Dissertations / Theses on the topic 'Tensile strength of rock'
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Shang, Junlong. "Persistence and tensile strength of incipient rock discontinuities." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/15527/.
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Rock discontinuities are fundamentally important to most rock engineering projects but predicting or measuring their properties such as roughness, aperture, shape and extent (persistence) are fraught with difficulty. So far the solution of how to measure or predict persistence is poorly researched partly because the concept of how to investigate the extent of rock discontinuities within a rock mass seems intractable, by any economical methods. In the majority of engineering applications it is a fairly widespread practice to follow a conventional approach, assuming a 100% persistence value. However that is certainly incorrect even if usually a conservative assumption. This project is a small step towards resolving this issue. A series of laboratory and field research activities were carried out to investigate incipient nature of rock discontinuities and the extent of rock bridges. Uniaxial tensile strength of incipient discontinuities was quantified in the laboratory using cylindrical rock samples. The tested samples included incipient joints, mineral veins and bedding. It has been confirmed that such visible yet incipient features can have high tensile strength, approaching that of the parent rock. Factors contributing to the tensile strength of incipient rock discontinuities have been investigated. It is concluded that the degree of incipiency of rock discontinuities is an important factor that should be differentiated as part of the process of rock mass classification to inform more realistic engineering design and that this might best be done with reference to the tensile strength relative to that of the parent rock. An original methodology has been developed in the laboratory using expansive chemical splitters in drillholes, to quantify the tensile strength of large-scale incipient rock joints. In these tests, smaller tensile strengths were obtained, which probably was the result of localised stress concentration, low pressurization rate and unavoidable variations of expansive tensile force arising from the chemical splitter. A technique ‘Forensic Excavation of Incipient Rock Discontinuities (FEIRD)’ was established and employed to investigate areal extent and incipient nature of discontinuities in the field. Large rock blocks, containing incipient features, were split using similar expansive grout techniques as developed in the laboratory. Test results were interpreted and discussed with respect to fracture mechanics, fractographic features (such as hackle and rib marks), as well as geological conditions affecting the incipiency of the tested discontinuities including degree and extent of weathering and mineralisation. One common observation from the tests conducted is that breakage of non-persistent sections of incipient rock joints (rock bridges) leads to the development of rough surfaces over those freshly broken areas, and this may have implications for rock fracture development more generally. Despite rock bridge failure (say as part of rock slope mass movement), the freshly formed surfaces might be expected to have relatively high strength compared to the pre-existing persistent sections. An important conclusion from this research is that areal extent of open rock discontinuities (persistence) can be investigated realistically using the FEIRD technique. It has been found that estimates of persistence from trace mapping on rock exposures can be wildly inaccurate and it is concluded that field studies using FEIRD techniques (perhaps at a larger scale than used for this research to date) can be used to understand and quantify better the true nature of rock mass fracture network connectivity and extent that are important parameters for many rock engineering endeavours.
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Simpson, Nathaniel Denis John. "An analysis of tensile strength, fracture initiation and propagation in anisotropic rock (gas shale) using Brazilian tests equipped with high speed video and acoustic emission." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for petroleumsteknologi og anvendt geofysikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-24284.
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This study attempts to further our knowledge of fracture behaviour by establishing an experimental system that links tensile strength, fracture initiation and propagation of an anisotropic rock (Mancos Shale) using an integrated Brazilian Test Setup equipped with Acoustic Emission and High Speed Video. The unique experimental conguration was applied to an anisotropic gas shale (Mancos Shale) in addition to other petroleum related reservoir rocks (such as sandstone and chalk). The variation in tensile strength, fracture initiation location, propagation time and the failure pattern are examined as a function between the layer plane and the loading direction. A time shift was shown to exist between the time at ultimate tensile stress and the time at fracture initiation. This phenomenon has been dubbed the Naet Shift.
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Andersson, J. Christer. "Rock Mass Response to Coupled Mechanical Thermal Loading : Äspö Pillar Stability Experiment, Sweden." Doctoral thesis, KTH, Jord- och bergmekanik, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4287.
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The geological disposal of nuclear waste, in underground openings and the long-term performance of these openings demand a detailed understanding of fundamental rock mechanics. A full scale field experiment: Äspö Pillar Stability Experiment was conducted at a depth of 450 m in sparsely fractured granitic rock to examine the rock mass response between two deposition holes. An oval shaped tunnel was excavated parallel to the σ3 direction to provide access to the experiment and also provide elevated stress magnitudes in the floor. In the tunnel floor two 1.75-m diameter 6-m deep boreholes were excavated so that a 1-m thick pillar was created between them. In one of the holes a confinement pressure of 700 kPa was applied and in the other displacement transducers were installed. The pillar volume was monitored by an Acoustic Emission System. Spatially distributed thermocouples were used to monitor the temperature development as the pillar was heated by electrical heaters. The excavation-induced stress together with the thermal-induced stress was sufficient to cause the wall of the open borehole to yield. The temperature-induced stress was increased slowly to enable detailed studies of the rock mass yielding process. Once the rock mass loading response was observed, the rock mass was unloaded using a de-stress slotting technique. This thesis focuses on the in-situ study of the rock mass response to coupled mechanical thermal loading and thermal-mechanical unloading. The experiment, its design, monitoring and observations are thoroughly described. An estimate of the yielding strength of the rock mass is presented and compared with laboratory test and results from other rock mass conditions reported elsewhere in the open literature. General conclusions about the effect of the confining pressure and the observations from the unloading of the pillar are also presented. Important findings are that the yielding strength of the rock mass has been successfully determined, low confinement pressures significantly affects the onset of yielding, the primary mode of fracture initiation and propagation is extensional, no significant time dependency of the yielding process was observed. The unloading studies also indicated that what appeared to be shear bands likely was a propagating zone of extensile failure that weakened the rock so that displacements in the shear direction could occur.QC 20100622
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Dinh, Quoc Dan. "Brazilian test on anisotropic rocks." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2011. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-76331.
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The present work describes investigations on the anisotropic strength behavior of rocks in the splitting tensile test (Brazilian test). Three transversely isotropic rocks (gneiss, slate and sandstone) were studied in the Lab. A total of more than 550 indirect tensile strength tests were conducted, with emphasis was placed on the investigation of the influence of the spatial position of anisotropic weakness plane to the direction of the load on the fracture strength and fracture or fracture mode. In parallel, analytical solutions were evaluated for stress distribution and developed 3D numerical models to study the stress distribution and the fracture mode at the transversely isotropic disc. There were new findings on the fracture mode of crack propagation, the influence of the disc thickness, the influence of the applying loading angle and angle of the loading-foliation for transversely isotropic materialInhalt der Arbeit sind Untersuchungen zum anisotropen Festigkeitsverhalten von Gesteinen beim Spaltzugversuch (Brazilian Test). Laborativ wurden drei transversalisotrope Gesteine (Granit, Schiefer und Sandstein) untersucht. Insgesamt wurden mehr als 550 Spaltzugversuche durchgeführt, wobei der Schwerpunkt auf die Untersuchung des Einflusses der räumlichen Lage der Anisotropieebene zur Richtung des Lasteintrages auf die Bruchfestigkeit und das Bruchbild bzw. den Bruchmodus gelegt wurde. Parallel dazu wurden analytische Lösungen zur Spannungsverteilung ausgewertet sowie numerische 3D-Modelle entwickelt, um die Spannungsverteilung sowie den Bruchmodus bei einer transversalisotropen Scheibe zu untersuchen. Es wurden neue Erkenntnisse zum Bruchmodus, der Rissausbreitung, des Einflusses der Scheibendicke, dem Einfluss des Lasteinleitungswinkel sowie des Winkels Lasteintrag - Anisotropieebene für transversalisotropes Material gewonnen
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Yin, Penghai. "Tensile Strength of Unsaturated Soils." Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/41841.
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Desiccation-induced soil cracking is of significant interest in several engineering disciplines, which include geotechnical and geoenvironmental engineering, mining engineering, and agriculture engineering. The hydraulic, mechanical, thermal and other physico-chemical properties of unsaturated soils can be predominantly influenced due to cracks. Reliable information of these properties is required for the rational design and maintenance of earth structures taking account of the influence the soil-atmosphere interactions (e.g., for expansive soil slopes, earth dams, and embankments). In spite of significant research studies published in the literature on the desiccation-induced cracks during the past century, the fundamental mechanism of crack initiation and propagation of soils induced by drying and shrinkage is still elusive. For this reason, the focus of this thesis is directed towards understanding the tensile strength of unsaturated soils which is associated with soil crack initiation criterion (i.e. maximum tensile stress criterion).
Tensile strength is the key property of soils for interpreting the initiation of soil cracking from a macroscopic point of view. A semi-empirical model is proposed for predicting the tensile strength of unsaturated cohesionless soils taking into account the effect of both the negative pore-water pressure in saturated pores and the air-water interfacial surface tension in unsaturated pores. The proposed model is calibrated and validated by providing comparisons between the model predictions and the experimental measurements on 10 cohesionless soils (i.e. five sandy soils and five silty soils) published in the literature. The proposed model is simple and requires only the information of Soil-Water Characteristic Curve (SWCC) and Grain Size Distribution curve (GSD), which can be obtained from conventional laboratory tests.
To investigate the influence of microstructure, a practical and reliable estimation approach for predicting the evolution of the microstructural void ratio of compacted clayey soils subjected to wetting and drying paths is proposed. The microstructural evolution of 13 examined soils were investigated quantitatively using the mercury intrusion porosimetry (MIP) results. The investigated soils include four high-plasticity clays, eight low-plasticity clays and a glacial till which is a relatively coarse-grained soil with some fines. Based on this study, a novel criterion has been developed for identifying different pore populations of compacted clayey soils. The “as-compacted state line” (ACSL) was proposed to estimate the initial microstructural void ratio based on the compaction water ratio. A constitutive stress is derived to interpret and predict the volumetric deformation of compacted clay aggregates. The linear elastic constitutive model is used for predicting the microstructural void ratio of the examined compacted soils following monotonic wetting and drying paths. The developed approach (i.e. the ACSL and the linear elastic constitutive model) is validated by providing comparisons between the predicted and interpreted microstructural void ratios for all the examined soils.
In addition to the matric suction and microstructure, the confining pressure also influences the tensile strength of unsaturated compacted clayey soils. The tensile strength tests on a compacted clayey soil by both the direct method (i.e. triaxial tensile test) and the indirect method (i.e. Brazilian split test) were performed. It is found that the tensile strength increases as the compaction water content decreases for the range investigated in this study, which could be explained by the variation of the inter-aggregated capillary bonding force and the change in microstructure. The increase in the confining pressure has been found to induce the change in failure mode (i.e. from pure tensile failure mode to combined tensile-shear failure mode). In spite of limitations associated with the Brazilian split test, tensile strength is widely determined using this test due to the simple procedure of specimen preparation and wide availability of test equipment in conventional laboratories. However, the Brazilian tensile strength is found to overestimate the tensile strength of compacted specimens with water content greater than the plastic limit. This is due to the considerable plastic deformation associated with the ductile failure instead of brittle failure.
In summary, this thesis is devoted to providing insight into the fundamental mechanisms associated with the desiccation-induced crack initiation by quantitatively investigating the various factors that influence the tensile strength of unsaturated soils, which include the matric suction, the microstructure, and the confining pressure from theoretical studies and laboratory investigations.
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Huang, Jian. "The Tensile Strength of Liquid Nitrogen." PDXScholar, 1992. https://pdxscholar.library.pdx.edu/open_access_etds/1134.
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The tensile strength or the negative pressure required to induce cavitation in a pure liquid has been a puzzling subject. On one hand, the classical nucleation theory has met great success in predicting the nucleation rates of superheated liquids. On the other hand, most of reported experimental values of the tensile strength for different liquids are far below the prediction from the classical nucleation theory. In this study, homogeneous nucleation in liquid nitrogen and its tensile strength have been investigated. In order to carry out the measurement of the tensile strength of liquid nitrogen, different approaches for determining the pressure amplitude were studied carefully. It is shown that Raman-Nath theory, as modified by the introduction of an effective interaction length, can be used to determine the pressure amplitude in the focal plane of a focusing ultrasonic transducer. The results obtained from different diffraction orders are consistent and in good agreement with other approaches including Debye's theory and solving the KZK (Khokhlov-Zabolotskaya-Kuznetsov) equation. The results from experiments in water demonstrated that as long as the nonlinearity is not too large, the experimentally determined pressure follows closely the calculated results using either Debye's theory or the KZK equation. In addition, the light diffraction contains enough information to calculate the second-order harmonic in the sound wave. In principle, it is possible that the contribution to the acoustic wave of the higher than the second-order harmonic can be obtained. The measurement of the tensile strength was carried out in a high pressure stainless steel dewar. A High intensity ultrasonic wave was focused into a small volume of liquid nitrogen in a short time period. A probe laser beam passes through the focal region of a concave spherical transducer with small aperture angle and the transmitted light is detected with a photodiode. When the voltage on the transducer reaches a critical point, nucleation in the focal region occurs and a characteristic signal associated with the nucleation was obtained. At this moment, the pressure amplitude at the focus is calculated based on the acoustic power radiated into the liquid. In the experiment, the electrical signal on the transducer is gated at its resonance frequency with gate widths of 20 ~s to 0.2 ms and temperature range from 77 K to near 100 K. The calculated pressure amplitude is in agreement with the prediction of classical nucleation theory for the nucleation rates from 106 to lOll (bubbles/cm3 sec). This work enhances our understanding of the nucleation process in liquids. It provides the direct experimental support that the validity of the classical nucleation theory can be extended to the region of the negative pressure up to 90 atm. This is only the second cryogenic liquid to reach the tensile strength predicted from the classical nucleation theory.
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Baltodano-Goulding, Rafael. "Tensile strength, shear strength, and effective stress for unsaturated sand." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4364.
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Thesis (Ph.D.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (February) Vita. Includes bibliographical references.
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McClain, Michael Patrick. "A micromechanical model for predicting tensile strength." Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-10052007-143117/.
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Nissen, Joel Alan. "The Tensile Strength of Liquid Helium Four." PDXScholar, 1988. https://pdxscholar.library.pdx.edu/open_access_etds/1357.
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It is well known that most liquids exhibit a tensile strength which is much smaller in magnitude than the tensile strength predicted by homogeneous nucleation theory. This lack of agreement is usually attributed to the difficulty of preparing liquid samples free from foreign gases which act as heterogeneous nucleation sites. Liquid helium occupies a unique place among liquids for tensile strength measurements because all foreign gases are frozen out at liquid helium temperatures. Furthermore, superfluid 4He should fill all crevices on solid surfaces, eliminating the chance of heterogeneous nucleation on helium vapor pockets. Despite the quantum mechanical nature of liquid helium, Becker-Doring theory of nucleation of the vapor phase from the liquid phase should be valid down to 0.3 K in 4 He, yet previous results have been in stark disagreement with the theory. In this study, a piezoelectric transducer in the form of a hemispherical shell was used to focus high-intensity ultrasound into a small volume of 4He . The transducer was gated at its resonant frequency of 566 kHz with gate widths of less than 1 msec in order to minimize the effects of transducer heating and acoustic streaming. The onset of nucleation was detected from the absorption of acoustic energy and the scattering of laser light from microscopic bubbles. A new theory for the diffraction of light from the focal zone of a spherical converging sound wave was developed to confirm calculations of the acoustic pressure amplitude at the focus of the piezoelectric transducer, calculations which were based on the acoustic power radiated into the liquid and the nonlinear absorption of sound. The experimental results were in agreement with homogeneous nucleation theory for a nucleation rate of approximately 1015 critical size bubbles/sec-cm3. This is only the third liquid for which the theoretical tensile strength has been reached and it confirms homogeneous nucleation theory over a range three times greater than any other experiment. A noticeable decrease in the magnitude of the tensile strength was noted at temperatures near the lambda transition and a hypothesis that bubbles are being nucleated heterogeneously quantized vortices is presented.
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Yamaguchi, Takashi. "Fundamental Study on High Strength Bolted Tensile Joints." Kyoto University, 1996. http://hdl.handle.net/2433/160789.
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本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものであるKyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第6407号
工博第1504号
新制||工||1025(附属図書館)
UT51-96-F286
京都大学大学院工学研究科土木工学専攻
(主査)教授 渡邊 英一, 教授 小林 昭一, 教授 土岐 憲三
学位規則第4条第1項該当
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Ifland, Chad. "TENSILE STRENGTH OF STEEL PLATES USING LONGITUDINAL WELDS." OpenSIUC, 2012. https://opensiuc.lib.siu.edu/theses/800.
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When a tension steel plate is welded to a gusset steel plate and a tension load is transmitted to the gusset plate by longitudinal welds along both edges at the end of the tension plate, the shear lag factor (U) is used to determine the design tensile strength for the plate. The shear lag factor is determined from the American Institute of Steel Construction (AISC) Manual. The shear lag factor is selected from the table based on the length of the weld and the width of the steel plate that is in tension. The thickness of the plates, boundary condition of the gusset plate, the size and strength of the weld is not taken into account when determining the shear lag factor. This study will investigate if these factors will affect the design tensile strength for a tension plate welded to a gusset plate by longitudinal welds. NISA, finite element analysis software, will be used to determine the ultimate load the tension plate can handle before it fractures. Then the results will be compared to the design strengths calculated by using the shear lag factors earlier stated.
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Douglas, Kurt John Civil & Environmental Engineering Faculty of Engineering UNSW. "The shear strength of rock masses." Awarded by:University of New South Wales. School of Civil and Environmental Engineering, 2002. http://handle.unsw.edu.au/1959.4/19138.
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The first section of this thesis (Chapter 2) describes the creation and analysis of a database on concrete and masonry dam incidents known as CONGDATA. The aim was to carry out as complete a study of concrete and masonry dam incidents as was practicable, with a greater emphasis than in other studies on the geology, mode of failure, and the warning signs that were observed. This analysis was used to develop a method of very approximately assessing probabilities of failure. This can be used in initial risk assessments of large concrete and masonry dams along with analysis of stability for various annual exceedance probability floods. The second and main section of this thesis (Chapters 3-6) had its origins in the results of Chapter 2 and the general interests of the author. It was found that failure through the foundation was common in the list of dams analysed and that information on how to assess the strength of the foundations of dams on rock masses was limited. This section applies to all applications of rock mass strength such as the stability of rock slopes. Methods used for assessing the shear strength of jointed rock masses are based on empirical criteria. As a general rule such criteria are based on laboratory scale specimens with very little, and often no, field validation. The Hoek-Brown empirical rock mass failure criterion was developed in 1980 for hard rock masses. Since its development it has become virtually universally accepted and is now used for all types of rock masses and in all stress regimes. This thesis uses case studies and databases of intact rock and rockfill triaxial tests collated by the author to review the current Hoek-Brown criterion. The results highlight the inability of the criterion to fit all types of intact rock and poor quality rock masses. This arose predominately due to the exponent a being restrained to approximately 0.5 to 0.62 and using rock type as a predictor of mi. Modifications to the equations for determining the Hoek-Brown parameters are provided that overcome these problems. In the course of reviewing the Hoek-Brown criterion new equations were derived for estimating the shear strength of intact rock and rockfill. Empirical slope design curves have also been developed for use as a preliminary tool for slope design.
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Edelbro, Catrin. "Evaluation of rock mass strength criteria." Licentiate thesis, Luleå, 2004. http://epubl.luth.se/1402-1757/2004/72.
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Zheng, Wei, and 鄭偉. "Shock vibration resistance and direct tensile strength of concrete." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31242753.
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Zheng, Wei. "Shock vibration resistance and direct tensile strength of concrete." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B23273124.
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Alzaylaie, Marwan. "Stiffness and strength of Dubai sedimentary rock." Phd thesis, Institut und Versuchsanstalt für Geotechnik der Technischen Universität Darmstadt, 2018. https://tuprints.ulb.tu-darmstadt.de/8153/1/Alzaylaie%282017%29_DissNr102.pdf.
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Safety, optimisation and the sustainability are the most important aspects for the design of any foundation system. An optimised and safe design of foundation systems for high-rise structures in difficult soil and groundwater conditions is based on a reduction of construction material used, construction time spent, energy consumed and the adequate consideration of the soil-structure interaction. This is also important for the high-rise structures like skyscrapers and bridge piers in Dubai, UAE. Due to the large loads most of these structures are founded in the Dubai sedimentary rock. Up to now the rock mechanical parameters for these rock layers have been defined on the very conservative side which led to over-dimensioned foundations in many cases. In a large research program the bearing behaviour of Dubai Sandstone and Dubai Siltstone has been investigated by field and laboratory tests, by in-situ pile load tests and the numerical back-analysis using the Finite-Element-Method (FEM). The comprehensive research investigations show, that the stiffness and strength of Dubai sedimentary rock is more than 20 times higher as it is assumed up to now. The thesis presents the scope of research, the epoch-making results and the significance for the engineering practice. The geotechnical data used in this thesis is collected from geotechnical investigation reports (195 boreholes) and static load tests (116) from more than 45 towers in Business Bay and Downtown Dubai as well as a case study evaluating one project located in Business Bay.
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Win, San San Civil & Environmental Engineering Faculty of Engineering UNSW. "Tensile strength of compacted soils subject to wetting and drying." Awarded by:University of New South Wales. School of Civil and Environmental Engineering, 2006. http://handle.unsw.edu.au/1959.4/31157.
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Knowledge of the stress-strain relationship of the compacted soils in tension is of importance for understanding of cracking that occurs in earth structures, in particular embankment dams and landfill barriers. Understanding the correlation between tensile properties and traditional soil parameters and soil suction is essential in identifying problems associated with desiccation induced cracking. A series of extensive laboratory experiments were performed on three different soils from existing embankment dams. This thesis concentrated on the investigation of tensile strength in relation to the type of soil, compaction water content, compaction density ratio, rate of loading, soil suction, moisture retention characteristics and the effect of drying and wetting. Stress-strain behaviour and tensile properties indicated a dependence on soil type and compaction criteria. The plasticity index, clay content and type of mineral has shown a significant influence on tensile strength. Compaction dry of optimum resulted in an increase in strength. Compaction wet of optimum showed a decrease in strength and small increase in strain at failure. Higher compaction effort resulted in higher tensile strength, tensile stiffness and brittle stress-strain behaviour. Difference in loading rate revealed response time for initial tensile deformation as well as sustainable duration up to failure point. The effect of soil suction plays an important role in drying during which specimens exhibited a considerable strength increase. The magnitude of strength increase may have been contributed by a combination of suction, air entry value and compaction density. The effect of wetting could cause decreasing in suction and thus a reduction in strength. Based on the findings, it was concluded that the desiccation-induced may not necessarily occur due to an associated increase in tensile strength. However, an increase in tensile strength is likely to be accompanied by an increase in shrinkage. Therefore, desiccation-induced cracking is related to the interaction between moisture loss, change in soil suction, tensile stress and shrinkage.
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Fields, Kelvin L. "Tension stiffening response of high-strength reinforced concrete tensile members." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0002/MQ35492.pdf.
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Newton, John Michael. "The tensile strength and fracture toughness of heavy clay bodies." Thesis, University of Sheffield, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296976.
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JUNIOR, JOAQUIM NUNES MARTINS. "TENSILE STRENGTH OF A CONCRETE ANCHORING SUBJECTED TO IMPACT LOAD." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2006. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=8724@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOEste trabalho tem como objetivo estudar a resistência de um sistema de ancoragem composto de pinos com cabeça embutidos no concreto, quando submetidos a cargas de impacto. A variável adotada foi a taxa de carregamento cujos valores mínimo e máximo foram 0,015 kN/s (estático) e 54.885 kN/s, respectivamente. O sistema de ancoragem foi projetado de forma que a ruptura fosse governada pelo arrancamento do cone de ruptura. Foram ensaiados onze blocos de concreto com um pino embutido no concreto, sujeitos a diferentes taxas de aplicação de carga. Foram também ensaiados quinze corpos-de-prova de concreto à compressão diametral e nove pinos à tração, também sujeitos a diferentes taxas de aplicação de carga. O objetivo desses ensaios foi verificar a influência da taxa de carregamento sobre as resistências dos materiais - concreto e aço - que participam do sistema de ancoragem. Os resultados mostraram que a área da superfície e a inclinação do cone de ruptura não sofrem grandes alterações. A carga de ruptura do cone de concreto cresce com a taxa de carregamento, e que esse crescimento pode ser descrito por uma função logarítmica. O mesmo foi observado para a resistência à tração do concreto por compressão diametral e para os pinos.
This work investigates the strength of a concrete anchor system constituted of headed studs embedded in concrete subjected to impact tension load. The main variable was the loading rate which varied from a minimum of 0,015 kN/s (static) to a maximum of 54885 kN/s. The anchor system was designed so that the failure was governed by concrete cone breakout. Eleven concrete blocks with a single headed stud were tested under different loading rates. In addition, fifteen concrete cylinders subjected to compression along a diameter (split cylinder test) and nine headed studs subjected to tension were tested under different loading rates in order to investigate the effects of the loading rate on the strength of concrete and steel separately. The results showed that the area and the angle of the concrete cone were not affected by the loading rate. The failure load of the concrete cone increases as the loading rate increases and this phenomenon can be described by a logarithmic function. The concrete split tensile strength and the steel tensile strength also increase as the loading rate increases.
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Mahjoub-Moghaddas, Hamid. "Tensile and shear impact strength of concrete and fibre reinforced concrete." Thesis, Cardiff University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261439.
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Simone, Anthony E. (Anthony Eugene) 1970. "The tensile strength of porous copper made by the GASAR process." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/38358.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1994.Vita.
Includes bibliographical references (leaves 124-126).
by Anthony E. Simone, Jr.
M.S.
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Kleiner, Mark. "Correlation Between Tensile Strength and Collagen Content in Cultured Skin Substitutes." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1106765630.
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Kamimura, Masaki. "Interfacial tensile strength between polymethylmethacrylate-based bioactive bone cements and bone." Kyoto University, 2003. http://hdl.handle.net/2433/148752.
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Srinivasan, Geetha. "Evaluation of indirect tensile strength to identify asphalt concrete rutting potential." Morgantown, W. Va. : [West Virginia University Libraries], 2004. https://etd.wvu.edu/etd/controller.jsp?moduleName=documentdata&jsp%5FetdId=3477.
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Thesis (M.S.)--West Virginia University, 2004.Title from document title page. Document formatted into pages; contains vii, 65 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 52-53).
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Mansoor, Zaheer Ahmad. "Xylan as Strength Enhancing Additive." Thesis, KTH, Skolan för kemivetenskap (CHE), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-145861.
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The effect of xylan from different plant species on tensile properties of spruce pulp was studied. Xylans from spruce, birch, wheat straw and rice husks were mixed with the fresh white liquor and added at the later stages of separate kraft cooks, in exchange of the black liquor removed from the system at that time. Results show that xylans, from rice husk, wheat straw and birch, gave stronger pulps. However it was only possible to attach small quantities of xylans onto the fibers. Moreover, pulps containing birch and rice xylan were easier to beat than the other pulps in the study.
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陳增源 and Chang-yuen Chan. "The initiation of catastrophic tensile instability in Niobium crystalsat 77K." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1995. http://hub.hku.hk/bib/B31234069.
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Neilson, Henry Jathuren. "Weibull Modulus of Hardness, Bend Strength, and Tensile Strength of Ni-Ta-Co-X Metallic Glass Ribbons." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1396008191.
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Hallam, M. A. "The fracture behaviour of oriented polyethylene." Thesis, University of Leeds, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377862.
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Tjäder, Erik. "Shafts and rock mass strength : Calibration using numerical models." Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-68249.
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Orepasses and ventilation shafts are examples of mine infrastructure that are subjected to increasingstresses as the production in the Kiirunavaara mine moves to deeper levels. Falloutsand damages in these kind of excavations are already occurring and the problem can be expectedto increase in the future. Information about the rock mass properties is necessary in order to predict the extent of stressinduced failures in the future. The main focus of this thesis was to calibrate rock mass strength parameters by using numerical models in combination with observations of actual damages. Orepasses are affected by wearing from falling rock, which can be difficult to take into account in a numerical model. Damages from ventilation shafts were therefore chosen as input in the numerical modeling. A material model for brittle failure was used in the calibration. Damage mapping of several ventilation shaft was done and damages with typical stress-induced characteristics were chosen for the calibration of strength parameters. Most of the calibration calculations were successful. Final results for each parameter were calculated as mean values from all successful calibrations. The result from the calibration was thereafter used as input values in a prognosis calculation for stress-induced damages in future mining. Two ventilation shafts with varying distance to the orebody were analyzed. The stress situation for future mining was simulated for two upcoming production levels, 1165 and 1223. The prognosis results showed that stress-induced failures will increase in both quantity and severity. The modeling results showed stress-induced failures with a depth up to 50 cm. It was also concluded that the horizontal distance to the orebody has a large influence on the occurrence of stress-induced failures in ventilation shafts.
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Meyers, Anthony G. "The determination of rock mass strength for engineering design /." Title page, contents and abstract only, 1993. http://web4.library.adelaide.edu.au/theses/09PH/09phm6134.pdf.
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Lazzari, Elisa. "Analysis of shear strength of rock joints with PFC2D." Thesis, KTH, Jord- och bergmekanik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-129740.
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Joints are the main features encountered in rock and sliding of rock blocks on joints is classified as the principal source of instability in underground excavations. In this regard, joints’ peak shear strength is the controlling parameter. However, given the difficulty in estimating it, shear tests are often performed. These are often quite expensive and also time consuming and, therefore, it would be valuable if shear tests could be artificially performed using numerical models. The objective of this study is to prove the possibility to perform virtual numerical shear tests in a PCF2D environment that resemble the laboratory ones. A numerical model of a granite rock joint has been created by means of a calibration process. Both the intact rock microparameters and the smooth joint scale have been calibrated against macroparameters derived from shear tests performed in laboratory. A new parameter, the length ratio, is introduced which takes into account the effective length of the smooth joint compared to the theoretical one. The normal and shear stiffnesses, the cohesion and the tensile force ought to be scaled against the length ratio. Four simple regular joint profiles have been tested in the PFC2D environment. The analysis shows good results both from a qualitative and from a quantitative point of view. The difference in peak shear strength with respect to the one computed with Patton´s formula is in the order of 1% which indicates a good accuracy of the model. In addition, four profiles of one real rough mated joint have been tested. From the scanned surface data, a two-dimensional profile has been extracted with four different resolutions. In this case, however, interlocking of particles along the smooth joint occurs, giving rise to an unrealistic distribution of normal and shear forces. A possible explanation to the problem is discussed based on recent developments in the study of numerical shear tests with PFC2D.
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Chan, Chang-yuen. "The initiation of catastrophic tensile instability in Niobium crystals at 77K /." Hong Kong : University of Hong Kong, 1995. http://sunzi.lib.hku.hk/hkuto/record.jsp?B19668910.
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OLIVEIRA, WALTER EDGLEY DE. "EXPERIMENTAL STUDY ON THE TENSILE STRENGTH OF ANCHORAGE PLATES EMBEDDED IN CONCRETE." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2003. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=4239@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOELETROBRAS TERMONUCLEAR S.A - ELETRONUCLEAR
Placas de ancoragem embutidas em concreto são empregadas, geralmente, com a finalidade de permitir a fixação de elementos para a introdução de cargas concentradas nas estruturas de concreto, bem como viabilizar as ligações estruturais entre componentes pré-fabricados. As placas são ancoradas no concreto através de pinos soldados a elas. Estas placas são bastante empregadas em estruturas de usinas nucleares onde um grande número de equipamentos e tubulações são apoiados na estrutura de concreto. A pesquisa é de natureza experimental e tem como objetivo investigar a redução da resistência à tração de placas de ancoragem com grupo de chumbadores, placas instaladas com pequena distância dos bordos do elemento de concreto, e também de duas placas adjacentes, devido a interferência de seus cones de ruptura. A eficiência de uma armadura de suspensão (que transmite a carga além do cone de ruptura), também é verificada. Os resultados experimentais sugerem uma notável redução da resistência à tração para placas com grupo de chumbadores, e que o uso da armadura de suspensão para placa instalada nas proximidades do bordo do elemento de concreto não é muito eficiente. A armadura de suspensão apresentou um bom rendimento quando foi empregada em placas com grupo de chumbadores. Os resultados teóricos obtidos através de equações desenvolvidas para estimativa da carga de ruptura, apresentaram, de maneira geral, uma boa aproximação quando comparados com os resultados experimentais.
Anchorage plates embedded in concrete are used with the purpose of allowing the fixation of elements for the introduction of concentrated loads into concrete structures, as well as to make possible the structural connections between prefabricated components. The plates are anchored in the concrete through studs welded to them. These plates are used in structures of nuclear power stations where a great number of equipments and pipings are fixed in the concrete structure. The research is of experimental nature and its objective is to investigate the reduction of the tensile strength of multiple studs group, anchorage plates located close to a free edge, and also of two adjacent plates, due to interference of failure concrete cones. The efficiency of an additional reinforcement (that transfers the load beyond the concrete cone), is also addressed. The experimental results suggest a significant reduction of the tensile strength for plates with studs group, and that the use of the additional reinforcement for anchorage plates located close to a free edge is not too efficient. The additional reinforcement presented a good efficiency when it was used in plates with studs group. The theoretical results obtained from equations developed to estimate the concrete failure load show, in a general way, a good agreement with the experimental results.
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Phillips, Erin Katherine. "Investigation of Required Tensile Strength Predicted by Current Reinforced Soil Design Methodologies." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/49246.
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Geosynthetic Reinforced Soil (GRS) is a promising technology that can be implemented
in walls, culverts, rock fall barriers, and bridge abutments. Its use in walls and abutments
is similar to Mechanically Stabilized Earth Walls (MSEW) reinforced with geosynthetics.
Both GRS and MSEW are reinforced soil technologies that use reinforcement to provide
tensile capacity within soil masses. However, the soil theories behind each method and
the design methodologies associated with GRS and MSEW technologies are quite
different.
Therefore, a study was undertaken to compare the required tensile strength predicted by
these various reinforced soil design methodologies. For the purposes of this study, the
required ultimate tensile strength was defined as the ultimate tensile strength needed in
the reinforcement after all applicable factors of safety, load factors, and reduction factors
were applied. The investigation explored both MSEW and GRS. GRS has been made an
FHWA "Every Day Counts" initiative. Due to the push to implement GRS technology, it
is critical to understand how GRS design methods differs from classic MSEW design
methods, specifically in the prediction of ultimate tensile strength required.
A parametric study was performed comparing five different reinforced soil analysis
methods. Two are current MSEW design methods and one was a proposed revision to an
existing MSEW design method. The final two were GRS design methods. These design
methods are among the most current and/or widely used design references in the United
States regarding reinforced soil technology. There are significant differences between the
methods in the governing soil theory particularly between GRS and MSEW design
methods. The goal of the study was to understand which design parameters had the most
influence on calculated values of the required ultimate tensile strength and nominal
"unfactored" tensile strength. A base case was established and a reasonable set of
parameter variations was determined. Two loading conditions were imposed, a roadway
loading scenario and a bridge loading scenario.
Based on parametric study findings, conclusions were drawn about which design
parameters had the most influence for different design methods. Additionally, the
difference in overall predicted required tensile strength was assessed between the various
methods. Finally, the underlying soil theory and assumptions employed by the different
methods and their influence on predicted required tensile strength values was interpreted.Master of Science
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Azizipesteh, Baglo Hamid Reza. "Effect of various mix parameters on the true tensile strength of concrete." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/12560.
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The primary aim of this research was to develop a method for determining the true uniaxial tensile strength of concrete by conducting a series of cylinder splitting, modulus of rupture (MOR) and cylinder/cube compression tests. The main objectives were: • Critically reviewing previous published research in order to identify gaps in current knowledge and understanding, including theoretical and methodological contributions to the true uniaxial tensile strength of concrete. In order to maintain consistency and increase the reliability of the proposed methods, it is essential to review the literature to provide additional data points in order to add additional depth, breathe and rigor to Senussi's investigation (2004). • The design of self compacting concrete (SCC), normal strength concrete (NSC) and high strength concrete (HSC) mixes and undertaking lab-based experimental works for mixing, casting, curing and testing of specimens in order to establish new empirical evidence and data. • Analysing the data, presenting the results, and investigating the application of validity methods as stated by Lin and Raoof (1999) and Senussi (2004). • To draw conclusions including comparison with previous research and literature, including the proposal of new correction factors and recommendations for future research. 29 batches of NSC, 137 batches of HSC, 44 batches of fly ash SCC and 47 batches of GGBS SCC were cast and their hardened and fresh properties were measured. Hardened properties measured included: cylinder splitting strength, MOR, cylinder compressive strength and cube compressive strength. A variety of rheological tests were also applied to characterise the fresh properties of the SCC mixes, including: slump flow, T50, L-box, V-funnel, J-ring and sieve stability. Cylinders were also visually checked after splitting for segregation. The tensile strength of concrete has traditionally been expressed in terms of its compressive strength (e.g. ft = c x c f ). Based on this premise, extensive laboratory testing was conducted to evaluate the tensile strength of the concretes, including the direct tension test and the indirect cylinder splitting and MOR tests. These tests however, do not provide sufficiently accurate results for the true uniaxial tensile strength, due to the results being based upon different test methods. This shortcoming has been overcome by recently developed methods reported by Lin and Raoof (1999) and Senussi (2004) who proposed simple correction factors for the application to the cylinder splitting and MOR test results, with the final outcome providing practically reasonable estimates of the true uniaxial tensile strength of concrete, covering a wide range of concrete compressive strengths 12.57 ≤ fc ≤ 93.82 MPa, as well as a wide range of aggregate types. The current investigation has covered a wide range of ages at testing, from 3 to 91 days. Test data from other sources has also been applied for ages up to 365 days, with the test results reported relating to a variety of mix designs. NSC, SCC and HSC data from the current investigation has shown an encouraging correlation with the previously reported results, hence providing additional wider and deeper empirical evidence for the validity of the recommended correction factors. The results have also demonstrated that the type (size, texture and strength) of aggregate has a negligible effect on the recommended correction factors. The concrete age at testing was demonstrated to have a potentially significant effect on the recommended correction factors. Altering the cement type can also have a significant effect on the hardened properties measured and demonstrated practically noticeable variations on the recommended correction factors. The correction factors proved to be valid regarding the effects of incorporating various blended cements in the HSC and SCC. The NSC, HSC and SCC showed an encouraging correlation with previously reported results, providing additional support, depth, breadth and rigor for the validity of the correction factors recommended.
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McDonald, Shelley (Shelley Elizabeth) Carleton University Dissertation Engineering Civil and Environmental. "Tensile strength of aged gray cast iron water mains in Gatineau, Quebec." Ottawa, 1996.
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Li, Guang. "The effect of moisture content on the tensile strength properties of concrete." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0004782.
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Conroy-Jones, Gene A. "The effects of curing, and aggregate type upon the tensile strength measurement of medium to high strength concrete." Thesis, Cardiff University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301797.
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McConnell, Brian James. "Factors controlling sandstone strength and deformability in uniaxial compression." Thesis, University of Bristol, 1989. http://hdl.handle.net/1983/2fde6a20-8069-4e9e-beb9-2c0b867385de.
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Strömberg, Frida. "Humidity’s effect on strength and stiffness of containerboard materials : A study in how the relative humidity in the ambient air affects the tensile and compression properties in linerboard and fluting mediums." Thesis, Karlstads universitet, Institutionen för ingenjörs- och kemivetenskaper, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-43474.
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The aim of this thesis was to investigate the difference between containerboard materials strength and stiffness properties in tension and compression, how the mechanisms behind compressive and tensile properties are affected by the relative humidity of the ambient air and how the relative humidity affects the compressive response of the fibre network. These properties are used to predict the lifetime performance of corrugated boxes and to prevent early collapses of the boxes and thereby waste or harm of the transported goods inside. The work also discusses the methods used to evaluate the different properties and how reliable the results are. The experimental part includes testing of linerboard and fluting materials from both virgin and recycled fibres, which have been conditioned at 50% and 90% relative humidity. The compression tests were filmed to evaluate if different compression failure modes can be related to the strength and stiffness of the material. The results indicated that the compressive strength and stiffness differ from the strength and stiffness values in tension at 90% relative humidity. Compressive strength is lower in both 50% and 90% relative humidity compared with the tensile strength. However, the compression stiffness shows a higher value than the tensile stiffness at 90% relative humidity. The study of the method for evaluating the compressive behaviour of the paper does not present a complete picture on what type of failure the paper actually experience.
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Grasselli, G. Grasselli G. "Shear strength of rock joints based on quantified surface description /." [S.l.] : [s.n.], 2001. http://library.epfl.ch/theses/?display=detail&nr=2404.
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Roko, Raoul Olatounbossoun. "Roughness influence on strength and deformation behavior of rock discontinuities." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185322.
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The influence of discontinuity roughness on the shear strength and deformation behavior of rock joint is analyzed. The study is divided into three parts: laboratory direct shear test on rock samples having different roughness characteristics, characterization of roughness profiles using variogram and probability density distribution and the application of dynamical systems theory to analyze the stability condition of the sliding motion. The relative motion along the rough joint is erratic particularly at a low normal load. A steady motion develops as the normal load increases. The kinematics of translational motion has two distinct characteristics: the translation occurs as a result of a gross and uniform motion (sliding) and/or through localized inhomogeneous motion (slipping). Three modes of volumetric changes are observed during the tangential motion: a dilatant-contractant behavior with the overall volumetric change being strictly dilatant, a dilatant-contractant behavior with the overall volumetric change varying from dilatant to contractant and the strictly contractant behavior. The size of the sheared zones is a function of the distribution of the asperities and of the interface strength. The coefficient of friction decreases as the normal load increases. It may or may not increase when the normal load is decreased. The probability density distribution of the height of the interface asperities is not always Gaussian. The variation of the experimental distribution (histogram) indicates that the asperities are not necessarily sheared off in order of decreasing height but rather on the basis of the condition underlying the existence of contact. The slope of the initial portion of the variogram and the sill, when it exists, are used to characterize the surface morphology of the discontinuity. The lower the slope, the smoother the surface. Two types of anisotropy are observed: geometic anisotropy (elliptic shape) and zonal anisotropy. The rate of collapse of the boundary of the loop describing the roughness of the interface describes the deformation of the discontinuity. The location of the orbit with respect to the stagnation line depends on the normalized stiffness. As the normalized shear stiffness increases, the orbit tends to collapse towards the stagnation axis.
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Kliche, Charles Alfred. "The effect of rock discontinuity surface roughness on shear strength." Diss., The University of Arizona, 1991. http://hdl.handle.net/10150/185356.
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In the evaluation of a slope for stability, it is important to determine useable values of various rack properties. One of the most important rock properties which must be determined is the internal angle of friction, Φ. Surface roughness can have a considerable effect upon the friction angle. The norm has been to adjust the friction angle for roughness by the average asperity angle, i, or to compensate by use of a Joint Roughness Coefficient. The objective of this investigation was to develop a method of mathematically quantifying rock discontinuity surface roughness without the need for a subjective determination based upon a visual comparison with some standard. This mathematical relationship then can be used in the evaluation process of the stability of a slope based upon the limit equilibrium concept. This investigation utilized the concept of fractal dimension to quantify the surface roughness along discontinuities in four rock types. It resulted in the development of a relationship between Joint Roughness Coefficient (JRC) and fractal dimension (D) for each of the four rock types of the form:(UNFORMATTED TABLE/EQUATION FOLLOWS): JRC(Pah) = -1002.11 + (1003.83)D, where: D(Pah) averages 1.00837. JRC(Dwd) = -995.58 + (996.92)D, where: D(Dwd) averages 1.00660. JRC(Min) = -925.47 + (927.90)D, where: D(Min) averages 1.00750. JRC(Met) = -1126.41 + (1127.84)D, where: D(Met) averages 1.00336.(TABLE/EQUATION ENDS)These equations for the relationship between JRC and D can be approximated by: JRC = 1000(D - 1). It was possible to substitute this approximate relationship into Barton's equation for shear strength of discontinuities. This resulted in a useable equation for peak joint shear strength which does not require a subjective determination of a "Roughness Coefficient". Instead, the fractal dimension of the discontinuity surface can be precisely mathematically determined. It was next possible to rewrite the equation for the factor of safety for the case of simple plane shear by substituting the equation for T(peak) into the limiting equilibrium equation. This then gave a method for estimating the factor of safety against sliding on a discontinuity given a measurement of the fractal dimension of the discontinuity surface.
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Maziliguney, Levent. "Tensile Behavior Of Chemically Bonded Post-installed Anchors In Low Strength Reinforced Concretes." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608439/index.pdf.
Full textAbstract:
After the 1999 Kocaeli Earthquake, the use of chemically bonded post-installed
anchors has seen a great growth for retrofits in Turkey. Currently, chemically bonded
post-installed anchors are designed from related tables provided by adhesive
manufacturers and a set of equations based on laboratory pullout tests on normal or
high strength concretes. Unfortunately, concrete compressive strengths of existing
buildings, which need retrofit for earthquake resistance, ranges within 5 to 16 MPa.
The determination of tensile strength of chemically bonded anchors in low-strength
concretes is an obvious prerequisite for the design and reliability of retrofit projects.
Since chemically bonded anchors result in the failure of concrete, adhesive-concrete
interface or anchored material, the ultimate resistance of anchor can be predicted
through the sum of the contributions of concrete strength, properties of anchored
material (which is steel for this work), and anchorage depth. In this work, all three
factors and the predictions of current tables and equations related to anchorages are
examined throughout site tests.
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Borstad, Christopher P. "Tensile strength and fracture mechanics of cohesive dry snow related to slab avalanches." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/36626.
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Fracture mechanics has been applied for over 30 years to explain the release of slab avalanches, but most
studies have focused on the initial shear fracture which governs the loss of slab stability rather than the
ultimate tensile fracture which releases the avalanche. The application of continuum fracture mechanics to snow—a porous material near the melting temperature—requires a homogenization scheme which accounts for the characteristic length scales associated with the diffuse nature of cracking in snow. An experimental campaign was conducted to measure the strength, fracture mechanical properties, and length scales in the tensile fracture of cohesive dry snow related to slab avalanches. Over 1000 natural snow samples were fractured in beam bending tests in a cold laboratory. Significant rate and size effects were observed in the experiments, though the loading rates were sufficiently high to justify an effective elastic analysis of the data.
Using beam theory, the tensile strength was calculated from hundreds of unnotched bending tests and compared with over 2000 synthesized tensile strength measurements from the literature. From the results of three different types of fracture experiments, the fracture toughness and effective fracture process zone length were calculated using equivalent elastic fracture mechanics, which approximately accounts for the nonlinearity engendered by the distributed nature of microcracking in snow. A thin-blade penetration resistance gauge was developed which characterizes structural variations in cohesive snow. The maximum force of penetration was the best index variable for correlating with tensile strength and fracture toughness. A nonlocal damage mechanics model, implemented in a finite element code, was calibrated using the results of ten series of experiments, providing a foundation for future predictive modeling applications related to slab avalanches. The tensile strength and fracture toughness of cohesive snow are now well constrained as functions of the snow density, penetration resistance, grain size, strain rate and sample size. The tensile fracture process zone was determined to be about 10-20 times the grain size, a length scale which necessitates the use of nonlinear fracture mechanics in the analysis of all but the very largest slab avalanches.
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Bae, Hae Ryong. "Effects of temperature on the tensile strength and elastic modulus of composite material." Thesis, Reading, Mass. : Addison-Wesley, 1985. http://hdl.handle.net/10945/21301.
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Wilcox, Robb C. (Robb Cameron). "The effect of weld penetration on the tensile strength of fillet welded joints." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/38096.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1995, and Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1995.Includes bibliographical references (leaves 105-107).
by Robb C. Wilcox.
M.S.
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Showalter, Karen L. "The effect of length on tensile strength parallel-to-grain in structural lumber." Thesis, Virginia Tech, 1985. http://hdl.handle.net/10919/41539.
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Two sizes (2x4 and 2x10) and two grades (2250f-1.9E and No. 2 KDl5) of Southern Pine lumber having three different test span lengths of 30, 90 and 120 inches were tested in tension parallel-to-grain. Results obtained from the tests indicated that the tensile strengths of the 30-inch test specimens were significantly higher than the tensile strengths of the 90- and 120-inch test specimens. A tensile strength-length effect model was developed for generating tensile strength values of lumber taking the length effect into consideration. The model generates tensile strength values for lumber longer than 30 inches in multiples of 30 inches, ie. 60-, 90- 120-inch lengths. The two sizes and two grades of Southern Pine lumber formed the data base for developing the model.
The tensile strength-length effect model utilized an MOE variability model which generated serially correlated MOE's along 30-inch segments for a piece of lumber using a second order Markov model. The segment MOE values were then used in a first-order Markov model to generate serially correlated tensile strength residuals for each 30-inch segment. The segment MOE values and the segment tensile strength residuals were then inputted into a weighted least squares regression to obtain the tensile strength parallel-to-grain for each 30-inch segment. The tensile strength of the generated piece of lumber was then determined using the weakest-link concept; the minimum segment tensile strength value was selected as the tensile strength of the generated piece of lumber.
Master of Science
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Parlapalli, Rohit. "Effect of twist on load transfer and tensile strength in carbon nanotube bundles." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1382372894.
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