Dissertations / Theses on the topic 'Fine specimens'

Through sculpture and drawing, I create my own versions of natural specimens primarily based upon the visual unity of disparate organisms. Invented specimens are composed using a variety of processes employing a mixture of atypical materials following the (20th, 21st century) Postmodern shift away from formalist and traditional uses of any singular medium. As well as a variety of art materials, the specimens are hybrids of organic and biomorphic elements, blurring boundaries between botanical, animal, fungal, metal, and mineral. Is my approach perhaps like Charles Darwin, observant and studious naturalist, or am I more like Dr. Frankenstein, science fiction maker of monstrosities?

Dissertation (Ph.D.)-- Worcester Polytechnic Institute.
Keywords: temperature measurement; heat flux maps; Cone Calorimeter; three-dimensional heat conduction; fire growth models; retainer frame; ceramic fiberboard; edge effect; one-dimensional heat conduction; heat flux mapping procedure; infrared camera; specimen preparation; edge frame; one-dimensional heat conduction model; thermal properties. Includes bibliographical references (p.202-204).

What if every craving that you ever felt stayed with you forever? Suppose facades couldn’t exist, and what should only be the deepest, densest core of a desire was formed into a mass, a body. Its will matching yours in its physical presence. I make creatures that are embodiments of emotions. In this study I mainly focus on desires and inhibitions surrounding romance. I explore anatomical structures and how material make-up can directly reflect emotional character. In this exploration, the materiality of clay allows for a thorough manipulation of the composition of the creatures. In this I am also able to manipulate the material properties of clay to reflect states of existential discomfort, pushing the limits of material structure and stability. The final presentation of these creatures are as specimens of inhibitions, drawing in the viewer with empathy and repulsion as a fantastic other.

This diploma thesis deals with the issue of the determination of the frost susceptibility of soils in the subgrades of road structures. The theoretical part compares the ways of testing the frost susceptibility in the Czech Republic and other selected countries of the European Union. Furthermore, it also deals with the development of the frost susceptibility index in the Czech Republic. The empirical part focuses on the laboratory testing of the frost susceptibility of the given sample of soil by the direct frost heave method. Moreover, it also deals with the simulation of penetration of frost by the subgrade and the possibility of shortening the length of the freezing during the direct testing the frost susceptibility.

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

Object categorization is one of the fundamental topics in computer vision research. Most current work in object categorization aims to discriminate among generic object classes with gross differences. However, many applications require much finer distinctions. This thesis focuses on the design, evaluation and analysis of learning algorithms for fine- grained object classification. The contributions of the thesis are three-fold. First, we introduce two databases of high-resolution images of arthropod specimens we collected to promote the development of highly accurate fine-grained recognition methods. Second, we give a literature review on the development of Bag-of-words (BOW) approaches to image classification and present the stacked evidence tree approach we developed for the fine-grained classification task. We draw connections and analyze differences between those two genres of approaches, which leads to a better understanding about the design of image classification approaches. Third, benchmark results on our two datasets are pre- sented. We further analyze the influence of two important variables on the performance of fine-grained classification. The experiments corroborate our hypotheses that a) high resolution images and b) more aggressive information extraction, such as finer descriptor encoding with large dictionaries or classifiers based on raw descriptors, is required to achieve good fine-grained categorization accuracy.
Graduation date: 2013

An experimental program for the understanding of the behavior of fine cohesionless soil under monotonic and cyclic loading and for the development and refinement of constitutive models has been undertaken. An experimental program for both loose and dense saturated fine Ottawa Silica sands under monotonic loading using both solid and hollow cylinder specimens has been conducted. The failure surfaces have been established from twenty drained monotonic load tests. Results were found in good agreement with the failure surfaces incorporated in Lade's constitutive model. The soil behavior and deformation characteristics under undrained conditions have been investigated under a cyclic experimental program for loose sand. Results indicated that the circular rotation of principal stress axes with a constant amplitude deviator stress, as well as the stress direction reversals have significant effects on the rate of pore water pressure buildup, the triggering of a liquefaction flow failure in contractive sand and the rate of accumulation of deformation. The rate of excess pore water pressure buildup is faster during a cyclic test with circular rotation of principal stress axes than during a cyclic triaxial shear test or a cyclic torsional shear test having same amplitude of shear stress. The rate is faster during a cyclic triaxial extension test than in a cyclic triaxial compression test or a cyclic torsional simple shear test with the same amplitude of shear stress. The deformation and significant pore water pressures are developed during the first cycle and more remarkably during the last cycle. The pore water pressures (and mean effective stress reduction) and developed fast when the stress path reaches the failure surface which was established in monotonic load tests. The pore water pressure and deformation increase fast in the case of shear stress reversal. The pore water pressure buildup and mean effective stress reduction are more pronounced during extension loading than in compression loading. Moreover, the amplitude of shear stress has significant effects for the pore water pressure development and deformation. Significant pore water pressure and deformation can occur, during the rotation of the principal stress axes, even when the deviator stress is maintained unchanged. (Abstract shortened with permission of author.)

碩士
逢甲大學
土木工程所
98
This thesis studies the post-fire-curing behaviors of fire-damaged concrete specimens with stirrups. A total of 48 low-strength concrete and 71 high-strength concrete specimens with size 12cmx24cm are made, The spacing of circular stirrups are 10cm and 5cm. The fire-damaged environments considered are 600℃, 800℃ with exposure time 120 minutes. The intermittent water curing time is 3 or 7 days, and the re-curing ages are 1, 8, 30, 60 or 90 days. All specimens were tested under uni-axial compression test to examine the effects of various conditions on the strength recovery. The results show that 5cm spacing of stirrups can substantially increase the compressive strength and corresponding strain of concrete, thus both the strength and strain of concrete with 5cm spacing of stirrups are the largest among all the concrete specimens. For concrete specimens with post-fire-curing, the strengths rise up with the increase of re-curing age, and the strengths of concrete specimen with stirrups are higher than those without stirrups. However, the strains of concrete decrease with the increase of re-curing age. Besides, the strength recovery of low-strength concrete is more obvious than that of high-strength concrete. The results also show that post-fire-curing can significantly increase the strength of specimens exposed to 600ﾟC but can not apparently improve the strength of specimens exposed to 800ﾟC.

碩士
逢甲大學
土木工程所
95
In this thesis, the carbon fiber reinforced polymer (CFRP) retrofitting behaviors of fire-damaged concrete specimens with post-fire-curing are investigated. A total of 153 cylindrical concrete specimens with 12cm in diameter and 24cm in height is made. These specimens are exposed to different temperature and exposure period of time. They are then re-cured in the air or water for four curing ages. The purposes of tests are to analyze the effects of various parameters on residual strength of fire-damaged specimens and establish analytical models to predict compressive strength of these specimens. The results indicate that the residual strength of fire-damaged specimens rises gradually with the curing age. After 180 days with air curing, the residual strength of fire-damaged specimens in 400℃ approaches the original strength of specimens, and the residual strength of fire-damaged specimens in 600℃ is 62% of the original strength of specimens. The residual strength of fire-damaged specimens in 600℃ rises better than that in 400℃ after 28 days with intermittent water curing. After 180 days with intermittent water curing, the residual strength approaches the original strength, no matter what the temperatures are. Besides, CFRP retrofitting can significantly increase both strength and ductility of fire-damaged concrete specimens. In conclusion, analytical models are established by multiple regression to predict compressive strength of fire-damaged specimens with different curing methods and CFRP strengthening.

碩士
國立臺灣大學
土木工程學研究所
93
Pore Water Pressure Generation with High Fines Content Specimens in Dynamic Triaxial Tests Abstract In the typical CKC cyclic triaxial tests, the researchers often use small and stiff tubes to connect the cap and bottom of the specimens to the pore water pressure sensors. They assume that there is no change in the volume of specimens and measure systems in undrained tests. In fact, the volume change exists in the triaxial measurement systems when water pressure changes. Therefore, when the pore water pressure changes in certain location of the sample, the soil in other location or at another end of the water pressure measurement of the pipeline can experience the pressure change only when water flow occurs. Flowing can occur and reflect the pore water pressure change rapidly for sand of high permeability, but there is lower permeability in the sand of a high fines content. The pore water pressure measurement cannot reflect the pore water pressure changes within the specimen immediately. This research pointed out the major factors of pore water pressure measurements for high fines content soil in dynamic triaxial tests as follow: (1)Permeability: There are different permeabilities for soils of different fines contents. The higher fines content the lower permeability of the soil, so it cannot reflect true pore water pressure situation within specimen immediately in the pore water pressure measurements. (2)Frequency of cyclic loading: There is a longer duration of loading during tests of lower frequency, and pore water pressure measurement can obtain better pore water pressure within the samples. (3)Cyclic stress ratio, CSR: Higher pore water pressure changes usually occur in the triaxial tests with larger CSR, and result in more volume change in the pipeline section.

碩士
國立成功大學
土木工程學系專班
100
This study made the small-scale tension specimens from the full-scale electroslag welded (ESW) box-column joints to perform post-fire tensile experiments. Two SN490B steel diaphragm plates were connected to an SN490B steel column plate by electroslag welding with backing plates to make a cruciform specimen. Three groups of cruciform specimens were manufactured by three different backing plate types, including normal type, inner-cut corner type and outer-cut corner type. In addition, each group of specimens was divided into two groups, separately treated as “non-fire damaged” and “water-cooling.” “Non-fire damaged” group was the control group without any heat treatment. The specimens in “water-cooling” group were heated to 900°C, kept in 900°C for 30 minutes, and then cooled down to room temperature rapidly in water. This heat treatment was used to simulate the water quenching action executed by firemen for ESW joints in a steel structure on fire. This study performed hardness test, metallographic etching test, standard tensile test and tensile experiment for the six combination specimens to investigate the mechanical property variations of the fire-heated and water-cooled ESW joints with three types of backing plates. The tensile experiment results showed that the tensile strength increased 50%, ductility decreased 65% and toughness modulus decreased 51% for the water-cooled ESW joints with the normal type backing plates. For the ESW joints with the outer-cut corner type backing plates, the tensile strength increased 51%, ductility decreased 62% and toughness modulus decreased 46%. For the ESW joints with the inner-cut corner type backing plates, the tensile strength increased 41%, ductility decreased 58% and toughness modulus decreased 43%. All the six specimens in the “non-fire damaged” group broke at the diaphragm plates with the failure mode of ductile fracture. The five specimens in the “water-cooling” group broke at the junction between the HAZ of electroslag weld and the diaphragm with the failure mode of brittle fracture. One specimen in the “water-cooling” group fractured at the junction between the electroslag weld and the column plate with the failure mode of brittle fracture.

碩士
國立成功大學
土木工程學系
102
In order to study the post-fire mechanical behaviors of fire-resistant steel and normal structural steel beam-to-column welded joints under cyclic loadings, this thesis made three different types of beam-to-column welded joint specimens by the three different combinations of SN490C-FR fire-resistant steel and SN490B normal structural steel, which were fire-resistant steel specimens, partial fire-resistant steel specimens and normal steel specimens. Each type of specimens were divided to five groups and the five groups experienced five different temperature treatments, which were room-temperature treating, air-cooling after reaching 800ºC for one hour, water-cooling after reaching 800ºC for one hour, air-cooling after reaching 900ºC for one hour, and water-cooling after reaching 900ºC for one hour, respectively to simulate the possible material property variations of weld metal and base metal in the beam-to-column welded connections of steel buildings after fire. As a result, the fifteen beam-to-column welded joint specimens conducted the hardness test first to understand the hardness variations of the pre-fire and post-fire beam-to-column welded joints in the three different types of specimens. After the hardness test, the same fifteen specimens proceeded the cyclic loading test and the followed tensile test to investigate macro mechanical properties and failure modes of the pre-fire and post-fire beam-to-column welded joints in the three different types of specimens. This research found that the specimens with room temperature treating and the specimens with air-cooling after reaching the high temperature above 800ºC for one hour all fractured at the base metal. The air-cooled specimens were equivalent to the specimens with normalizing treating, which softened the base metal and the weld metal. However, the tensile strength of weld metal was still higher than that of base metal. As a result, the fracturing occurred at the base metal. The specimens with water-cooling after reaching the high temperature above 800ºC for one hour all fractured at the weld metal or the HAZ. The water-cooled specimens were equivalent to the specimens with quenching treating. The quenching treating made the austenite in the specimens transform to martensite. The more the martensite in the specimen, the higher the tensile strength of the specimen. The martensite content in a specimen was related to the carbon content of steel. Since the carbon content of base metal was higher than that of weld metal, the strength of base metal was higher than that of weld metal. As a result, the water-cooled specimens in this study fractured at the weld metal or the HAZ.

碩士
國立成功大學
土木工程學系
102
In order to investigate post-fire behaviors of the fire-resistant steel and normal steel beam-to-column welded joints under fast tensile force, this study fabricated three kinds of beam-to-column welded joint specimens by SN490B normal structural steel and SN490C-FR fire-resistant steel, which were fire-resistant steel specimens, normal steel specimens and partial fire-resistant steel specimens. Each kind of the specimens were subject to five different temperature treatments (including room-temperature treating, air-cooling after reaching 800ºC for one hour, water-cooling after reaching 800ºC for one hour, air-cooling after reaching 900ºC for one hour, and water-cooling after reaching 900ºC for one hour) to simulate the post-fire material changes of weld metal and base metal in beam-to-column welded connections. This study conducted macroscopic examination, metallographic test, hardness test and fast tensile test for the specimens. The test results showed that, under the fast tensile forces, the normal steel specimen with the temperature treatment of water-cooling after reaching 900ºC for one hour broke at the HAZ between the ESW weld pass and the diaphragm plate with the failure mode of brittle fracture. The partial fire-resistant steel specimen broke at the HAZ between the FCAW weld pass and the beam flange plate with the failure mode of brittle fracture as well. Due to lack of fusion in the ESW weld pass, the fire-resistant steel specimen fractured at the lack of fusion zone between the ESW weld pass and the diaphragm plate with the failure mode of brittle fracture. All the other specimens broke at the base metal of beam flange plate or diaphragm plate.

碩士
國立成功大學
土木工程學系
103
This study used a 3D nonlinear finite-element software to develop simplified numerical models of the cross-shaped weld zones of beam-to-column welded joints, and to performed numerical simulations of the simplified cross-shaped weld zone numerical models for investigating the post-fire mechanical behaviors of the cross-shaped weld zones of fire-resistant and normal structural steel beam-column joints under tensile-compressive cyclic loadings. In addition, the strain hardening parameters of the fire-resistant grade and normal grade steel materials and weld metals under cyclic loading before and after fire were incorporated into the numerical models to simulate the cyclic loading test results of the fifteen simplified cross-shaped specimens. The fifteen specimens were composed of three types of steel allocations (i.e., fully normal structural steel allocation, partially fire-resistant steel allocation and fully fire-resistant steel allocation) and five temperature treatments (i.e., room-temperature treatment, air-cooling after reaching 800ºC for 1 hour, water-cooling after reaching 800ºC for 1 hour, air-cooling after reaching 900ºC for 1 hour, and water-cooling after reaching 900ºC for 1 hour). The numerical simulation results were compared with the realistic test results for the related investigations. This study found that compared with the test results, the numerical results damaged earlier and their maximum tensile forces were 10% to 15% lower. Therefore, the numerical results were more conservative.

碩士
國立高雄第一科技大學
營建工程系
90
Among the safety evaluation methods of post-fire cement structures as suggested by the British Cement Studies Society, there is one that uses colors for gradation of fire-damaged extent. Therefore, the surface color change of post-fire cement can be used to deduce the temperature of the spot on fire. This research applies image analyzing technique to study the surface color change of the specimens of post-fire sand and cement, and then investigate the intensities and compressive strengths of the surface colors of R.G.B., RG, RB, GB, RGB, H.S.I. of sand and cement specimens after burning at 25oC, 400oC, 600oC, 800oC and 1000oC, under different water-lime ratios. The results can be a reference for inference of the highest temperature of the spot on fire and the fire-damaged extent in the future. As cement encounters high temperature, the surface color will be changed accordingly. Since the change cannot be easily visible by eyes, it has to rely on camedia to catch the image. Through USB transmission cable, the data are entered in computer and filed. Then use the image analyzing techniques with basic statistical principles as the foundation — color channel image analyzer (Windows software written in Delphi) to analyze the fire-damaged images of the specimens of sand and cement. Through statistics, we can know the intensities of R.G.B. and H.S.I. of the specimens of sand and cement under different water-lime ratios, different temperature and different time extension, and have an analytic diagram drawn. It shows that when the temperature is below 800oC, the intensity of surface color R.G.B. of sand and cement specimens tends to be decreasing; when the temperature is above 800oC, it tends to be increasing. It refers that the surface color change of the three primary colors R.G.B. of the fire-damaged specimens of sand and cement is: red the greatest, blue the next, and green the smallest. Meanwhile, it is found that time extension also affects the R.G.B.. Besides, from the regression analysis of compressive strength and H value, S value, it is known that the correlation between them is very high. It deserves further research and development on their relationship. And the research can be a reference for future decision-making of whether a fire-damaged building should be dismantled for rebuilding or merely renovated so as to minimize the evaluation expenses and shorten the time for apprasiement and testing. It has high practical value.

碩士
國立臺灣科技大學
機械工程系
104
In recent years, the additive manufacturing has been known by people because of 3D printers which are gradually used in many applications. However, the mechanical properties of the products made by 3D printers are usually weaker than those made by other manufacturing methods. To resolve this problem, many researchers tried to use various types of mesh structure or to use the materials with higher strengths. In this study, we adopted a different approach by considering various paths on the impact of mechanical properties made by the FDM-type 3D printer. To generate various paths, in this study we improved the control program of a 5-axis FDM machine and made it operate smoothly. The material used in the study was PLA. Six different types of paths generated by this machine were used to make specimens for tensile tests. From the test results, the specimens with only longitudinal paths had the largest tensile strength among all the specimens. It may be inferred that there is a relationship between the types of paths and the direction of the force applied to the specimen.

碩士
逢甲大學
土木工程所
98
ABSTRACT This research studies the behaviors of Carbon Fiber Reinforced Plastics (CFRP) confining concretes exposed to fire, acid, alkaline and salty environments. First, 99 concrete cylindrical specimens, with size of Φ12cm×24cm, were designed and cast. These specimens were pre-loaded and then confined by CFRP. 27 of these specimens were externally adhered by fireproof material (Firecut F-1) with different thicknesses and 18 of them were not. Next, these specimens were all exposed to different temperatures (300, 400, 500, 600 or 700℃) with 30 or 60 minutes exposure time. Another 54 specimens were subject to acid, alkaline or salty test with different concentrations and soaking periods. All the specimens were then loaded by uni-axial compression test. The strength of concrete specimen was evaluated. The environmental influences on the confining effects of CFRP were also investigated. The test results show that the strength of CFRP confining concrete specimens exposed to fire environments over 300℃ are significantly decreased. However, CFRP confining concrete specimens adhered by fireproof materials are exposed to fire environments, they will not lose all the confinements and still retain most of the original strength. The fireproof material can really protect CFRP confining concretes from high temperatures. The results also show that the higher the concentration of acid, alkaline or salt is in the environment, the more the CFRP material loses its confining effect and thus the concrete loses its strengh. Key words: concrete, CFRP, confining effect, fire-proof material, acid, alkaline or salty test, uniaxial compression test

碩士
國立臺灣科技大學
營建工程技術學系
82
The fireproof capacity of coated steel structure is maintain by fire resistance rating(t), and the rating is close to section scale factor (W/D, unit weight/section fired circumambience) of steel structure and coating material thickness(T). The study is according to the view of section scale factor transfer, put all kinds of H style to be 45cm2 but differ thickness steel plate, make to small scale specimen, therefore, applying standard curve time-temperature under CNS 12514 to proceed truly fire resisting test of single degree heated model for small scale specimen ,and realize the truly relationship of t, T and W/D. However, according to theory analysis the feasibility of using small-scaled specimen replace coating steel structure and proceed the appraise of fireproof capacity. The kinds of coating steel structures are so much, so only study the model of wet coated structure (horizon-heating) painted around H style section.@　The study result detect that the mutidegree coating steel beam structure will transfer single degree small scale specimen and proceed fire resisting test by section scale factor, but must consider water evaporate condition and the affect of small specimen lost heat in high temperature. During the relationship of t, T and W/D, t is proportional with T and W/D. Form the result, the paper point of sprayed thickness of beam transfer formula common using now, and the managing method for examining the external qualify materials that recognized by the domestic authorities concerned, to provide the actual suggestion for the accordance of improving and examining.

Being able to extrapolate interaction values from a database of pullout resistance testing results may possibly help with narrowing down the most suitable reinforcement/fill material combinations for a Mechanically Stabilized Earth wall, thereby reducing the number of tests needed for a design and maximizing the efficiency of the system. The objectives of this thesis include the following: collect and organize a broad collection of data in a way that can assist in preliminary selection of interaction properties for uniaxial geogrids; analyze the collection of data for trends related to geogrid polymer type; analyze the collection of data for trends related to the presence of fines in the fill material; compare the collected data to previous studies on the effects of geogrid specimen length on pullout performance; and compare the collected data to previous studies on the effect of geogrid rib thickness to mean particle size ratio on normalized bearing stress and CI values. The data from 101 pullout tests are presented in tabular and graphic form so that the coefficient of interaction may be interpolated for many geogrid/fill material combinations. The effect of polymer type (PET vs HDPE) was shown to have little effect on how a geogrid performs in a fill material. In one case, the two polymer types exhibit differing trends within the same fill material. The presence of fines (>12% by weight) in the fill material results in a significant decrease in the coefficient of interaction when compared to clean granular fills. The effects of geogrid embedment length have significant effects on the results of geogrid pullout tests. Samples with shorter lengths were shown to carry a greater load per unit area than longer samples. Normalized bearing stress is shown to be heavily influenced by the geogrid transverse rib thickness to mean particle size ratio (B/D50). For a particular fill material, normalized bearing stress decreases linearly with increasing B/D50. For a particular geogrid, normalized bearing stress is shown to have a bi-linear behavior with increasing B/D50. Initially, normalized bearing stress increases with increasing B/D50. After reaching a peak, normalized bearing stress begins to decrease with increasing B/D50.
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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.