D a été développé pour simuler l’essai de traction d’un composite sec et pré-imprégné. Il a permis d’une part de prédire le comportement global du matériau et d’autre part d’apporter une meilleure compréhension de ce comportement grâce à l’analyse des états de déformation et de contrainte au niveau du fil, de la matrice et de l’interface. Enfin, une comparaison de l’effet des deux procédés de pré-imprégnation a été établie à l’échelle du composite textile-matrice au moyen d’essais de traction et d’analyse de corrélation d’image. Cinq différents types de tissu de verre unidirectionnel ont été utilisés. La pré-imprégnation par voie sèche a démontré la plus forte amélioration des performances du composite quel que soit le grammage du tissu, contrairement à la pré-imprégnation par voie humide qui trouve sa limite quand le textile devient dense
In recent years, mineral matrix composites have gained great interest in the field of civil engineering, thanks to their multiple advantages such as high tensile strength, pseudo-ductile behavior, ease of implementation, non-toxicity and substrate compatibility. However, the efficiency of these composites is often limited because of the low adhesion of the reinforcement to the matrix. This is due to the low penetrability of matrix particles into the space between the inner filaments of the yarn, which leads to premature failure of the material. The purpose of this work is to improve the yarn-matrix adhesion by pre-impregnating the reinforcement in order to optimize the mechanical behavior of composites. Two pre-impregnation methods were used : conventional pre-impregnation in a wet manner and pre-impregnation in a dry manner. This last is based on an alternating electrostatic field used to impregnate yarns with powder. The first method has already been used in the literature and has improved the mechanical properties of the composite. However, it is suited only for the manufacturing of simple prefabricated elements, unlike the second method, which can be applied for the construction of large elements, or for strengthening or repairing structures in site. This study is based on a multi-scale analysis to investigate the bond problem at the interface scale (yarn-matrix) and at the composite scale (yarn-matrix and textile-matrix). First, pull-out tests were conducted on glass yarns embedded in an ettringitic matrix. Eight configurations were studied to evaluate the effect of the pre-impregnation process and the type of dry pre-impregnation powders. It results that the pull-out behavior is improved by pre-impregnating the yarn in wet and dry manner but, it should be noted that in dry process, the improvement is significant only when using very fine particle powders. A numerical modeling of the pull-out test was also carried out in order to identify the yarn-matrix interface properties. Based on these results, an experimental and numerical study of the tensile behavior of yarn-matrix composites was then carried out. Five configurations were selected, after excluding the yarn pre-treatments that had a negative effect on the yarn-matrix bond. It was found that both processes contribute to a significant increase in the mechanical properties of the composite. In addition, a 3D numerical model has been developed to simulate the tensile test of a dry and pre-impregnated composite. It allowed on the one hand to predict the global behavior of the material and on the other hand to provide a better understanding of this behavior by analyzing the deformation and stress states at the level of the yarn, the matrix and the interface. Finally, a comparison of the effect of the two pre-impregnation processes was established at the textile-matrix composite scale by means of tensile tests and image correlation analysis. Five different types of unidirectional glass fabric were used. The dry pre-impregnation has shown the best improvement in composite performance regardless of fabric density, unlike the wet pre-impregnation, which has its limits when the textile becomes dense

Le travail de thèse porte sur la modélisation numérique par la méthode des éléments discrets (MED) du renforcement des sols granulaires par des géogrilles. L'objectif principal de ces travaux est d'améliorer la compréhension des mécanismes d'interaction entre la géogrille et les matériaux granulaires, en particulier ceux liés aux micro-mécanismes. En perspective, ces travaux peuvent contribuer au développement et à l'optimisation de nouveaux produits pour des applications spécifiques. Les géogrilles, en tant qu'éléments de renforcement des couches granulaires ont, par le passé, démontré leur efficacité à travers le monde. Dans de nombreux cas, ces structures apportent une solution le plus souvent économique, sûre et respectueuse de l'environnement. Cependant, le développement et l'optimisation de cette solution doivent tenir compte du comportement d'interaction complexe entre le renforcement et le matériau granulaire. Ainsi, l'utilisation de méthodes numériques capables de reproduire le comportement mécanique de la géogrille (étirement, flexion, cisaillement et torsion) et le comportement du sol à l'échelle du grain au voisinage de la géogrille (effet de roulement, de frottement et de butée) peut contribuer grandement à une meilleure compréhension de l'interaction sol-géogrille. Les modèles numériques basés sur la MED offre cette possibilité tout en ne nécessitant qu'un nombre relativement restreint de paramètres. Toutefois, la mise au point d'un modèle numérique de géogrilles représentatif des produits actuels reste une demande non satisfaite. Cette thèse comprend une nouvelle proposition de modélisation des géogrilles par la méthode des éléments discrets, basée sur l'utilisation d'éléments déformables. Les développements numériques ont été réalisés à partir du code open source YADE. Ils avaient pour objectif la définition d'une géométrie de géogrille générique constituée de brins de forme aplatie, comme c'est généralement le cas dans la pratique. Des simulations numériques d'essais d'extraction de géogrilles ont permis d'analyser le comportement d'interaction entre la grille et le sol granulaire et d'étudier la mobilisation progressive des forces de tension dans le renforcement. Des échantillons numériques comportant des particules sphériques ou non sphériques (clumps constitués de plusieurs sphères imbriquées) de différentes tailles ont été utilisés. Les résultats obtenus montrent que la forme des particules et leur taille relative (comparativement à la taille des ouvertures de la géogrille) ont une influence significative sur la mobilisation et l'intensité des forces d'extraction. Il a également été possible de vérifier que les efforts mobilisés dans les brins transversaux de la géogrille au cours des tests d'extraction sont nettement inférieurs à ceux des brins longitudinaux, mais qu'ils ne sont pas négligeables. Bien que la détermination des paramètres de contact reste une difficulté pour des applications à des cas réels, le modèle numérique discret semble être un outil pertinent et très prometteur pour l'étude de l'interaction entre tout type de géogrille et matériaux granulaires
The thesis topic is the geogrid-reinforced layer based on the Discrete Element Method (DEM). The main objective of the research is to improve the understanding of the interaction between generic geogrids and granular materials, especially those related to micromechanisms. The perspective is that this work can contribute to new studies related to the use of geogrids to optimize the design of such reinforcement. Geogrids as granular layer reinforcement elements have a successful application history throughout the world. In many cases, these structures provide a significantly economical, safe, and environmentally friendly solution. However, the development and optimization of this solution must deal with the complex behavior between the reinforcement and granular material. Thus, the use of numerical methods capable of reproducing the geogrid mechanical behavior (i.e., stretching, bending, shearing, and twisting) and the grain scale soil behavior at the vicinity of the geogrid (i.e., rolling, friction, and abutment effect) can contribute greatly to a better understanding of the soil-geogrid interaction. DEM-based models have this feature with a relatively small number of parameters. Despite this, representative geogrid modeling is still a demand. This thesis comprises a new proposal for discrete geogrid modeling using deformable elements. The numerical construction involved the extensible open-source framework for discrete numerical models YADE and focused on obtaining a realistic flat shape for members of a generic geogrid. Geogrid pullout simulations made it possible to verify the mechanical behavior of the samples and to evaluate the mobilization of forces in the reinforcement. The simulations comprised samples with different amounts of spherical and non-spherical particles. The results obtained were consistent and showed that the particle angularity and the relative size between geogrid openings and particles have a significant influence on the reinforcement strength mobilization. It was also possible to verify that the stresses mobilized in the transverse members of the geogrid during its pullout are significantly lower than those of the longitudinal members, but they are not negligible. Despite the determination of contact parameters is still a difficulty for real cases, the discrete numerical model presented contributes to future studies aiming at the interaction between geogrid and granular materials

HUESKER SYNTHETIC GMBH
No presente trabalho foi estudado o comportamento de um muro de solo reforçado com 5m de altura e 1700m de extensão, construído como parte do dique que compõe o Depósito de Resíduos de Bauxita 7 da ALCOA Alumínio S.A. em Poços de Caldas, MG. Neste muro foram empregados um solo residual siltoargiloso obtido no local e geogrelhas. O muro foi instrumentado para medição de deslocamentos horizontais e verticais durante a construção. Na mesma área, também foi construído um aterro experimental de 2,6m de altura que permitiu a realização de 16 ensaios de arrancamento de grandes dimensões. Foram realizados ensaios de laboratório para definir os parâmetros de resistência e deformabilidade do solo. Os parâmetros obtidos foram empregados em simulações numéricas da construção do muro e dos ensaios de arrancamento pelo Método dos Elementos Finitos, utilizando-se o programa PLAXIS 2D v.8. Os resultados obtidos demonstraram que os deslocamentos ocorridos durante a construção do muro são comparáveis a valores reportados por outros autores. As previsões numéricas da construção do muro e dos ensaios de arrancamento apresentaram boa concordância com os resultados medido em campo. Constatou- se que a resistência ao arrancamento obtida foi superior às previsões baseadas em formulações tradicionais da literatura.
The behavior of a 5m high and 1700m long reinforced soil wall was studied in this work. The wall constitutes the upper part of a dike constructed in Poços de Caldas-MG, Brazil, by Alcoa Aluminum S.A. to contain Bauxite residues. The wall was constructed using geogrids and a residual silty-clay. Two wall sections were instrumented. Horizontal and vertical displacements were monitored during construction. An 2.6m high experimental fill was constructed to conduct 16 large-scale pullout tests. Soil laboratory tests were conducted to define the strength and deformability parameters. The construction of the wall and the pullout tests were simulated using the PLAXIS 2D v.8 Finite Element Method code. The numeric predictions agree well with the field results. The measured horizontal displacements show good agreement with results reported by other authors and the pullout resistance was found to be greater than the values estimated by traditional methods.

A estabilidade primária dos implantes odontológicos é determinante para a osseointegração e depende dos fatores qualidade, quantidade óssea e tipo de implante. O objetivo desse estudo foi avaliar a influência do formato de implantes convencionais e modificados e do tipo de substrato na estabilidade primária por meio da correlação de ensaios de desempenho e frequência de ressonância e análise microestrutural. No estudo foram utilizados 54 implantes Neodent®: 27 cilíndricos, sendo 9 hexágono externo (Titamax Ti Cortical - 4,0 mm x 11 mm), 9 hexágono interno (Titamax II Plus - 3,75 mm x 11 mm) e 9 cone morse (Titamax CM - 4,0 mm x 11 mm); e 27 implantes cônicos de 4,3 mm x 10 mm, sendo 9 hexágono externo (Alvim Ti), 9 hexágono interno (Alvim II Plus) e 9 cone morse (Alvim CM). Os implantes foram inseridos em osso artificial da marca Nacional® nas densidades de 15, 20 e 40 PCF e osso de costela suína. Para os ensaios de desempenho foi quantificado o torque de inserção com um torquímetro digital e a força máxima de arrancamento utilizando uma Máquina Universal de Ensaios. Para avaliar a frequência de ressonância foi utilizado o aparelho Ostell® e para a análise morfológica um Microscópio Eletrônico de Varredura, sob aumentos de 40 e 100 vezes. Após a realização dos ensaios com os implantes convencionais, os modelos Alvim CM e Titamax Ti Cortical (n=9) tiveram sua morfologia externa alterada com a prolongação dos chanfros desde o terço apical até o nível da plataforma protética e foram submetidos aos mesmos testes propostos para os parafusos originais. Verificada a normalidade dos dados utilizou-se o teste de análise de variância ANOVA, comparação de médias Tukey (α=5%) e correlação de Pearson. Para os implantes convencionais, o Alvim CM apresentou maior média em todos os ensaios realizados, sendo estatisticamente diferente dos implantes cilíndricos quando analisado o torque de inserção no osso (73,33 N.cm) e força de arrancamento na poliuretana de 40 PCF (910,36 N) e osso (553,79 N). Os implantes Titamax II Plus tiveram as menores médias, diferente estatisticamente dos cônicos quando analisado o torque de inserção (22,22 N.cm) e frequência de ressonância no osso (72,83 ISQ) e força de arrancamento na poliuretana de 40 PCF (61,97 N) e osso (86,40 N). A análise dos ensaios de desempenho e frequência de ressonância apresentou correlação moderada de acordo com o p de Pearson (0,30 a 0,70) e a comparação entre as fotomicrografias não mostrou alteração morfológica dos implantes. A modificação realizada no parafuso Alvim CM proporcionou um aumento significativo no torque de inserção (p=0,000), diminuição das médias de arrancamento (p=0,000) e manteve semelhança com as médias de frequência de ressonância (p=0,169) quando comparado ao implante convencional. O Titamax Ti modificado aumentou significativamente o torque de inserção (p=0,043) e provocou diminuição significativa para a frequência de ressonância (p=0,002) e ensaio de arrancamento (p=0,000). Conclui-se que o formato dos implantes interfere na estabilidade primária, sendo os implantes cônicos indutores de maior estabilidade. A análise de correlação das metodologias empregadas demonstrou a associação positiva das mesmas para complementação da análise da estabilidade primária
The primary stability of dental implants is critical for osseointegration and depends on factors quality, bone quantity and type of implant. The aim of this study was to evaluate the influence of conventional and modified implants and the type of substrate shape on primary stability through the correlation of performance tests and frequency of resonance and microstructural analysis. In the study 54 Neodent® implants were used: 27 cylindrical, 9 hexagonal (Titamax Ti Cortical - 4.0 mm x 11 mm), 9 internal hexagon (Titamax II Plus - 3.75 mm x 11 mm) and 9 morse taper (Titamax CM - 4.0 mm x 11 mm); and 27 tapered implants of 4.3 mm x 10 mm and 9 external hexagon (Alvim Ti), 9 internal hexagon (Alvim II Plus) and 9 morse taper (Alvim CM). The implants were inserted into artificial bone of National ® brand at densities of 15, 20 and 40 PCF and pork rib bone. For testing the performance was quantified insertion torque with a digital torque meter and the maximum pullout strength using a universal testing machine. To evaluate the resonance frequency was used Ostell ® device and the morphological parsing an Scanning Electron Microscope under increases of 40 and 100 times. After the tests with conventional implants, models CM Alvim and Titamax Cortical Ti (n=9) had their external morphology changed with the prolongation of the bevels from the apical to the level of prosthetic platform and underwent the same tests proposed for the original screws. Checked for normality of the data used in the test of ANOVA, Tukey comparison (α=5%) and Pearson correlation. For conventional implants, the CM Alvim showed higher average in all tests, with statistically different when analyzed cylindrical implant insertion torque on bone (73.33 N.cm) and pullout strength in polyurethane 40 PCF (910.36 N) and bone (553.79 N). Implants Titamax II Plus had the lowest average, statistically different when analyzed the tapered insertion torque (22.22 N.cm) and resonance frequency in bone (72.83 ISQ) and pullout strength in 40 PCF polyurethane (61.97 N) and bone (86.40 N). The analysis of the performance tests and had moderate resonance frequency correlation according op Pearson (0.30 to 0.70) and comparing the photomicrographs showed no morphological alteration of the implants. The modification made to the screw Alvim CM provided a significant increase in insertion torque (p=0.000), decrease of average pullout (p=0.000) and remained similar to the average resonance frequency (p=0.169) when compared to the implant conventional. The Titamax Ti modified significantly increased insertion torque (p=0.043) and caused a significant decrease in the resonance frequency (p=0.002) and pullout test (p=0.000). It is concluded that the shape of the implants interfere with the primary stability, with the inductors tapered implants stability. Correlation analysis of the methodologies used showed a possible association of these for further analysis of primary stability

Zur Untersuchung der Schädigungs- und Versagensmechanismen eines in Beton eingebetteten Multifilamentgarns im Auszugversuch wurde die Schallemissionsanalyse zur Identifizierung und Lokalisierung von Filamentbrüchen eingesetzt. Im ersten Schritt wurden dazu die Schall emittierenden Ursachen (Filamentriss, Filamentablösung und Mikroriss im Beton) für eine Differenzierung charakterisiert. Es wurden Versuche zur Erzeugung von isolierten Signalen durchgeführt, welche mit Hilfe der Signal- und Frequenzanalyse untersucht wurden. Bei dem durchgeführten Garnauszugversuch konnte eine hohe Lokalisierungsgenauigkeit der Filamentbrüche erzielt werden. Der Schädigungsverlauf des Garns während des Auszugversuchs konnte detailliert untersucht werden.

Doctor of Philosophy
Department of Civil Engineering
Robert J. Peterman
This dissertation describes a testing program to evaluate the bond and splitting propensity characteristics of 5.32-mm-diameter prestressing wires. Prestressing wire reinforcement is used primarily in the production of prestressed concrete railroad ties. Twelve different 5.32-mm-diameter wires were tested in this study in order to measure bonding characteristics of the reinforcement. Establishment of the bond-slip characteristics of these reinforcement at both transfer of prestress (transfer bond) and under flexural loading (flexural bond) is necessary to enable the accurate modeling of these ties using finite elements. Transfer bond and flexure bond of various indent patterns were tested using tensioned pullouts. Specimens of various sizes with single or multiple wires were tested to determine the effects of cover and wire number on bond. Indents were machined on smooth prestressing wires to accurately compare indent geometries. Lateral expansion was tested to determine which wires have higher propensity to cause cracking or splitting. Crossties were instrumented to compare resulting lateral expansion with results found in the laboratory. The results from the testing program showed that the tensioned pullout test was able to be used to predict the transfer length of prisms made with the same reinforcement. The results also showed that the indent geometries were able to be used to predict the splitting of specimens based on the amount of slip the wire had experienced. The testing also showed the importance of concrete cover with the relation to splitting potential.

When subjected to a combination of moment and shear force, a reinforced concrete (RC) beam with either little or no transverse reinforcement can fail in shear before reaching its full flexural strength. This type of failure is sudden in nature and usually disastrous because it does not give sufficient warning prior to collapse. To prevent this type of shear failure, reinforced concrete beams are traditionally reinforced with stirrups. However, the use of stirrups is not always cost effective since it increases labor costs, and can make casting concrete difficult in situations where closely-spaced stirrups are required. The use of steel fiber reinforced concrete (SFRC) could be considered as a potential alternative to the use of traditional shear reinforcement. Concrete is very weak and brittle in tension, SFRC transforms this behaviour and improves the diagonal tension capacity of concrete and thus can result in significant enhancements in shear capacity. However, one of the drawbacks associated with SFRC is that the addition of fibers to a regular concrete mix can cause problems in workability. The use of self-consolidating concrete (SCC) is an innovative solution to this problem and can result in improved workability when fibers are added to the mix. The thesis presents the experimental results from tests on twelve slender self-consolidating fiber reinforced concrete (SCFRC) beams tested under four-point loading. The results demonstrate the combined use of SCC and steel fibers can improve the shear resistance of reinforced concrete beams, enhance crack control and can promote flexural ductility. Despite extensive research, there is a lack of accurate and reliable design guidelines for the use of SFRC in beams. This study presents a rational model which can accurately predict the shear resistance of steel fiber reinforced concrete beams. The thesis also proposes a safe and reliable equation which can be used for the shear design of SFRC beams.

The first objective of this thesis was to determine the material properties of grade 270 and grade 300 prestressing strand of various sizes. Tension tests were performed on each type of strand. The data from these tests was used to determine modulus of elasticity, yield stress, ultimate stress, and ultimate elongation for each strand. The yield stresses and ultimate stresses for many of the strands did not meet the requirements found in ASTM A416. The ultimate elongation results far exceeded the requirements and the measured elastic moduli were near the modulus recommended by AASHTO LRFD. A secondary objective from the tension tests was to evaluate a gripping method which used aluminum tubing to cushion the strands against notching. The grips performed very well. Most of the strand breaks did not occur in the grips and when a strand did break in the grips, the failure occurred after significant post-yield elongation. The second objective was to evaluate the bond properties of grade 270 and grade 300 prestressing strands. The North American Strand Producers (NASP) Bond Test and Large Block Pullout Test (LBPT) were performed on six different strand grade and strand size combinations. Both of the tests are simple pullout tests on untensioned strand. The results for each strand type were compared to one another as well as to measured transfer and development lengths from beams using the strand from the same reel. All of the strands showed sufficient bond in the beams, but one strand type did fail both the NASP Test and the LBPT. Both pullout tests were acceptable methods to evaluate strand surface condition and the benchmarks set for 0.5 in. diameter regular strand were conservative for the strands used in this thesis. Little difference was evident in the bond performance of grade 270 and grade 300 prestressing strand.
Master of Science

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Um aspecto particular no dimensionamento de maciços reforçados com geossintéticos consiste na análise da estabilidade interna. A ruptura interna pode ocorrer quando as solicitações impostas ao elemento de reforço superam a resistência à tração, ou quando ocorre o arrancamento do reforço da massa de solo, por ancoragem insuficiente. A distribuição das deformações e das tensões ao longo do comprimento enterrado do reforço não é uniforme, e este aspecto não é considerado no dimensionamento. Desta forma, modelos analíticos e numéricos aparecem como alternativas capazes de reduzir incertezas no dimensionamento de maciços reforçados, permitindo a adoção de soluções menos conservativas. O presente trabalho propõe um modelo analítico para a reprodução do mecanismo de transferência de esforços e deslocamentos ao longo do comprimento de geotêxteis sob condição de arrancamento, e apresenta a modelagem numérica de ensaios de arrancamento, fazendo uso do programa Plaxis, de elementos finitos. A partir dos resultados de um extenso programa experimental de ensaios de arrancamento instrumentados, em geotêxteis (Espinoza,2000), os modelos analítico e numérico foram validados e discutidos. Posteriormente, apresenta-se a simulação de um ensaio de arrancamento hipotético fazendo uso de ambos os modelos. Os resultados sugerem que os modelos analítico e numérico foram adequados na previsão dos esforços, deformações e deslocamentos ao longo do comprimento de geotêxteis em solicitações de arrancamento. Observou-se um melhor ajuste entre as previsões do modelo analítico e os resultados experimentais, justificado pela adoção do modelo não linear para o elemento geotêxtil. A distribuição de esforços e deslocamentos ao longo de geotêxteis é complexa, e a boa concordância dos modelos com os resultados experimentais reforça a potencialidade dos modelos para uso futuro.
The internal stability analysis is a particular aspect in the design of reinforced soil with geotextiles. Internal failure may occur when the stresses transmitted to the reinforcing element exceeds the tensile strength or when it is pulled out, due to insufficient anchorage. The stress strain distribution along the embedded length of the reinforcement is not uniform, and this condition is not incorporated in the design. Thus, analytical and numerical models appear as alternatives to reduce uncertainties in the design of reinforced soil structures, allowing the adoption of less conservative solutions.The present research proposes an analytical model that reproduces load transfer mechanism and displacements along the length of geotextiles under pullout condiction, and also presents a numerical simulation of pullout tests, making use of Plaxis FEM program. Based on the results of an extensive program of pullout tests in instrumented samples of geotextiles (Espinoza, 2000), the analytical and numerical models were validated and discussed. The simulation of a hypothetical pullout test making use of both models is also presented.The results suggest that the analytical and numerical models are suitable to predict loads, strains and displacements along the geotextiles length, submitted to pullout. The analytical model provided a better fit for the experimental results, since it incorporates a non-linear behavior for the geotextile. The distribution of loads and displacements along the geotextiles is complex, and the good agreement between the models and the experimental results emphasizes the capability of the models for further use.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Foi desenvolvido um ensaio imunoenzimático do tipo ELISA indireto para a detecção de resposta sorológica de aves para Salmonella sorotipos Gallinarum, Pullorum, Enteritidis e Typhimurium. Utilizou-se antígeno solúvel obtido por meio de sonicação de cultura de Salmonella Gallinarum (AgSG), Salmonella Enteritidis cepa aflagelar (AgSE) e Salmonella Typhimuirum cepa aflagelar (AgTM), os conjugados peroxidase e fosfatase alcalina e amostras de soros positivos e negativos de vários sorotipos de salmonelas. Os resultados demonstraram que o AgSG pode ser utilizado diluído a 1:25.000 (peroxidase e fosfatase alcalina). Observou-se que o ELISA contendo S. Gallinarum como antígeno e fosfatase alcalina como enzima, propicia a separação de reações positivas para Gallinarum e Pullorum de Enteritidis. O AgSE pode ser utilizado diluído a 1:10.000 (peroxidase) ou 1:5.000 (fosfatase alcalina). Nestas condições, o ELISA/AgSE detectou resposta sorológica para os sorotipos Enteritidis, Gallinarum e Pullorum. O ELISA com o AgTM demonstrou que o antígeno pode ser diluído a 1:20.000 para ambos os conjugados. O ELISA/AgTM demonstrou reatividade entre salmonelas dos grupos B e D. Todas as amostras de soros testes devem ser analisadas diluídas a 1:1.000. Concluindo, o ELISA mostrou-se um teste útil para identificar aves com reação sorológica contra S. Gallinarum, S. Pullorum, S. Enteritidis e S. Typhimurium, podendo ainda identificar aves com sorologia positiva para S. Gallinarum, S. Pullorum sem que haja reação cruzada com amostras de soro de aves vacinadas ou infectada por S. Enteritidis.
This study was done to assess the enzyme-linked immunosorbent assays (ELISA) for detection chicken serologic response against Salmonella enterica sorotypes Gallinarum, Pullorum, Enteritidis and Typhimurium. The test was performed using soluble proteins from Salmonella Gallinarum strain 9 (AgSG), from non-flagellate Salmonella Enteritidis strain (AgSE) and from not flagellate Salmonella Typhimurium (AgTM) strain as detecting antigen and peroxidase and alkaline phosphatase enzymes, as conjugate. According to the results, the antigen has to be diluted at 1:25.000 (AgSG, peroxidase and alkaline phosphatase). In addition, using alkaline phosphatase enzyme, the assay was helpful to separate positive serological reaction to serotypes Gallinarum and Pullorum from Enteritidis. To the ELISA/AgSE, the antigen has to be diluted at 1:10.000 for peroxidase assay and at 1:5.000 for alkaline phosphatase assay. In this condition, the ELISA/AgSE can detect serological reaction to S. Enteritidis, S. Gallinarum and S. Pullorum. To the ELISA/AgTM the antigen has to be diluted at 1:20.000 to both enzymes. In this condition the ELISA/AgTM showed sensibility but was no possible to separate positive serological reaction to serotype concerning at the group B and group D. In all test, the sample of serum has to be diluted at 1:1.000. Therefore, the ELISA was able to identity reactors birds to Salmonella antigens and also to detect serological response to S. Gallinarum, S. Pullorum antigen with no cross-reaction with serum samples taken from birds either challenged or vaccinated against S. Enteritidis.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Retaining structures with nails have been used in recent decades to contain excavation works in several Brazilian cities, including Goiânia. The nails are made of steel bars inserted in inclined or horizontal drilling, with small diameter and involved in cement grout, to ensure the stability of vertical excavations by frictional forces developed in the contact between the soil and nail. Therefore, it is important to understand this friction to design retaining structures. There are lots of calculation methods proposed by many authors to design nails and verify the stability of these structures. The main objective of this work was to review some calculation methods, conduct pullout tests in the field and laboratory tests with samples taken in situ, to evaluate calculation methodologies or parameters that best apply to the soil studied in Goiânia. Among several proposals to estimate the media shear stress in the soil-nail interface (qs) based on SPT, that showed better results in this paper are those from graph lower limit proposed by Ortigão e Palmeira (1997), Springer (2006) and a proposal based on Décourt & Quaresma (1978) to calculate pile lateral friction, using the proper parameter b. Other propositions based on soil type and parameters of the soil that showed good fits were Wong (1995) and Juran et al. (1990). The relation between qs and the shear stress of soil (ts) resulted values between 0,55 and 0,85. Displacement readings were performed during loading and unloading phase, was observed that for small loads, plastic deformations occured in the nail, so is recommended in cases of nail’s numerical analyzes adopt elastic-plastic models. Predictions of nail's elastic deformation, based on piles theory showed good results, however significant plastic deformation occured in nails. The results of shear tests were compared with the pullout tests, indicating that the reduction factor of laboratory results is necessary.
Estruturas de contenção com utilização de grampos têm sido cada vez mais empregadas nas últimas décadas com intuito de conter grandes escavações em diversas cidades brasileiras, incluindo Goiânia. Os grampos consistem em barras de aço introduzidas em perfurações inclinadas ou horizontais de pequeno diâmetro e posterior injeção de calda de cimento, de forma a garantir a estabilidade de escavações verticais pelas forças de atrito desenvolvidas no contato solo-grampo. Sendo assim, é fundamental o conhecimento deste atrito para o dimensionamento destas contenções. Existem vários métodos de cálculo propostos por diversos autores para o dimensionamento de grampos e verificação da estabilidade dessas estruturas. O objetivo principal deste trabalho foi o de revisar alguns desses métodos de cálculo, realizar ensaios de arrancamento em campo e também ensaios em laboratório com amostras retiradas de uma obra com múltiplos subsolos, para avaliar as metodologias de cálculo ou parâmetros que melhor se aplicam aos solos estudados da cidade de Goiânia. Dentre as diversas proposições para estimativa da tensão cisalhante média no contato sologrampo (qs) aquelas baseadas em ensaio SPT que obtiveram melhores resultados neste trabalho foram o limite inferior do gráfico proposto por Ortigão e Palmeira (1997), Springer (2006) e uma proposição baseada no Método Décourt e Quaresma (1978) para atrito lateral em estacas, com o ajuste adequado do parâmetro b. Outras proposições baseadas no tipo e parâmetros do solo que apresentaram bons ajustes foram Wong (1995) e Juran et al. (1990). Foram feitas comparações entre qs e a tensão cisalhante do solo (ts) encontrando para esta razão valores entre 0,55 e 0,85. Como foram realizadas leituras de deslocamentos tanto na fase de carregamento quanto na fase de descarregamento, notou-se que para pequenas aplicações de carga já acontecem deformações plásticas no grampo sendo recomendado nos casos de análises numéricas em grampos a adoção de modelos elasto-plásticos. As previsões de deformações elásticas dos grampos, baseadas em teorias de estacas apresentou uma boa aproximação dos ensaios, que entretanto apresentaram relevante deformação plástica nos ensaios realizados. Os resultados de ensaios de cisalhamento em amostras indeformadas dos solos foram comparados com os ensaios de arrancamento, indicando que o fator de redução dos resultados de laboratório é necessário.

Solo grampeado é uma alternativa eficiente utilizada em obras de reforço de solos. É resultante da inclusão de reforços, denominados grampos, em um maciço em corte. A resistência ao cisalhamento da interface solo-grampo é um dos parâmetros mais importantes para fins de projeto. Este parâmetro é determinado a partir da experiência dos projetistas e se baseia principalmente no tipo de solo e em ensaios de campo (arrancamento, sondagens a percussão e pressiométricos). Neste contexto, a realização de ensaios de arrancamento in situ é extremamente importante para a quantificação deste parâmetro e, conseqüentemente, para a elaboração de projetos mais econômicos e seguros. A execução de ensaios de arrancamento em laboratório permite verificar condições muitas vezes não encontradas em campo. Este trabalho apresenta os resultados de ensaios de arrancamento de grampos realizados em laboratório. Também foi analisada a evolução da força nos grampos e dos deslocamentos do solo. Os grampos foram instalados em um protótipo de solo grampeado sobre o qual se aplicou uma sobrecarga de 50 kPa através de uma bolsa de ar comprimido. Os ensaios de arrancamento permitiram quantificar valores de resistência ao cisalhamento de interface da ordem de 145 kPa, mobilizados com pequenos deslocamentos dos grampos. O arrancamento de grampos instrumentados indicou que cerca de 90% do comprimento total dos grampos foi solicitado. Ao final dos ensaios de arrancamento, os grampos foram extraídos completamente do maciço de solo o que permitiu comprovar a sua integridade física. Os deslocamentos do solo foram máximos próximo ao topo do protótipo e na direção horizontal. Os resultados demonstram a viabilidade de estudar o comportamento do maciço reforçado a partir do comportamento do protótipo de solo grampeado construído em laboratório.
Soil nailing is an efficient soil reinforcement technique which uses inclusions, namely nails, in soil slopes. Unit skin friction is one of the most important parameters used in soil nailing design. The definition of this parameter is commonly based on local experience and correlations to some in situ tests. This work presents the results obtained from the pullout test carried out in a soil nailed wall prototype built in laboratory. Forces acting in nails were measured by strain gage instrumentation. Soil displacement was measured in short and long terms. The pullout tests were carried out after the application of a uniform surcharge given by a compressed air bag. The results showed that unit skin friction was about 145 kPa, mobilized with little nail displacements. About 90% of nail length were solicited during pullout tests, according to tests performed in strain gage instrumented nails. Nail extraction showed a high level of nail integrity. Soil displacements were higher close to the wall top, near the face. These results demonstrate the feasibility of using of laboratory prototype studies to investigate the geotechnical behavior of soil nailing structures.

Apesar do largo emprego da técnica de solo pregado em nosso país, pouquíssima pesquisa foi realizada sobre a resistência ao cisalhamento de interface solo-reforço (qs) e sobre a importância deste parâmetro no desempenho desta técnica de reforço in situ de taludes e escavações. Busca-se com esta tese, avaliar experimentalmente, a influência de diferentes metodologias executivas do chumbador (número de injeções) neste parâmetro. As informações para o desenvolvimento deste trabalho foram obtidas a partir de ensaios de arrancamento realizados em chumbadores construídos em duas obras nas cercanias da cidade de São Paulo, ou seja, em escala real. De forma complementar, também foi construído uma estrutura de solo pregado em laboratório. A partir dos ensaios realizados, observaram-se melhorias significativas na resistência ao cisalhamento de interface a partir das injeções do chumbador e estabelecer equações que relacionam o valor de qs com o volume injetado de calda de cimento, sendo uma importante ferramenta para analisar o desempenho do chumbador. O monitoramento ao longo do ensaio permitiu analisar os mecanismos de distribuição das cargas. Por fim, é apresentada uma proposta de metodologia para a realização do controle de qualidade do chumbador.
Besides the soil nailing technique being common practice in Brazil, there is little research on the shear strength of the soil-reinforcement interface (qs) and on the importance of this parameter on the performance of this in situ reinforcement technique of slopes and excavations. Accordingly, this study has the objective to experimentally evaluate the influence of different executive methodologies of the nail (i.e. number of grout injections) on the parameter qs. Data were obtained from in situ, full scale pullout tests performed on nails built in two construction sites near Sao Paulo city. Additionally, a soil nailing structure was built in laboratory. The results show that significant improvement is achieved on the soil-nail interface shear strenght by the number of grout injections. Moreover, the pullout tests on the nails provided quantification of this improvement. Consequently, it was possible to establish equations that relate the value of qs to the volume of cement grout injected, which is as important tool to evaluate the performance of the nail. Monitoring of the instrumentation during execution of the pullout tests allowed evaluation of the mechanisms of load distribution along the nails. Finally, a methodology is proposed for a quality control procedure on soil-nailed walls.

In the present work, the load-bearing behaviour of Textile Reinforced Concrete (TRC), which is a composite of a fine-grained concrete matrix and a reinforcement of high-performance fibres processed to textiles, exposed to uniaxial tensile loading was investigated based on numerical simulations. The investigations are focussed on reinforcement of multi-filament yarns of alkali-resistant glass. When embedded in concrete, these yarns are not entirely penetrated with cementitious matrix, which leads associated with the heterogeneity of the concrete and the yarns to a complex load-bearing and failure behaviour of the composite. The main objective of the work was the theoretical investigation of effects in the load-bearing behaviour of TRC, which cannot be explained solely by available experimental results. Therefore, a model was developed, which can describe the tensile behaviour of TRC in different experimental test setups with a unified approach. Neglecting effects resulting from Poisson’s effect, a one-dimensional model implemented within the framework of the Finite Element Method was established. Nevertheless, the model takes also transverse effects into account by a subdivision of the reinforcement yarns into so-called segments. The model incorporates two types of finite elements: bar and bond elements. In longitudinal direction, the bar elements are arranged in series to represent the load-bearing behaviour of matrix or reinforcement. In transverse direction these bar element chains are connected with bond elements. The model gains most of its complexity from non-linearities arising from the constitutive relations, e. g., limited tensile strength of concrete and reinforcement, tension softening of the concrete, waviness of the reinforcement and non-linear bond laws. Besides a deterministic description of the material behaviour, also a stochastic formulation based on a random field approach was introduced in the model. The model has a number of advantageous features, which are provided in this combination only in a few of the existing models concerning TRC. It provides stress distributions in the reinforcement and the concrete as well as properties of concrete crack development like crack spacing and crack widths, which are in some of the existing models input parameters and not a result of the simulations. Moreover, the successive failure of the reinforcement can be studied with the model. The model was applied to three types of tests, the filament pull-out test, the yarn pull-out test and tensile tests with multiple concrete cracking. The results of the simulations regarding the filament pull-out tests showed good correspondence with experimental data. Parametric studies were performed to investigate the influence of geometrical properties in these tests like embedding and free lengths of the filament as well as bond properties between filament and matrix. The presented results of simulations of yarn pull-out tests demonstrated the applicability of the model to this type of test. It has been shown that a relatively fine subdivision of the reinforcement is necessary to represent the successive failure of the reinforcement yarns appropriately. The presented results showed that the model can provide the distribution of failure positions in the reinforcement and the degradation development of yarns during loading. One of the main objectives of the work was to investigate effects concerning the tensile material behaviour of TRC, which could not be explained, hitherto, based solely on experimental results. Hence, a large number of parametric studies was performed concerning tensile tests with multiple concrete cracking, which reflect the tensile behaviour of TRC as occurring in practice. The results of the simulations showed that the model is able to reproduce the typical tripartite stress-strain response of TRC consisting of the uncracked state, the state of multiple matrix cracking and the post-cracking state as known from experimental investigations. The best agreement between simulated and experimental results was achieved considering scatter in the material properties of concrete as well as concrete tension softening and reinforcement waviness
Die vorliegende Arbeit beschäftigt sich mit Untersuchungen zum einaxialen Zugtragverhalten von Textilbeton. Textilbeton ist ein Verbundwerkstoff bestehend aus einer Matrix aus Feinbeton und einer Bewehrung aus Multifilamentgarnen aus Hochleistungsfasern, welche zu textilen Strukturen verarbeitet sind. Die Untersuchungen konzentrieren sich auf Bewehrungen aus alkali-resistentem Glas. Das Tragverhalten des Verbundwerkstoffs ist komplex, was aus der Heterogenität der Matrix und der Garne sowie der unvollständigen Durchdringung der Garne mit Matrix resultiert. Das Hauptziel der Arbeit ist die theoretische Untersuchung von Effekten und Mechanismen innerhalb des Lastabtragverhaltens von Textilbeton, welche nicht vollständig anhand verfügbarer experimenteller Ergebnisse erklärt werden können. Das entsprechende Modell zur Beschreibung des Zugtragverhaltens von Textilbeton soll verschiedene experimentelle Versuchstypen mit einem einheitlichen Modell abbilden können. Unter Vernachlässigung von Querdehneffekten wurde ein eindimensionales Modell entwickelt und im Rahmen der Finite-Elemente-Methode numerisch implementiert. Es werden jedoch auch Lastabtragmechanismen in Querrichtung durch eine Unterteilung der Bewehrungsgarne in sogenannte Segmente berücksichtigt. Das Modell enthält zwei Typen von finiten Elementen: Stabelemente und Verbundelemente. In Längsrichtung werden Stabelemente kettenförmig angeordnet, um das Tragverhalten von Matrix und Bewehrung abzubilden. In Querrichtung sind die Stabelementketten mit Verbundelementen gekoppelt. Das Modell erhält seine Komplexität hauptsächlich aus Nichtlinearitäten in der Materialbeschreibung, z.B. durch begrenzte Zugfestigkeiten von Matrix und Bewehrung, Zugentfestigung der Matrix, Welligkeit der Bewehrung und nichtlineare Verbundgesetze. Neben einer deterministischen Beschreibung des Materialverhaltens beinhaltet das Modell auch eine stochastische Beschreibung auf Grundlage eines Zufallsfeldansatzes. Mit dem Modell können Spannungsverteilungen im Verbundwerkstoff und Eigenschaften der Betonrissentwicklung, z.B. in Form von Rissbreiten und Rissabständen untersucht werden, was in dieser Kombination nur mit wenigen der existierenden Modelle für Textilbeton möglich ist. In vielen der vorhandenen Modelle sind diese Eigenschaften Eingangsgrößen für die Berechnungen und keine Ergebnisse. Darüber hinaus kann anhand des Modells auch das sukzessive Versagen der Bewehrungsgarne studiert werden. Das Modell wurde auf drei verschiedene Versuchstypen angewendet: den Filamentauszugversuch, den Garnauszugversuch und Dehnkörperversuche. Die Berechnungsergebnisse zu den Filamentauszugversuchen zeigten eine gute Übereinstimmung mit experimentellen Resultaten. Zudem wurden Parameterstudien durchgeführt, um Einflüsse aus Geometrieeigenschaften wie der eingebetteten und freien Filamentlänge sowie Materialeigenschaften wie dem Verbund zwischen Matrix und Filament zu untersuchen. Die Berechnungsergebnisse zum Garnauszugversuch demonstrierten die Anwendbarkeit des Modells auf diesen Versuchstyp. Es wurde gezeigt, dass für eine realitätsnahe Abbildung des Versagensverhaltens der Bewehrungsgarne eine relativ feine Auflösung der Bewehrung notwendig ist. Die Berechnungen lieferten die Verteilung von Versagenspositionen in der Bewehrung und die Entwicklung der Degradation der Garne im Belastungsverlauf. Ein Hauptziel der Arbeit war die Untersuchung von Effekten im Zugtragverhalten von Textilbeton, die bisher nicht durch experimentelle Untersuchungen erklärt werden konnten. Daher wurde eine Vielzahl von Parameterstudien zu Dehnkörpern mit mehrfacher Matrixrissbildung, welche das Zugtragverhalten von Textilbeton ähnlich praktischen Anwendungen abbilden, durchgeführt. Die Berechnungsergebnisse zeigten, dass der experimentell beobachtete dreigeteilte Verlauf der Spannungs-Dehnungs-Beziehung von Textilbeton bestehend aus dem ungerissenen Zustand, dem Zustand der Matrixrissbildung und dem Zustand der abgeschlossenen Rissbildung vom Modell wiedergegeben wird. Die beste Übereinstimmung zwischen berechneten und experimentellen Ergebnissen ergab sich unter Einbeziehung von Streuungen in den Materialeigenschaften der Matrix, der Zugentfestigung der Matrix und der Welligkeit der Bewehrung

Grande percentagem do território brasileiro é coberta por solos finos (% passando peneira # 200 > 50%), geralmente de origem tropical, que poderiam ser classificados como solos de baixa capacidade de drenagem. Estes solos não atendem às recomendações técnicas para solos de aterro de estruturas reforçadas, conforme exigido pela AASHTO e BS 8006. Neste trabalho foi avaliado experimentalmente um dos parâmetros mais importantes de projeto de Terra Armada, que condiciona o mecanismo de transferência de carga, o coeficiente de atrito aparente solo-fita metálica (f*). Foi avaliada a influência das características dos solos para as classes de solos estabelecidas pela NBR 9286/86 para o caso de fitas metálicas, e, dos critérios que sustentam o uso de fitas poliméricas, sob diversas tensões verticais atuantes nas fitas, simulando o efeito da profundidade. As informações foram obtidas através de ensaios de arrancamento de fitas metálicas e poliméricas realizados em laboratório e depois comparadas aos resultados teóricos da norma e àqueles preconizados para o uso de fitas poliméricas. Os ensaios realizados com as fitas em solo não convencional 1 e em areia mal graduada, mostraram que para profundidades equivalentes a tensões verticais até 50 kPa, os dois tipos de inclusões possuem valores de coeficiente de interação com o solo maiores que a unidade, isso tornaria razoável o seu uso sob o ponto de vista deste parâmetro e nas condições da realização dos ensaios, quando comparado com a norma, e com os critérios que sustentam o uso das fitas poliméricas em técnica de solo armado. No entanto, para maiores profundidades, a interação apresenta uma tendência de diminuição. O solo não convencional 2 valores da interação muito baixos. Foram instalados strain gages ao longo do comprimento das fitas para monitoramento dos esforços no maciço. Nota-se que esforços elevados ocorreram nas regiões mais próximas do ponto de aplicação da força de arrancamento.
A large percentage of Brazil\'s territory is covered with fine tropical soil (50% passing #200) which can be classified as soils with low drainage capacity. These soils do not meet the technical recommendations for backfill of reinforced soil structures by AASHTO and BS 8006. This paper presents the result of an experimental evaluation of one of the most important design parameters of mechanically stabilized earth with concrete wall facing. The apparent friction coefficient of soil-steel strips and soil-polymeric strips is the project parameter. Also was evaluated the influence of soil characteristics for soil types listed by the NBR 9286/86 for metal strips and for the criteria that support the use of polymeric strips. The evaluation included the application of different vertical stresses on the strips simulating the effect of depth. The information obtained from pullout tests performed in laboratory was compared to the standard theoretical values and design values for polymeric strips. Tests performed on strips in nonconventional soil (1) and poorly graded sand showed that at depths equivalent to vertical stresses up to 50 kPa the two types of inclusions have coefficients of interaction greater than unity, which appears reasonable. Therefore, such soils can be used as backfill soils in the conditions tested and at equal or lesser stress levels. Nonconventional soil (2) showed low value of the friction coefficient. The strain gages installed along the length of the strips recorded the distribution of tensile stress in pull-out tests. Higher tensile stress was recorded by the gages nearest the point of application of the pull-out force.

Este trabalho apresenta um estudo comparativo da eficiência de diferentes geossintéticos no reforço de base de pavimentos de obras viárias com ensaios de arrancamento de pequeno porte. Utilizou-se geogrelhas de polipropileno, poliéster e de fibra de vidro e geotêxtil tecido de polipropileno. Um solo com 58% de argila (subleito) e um pedregulho areno-siltoso (camada de base) foram empregados. Os ensaios de arrancamento foram executados com diferentes combinações entre solos e geossintéticos. Nestes foi utilizado um novo sistema de medida direta de deslocamentos ao longo da inclusão com sensores óticos a laser. Além de analisar os resultados com curvas força de arrancamento x deslocamentos, foi possível utilizar gráficos rigidez x deformação para determinar o melhor geossintético no reforço de base de pavimentos. Como o corpo-de-prova de geossintético é de tamanho reduzido, garante-se a mobilização completa do reforço durante o ensaio de arrancamento e assim, é possível obter a deformação do mesmo. A abertura frontal da caixa de arrancamento tem influência no valor da força máxima ao arrancamento registrada no ensaio. Os resultados mostram que a interação solo-reforço é mais importante que a rigidez não-confinada do geossintético no comportamento do material em situação de confinamento no interior do maciço de solo. Observou-se que a resistência de junta, a geometria e o agulhamento da geogrelha, além da granulometria do solo, afetam a rigidez inicial do sistema. A melhor opção para os solos e geossintéticos estudados segue a seguinte ordem: (1) geogrelha de polipropileno, (2) geogrelha de poliéster, (3) geotêxtil tecido de polipropileno e (4) geogrelha de fibra de vidro.
This work presents an evaluation of various geosynthetics efficiency in reinforced base course of road pavements using small scale pullout tests. It was used polypropylene, polyester and glass fiber geogrids and polypropylene woven geotextile. A soil with 58% of clay (subgrade), and a sandy-silty gravel (base course) were used. The pullout tests were conducted with different combinations among soils and geosynthetics. In these tests, a new system of direct measurement of inclusion displacements with laser optical sensors was used. Beyond analyzing the results with curves pullout force x displacements, it was possible to use graphics rigidity x deformation in order to determinate the best geosynthetic in base course reinforcement. As the geosynthetic specimen is of small size, the complete mobilization of the reinforcement is guaranteed and, therefore, it is possible to obtain its deformation. The frontal aperture of the pullout box influences the maximum pullout resistance. The results show that the soil-reinforcement interaction is more important than the unconfined rigidity of the geosynthetic on the material behavior in confinement situation inside the soil block. The joint resistance, the geogrid geometry and its nailing, besides the soil particles size, affect the initial system rigidity. Therefore, they are important for base course reinforcement of road pavements. The results showed that the best option for the soils and geosynthetics studied are in the following order: (1) polypropylene geogrid, (2) polyester geogrid, (3) polypropylene woven geotextile and (4) glass fiber geogrid.

This thesis reports on experimental investigations of the mechanisms inherent in the joint action of short and continuous fibres in high-performance, cement-based composites. Experiments on different levels of observation (macro- meso- and micro-levels) were performed to provide detailed insights into the various effects of adding different types of short fibres (dispersed AR glass, integral AR glass and dispersed carbon fibres) on the strength, deformation, and failure behaviour of textile-reinforced concrete (TRC) subjected to tensile loading. Moreover, visual inspections of the specimens' surfaces and microscopic investigation of the fracture surfaces and the interface zone between fibre and matrix were performed and evaluated. Subsequently, the mathematical descriptions for TRC with short fibres under deformation controlled tensile loading conditions were derived based on a multi-scale rheological-statistical modelling approach. Based on a literature review, the state of the art is presented and discussed to identify key questions that are yet to be answered satisfactorily. This provides the starting point for the investigations presented in this thesis. The experimental program on the macro-level included uniaxial tension tests performed on thin, narrow plates reinforced by: a) only textile reinforcement, b) only short fibres, and c) hybrid reinforcement (both textile reinforcement with the addition of short fibres). Special attention was directed toward the course of the stress-strain relationship, crack pattern development, and fibre failure behaviour. The stress-strain curves resulting from uniaxial tension testing demonstrated clearly the positive influence of all types of short fibre on the mechanical performance of TRC. While the first-crack stress in TRC specimens increased significantly due to the addition of short fibres, an expansion of the strain region, where multiple cracks form, was observed for the stress-strain curves for TRC with added short fibres. The visual inspection of the specimens\' surfaces showed a higher number of cracks and finer crack patterns for given strain levels in the cases when short fibres were added to TRC. Moreover, depending on fibre type, the positive effects of the addition of short fibres on both tensile strength and work-to-fracture of the composite were found to vary significantly. The findings at the micro- and meso-levels of observation provided to a great extent a core of understanding of some particular mechanical behavioural properties of TRC with short fibres at the macro-level of observation. Thus, in addition to the experimental testing performed on composite materials with different parameter combinations, investigations of the action of individual material components, i.e., multifilament-yarns and single short fibres, embedded into cement-based matrices were carried out. It was found that short fibres indeed improve the bond between multifilament-yarns and the surrounding matrix. By their random positioning on the yarn\'s surface, short fibres built new adhesive cross-links which provided extra connecting points to the surrounding matrix. Furthermore, the water-to-binder ratio of the matrix influenced bond quality between fibre and matrix, i.e., various degrees of matrix-fibre bond were observed. As a result, the mechanical behaviour of the composite varied with w/b: While the good bond of the fibre embedded in a matrix with a low water-to-binder ratio leads to increase in stiffness and strength of the composite, fibres with weak bonding can be considered as defects with respect to stiffness as they lead to a decrease in the value. The thesis further derives the mathematical relationships for TRC with the addition of short fibres under deformation-controlled tensile loading. A physically based rheological model consisting of simple rheological elements was developed based on the experimental results on the micro-scale, using single-fibre pullout tests. Special attention was paid to the gradual de-bonding process and the resulting force-displacement branch. The model adequately reproduced both relevant fibre failure scenarios: fibre fracture and fibre pullout. By means of statistical procedures the combination of these models led to description of the stress-crack opening behaviour of an individual crack bridged by the given number of short fibres. The stress-strain relation for TRC with short fibres subjected to tensile loading was then derived. The concept followed at the macro-level of observation was modelling separately the three main regions of the characteristic stress-strain curve. The regions of crack-free material and crack-widening were considered linear and described based on the corresponding characteristic values of each region. The behaviour of the multiple cracking region was derived by considering an increasing number of cracks in serial interconnection and the contribution of the uncracked matrix in between. The stress transfer, i.e., bridging stress, across the crack was determined based on the contribution of both short fibres and multifilament-yarns. Behaviour of individual cracks was adjusted by varying the number of bridging fibres in different cracks and by varying the yarn bridging stress according to range observed in the pullout experiments
In der vorliegenden Arbeit wird über Untersuchungen zu den Mechanismen der Wechselwirkungen zwischen Kurz- und Endlosfasern in zement-basierenten Hochleistungskompositen berichtet. Hierzu wurden experimentelle Untersuchungen auf verschiedenen Betrachtungsebenen (Makro-, Meso- und Mikroebene) durchgeführt mit dem Ziel, detaillierte Erkenntnisse zu den Auswirkungen der Zugabe von verschiedenen Arten von Kurzfasern (disperse und integrale AR-Glasfasern, Kohlenstofffasern) hinsichtlich des Festigkeits-, Verformungs- und Bruchverhaltens von Textilbeton (engl.: textile-reinforced concrete = TRC) unter Zugbeanspruchung zu gewinnen. Die Bruchflächen sowie die Gestalt der Interphase zwischen der Bewehrung aus Textilien oder Kurzfasern und der umhüllenden zemengebundenen Matrix wurden mit optischen und elektronenmikroskopischen Verfahren hinsichtlich der Wechselwirkungsphänomene ausgewertet. Die Ergebnisse der experimentellen Arbeiten bildeten den Ausgangspunkt für die mathematischen Beschreibungen für TRC mit Kurzfasern unter verformungsgesteuerter Zugbelastung. Die Formulierungen erfolgten auf Grundlage multiskalarer rheologisch-statistischer Modellansätze. In einer Literatursichtung wurde zunächst der Kenntnisstand zu den Materialien und zum Verhalten von TRC und Faserbeton unter Zugbeanspruchung dargestellt und diskutiert. Die noch zu erforschenden Fragen wurden präzisiert und die Grundlagen für deren Untersuchung geschaffen. Bei den Experimenten auf der Makroebene wurden drei Bewehrungsvarianten betrachtet: a) textile Bewehrung, b) Kurzfaserbewehrung, und c) hybride Bewehrung (Textil und Kurzfasern). An Dehnkörpern wurde die Spannungs-Dehnungsbeziehung unter einachsiger Zugbelastung studiert und dabei das Rissbild und die Phänomene des Faserversagens detailliert beobachtet. Anhand der Spannungs-Dehnungsbeziehungen konnte gezeigt werden, dass die Zugabe von Kurzfasern bei allen untersuchten Kurzfaserarten zu einer erheblichen Verbesserung der Leistungsfähigkeit von Textilbeton führt. Dies zeigte sich unter anderem in einer ausgeprägten Anhebung der Erstrissspannung sowie der Entwicklung von zahlreicheren und damit feineren Rissen, die zu einer Verbesserung der Duktilität führten. Ebenso wurden Steigerungen der Zugfestigkeit und der Energiedissipation festgestellt. In welchem Maß diese Änderungen stattfinden, hängt von der Art der Kurzfasern ab. Die Experimente auf der Mikro- und Mesoebene wurden so konzipiert, dass sie die Erkundung der Mechanismen, die den auf der Makroebene beobachteten Phänomenen zugrunde liegen, unterstützten. Auf der Mesoebene wurden Mulitifilamentgarnauszugversuche (mit und ohne Kurzfasern in der Matrix) und auf der Mikroebene Einzelfaserauszugsversuche für alle betrachteten Kurzfasertypen durchgeführt. Es wurde festgestellt, dass die Kurzfasern den Verbund zwischen Matrix und Multifilamentgarn verbessern. Kurzfasern können bei zufälliger Positionierung an der Garnoberfläche zusätzliche Haftbrücken bzw. Verbindungsstellen zu umgebender Matrix bilden. Für die Verbundqualität zwischen Faser und Matrix ist der Wasser-Bindemittel-Wert (W/B-Wert) von entscheidender Bedeutung. Bei einer Matrix mit niedrigem W/B-Wert führt die gute Qualität des Verbunds der eingebetteten Fasern zu einer Erhöhung der Steifigkeit sowie der Festigkeit des Komposites. Bei hohem W/B-Wert haben die Fasern einen schlechten Verbund zur Matrix und müssen überwiegend als Fehl- bzw. Schwachstellen betrachtet werden. Festigkeit und Steifigkeit des Komposits nehmen daher ab. Die Ableitung mathematischer Beziehungen für Textilbeton mit Zugabe von Kurzfasern unter verformungsgesteuerter Zugbelastung erfolgte aufbauend auf den Ergebnissen der experimentellen Untersuchungen auf der Mikroebene. Die Einzelfaserauszugsversuche wurden mit Hilfe eines physikalisch basierten Modelles nachgebildet, das aus einfachen rheologischen Elementen besteht. Phänomene wie die graduelle Ablösung der Faser, Faserbruch und Faserauszug wurden durch eine entsprechende Kombination und Parametrierung der rheologischen Elemente abgebildet. Im Ergebnis wurden zutreffende Kraft-Rissöffnungsbeziehungen modelliert. Auf der Mesoebene wurde ein einzelner Riss modelliert, der sowohl durch Multifilamentgarne als auch Kurzfasern überbrückt werden kann. Der rissüberbrückenden Wirkung der zahlreichen Kurzfasern wurde mit Hilfe statistischer Methoden rechnung getragen, die unterschiedliche Faser-Risswinkel und Einbindelängen berücksichtigen. Die resultierende Spannungs-Rissöffnungskurve umfasst die rissüberbrückende Wirkung von Multifilamentgarnen und Kurzfasern. Auf der Makroebene kann die charakteristische Spannungs-Dehnungsbeziehung von TRC unter Zugbelastung in 3 Bereiche (Zustände I, IIa, IIb) unterteilt werden. Die Kurvenverläufe im Zustand I (ungerissenen) sowie Zustand IIb (abgeschlossenes Rissbild) wurden als linear betrachtet und basierend auf den entsprechenden charakteristischen Werten des jeweiligen Zustands beschrieben. Das Verhalten im Zustand IIa (multiple Rissbildung) wurde durch die Reihenschaltung einer zunehmenden Anzahl von Rissen sowie den Beitrags der ungerissenen Matrix zwischen den Rissen modelliert

碩士
國立臺北科技大學
土木與防災研究所
93
The concrete material is used in the construction projects now, and is still playing a very important role. No matter it is in main structures or secondary structures, the usage of the concrete count is much steres. The material is used in big quantity and its variability is complex, it will influence the security of the structures directly whether the quality of the concrete is good or bad. And the strength is a reference index of the concrete quality, we can know whether the concrete perform its efficiency or not via the number of strength. This research utilizes the pullout test method to assess the intensity of concrete. This method is one kind of non-destructive test methods. To use this method, we can find out the relationship between the strength of the concrete and the pullout strength. After record its physical values, we establish the relation curve between the two values. When the curve was set up, we can predict effectively whether the concrete reach the set intensity. This method of non-destructive test methods is not common in our country, but it is still necessity to be popularized. Because we discover the relationship between the pullout strength that was calculated from the maximum pullout force and the strength of cylinder specimen is greatest while getting the results. The machine of the pullout test method is cheaper than machines of other non-destructive test methods, and the method can present the accurate results. So this kind of detection technique waits to popularize in fact, it is believed that it can make better quality in construction projects.

碩士
淡江大學
土木工程學系碩士班
98
In this study, using the FEM software ABAQUS to establish 2D and 3D anchor model to study the singal propagation characteristics and attenuation mechanisms. Research project is divided into two parts, first, anchor pullout test simulation by 2D and 3D model refer to the analytical model proposed material model and to compare experimental and theoretical models. Second, simulation for the signal using by theoretical model suggested the impulse load and the initial conditions for 2D and 3D simulation, and using the signal time difference for feed-back analysis. The observation are summarized as follows: (1) From the analysis domain size discussion result show that, depth change didn’t affect anchor pullout test simulation results; width change affect anchor pullout test simulation results. Width of 20 meters can get reasonable results. (2)From the old anchor pullout test simulation results show that 2D model from drawing curves and the test results were similar, while 3D model of the results obtained have high load-carrying capacity. (3) 2D and 3D model can simulate the uninstall process of drawing curves and improve the shortcomings of one-dimensional model, clearly depends on the capacity of anchors in the length of the fixed side. (4) In the signal simulation, 2D model of the signal similar to the test result, but old anchor 3D model of the signal significantly different between the test result. (5)In the feed-back analysis, using the 2D and 3D analysis of the time difference location method proposed by others. The result show that, surface damage (damage location in the depth 3m) , the result varies with the actual location within about 2m. Deep damage (damage location in depth of 10m or more), the result varies with the actual location within about 1m. The result has large errors because of calculation process, the small error will be significant changes in the result.

碩士
國立臺灣科技大學
營建工程系
97
In order to investigate the soil-geogrid interface behavior in the finite element method. The study includes numerical and laboratory tests. In laboratory, small scale pullout tests and ASTM pullout test result as the numerical interface parameter data base. According to the simulation result to build a soil-geogrod interface parameter rule. Then transfer the interface parameters to predict out ASTM test curve by small scale pullout numerical model. The results showed that: (1) Soil-geogrid interface parameters is a positive correlation between confining pressure, the greater confining pressure is greater interface parameters. There are 18 groups based on the test results of the analysis interface parameters, the cohesive strength (Sb) and the shear stiffness (Kb) from small-scale pullout test are higher than ASTM test interface parameters. (2) The numerical analysis simulation result test out of the peak impedance and interface friction angle values of absolute error percentage of less than 10%, that have to prove that the numerical results very close to the experimental data. (3) The pullout curve in the elastic stage, small-scale and the ASTM tests of the geogrid axial force and axial strain behavior have the same distribution patterns.In the yieldind and ultimate stage, the geogrid axial force and axial strain behavior just a little difference，prove that the small-scale and ASTM pullout test results to design reinforced retaining walls will have the similar results.

碩士
國立海洋大學
河海工程學系
83
Bond stress devlopment is important in RC structure designs , thus the interface properties of the rebar-concrete interface should be studied . In this research , experimental data were used to find four interface parameters proposed by Stang et al . Results show that all those four parameters : K、D、G and qy are constants when same concrete and steel rebar are used , they do not vary with respect to different embedded lengths . , if the interface area effect and rib's effect are conside .

碩士
中華技術學院
土木防災工程研究所
97
In the grid, the cross rods can help to stabilize the communication of stress in reinforcement, increase surface’s friction, decrease displacement, and strengthen the anchor effection. When a grid without the cross rods, the vertical rods have to support additional stress, decrease peak point of the pullout resistance, which leads to a earlier break-down. The research is to study the dynamics behavior of interface when the geogrid be pulled out in the different cross rod spacing. Tests were all taken place in large-multiple geotextile experimental instrument which interior diameter is 180cm in length, 70cm in width, and 85cm in height. Three modeling test samples were choosen in different cross rod spacing and in the circumstances of a single surroundings pressure of 60kN/m2 . The results show that no matter what the cross rod spacing (1S~2.38S), the pullout resistance was nearly in the standard geogrid spacing which is (1S) discrete range. If different cross rod spacing (1.94S~2.38S) needs to contribute, the displacement from the pullout point have to be beyond 40mm.

碩士
中原大學
土木工程學系
85
Earth reinforcement has been widely used in Taiwan in recent years. Direct shear test and pull-out test are commonly applied to determine the mechanical propoerties at the interface between the soil and reinforcement. Many factors can affect the results of pull-out test; and they mainly come from three aspects, the test device, the soil specimen, and the reinforcement specimen. This study researches some of these concerns in laboratory tests. 　　Four types of geogrids and one type of sandy soil are used in this study, in conjunciton with a large-scale pull-out testing device. To eliminate the boundary effects on the accuracy of the pull-out test, a series of pull-out tests have been carried out using different sleeve lengths, different geogrid specimen widths, and different displacement rates. Earth pressure cells are installed for monitoring purpose at suitable locations at the front and lateral walls of the shear box. The length of the shear box is varied from 1.5m to 2.5m to fit geogrids of 1.0m, 1.5m, and 2.0m in length, in order to perform the pull-out test. To measure the deformation of geogrid, steel hooks and inextensible tell-tale wires are attached to the nodes of the geogrids with the displacement transducers located outside the shear box. 　　Findings indicate that the boundary effect has a significant impact on the results of the test, and it should be adequately regulated by sleeve length and width of specimen. Different displacement rates show different strength transmission mechanisms. Stiff geogrid of low extensibility is more capable of transferring tension exerted on it to the free ends than is a flexible geogrid. Deformation of the flexible geogrid centered at the pull end, and the associated tension onit, are completely non-uniform. As long as the anchor strength is sufficient, geogrids all exhibited a rupture failures. In this condition, an increase in geogrid length has a small effect on pull-out behavior; however, the deformation of the geogrid is distributed more evenly towards the free ends and the pull-out interaction coefficient decreases accordingly.

碩士
逢甲大學
土木及水利工程研究所
88
Since steel structures are increasingly used in all kinds of constructions, proper anchorage between the concrete components becomes an important task for the civil engineers. Steel-to-concrete anchors can be classified as cast-in-place anchors and post-installed anchors. The latter, in general.provide better flexibility in construction than the former. However, current design standards do not contain rational design recommendations for most of the post-installed anchors. Therefore, the main objective of this research is to study the behavior of the post-installed adhesive anchors. Firstly, research papers concerning anchors are reviewed in order to determine the representative factors that influence the behavior of adhesive anchors. Three factors including anchor size, embedment length, and concrete compressive strength are found to be the most significant factors. Then the effects of such factors on the failure capacity and failure mode of the anchors are investigated by means of a series of pull-out tests. Finally, the test results are analyzed and compared with the results from other literature. The experimental results indicate that as the increase of anchor size, embedment length, or concrete compressive strength, the anchor capacity raises. Among these three factors, the embedment length influences the failure capacity and failure mode the most. Once the embedment length exceeds a certain depth (which seems to be a factor of anchor diameter), anchor steel fracture occurs and the anchor system reaches its ultimate capacity. Combined cone-bond failure or cone failure takes place when the embedment length is moderate or short. If embedment length is relatively short, bond failure happens.

碩士
逢甲大學
土木及水利工程所
91
Concrete must be reinforced with materials strong in tension because of its small tensile capacity. Conventionally, concrete has been reinforced with steel reinforcing bars. To transfer the forces from the concrete to the steel reinforcement, a good shear bond must be developed between the concrete and the steel. Steel reinforcing bars are manufactured with deformed surface to enhance shear transfer. In addition, it needs enough embedment length to develop the full capacity of the rebar. However, if the RC structures are exposed to deteriorative environments, it could leads to corrosion of the reinforcing steel. The whole structure might lose its loading capacity and reduce its service life. This urges the researches of finding a substitute for steel rebar or invention of new corrosion prevention technology. The FRP (fiber reinforced plastic) rebar with good corrosion resistance and high stiffness weight ratio will be a good candidate for this purpose. In this study, a filament winding technique is applied to commercially available FRP rods (with smooth surface) to produce different winding pitch, lug height, and winding angle. This simulated lug will provide the shear transfer mechanism between the FRP rod and concrete. These FRP rods are embedded in the concrete block during the concrete casting. A pullout test of FRP rod from the concrete cylinder was performed to examine the shear transfer capacity made from different winding pitch, lug height, and winding angle. The bond-slip data were recorded during the experiment. The optimum winding method to produce qualified bond, and the required development length for FRP rod are addressed. Results show that the bond stress of FRP rod with longitudinal and oblique angle winding is better than the bond stress of a FRP rod with 90 degree winding. The process of the former is simple and easy to use than the latter.

碩士
朝陽科技大學
營建工程系碩士班
95
The research is proceeding vertical anchors with 26 anchors in the Gravel Formation and processing the putout test experiment. During the experiment, there are 10 anchors have the prombles, through the percolating system of this essay, it percolates the problem anchors and than discuss the reason. The probable reasons can be the site was disturbed, or it was caused by the bad construction, or the total length was too short (>2.0m). According to the limitation of environment, the anchors of the experiment has three different kind of ways to construct, we found out that the wet drill and putout tube grouting will easily make the anchor has the situation of load not enough. The depth of the shallow anchor and deep anchor is about 1.5~2.0m. Combining with expert’s analytic result, we found out the research from data [26] that have higher ultimate load, if not consider the formation, the possible reason should be the pressure grouting. So, using pressure grouting with anchor in gravel formation could be better load. Tension anchor of unbounded length=0m the ultimate load about 28.4 ton/m (287 kN/m), tension anchor of unbounded length=1.0m the ultimate load about 45.8 ton/m (450 kN/m), tension anchor of unbounded length=2.0m the ultimate load about 55 ton/m (540 kN/m) in gravel formation. The anchor in different kind of formation, the load-residual displacements will be different. Such as the anchor in the Taipei silty sand must produce more displacements, than it will produce more ultimate friction resistance. On the contrary, the anchors in the Taichung gravels formation just need a little displacement; it will produce highest ultimate friction resistance. From the pullout test, we found out that the anchorage behavior of anchor in gravel formation can provide practical reference and application on engineering in the future.

Hochduktiler Beton ist ein mit kurzen Kunststofffasern bewehrter Hochleistungs-verbundwerkstoff auf Zementbasis, der unter Zugbelastung eine hohe nichtelastische Verformbarkeit und ein verfestigendes Materialverhalten aufweist. Dieses Verhalten wird durch die Zugabe von diskontinuierlich verteilten Kurzfasern aus Kunststoff erzielt. In der vorliegenden Arbeit wurden einachsige Bauteilzugversuche durchgeführt auf deren Basis das globale und lokale Zugtragverhalten der großformatigen Versuchskörper beschrieben werden kann. Ausgangspunkt sind experimentelle Untersuchungen zum Tragverhalten des Stabstahls und des hochduktilen Betons sowie zu deren gemeinsamen Verbundverhalten. Die Untersuchungen zeigen, dass der Herstellungsprozess das Betongefüge und damit auch das mechanische Verhalten von hochduktilem Beton beeinflusst und dieser auf Grund seiner Zusammensetzung ein ausgeprägtes Schwindverhalten aufweist. Beides muss bei der Untersuchung großformatiger Versuchskörper berücksichtigt werden. Dazu wurden sowohl unbewehrte als auch bewehrte Dehnkörper mit unterschiedlichem Bewehrungsgehalt unter kontrollierten Herstellungsbedingungen in einem konventionellen Mischwerk hergestellt. Die Ergebnisse der experimentellen Untersuchung erlauben die Abbildung des Last-Verformungsverhaltens unter Berücksichtigung der hohen Schwindmaße durch isoliert ermittelte Spannungs-Dehnungs-Beziehungen des hochduktilen Betons und des reinen Stahls. Dieses Verfahren erlaubt eine einfache Beschreibung des kombinierten Tragverhaltens unter Berücksichtigung der rissüberbrückenden Wirkung der Fasern.
SHCC is an advanced construction material developed especially for strain-hardening, quasi-ductile behaviour. Both are achieved through the combined interaction of short polymer fibres dispersed in the cementitious matrix. The resulting tensile behaviour of SHCC is characterized by a progressive formation of multiple cracks and high strain capacity, which influences the structural behaviour especially in combination with steel reinforcement. This thesis reports on experimental investigations to analyse the load-bearing behaviour of R/SHCC members. The investigations included the determination of relevant material properties as well as uniaxial tension tests on steel reinforced slab elements. The aim was to study the effect of multiple cracking on the bond interaction with steel reinforcement and their combined load-deformation behaviour. Specific attention was also given to the influence of the production process and shrinkage behaviour of SHCC. It was shown that production and size related changes of material properties influence the cracking behaviour of SHCC, which can lead to a significant reduction of tensile strain capacity in a structural element. The interaction with steel reinforcement, on the other hand, was found to facilitate multiple cracking and enhance tensile strain capacity during the stage of elastic steel deformations. However, a mutual dependency of SHCC fracture and plastic steel deformations could be observed in the post-yielding stage of the steel rebar. The experimental results were discussed with respect to their implications for constitutive modelling of the tensile load-bearing behaviour. The resulting relationships are based upon the individual material behaviour as well as their bond interaction. Further to that, the effects of SHCC shrinkage and early strain-hardening of steel reinforcement were assessed based on the experimental data. These results contribute to the understanding of the mechanical processes in order to determine the behaviour of steel reinforced SHCC for practical applications.

Being able to identify blended dredged material and crushed glass of different proportions as materials suitable for Mechanically Stabilized Earth walls could help the adoption of these materials in civil engineering thereby reducing the environmental impact of these waste materials. The objectives of this thesis include the following: Collect and organize data to facilitate material selection based on interaction properties with uniaxial geogrids; analyze the data for trends for varying percentages of crushed glass vs. dredged materials; compare the properties of different blends with those of a well-documented uniform sand; compare the pullout data with that of previous studies related to the presence of fines in the fill material; and compare the pullout data to that of previous studies on the effect of geogrid rib thickness. The main findings of this thesis study include the following: A blend of 80% crushed glass and 20% dredged material is a legitimate alternative backfill material for reinforced soil slopes. The use of 100% crushed glass as a fill material is not recommended due to glass particles embedding into the geogrid thereby reducing the tensile capacity of the geogrid. Blends with lower percentages of crushed glass and higher percentages of dredged material may be appropriate based on the requirements of individual designs. The increased thickness of the UX1700 geogrid over the UX1400 geogrid contributed to higher a pullout resistance for each combination of fill material and normal stress.
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Geogrids have been used for decades as reinforcement for mechanically stabilized earth retaining walls and base layers of pavements. However, literature on these applications is contradictory regarding the displacement and strain levels at which the bearing mechanism of interaction between soil and geogrid is developed along the transverse ribs of geogrids. No data are available on the deflections and displacement profiles of transverse ribs during loading of geogrids. Field and laboratory data on strain distributions along geogrids are limited. Accordingly, the objective of this study is to better understand the mechanisms of soil-geogrid interaction that develop at different stages of pullout tests, especially at small displacements and strains. Moreover, the behavior of transverse ribs throughout pullout testing is evaluated. Pullout loads were obtained from a load cell synchronized with two 5 MP cameras. Images of the geogrid were analyzed using the Particle Image Velocimetry (PIV) technique to obtain displacement profiles along the entire geogrid specimen throughout the duration of the test. Five transparent pullout tests were conducted using a confining pressure of 35 kPa (5 psi) on polypropylene geogrids with different configurations. Displacements along the polypropylene geogrid used in this study are well represented by an exponential equation. The bearing mechanism along transverse ribs was observed to develop at small viii displacements. The contribution of the bearing mechanism was first observed at 25 % of the maximum pullout force. Interference between transverse ribs was first observed at approximately 60 % of the maximum pullout force. High interference between transverse ribs was observed when the ratio of spacing between transverse ribs (S) over the thickness of the transverse ribs (B) was equal to 24. Negligible interference was observed when S/B was equal to 57. Displacements of soil particles were observed when the ratio distance from the soil-geogrid interface (d) over the D₅₀ of the soil was equal to 3, but they were orders of magnitude smaller than the displacements of the geogrid specimens. The observed boundary of the zone of influence of geogrids was for values of 3 < d/D₅₀ < 7 for the transparent soil used in this study.
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碩士
國立臺灣科技大學
機械工程系
99
The vertebral column is one of the most important structures in the human body. When the vertebrae body or the intervertebral disc has been damaged, a vertebral body replacement surgery is usually needed. Therefore, through this kinds of surgery, the damaged vertebrae body or intervertebral disc will be removed, and replacing it with the vertebral body cage. However, simply implanting the vertebral body cage could not adjust the stability of the fusion segment, in which, the supplementary pedicle screw fixation has been widely used for increasing rigidity of spinal implant construct, in order to produce the bone fusion under the stabilized motion segment. If the vertebral bodies are affected by osteoporosis, the general pedicle screws are unable to apply enough screw-bone interface strength for osteoporotic bodies, and high risks resulted from loosening or failure of the fixation systems. In this case, if the screw-bone interface strength can be increased, thus, the effect of stability can be facilitated. The vertebroplasty, a kind of surgery which helps facilitate or repair the vertebrae body through injecting bone cement into the weaker or the fracture part of the vertebrae body, is performed. Thus the bone holding power of vertebrae body and the pedicle screw will gradually increase when the pedicle screw is implanted. Biomechanical tests and the finite element method will be used and discussed on assessing three different types of implantation of cannulated pedicle screw in this research. The first type is simply implant the pedicle screw into the vertebrae body without using the bone cement for facilitation. In the second experiment, the syringe will be used to inject PMMA bone cement into the vertebrae body first, and then inject the cannulated pedicle screw. The cannulated pedicle screw is implanted first then the PMMA bone cement is injected from the pedicle screw in the third experiment. To make these biomechanical tests more clinical for this research, therefore, the human thoracolumbar specimens are being used to progress in the pedicle screw pull out experiment. The result had shown that injecting the PMMA bone cement into the vertebrae body first, then implanting the cannulated pedicle screw, had the best biomechanical performance including the pull out strength, the displacement at maximal strength, and the total energy absorption. Therefore, the best implantation of the pedicle screw for osteoporosis patients will be suggested to use the second type of the implantation for stable vertebrae body surgery.

碩士
國立屏東科技大學
土木工程系所
95
The shear strength behavior between aggregates and geogrids interface was investigated by the direct shear test (ASTM D5321) and pullout test (ASTM D6706). Three different types of uniaxial geogrids with various apertures or percentage of openings and four different types of poor graded or uniform graded soils were used in the study. The nominal tensile strength of the geogrids ranged from 200 to 260 kN/m. The aperture sizes were 15x15, 30x30, and 50x50 mm. The percent of opening varied from 33% to 50%. The medium particle size (D50) of the test soils ranged from 0.8 mm to 15.0 mm. In general, one side shearing behavior was observed for direct shear test, and more passive bearing capacity resistance could be developed as soil particles penetrated through the geogrid openings during pullout test. The increase of particle size would increase the shear strength 22% to 74% for direct shear tests and 76% to 135% for pullout tests, respectively. Passive resistance ranged from 4% to 27% and 27% to 70% of the total resistance for direct shear and pullout tests. Optimized opening ratio for developing ultimate shearing resistance is ranging from 0.4 to 1.0. The friction efficient for the direct shear test ranged from 0.68 to 0.98. The pullout interaction coefficient, Ci, would decrease as increasing the normal pressure and ranged from 0.47 to 0.95. In general, the friction efficient is about two third of the pullout interaction coefficient.

In der vorliegenden Arbeit wird die Frage untersucht, ob effektive Eigenschaften von Verbunden auch nach dem Auftreten einer Dehnungslokalisierung aufgrund von entfestigendem Materialverhalten noch durch numerische Homogenisierungsmethoden berechnet werden können. Ihr Nutzen für diesen Anwendungsfall wird in der Literatur kritisch beurteilt. Aus diesem Grund werden hier systematisch alle Teilaufgaben betrachtet, die zu diesem Zweck gelöst werden müssen. Die erste dieser Aufgaben ist die Charakterisierung der einzelnen Verbundbestandteile. Zur Demonstration einer experimentell gestützten Charakterisierung wird ein glasfaserverstärktes Epoxidharz als Beispielmaterial gewählt. Neben der Beschreibung von Faser- und Matrixmaterial wird besonderes Augenmerk auf die Charakterisierung der Grenzschicht zwischen beiden gelegt. Die für die Glasfasern vorliegenden Festigkeitsmessungen entsprechen nicht der Kettenhypothese. Daher werden zahlreiche Verallgemeinerungen der Weibull-Verteilung untersucht, um störende Effekte zu erfassen. Schließlich werden Wahrscheinlichkeitsverteilungen hergeleitet, die Faserbrüche im Bereich der Einspannung einbeziehen. Die Messwerte können von diesen Verteilungen gut wiedergegeben werden. Zusätzlich macht ihre Anwendung das aufwändige Aussortieren und Wiederholen jener Experimente unnötig, bei denen der Faserbruch im Klemmbereich auftritt. Zur Modellierung der Grenzfläche wird ein Kohäsivzonengesetz entwickelt. Die Bestimmung seiner Parameter erfolgt anhand von Daten aus Pullout- und Einzelfaserfragmentierungsversuchen. Aus diesen ermittelte Festigkeiten und Energiefreisetzungsraten weisen eine sehr gute Übereinstimmung zwischen beiden Versuchen auf. Dabei erfolgt die Parameteridentifikation mithilfe von Finite-Elemente-Modellen anstatt der häufig genutzten vereinfachten analytischen Modelle, welche üblicherweise eine schlechtere Übereinstimmung erreichen. Sobald eine Dehnungslokalisierung auftritt, ist neben der Materialmodellierung auch das Homogenisierungsschema zu verallgemeinern. Zu diesem gehören die Generierung repräsentativer Volumenelemente, Randbedingungen (RB) und ein Mittelungsoperator. Anhand des aktuellen Standes der Literatur werden die Randbedingungen als ein signifikanter Schwachpunkt von Homogenisierungsverfahren erkannt. Daher erfolgt die Untersuchung periodischer RB, linearer Verschiebungsrandbedingungen und minimal kinematischer RB sowie zweier adaptiver RB, nämlich Lokalisierungspfad-ausgerichteter RB und generalisiert periodischer RB. Unter der Bezeichnung Tesselationsrandbedingungen wird ein weiterer Typ adaptiver RB vorgeschlagen. Zunächst erfolgt der Beweis, dass alle drei adaptiven RB die Hill-Mandel-Bedingung erfüllen. Des Weiteren wird mittels einer Modifikation der Hough-Transformation ein systematischer Fehler derselben bei der Bestimmung der Richtung von Lokalisierungszonen eliminiert. Schließlich werden die Eigenschaften aller Randbedingungen an verschiedenen Beispielen demonstriert. Dabei zeigt sich, dass nur Tesselationsrandbedingungen sowohl beliebige Richtungen von Lokalisierungszonen erlauben als auch fehlerhafte Lokalisierungen in Eckbereichen ausschließen. Zusammengefasst können in der Literatur geäußerte grundlegende Einschränkungen hinsichtlich der Anwendbarkeit numerischer Homogenisierungsverfahren beim Auftreten von Dehnungslokalisierungen aufgehoben werden. Homogenisierungsmethoden sind somit auch für entfestigendes Materialverhalten anwendbar.
The thesis at hand is concerned with the question if numerical homogenization schemes can be of use in deriving effective material properties of composite materials after the onset of strain localization due to strain softening. In this case, the usefulness of computational homogenization methods has been questioned in the literature. Hence, all the subtasks to be solved in order to provide a successful homogenization scheme are investigated herein. The first of those tasks is the characterization of the constituents, which form the composite. To allow for an experimentally based characterization an exemplary composite has to be chosen, which herein is a glass fiber reinforced epoxy. Hence the constituents to be characterized are the epoxy and the glass fibers. Furthermore, special attention is paid to the characterization of the interface between both materials. In case of the glass fibers, the measured strength values do not comply with the weakest link hypothesis. Numerous generalizations of the Weibull distribution are investigated, to account for interfering effects. Finally, distributions are derived, that incorporate the possibility of failure inside the clamped fiber length. Application of such a distribution may represent the measured data quite well. Additionally, it renders the cumbersome process of sorting out and repeating those tests unnecessary, where the fiber fails inside the clamps. Identifying the interface parameters of the proposed cohesive zone model relies on data from pullout and single fiber fragmentation tests. The agreement of both experiments in terms of interface strength and energy release rate is very good, where the parameters are identified by means of an evaluation based on finite element models. Also, the agreement achieved is much better than the one typically reached by an evaluation based on simplified analytical models. Beside the derivation of parameterized material models as an input, the homogenization scheme itself needs to be generalized after the onset of strain localization. In an assessment of the current state of the literature, prior to the generation of representative volume elements and the averaging operator, the boundary conditions (BC) are identified as a significant issue of such a homogenization scheme. Hence, periodic BC, linear displacement BC and minimal kinematic BC as well as two adaptive BC, namely percolation path aligned BC and generalized periodic BC are investigated. Furthermore, a third type of adaptive BC is proposed, which is called tesselation BC. Firstly, the three adaptive BC are proven to fulfill the Hill-Mandel condition. Secondly, by modifying the Hough transformation an unbiased criterion to determine the direction of the localization zone is given, which is necessary for adaptive BC. Thirdly, the properties of all the BC are demonstrated in several examples. These show that tesselation BC are the only type, that allows for arbitrary directions of localization zones, yet is totally unsusceptible to spurious localization zones in corners of representative volume elements. Altogether, fundamental objections, that have been raised in the literature against the application of homogenization in situations with strain localization, are rebutted in this thesis. Hence, the basic feasibility of homogenization schemes even in case of strain softening material behavior is shown.

Accelerated bridge construction (ABC) has become a popular alternative to using traditional construction techniques in new bridge construction and existing bridge deck replacement because of the reduction of time spent in field activities. A key feature of bridges built using ABC techniques is the extensive use of prefabricated components. Prefabricated components are joined in the field using small volume closure pours involving high performance materials (steel and concrete) to ensure adequate transfer of forces between components. To date, the materials developed for closure pours have been based on proprietary components, so a need has arisen for development of mixes that use generic components. The goal of this research was to create a method to develop concrete mixtures that are designed using generic constituents and that satisfy performance requirements of accelerated bridge construction closure pours in New England, primarily high early strength and long-term durability. Two concrete mixtures were developed with a primary goal of reaching high-early strength while maintaining constructability. The secondary goal of the concrete mixtures was to be durable; therefore, measures were taken during the development of the concrete mixture to generate a mixture that also had durable properties.