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Brooks, Heather Margaret. "Axial capacity of piles supported on intermediate geomaterials." Thesis, Montana State University, 2008. http://etd.lib.montana.edu/etd/2008/brooks/BrooksH0808.pdf.
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Pile foundations used to support bridges and other structures are designed and installed to sustain axial and lateral loads without failing in bearing capacity and without undergoing excessive movements. The axial load-carrying capacity of a driven pile is derived from friction or adhesion along the pile shaft and by compressive resistance at the pile tip. There are well established analytical methods for evaluating pile capacity and for predicting pile driving characteristics for cohesive soil, cohesionless soil, and rock. However, past experience indicates these methods may not be reliable for piles driven into intermediate geomaterials (IGMs), which often exhibit a wide array of properties with characteristics ranging from stiff or hard soil to soft weathered rock. Methods to determine the axial capacity, driving resistance, and long-term resistance of piles driven into intermediate geomaterials are not well established. Nine projects, in which piles were driven into IGMs, from the Montana Department of Transportation were analyzed. Each project contained information from CAPWAP dynamic analyses, construction records, and design reports. The purpose of any analyses, of the nine projects, was to better predict the behavior of piles in IGMs. IGMs were divided into two broad types, cohesive and cohesionless. The computer program DRIVEN is often used to predict the axial capacities of piles; however, in IGMs the design method is unreliable. Attempts were made to determine trends within the available data. Normalized resistances for shaft and toe capacities did yield slight correlations of shaft resistance to pile length in IGMs. Iterative solutions using DRIVEN to match the CAPWAP ultimate capacity did not provide meaningful trends or correlations. Slight modification of MDT\'s original DRIVEN inputs was required in most cases to match the CAPWAP ultimate capacity. Because no meaningful trends were found from analysis, other capacity calculation methods were used to determine other methods that accurately predict pile capacity within IGMs. The Washington Department of Transportation Gates formula is the most accurate method of those attempted. More research is required for further analysis of piles in IGMs.
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Coop, Matthew R. "The axial capacity of driven piles in clay." Thesis, University of Oxford, 1987. http://ora.ox.ac.uk/objects/uuid:5b1244f1-9e91-434a-ad15-5cc670c935a9.
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An instrumented model pile was used to investigate the fundamental behaviour in clay soils of driven cylindrical steel piles used for offshore structures. Four test-bed sites were chosen; two in stiff heavily consolidated clays, and two in normally/lightly overconsolidated clays. Data from these sites confirm that a residual shear surface is formed along the pile during installation, the location of which relative to the shaft surface appears to depend on the shaft roughness. Comparisons with other site investigation data and cavity expansion theoretical predictions indicate that stress relief immediately behind the pile tip during driving gives rise to total radial stresses and pore pressures measured on the pile shaft which are lower than predicted. This stress relief is particulary severe in the stiffer clays. The data did however show that the installation total radial stresses and pore pressures are governed by the initial in-situ stresses and undrained shear strength as is predicated by the theory. During reconsolidation, pore pressures close to the instrument rise initially in all clays, and radial effective stresses drop. The slow recovery in radial effective stress during the later stages of reconsolidation was in some cases insufficient to return it to levels recorded during installation. However, the generation of negative pore pressures during undrained loading increased the radial effective stress and shaft friction at failure. This effect is particularly important in the normally consolidated clays, and is responsible for the set-up of shaft capacity seen in such clays, which might not be observed if the loading were drained. The observed behaviour was therefore quite different from the monotonic increase in radial effective stress during reconsolidation, followed by decrease during undrained loading which was expected from a review of current theory.
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Garner, Michael Paul. "Loading Rate Effects on Axial Pile Capacity in Clays." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd2016.pdf.
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Badri, Dhuruva. "Determination of axial pile capacity of prestressed concrete cylinder piles." [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0001449.
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Che, Wai Fong. "Axial bearing capacity prediction of driven piles using artificial neural network." Thesis, University of Macau, 2003. http://umaclib3.umac.mo/record=b1445140.
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Niazi, Fawad Sulaman. "Static axial pile foundation response using seismic piezocone data." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52195.
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Ever since the use of cone penetration testing (CPT) in geotechnical site investigations, efforts have been made to correlate its readings with the components of static axial pile capacity: unit base resistance (qb) and unit shaft resistance (fp). Broadly, the pile capacity analysis from CPT data can be accomplished via two main approaches: rational (or indirect) methods, and direct methods. The rational methods require a two-step approach, whereby CPT data are first used to provide assessments of geoparameters that are further utilized as input values within a selected analytical framework to enable the evaluation of the pile capacity components. In contrast, direct CPT methods use the measured penetrometer readings by scaling relationships or algorithms in a single-step process to obtain fp and qb for full-size piling foundations. The evolution of the CPT from mechanical to electrical to electronic versions and single-channel readings (i.e., measured tip resistance, qc) to the piezocone penetration test (CPTu), that provides three readings of point stress (qt), sleeve friction (fs), and porewater pressure (u1 or u2), has resulted in the concurrent development of multiple CPT-based geotechnical pile design methods. It is noted, however, that current CPT-based methods focus only on an estimate of "axial pile capacity", corresponding to a limiting load or force at full mobilization.
A more comprehensive approach is sought herein utilizing the CPT readings towards producing a complete nonlinear load-displacement-capacity (Q-w-Qcap) on axial pile response. In particular, the seismic cone penetration test (SCPT) provides the profile of shear wave velocity (Vs) that determines the fundamental small-strain shear modulus: Gmax = gt?Vs2, where gt = total mass density of soil. With the penetrometer readings useful in assessing foundation capacity, the stiffness Gmax finds application within elastic continuum solutions towards evaluating the load-displacement (Q-w) response.
In this study, a concise review of the deep foundation systems is presented, including pile types and characteristics, various arrangements of axial pile load testing in static mode, and interpretations of the load test data. In addition a comprehensive state-of-the-art review of CPT-based rational and direct methods of pile capacity evaluations is compiled. It is recognized that the direct methods offer more convenience in their straightforward approach in estimation of the pile capacity. The piezocone-based UniCone direct method proposed by Eslami and Fellenius (1997) is selected for further refinements, as it utilizes all three CPT readings in its design formulations. Concerning the analysis of pile deformations under axial loading, a brief review covers designs employing empirical formulations, analytical solutions, load-transfer (t-z) methods, numerical simulations, variational approaches, and those using hybrid methods. Specifically, the analytical elastic solution by Randolph and Wroth (1978; 1979) is covered in more detail since it is simple and convenient in application with extended applications to uplift and bidirectional O-cell types of loadings. This elastic approach also serves well in modeling a stacked pile solution for layered soil profiles. The last part of the review covers various shear modulus reduction schemes, since evaluation of the applicable stiffnesses is considered to be the most delicate phase in the nonlinear Q-w response analysis of axially loaded piles. It is identified that the most appropriate scheme applicable to static axial loading of pile foundations is the one that can be derived from the back-analyses of actual load tests within the framework of analytical elastic solution.
In order to conduct a comprehensive research study on the axial Q-w-Qcap response of deep foundations from CPT readings, a large database is compiled. This includes 330 case records of pile load tests at 70 sites from 5 continents and 19 different countries of the world, where pile foundations were load tested under top-down compression or top-applied uplift (tension) loading, or both, or by bi-directional Osterberg cell setups. All test sites had been investigated using CPT soundings; in most cases by the preferred SCPTu that provides all four readings from the same sounding: qt, fs, u2, and Vs. In a few cases, sites were subjected to CPT or CPTu and the profiles of shear wave velocities were obtained by other field geophysical techniques, otherwise by empirical estimations.
Results of the new correlation efforts are offered to derive coefficients Cse for shaft component and Cte for base component of the axial pile capacity from CPTu data. The UniCone type of soil classification chart is refined by delineating 11 soil sub-zones along with their respective Cse, in contrast to the 5 zones originally proposed. The CPT material index, Ic (Robertson, 2009) is then used to establish direct correlations linking Cse vs. Ic and Cte vs. Ic. Statistical relationships offer continuous functions for estimating the coefficients over a wide range of Ic values, thereby eliminating the need for use of the soil classification chart as well as improving the reliability in the evaluations of fp and qb. The effects of the pile loading direction (compression vs. uplift) and loading rate are also incorporated in the proposed design formulations.
New sets of shear stiffness reduction curves are developed from the back-analysis of pile load tests and Gmax profiles obtained from the SCPT data. Alternative functions formats are provided in terms of hyperbolic tangent expressions or exponential curves, developed as normalized shear stiffness (G/Gmax) vs. logarithm of percent pseudo-strain (gp = w/d, where w = pile displacement and d = pile diameter). These charts offer convenience in the axial Q-w analysis of different pile categories within the framework of analytical elastic solution. The results also account for the plasticity characteristics of the soil formations within the database.
A stacked pile model for Q-w analysis is presented in which certain adaptations are proposed in the elastic continuum solution. These adaptations enable plotting of separate modulus reduction curves (G/Gmax vs. gp) as function of depth for each layer, and treating pile as a stack of smaller pile segments embedded in a multi-layered soil media. The solution can be used to address the question of progressive failure with depth in a multi-layer soil media that exhibits nonlinear soil stiffness response.
Finally, the closed-from analytical elastic pile solution for predicting the Q-w response is decoupled and modified to account for different setup cases and multi-stage loading of bi-directional O-cell tests. The decoupling accounts for separate assessments of the response to axial loading for different segments of pile shaft and different stages of loading, while the modifications include: (1) reduced maximum radius of influence for the upward displacements of the upper shaft segment, and (2) modeling the non-linear ground stiffness from the back-analysis of a well-documented dataset of O-cell load tests.
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Sun, Miao. "Use of Material Tailoring to Improve Axial Load Capacity of Elliptical Composite Cylinders." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/29693.
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This study focuses on the improvement of the axial buckling capacity of elliptical composite cylinders through the use of a circumferentially-varying lamination sequence. The concept of varying the lamination sequence around the circumference is considered as a viable approach for off-setting the disadvantages of having the cylinder radius of curvature vary with circumferential position, the source of the reduced buckling capacity when compared to a circular cylinder with the same circumference. Post-buckling collapse behavior and material failure characteristics are also of interest. Two approaches to implementing a circumferential variation of lamination are examined. For the first approach the lamination sequence is varied in a stepwise fashion around the circumference. Specifically, each quadrant of the cylinder circumference is divided into three equal-length regions denoted as the crown, middle, and side regions. Eight different cylinders designs, whereby each region is constructed of either a quasi-isotropic or an axially-stiff laminate of equal thickness, are studied. Results are compared to the baseline case of an elliptical cylinder constructed entirely of a quasi-isotropic laminate. Since the thickness of the quasi-isotropic and axially-stiff laminates are the same, all cylinders weight the same and thus comparisons are meaningful. Improvements upwards of 18% in axial buckling capacity can be achieved with one particular stepwise design. The second approach considers laminations that vary circumferentially in a continuous fashion to mitigate the effects of the continuously-varying radius of curvature. The methodology for determining how to tailor the lamination sequence circumferentially is based on the analytical predictions of a simple buckling analysis for simply-supported circular cylinders. With this approach, axial buckling load improvements upwards of 30% are realized. Of all the cylinders considered, very few do not exhibit material failure upon collapse in the post-buckled state. Of those that do not, there is little, if any, improvement in bucking capacity. Results for the pre-buckling, buckling, post-buckling, and material failure are obtained from the finite-element code ABAQUS using both static and dynamic analyses. Studies with the code demonstrate that the results obtained are converged.Ph. D.
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Müller, Matthias. "Predicting the ultimate axial load capacity of joints formed using V-band retainers." Thesis, University of Huddersfield, 2011. http://eprints.hud.ac.uk/id/eprint/12144/.
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V-band retainers are widely used in the automotive, aircraft and aerospace industries to connect a pair of circular flanges to provide a joint with good axial strength and torsional rigidity. V-band retainers are manufactured using a cold roll forming process. Despite their wide application, once assembled to a pair of flanges little is known about the interaction between flange and band. Moreover the failure mode of V-band retainers when applying an axial load is not fully understood. In this thesis the ultimate axial load capacity of V-band retainers is predicted using finite element and theoretical models and validated using experimental testing. It was shown that the ultimate axial load capacity was strongly dependent on the joint diameter, increasing between 114mm and 235mm, and decreasing beyond that. Moreover, the peak in ultimate axial load capacity was dependent on parameters such as the axial clamping load and coefficient of friction, and its position lay between 235mm and 450mm, as predicted by the finite element models. Other geometrical parameters such as flange and band thickness showed large impacts on the ultimate axial load capacity as well. A theoretical model was developed that allowed the ultimate axial load capacity to be calculated from a single formula for larger bands and using a simple algorithm for smaller bands. This model supported the findings that, depending on the band diameter, the ultimate axial load capacity had a peak, but predicted its position at approximately 181mm. This position at 181mm was validated by the experimental data. However, when compared to the tests, the finite element and theoretical models both over-predicted the ultimate axial load capacity. Both the finite element models and practical tests showed that for small V-bands axial failure is due to a combination of section deformation and ring expansion, whereas large V-bands fail due to ring expansion only. These two distinct types of behaviour were incorporated into the theoretical model. The hardness development throughout the cold roll forming process was predicted using finite element models. This was validated by hardness measurements, for which a new technique was generated, that directly linked plastic strain and hardness values.
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Koen, Johan Alexander. "An investigation into the axial capacity of eccentrically loaded concrete filled double skin tube columns." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/96797.
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Thesis (MSc)--Stellenbosch University, 2015.ENGLISH ABSTRACT: Concrete filled double skin tube (CFDST) columns is a new method of column construction. CFDST columns consists of two steel hollow sections, one inside the other, concentrically aligned. The cross-sections of the two hollow sections does not have to be the same shape. Concrete is cast in between the two hollow sections resulting in a CFDST. This study only considers CFDST columns constructed with circular steel hollow sections. The advantages of CFDST construction include: ● The inner and outer steel hollow sections replaces the traditional steel reinforcement that would be used in a normal reinforced concrete column. This reduces the construction time since there is no need to construct a reinforcing cage. ● The steel hollow sections acts as a stay in place formwork, eliminating the need for traditional formwork. This also reduces construction time. ● The steel hollow sections confine the concrete, making it more ductile and increasing its yield strength. The objective of this study is to identify methods that can predict the axial capacity of eccentrically loaded circular CFDST columns. Methods chosen for the investigation are: 1. Finite element model (FEM). A model was developed to predict the behaviour of eccentrically loaded CFDST columns. The FE model uses a concrete material model proposed in literature for stub columns. The aim was to determine whether the material model is suited for this application. 2. The failure load of CFDST columns under concentric loading was calculated using a model obtained in literature. These capacities were compared to the experimental test results of eccentrically loaded CFDST columns to establish a correlation. This study found that the concrete material model used does not adequately capture the behaviour resulting in the axial response of the column being too stiff. The difference between the eccentrically loaded experimental test results and the calculated concentrically loaded capacity showed a clear trend that could be used to predict the capacity of eccentrically loaded CFDST columns.
AFRIKAANSE OPSOMMING: Beton-gevulde dubbel laag pyp (BGDLP) kolomme is ‘n nuwe metode van kolom konstruksie. BGDLP kolomme bestaan uit twee staal pyp snitte, die een binne die ander geplaas met hul middelpunte opgelyn, die dwarssnit van die twee pype hoef nie dieselfde vorm te wees nie. Beton word dan in die wand tussen die twee pyp snitte gegiet. Die resultaat is ‘n hol beton snit. Hierdie studie handel slegs oor BGDLP kolomme wat met ronde pyp snitte verwaardig is. Die volgende voordele kan aan BGDLP toegeken word: ● Die binne en buite staalpype vervang die tradisionele staal bewapening was in normale bewapende-beton gebruik sou word. Dus verminder dit die tyd wat dit sal neem om die kolom op te rig. ● Die staalpypsnitte is ook permanente vormwerk. Dit doen dus weg met die gebruik van normale bekisting, wat ook konstruksie tyd spaar. ● Die buite-staalpypsnit bekamp die uitsetting van die beton onder las. Hierdie bekamping veroorsaak dat die beton se gedrag meer daktiel is en ‘n hoër falings spanning kan bereik. Die doel van die studie is om metodes te identifiseer wat gebruik kan word om die aksiale kapasiteit onder eksentriese laste van BGDLP kolomme te bepaal. Twee metodes was gekies: 1. Eindige element model. ‘n Model was ontwikkel om die gedrag van BGDLP kolomme te voorspel. Die mikpunt was om te bepaal of ‘n beton materiaal gedrag model vanuit die literatuur gebruik kan word om BGDLP kolomme te modelleer. 2. Die swiglas van BGDLP kolomme onder konsentriese belasting was bereken vanaf vergelykings uit die literatuur. Hierdie swiglaste was vergelyk met die eksperimentele toets resultate vir eksentriese belaste BGDLP kolomme om ‘n korrelasie te vind. Hierdie studie het bewys dat die beton materiaal model uit die literatuur kan nie gebruik word om die swiglaste van BGDLP kolomme te bepaal nie. Die model het die gedrag te styf gemodelleer. Die verskil tussen die berekende konsentriese belaste swiglas en die eksperimentele resultate van eksentriese BGDLP kolomme was voorspelbaar en kan gebruik word om die swiglas van eksentriese belaste BGDLP kolomme te voorspel.
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Mu, Feng. "Analysis and prediction of the axial capacity and settlement of displacement piles in sandy soil." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/HKUTO/record/B39558988.
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Mu, Feng, and 牟峰. "Analysis and prediction of the axial capacity and settlement of displacement piles in sandy soil." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39558988.
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Monzón, A. Juan Carlos (Monzón Alvarado). "Review of CPT based design methods for estimating axial capacity of driven piles in siliceous sand." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/34667.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2006.Includes bibliographical references (leaves 81-83).
The Cone Penetration Test has been used for more than 30 years for soil exploration purposes. Its similarities in mode of installation with driven piles provides the potential of linking key variables of pile design and performance, such as base resistance and shaft friction, to measured cone tip resistance. Large scale pile load tests, performed in the last two decades, have shown better agreement with recent CPT based design criteria, than with conventional American Petroleum Institute (API) earth pressure approach design guidelines. The CPT based design methods provide a more coherent framework for incorporating soil dilation, pile size effect, pile plugging during installation, and the friction at the pile-soil interface. A review, of four recent CPT based design methods and the API design guidelines, for estimating axial capacity of driven piles in siliceous sands was performed by comparing their predictive performance to six documented on-shore piles with load tests. First, a detailed site investigation based on CPT data was performed to validate the provided soil profile, and to evaluate the accuracy of the CPT readings to identify and classify soil strata.
(cont.) Three piles were selected for further study and axial capacity calculations. Three of the design methods, UWA-05, ICP-05 and NGI-05, prove to accurately predict axial pile capacities for on-shore short piles founded on sites where sand dominates. Analysis against a larger and more detailed database is required to validate their performance in multilayer soil profiles.
by Juan Carlos Monzón A.
M.Eng.
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El, Haffar Ismat. "Physical modeling and study of the behavior of deep foundations of offshore wind turbines in sand." Thesis, Ecole centrale de Nantes, 2018. http://www.theses.fr/2018ECDN0021/document.
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La capacité axiale et latérale des pieux foncés dans du sable de Fontainebleau NE34 ont été étudié à l’aide d’essais sur modèles réduits centrifugés. L’effet de la méthode d’installation, de la densité et de la saturation du sable, du diamètre du pieu, de la géométrie de sa pointe (ouvert /fermé) et de sa rugosité sur la capacité axiale a été étudié. Une augmentation significative de la capacité en traction est observée dans les pieux foncés cycliquement, contrairement aux pieux foncés d’une manière monotone à 100 × g. La saturation du sable dense accélère la formation du bouchon lors de l'installation du pieu. L'augmentation de la rugosité du pieu et de la densité du sable accroissent significativement le frottement latéral des pieux testés. Dans tous les cas, les capacités de pieux sont comparées aux codes de dimensionnement des éoliennes offshore. Une étude paramétrique de l'effet de la méthode d'installation, de l'excentricité de la charge et de la saturation du sable sur la réponse latérale des pieux foncés est ensuite réalisée grâce à l'utilisation d'un pieu instrumentée. Le pieu est chargé d’une manière monotone puis un millier de cycles sont appliqués. Une nouvelle méthode a été développée pour la détermination des constantes d'intégration pour déterminer le profil de déplacement latéral du pieu. La méthode d'installation influence directement le comportement global (moment maximum et déplacement latéral) et local (courbes p-y) des pieux. L'effet de l'excentricité de la charge et de la saturation du sable sur le comportement des pieux est également présenté. Dans chaque cas, une comparaison avec les courbes p-y extraites du code DNVGL est réaliséeThe axial and lateral capacity of piles jacked in Fontainebleau sand NE34 are studied using centrifuge modelling at 100×g. The effect of the installation method, sand density and saturation, pile diameter and pile tip geometry (open or closed-ended) and pile roughness on the axial capacity of piles are firstly studied. A significant increase in the tension capacity is observed in cyclically-jacked piles unlike piles monotonically jacked at 100×g. The saturation of dense sand accelerates plug formation during pile installation. The increase in pile roughness and sand density increases significantly the shaft resistance of the piles tested here. For all the cases, pile capacities are compared with the current design codes for offshore wind turbines. A parametric study of the effect of the installation method, load eccentricity and sand saturation on the lateral response of jacked piles is then realized using of an instrumented pile. The pile is loaded monotonically, then a thousand cycles are applied. A new methodology has been developed for determining of the constants needed in the integration procedure to identify the lateral displacement profile of the pile. The installation method influences directly the global (maximum moment and lateral displacement) and local behaviour (p-y curves) of the piles. The effect of the load eccentricity and sand saturation on the behaviour of the piles is also presented. In each case a comparison with the p-y curves extracted from the DNVGL code is realized
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Passini, Larissa de Brum. "Instalação e capacidade de carga axial de estacas modelo fluidizadas em solos arenosos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/131011.
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O objetivo desta tese foi verificar a viabilidade de utilização de jatos de água verticais circulares, únicos e contínuos, provenientes da ponteira de uma estaca torpedo, para auxiliar sua instalação por peso próprio no leito marinho, através da fluidização do solo. Foram realizados ensaios de laboratório, em modelo reduzido, utilizando hastes para simular estacas torpedo (sem aletas) seguindo a lei de semelhança pelo número de Froude. Os ensaios de instalação por peso próprio, com e sem fluidização, ocorreram sem altura de queda, com a estaca modelo em contato com a superfície do leito. Trabalhou-se com três diâmetros de estacas, seis massas, quatros vazões e areia fina saturada compactada em duas densidades relativas iniciais (média e densa). Os ensaios de arrancamento, em leito arenoso fluidizado e não fluidizado, foram realizados imediatamente, 4, 24 e 48 horas após a instalação dos modelos. A metodologia de instalação proposta mostrou-se viável, quando o jateamento é aplicado desde a superfície em solo arenoso. As profundidades instaladas atingidas por fluidização (L/de > 50) foram consideravelmente superiores às profundidades cravadas por apenas peso próprio (L/de < 5). A geometria da zona perturbada durante a instalação por fluidização dos modelos, permaneceu constante e paralela ao fuste, com geometria de aproximadamente 2de em relação ao modelo, independentemente da vazão aplicada e da densidade relativa inicial do solo. A partir das leis de análise dimensional, uma expressão para a profundidade instalada das estacas modelo foi proposta, mostrando que a mesma é função do peso e da geometria do modelo, das propriedades físicas do solo e do fluido, e de sua vazão. Quanto maior a massa do modelo e a vazão aplicada e menor a densidade relativa, maior a profundidade atingida e maior a velocidade inicial de instalação. Constatou-se que a capacidade de carga axial dos modelos depende da densidade relativa, do diâmetro do modelo e do método de instalação (com e sem fluidização). Independentemente da densidade relativa inicial, o solo fluidizado convergiu para a mesma densidade relativa final, próxima as suas condições no estado crítico. As estacas em solo fluidizado apresentaram ganho resistência com o tempo (efeito de setup), com capacidade de carga inferior às estacas cravadas em solo não fluidizado.The aim of this thesis was to investigate the feasibility of using circular vertical water jets, single and continuous, from the tip of a torpedo pile, to assist its installation by own weight on the seabed, through soil fluidization. Laboratory model tests were carried out, using tubes to simulate torpedo piles (without wings) following the law of similarity defined by the Froude number. The installation tests by the pile own weight, with and without fluidization, occurred without drop height, with the piles in contact with the surface of the bed. Three diameters of model piles and six masses, four flow rates and saturated sand at two initial relative densities (medium and dense) have been used in this set of experiments. Pullout tests in fluidized and nonfluidized soils were performed immediately, 4, 24 and 48 hours after the installation of the models. The proposed installation methodology proved to be feasible when the fluidization is applied from the surface in sandy soils. The installation depths achieved by fluidization (L/de > 50) were significantly higher than the depths reached by pile own weight (L/de < 5). The geometry of the perturbed zone during model installation by fluidization remained constant and parallel to the shaft in a geometry of about 2de of the pile model, regardless of the applied flow rate and the initial relative density of the soil. Following the laws of dimensional analysis, an expression for the embedment of fluidized piles is derived, showing that the penetration depth is a function of pile weight and geometry, fluidized water jet flow rate and velocity, as well as the soil and fluid properties. Increasing the model mass and fluidized flow rate and decreasing the relative density leads to an increase in the depth reached and the initial speed of installation. The axial load capacity of the models depends on the soil relative density, piles diameter and installation method (with and without fluidization). Regardless the initial relative density, the fluidized soil converged to the same final relative density, near its conditions of critical state. Piles installed in fluidized soil presented gain of axial capacity over time (setup effect) with lower resistance than piles driven in nonfluidized soil.
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Benzaria, Omar. "Contribution à l’étude du comportement des pieux sous chargements cycliques axiaux." Thesis, Paris Est, 2012. http://www.theses.fr/2012PEST1112/document.
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Dans le cadre du Projet National SOLCYP, le présent travail avait pour but d'étudier la réponse des pieux sous chargements axiaux pour les phases avant, pendant et après cycles. Pour atteindre cet objectif, une étude expérimentale étendue a donc été réalisée par le moyen de deux compagnes d'essais de chargements cycliques sur différents types de pieux instrumentées (battus, forés, vissés) dans deux sites expérimentaux : le site de Merville dans l'argile surconsolidée des Flandres et le site de Loon-Plage près de Dunkerque dans les sables denses des Flandres. Les essais cycliques comportaient des essais en compression, en traction et alternés avec des séries de cycles à forte amplitude conduisant à la rupture cyclique et des séries d'amplitude modérée à très grands nombres de cycles (N>5 000 cycles).L'interprétation de ces essais a englobé, d'une part, une analyse globale du comportement des pieux sous chargements cycliques notamment (i) la réduction de la capacité du pieu; (ii) le nombre de cycles que le pieu peut support avant la rupture (iii) l'évolution du déplacement en tête des pieux (rigidité cyclique). D'autre part, elle a intégré une étude locale en particulier sur la dégradation du frottement latéral et l'évolution de la résistance de pointe du pieu. Cette thèse, basée sur l'étude expérimentale, a permis la formulation des conclusions pratiques sur le comportement des pieux sous chargements cycliques axiaux et a proposé des perspectives pour bien cerner cette problématiqueAs part of the French National research project SOLCYP, the purpose of this work was study the behavior of the piles under axial loadings for the phases before, during and after cycles.To achieve this objective, an extensive series of static and cyclic axial pile load tests have been carried out in two experimental sites of the North of France: the overconsolidated Flandrian clays (Merville experimental site) and in dense Flandrian sands (Loon-Plage experimental site). Tests were performed on driven closed-ended pipe piles, bored piles and screwed. All piles were instrumented with retrievable extensometers for measuring the load distribution along the pile wall.Cyclic load tests were composed of series of cycles of constant load amplitude. A large range of load histories were applied including series of small amplitude cycles and great number of cycles (N > 5000) and series of large amplitude cycles leading to cyclic failure after a small number of cycles..A large volume of data has been interpreted to describe the effects of axial cyclic loads on the behavior of the piles. The interpretation of these tests included, on the one hand, a global analysis focusing on (i) the potential reduction on the ultimate axial capacity; (ii) the number of load cycles of a given load that the pile can sustain before cyclic failure and (iii) the evolution of displacements of the pile head during cyclic loading (pile stiffness). In addition, it integrated a local study in particular on shaft friction degradation along the pile wall and evolution of the resistance of point of the pile.This thesis, based on the experimental study, allowed the formulation of the practical conclusions on the behavior of the piles under axial cyclic loadings and proposed prospects for determining these problems well
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Leo, Riccardo. "The axial response of offshore piles in sand from large scale tests." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
Find full textAbstract:
This thesis focuses on deep foundations used in offshore environment, in particular for offshore wind turbines. Piles are necessary when the bearing capacity of the shallow soil layers is not enough to ensure stability. Piles can work on both axial and lateral response. In the thesis only axially loaded piles will be considered. The analysis of the axial behavior of piles should be considered in terms of ultimate capacity as well as the load transfer mechanism between the pile and the soil.
The technical aim of this thesis concerns the understanding of the load transfer curves, their extrapolation and the exploration of load distribution along the pile during a given load. To achieve this, a thorough study of literature on current design methods is carried out and two instrumented piles will be analysed in order to understand how the load is distributed along the pile shaft and how experimental load transfer curves can be extrapolated.
The more general aim of this work is to optimize design procedures and try to reduce the cost related piles and their installation in offshore environment, since it is quite known to be higher than onshore fields, as it will be explained in the first chapter of this thesis.
A geotechnical software IGtH Pile developed by the Institute of geotechnical Engineering (IGtH), Leibniz Universität Hannover will be used in the evaluation of the ultimate capacity and the results will be compared with a Matlab code developed at the IWES research institute.
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Forni, Fabio. "Investigating the axial response of pile foundations for offshore wind turbines." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
Find full textAbstract:
I crescenti problemi legati ai cambiamenti climatici rendono l'impiego delle energie rinnovabili sempre più interessante.
In questa ottica, in Germania si sta pianificando di aumentare la produzione di energia pulita attraverso lo sfruttamento dell’energia eolica. Nuovi impianti di turbine eoliche sono previsti nel Mare del Nord in acque medio profonde (25-45m) dove la parte immersa della struttura della turbina eolica (chiamata sottostruttura) è spesso costituita da una struttura jacket (traliccio) o tripod (a treppiedi). Questo tipo di sottostrutture trasmettono principalmente carichi assiali alle fondazioni (in genere fondazioni su palo), e il carico a trazione è la forza che maggiormente ne influenza il dimensionamento.
Molte compagnie energetiche tedesche sono interessate a migliorare l’efficienza e i costi dei loro impianti eolici e, per questo, incaricano università ed istituti di ricerca (come il Fraunhofer IWES) per indagarne gli aspetti, come ad esempio il comportamento delle fondazioni offshore.
All’autore di questa tesi è stata data l’opportunità di studiare e lavorare al Fraunhofer IWES e perciò questa tesi tratterà del compramento di pali caricati assialmente e staticamente pensati per sottostrutture jacket o tripod per turbine eoliche.
Nello studio effettuato per questa tesi, i dati seprimentali, ottenuti da una campagna sperimentale condotta (in larga scala 1:10 1:5) su pali infissi in terreno sabbioso, sono confrontati attraverso l’impiego delle load-transfer curves (funzioni che descrivono il comportamento d’interfaccia palosuolo) usando sia un’approccio classico (fornito dal metodo di calcolo API Main Text) sia approcci più recenti (dati dai metodi di calcolo CPT).
Uno script Matlab creato appositamente dall’autore di questa tesi riesce ad implementare 11 diversi tipi di load-transfer curves. Il lavoro di tesi si conclude con un esempio pratico in grado di fornire un’idea di come questo script può essere usato nella progettazione.
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Mahgub, Munir. "Behaviour of elliptical tube columns filled with self-compacting concrete." Thesis, University of Bradford, 2016. http://hdl.handle.net/10454/14787.
Full textAbstract:
The present research is conducted to investigate the behaviour of elliptical tube columns filled with self-compacting concrete (SCC). In total, ten specimens, including two empty columns, were tested to failure. The main parameters investigated were the length and the sections of the columns, and the concrete compressive strength. Artificial Neural Network (ANN) model was developed to predict the compressive strength of SCC using a comprehensive database collected from different previous studies. The database was used to train and test the developed ANN. Moreover, parallel to the experimental works, a three dimensional nonlinear finite element (FE) model using ABAQUS software was developed to predict the behaviour of SCC elliptical tube columns. The proposed ABAQUS model was verified against the current experimental results. The experimental results indicated that the failure modes of the SCC filled elliptical steel tube columns having large slenderness ratios were dominated by global buckling. Moreover, the composite columns possessed higher critical axial compressive capacities compared with their hollow section companions due to the composite interaction. However, due to the large slenderness ratio of the test specimens, the change of compressive strength of concrete core did not show significant effect on the critical axial compressive capacity of concrete filled columns although the axial compressive capacity increased with the concrete grade increase. The comparisons between the axial compressive load capacities obtained from experimental study and those predicted using simple methods provided in Eurocode 4 for concrete-filled steel rectangular tube columns showed a reasonable agreement. The proposed three dimensional FE model accurately predicted the failure modes, the load capacity and the load-deflection response of the columns tested. The experimental results, analysis and comparisons presented in this thesis clearly support the application of self-compacting concrete filled elliptical steel tube columns in construction engineering practice.
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Teepakorn, Chalore. "Numerical simulation and experimental study of membrane chromatography for biomolecule separation." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10299/document.
Full textAbstract:
La chromatographie membranaire est une alternative à la chromatographie classique sur résine basée sur le transport convectif des solutés à travers une membrane microporeuse plutôt que par le transport diffusif des solutés dans les particules de résines. Cette technique présente les avantages de diminuer les phénomènes de diffusion, de réduire les temps de séjour et les pertes de charge, et de permettre la purification rapide de quantités importantes de molécules. La chromatographie membranaire connaît un fort succès commercial. Une gamme importante de membranes chromatographiques mettant en jeu différents mécanismes de rétention (échange d’ions, affinité, etc.) et différentes géométries (feuille, spirale, etc.) est actuellement commercialisée. Malgré ce succès, différents aspects relatifs à la chromatographie membranaire restent mal connus. Cette thèse de doctorat se propose de répondre à certaines questions relatives à cette techniqueMembrane chromatography (MC) is an alternative to traditional resin packed columns chromatography. The solute mass transport in the membrane occurs in convective through-pores rather than in stagnant fluid inside the pores of the resins particles, which is limited by the slow diffusive transport. MC offers the main advantage of reducing diffusion phenomena, shorter residence time and lowered pressures drops, and thus, facilitates rapid purification of large quantities of molecules. A wide range of chromatographic membranes involving different molecules retention mechanisms (ion exchange, affinity, etc...) is now commercialized. Despite their success, the influence of the geometry of the membrane chromatography devices remains relatively unexplored from a theoretical point of view. This doctoral thesis is aimed to clarify some ambiguous points related to this technique
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Erguner, Kamil. "Analytical Examination Of Performance Limits For Shear Critical Reinforced Concrete Columns." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12611220/index.pdf.
Full textAbstract:
Most of the older reinforced concrete (RC) buildings have columns that are deficient
when the current code requirements are considered. Therefore, performance of the columns
determines the performance of the structure under the effects of earthquake induced lateral
loads. It is recognized that no provision is proposed in TEC2007 to estimate the failure type
called flexure-shear. Behavior of columns having probability of failing in flexure-shear
failure mode is mostly underestimated by TEC2007 procedures. In addition, failure type
classification of columns performed according to the linear and nonlinear procedures of
TEC2007 needs to be examined with respect to the test results to cover all failure types
including flexure-shear failure in order to lead the engineers develop economical and
realistic retrofit solutions.
In this study, different methods are explored to obtain reliable estimates for the
performance of code deficient shear critical RC columns. Special considerations are given to
Axial-Shear-Flexure interaction (ASFI) approach due to its mechanical background.
After examination of different approaches, ASFI method with proposed
modifications was selected as the most reliable model and lateral load-displacement analyses
were performed on a database of shear critical columns. Findings were compared with the
estimations of the nonlinear procedure given in Turkish Earthquake Code (TEC2007) for
database columns. In addition, drift capacity equations and simplified safe drift capacity
equations are proposed in light of statistical studies on the selected column specimens.
In the last part of the study, performance evaluation of columns according to
nonlinear procedures of FEMA 356, TEC2007, ASCE/SEI 41 update supplement, and
EUROCODE 8 were conducted.
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Conti, Claudio. "Small-scale physical modelling of piled foundations for offshore wind turbines application." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
Find full textAbstract:
Nowadays, finding alternative energy sources is becoming more and more important. Europe is particularly focusing on wind energy and in offshore wind energy especially. An issue concerning offshore wind energy which is gaining more and more attention is the noise emissions due to impact driven pile foundation. The noise caused by the installation process has been judged as “potentially dangerous for marine fauna” from the German Authorities.
This research thesis is part of a project which examines a viable alternative installation method for the displacement of pile foundations for offshore wind energy called pile jacking. This technology should be developed to be cost-efficient, flexibly scalable and to produce considerably reduced vibration and air pollution emissions during its placement in the sea bed. Jacked piles technology would eliminate almost any noise deriving from the hammer impact.
As most offshore piled foundations have been installed by impact driving technology, the question arises as to how piles with different the stiffness and the capacity , can otherwise be installed.
In order to delineate the significant variables affecting the load-bearing capacity and especially the ultimate uplift capacity of a pile in saturated sand, a small-scale test campaign in scale 1:30 has been performed at the Test Center for Support Structures in Hanover. The campaign was supervised by the Department for Support Structures of Fraunhofer IWES. A testing schedule comprising of 15 small-scale geotechnical physical experiments was conducted on open-ended piles to an embedded length of 75 cm using two method of pile installation: static jacking and impact driving.
The aim of this thesis is to obtain preliminary experimental data and set out the main features of this technology.
The results obtained by this study reveal that static jacking installation lead to higher resistances and is overall beneficial to the mechanical load bearing behavior of pile foundations.
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Calvente, René Matias. "Méthodologie de contrôle en place des micropieux à partir d'essais dynamiques." Thesis, Clermont-Ferrand 2, 2014. http://www.theses.fr/2014CLF22471/document.
Full textAbstract:
L’état de l’art réalisé dans le cadre de ce travail a permis d’identifier une grande variété de techniques de réalisation de micropieux avec des comportements effort-déformation difficiles à prédire. Quant aux méthodes de contrôle, du point de vue de l’intégrité il existe deux méthodes développées pour les pieux lesquelles ne sont pas toujours applicables aux cas de micropieux ; et du point de vue du contrôle du comportement mécanique, il existe un essai assez utilisé pour le contrôle de micropieux : l’essai d’arrachement. Cet essai est facile à réaliser et à interpréter, cependant il est onéreux (long temps d’essai) et difficile à mettre en place. Un autre type d’essai, utilisé dans le contrôle de fondations profondes, est l’essai de chargement dynamique. La recherche bibliographique a permis d’identifier les avantages et inconvénients de ce type d’essai adaptés et déjà validés dans le contrôle de pieux. Nous avons donc proposé une nouvelle méthodologie basée sur des essais de chargement dynamique à faible contrainte nécessitant des énergies de battage beaucoup moins importantes que dans les essais de chargement dynamique classiques. Le protocole et dispositif d’essai de la méthodologie ont été calibrés et validés à partir de simulations numériques afin notamment de justifier les choix de l’énergie d’impact, de la masse du marteau et de l’amortisseur à utiliser. Les observations numériques sont ensuite vérifiées expérimentalement sur des micropieux à échelle réelle mis en place dans un site expérimental développé dans le cadre de ce projet. La méthodologie de contrôle en place de la résistance en service de micropieux développée, c’est une méthode originale simple à réaliser, facile à mettre en oeuvre et d’interprétation immédiate. Elle a été validée aussi dans le cas de micropieux à échelle réelle en conditions maitrisées dans le site expérimental et non maitrisées dans trois chantiers réels de micropieux. Finalement, le progrès dans les recherches, a permis le développement d’une méthodologie de contrôle de la résistance limite de micropieux. Pour cela nous proposons d’utiliser un modèle analytique de prédiction du comportement effort-déformation alimenté par les résultats de l’essai de chargement dynamique à faible déformation et d’un essai complémentaire de reconnaissance des paramètres à la rupture du sol. L´objectif de ce développement est de proposer une prédiction de la résistance limite du micropieux testé sans compromettre son intégrité. L’application de la méthodologie a montré qu’elle donne des résultats très proches de ceux observés dans les essais statiquesThe review of the state-of-the-art of micropiles produced as part of this work allows to identify a wide variety of construction methodologies which have a stress-strain behavior difficult to predict. As for the testing methods, there are methods for assessing the condition of piles or shafts but they are not always applicable to the micropiles; and in terms of the control of mechanical behavior, the most used load testing micropile is the uplift static load test. The static load test is easy to perform and interpret, however the reaction system is cumbersome and slow to erect, therefore this test is time and cost consuming. Another type of test that can be used in the control of deep foundations is the dynamic load testing. The literature review helped to identify the advantages and disadvantages of this type of test that has been adapted and validated in control of pile behavior. The new methodology proposed in this work is based on low-strain dynamic test requiring a smaller impact energy than a high-strain dynamic test. The testing protocol and loading device of the methodology have been calibrated and validated by numerical simulations in order to justify the choice of the impact energy, the weight of hammer and the cushion that will be used. The numerical observations are then verified by experiences in full-scale micropiles installed in an experimental site developed as part of this project. The developed in situ control methodology of the resistance in service of micropiles is an original method, easy to carry out, simple to execute and with an immediate interpretation. This methodology has been validated on full-scale micropiles in contained conditions and also in uncontained conditions in three real projects of micropiles. Finally, the advances in the investigations have led to develop a methodology for control the micropile’s ultimate resistance. We propose to use an analytical model for predicting the stress-strain behavior, which must be supplied with the results of the low-strain dynamic micropile test and of a complementary geotechnical test in order to examine the parameter of soil failure. The goal of this development is to provide a method for predict the micropile’s ultimate resistance without compromising its integrity. The results of the application of the new method to the experimental micropiles are in close agreement with the results observed in the static load test
La revisión del estado del arte en relación a micropilotes, realizada en este trabajo, ha permitido identificar una gran variedad de técnicas de construcción, donde la predicción de sus comportamientos mecánicos, es una tarea difícil de realizar. Con respecto a los métodos de control, desde el punto de vista de la integridad, existen actualmente métodos no siempre aplicables a los micropilotes, y desde el punto de vista del control del comportamiento mecánico, el ensayo más utilizado es el ensayo de arrancamiento. El ensayo de arrancamiento es de fácil realización e interpretación, sin embargo es oneroso, por su larga duración y la necesidad de disponer de equipos muy pesados.Otro tipo de ensayo, que es utilizado para el control de fundaciones profundas en general, es el ensayo de carga dinámica, cuyas ventajas y desventajas han sido identificadas en la investigación bibliográfica.La nueva metodología propuesta, motivo de este trabajo, está basada en los ensayos de carga dinámica a baja deformación, donde se necesita una energía de impacto mucho menos importante que en el caso de los ensayos clásicos de carga dinámica.El protocolo de la metodología y su dispositivo de ensayo han sido calibrados y validados a partir de simulaciones numéricas con el fin de, principalmente, justificar la elección de la energía de impacto, de la masa del martillo y del amortiguador a utilizar. Las observaciones numéricas han sido, luego, verificadas experimentalmente sobre micropilotes a escala real, instalados en un sitio experimental desarrollado en el marco de este proyecto.La metodología de control in situ, de la resistencia en servicio de micropilotes, desarrollada en este trabajo, es un método original, simple de realizar, con un sistema fácil de instalar y de interpretación inmediata. Ella ha sido validada, en el caso de micropilotes a escala real en condiciones controladas en el sitio experimental, y no controladas en el caso de tres proyectos reales.Además, el avance en las investigaciones, dio lugar al desarrollo de una metodología de control de la resistencia límite de micropilotes. Para ello proponemos utilizar un modelo analítico de predicción del comportamiento esfuerzo-deformación alimentado por resultados del ensayo de carga dinámica a baja deformación y de un ensayo complementario de reconocimiento de los parámetros de ruptura del suelo. El objetivo de este desarrollo es de proponer un método de predicción de la resistencia límite de micropilotes sin comprometer su integridad. La aplicación de la metodología ha mostrado que los resultados son muy cercanos a los observados en los ensayos de carga estática
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Kozáková, Marcela. "Ověření spolupůsobení základové desky a piloty." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-390244.
Full textAbstract:
The doctoral thesis deal with the interaction between the foundation plate and deep foundation in the form of bored piles in the case of skeleton construction. The issue of tension redistribution from the column between the plate and the pile is investigated on specific object – „Shopping and entertainment center Fórum Nová Karolina”. On this object were selected columns monitored and load tests of the piles was executed. Values of the axial loading of the piles and the actual deformation of the construction have been derived from measurements and tests. They were compared with the results of structural behavior by numerical modeling.
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Michler, Le. "Entwicklung eines Versuchsstandes zur zweiaxialen Beanspruchung von textilbewehrtem Beton." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-25129.
Full textAbstract:
Im Rahmen der vorliegenden Arbeit wird das Versuchskonzept für zweiaxiale Zug-Zug-Versuche an textilbewehrten Betonscheiben behandelt. Diese Arbeit soll einen Beitrag leisten, die Kenntnisse aus dem Maschinenbau, der Mechanik in den Bereich der Bauingenieure und Baustoffe umzusetzen, um alle Effekte, die vom Versuchstand verursacht werden, öffentlich zu machen. Es ist ein Versuchskonzept zu erarbeiten, wie ein experimenteller Zug-Zug-Versuch optimal zu gestalten ist, um das Tragverhalten des textilbewehrten Betons genau zu ermitteln. Die Arbeit ist hauptsächlich in zwei Teile gegliedert. Der erster Teil befasst sich mit dem Thema „Versuchsvorbereitung“. Es beinhaltet folgende Hauptpunkte: • Der erste Punkt beschäftigt sich mit der Auswertung durchgeführter Versuche und deren Versuchsaufbauten. Hier werden Aspekte von der konstruktiven Auslegung der Rahmen bis zur Steuerung der Prüfmaschine behandelt. Es wird diskutiert, welche Effekte auf das Versuchsergebnis vom gewählten Hydrauliksystem bzw. von den Hydraulikzylinder und der Steuerung des Öldrucks ausgehen können. • Im zweiten Punkt wird eine Finite–Element–Simulationen durchgeführt, um die zweiaxialen Zug-Zug-Versuchskörper zu konzipieren. Mit Hilfe von einem Finite–Element– Programm, hier ATENA, wird die Probengeometrie mit den Randbedingungen des Versuchs nachgebildet und optimiert. • Der dritte Punkt beschäftigt sich mit dem Thema „Lasteinleitung“. Ein Konzept für die Verbindung und Kraftübertragung von Stahlplatten (Stahllasche) zur Lasteinleitung in „Beton“ soll entwickelt werden. • Der vierte Punkt beschreibt die gewählte Messmethode der Versuchsdurchführung, und wertet deren Potenzial und Möglichkeiten . Der zweiter Teil der vorliegenden Arbeit beschreibt detailliert die fünf durchgeführten zweiaxialen Zug–Zug–Versuche an mit AR-Glas textilbewehrten Betonscheiben. Die textilbewehrten Betonscheiben werden am Rahmen der zweiaxialen Prüfmaschine eingehängt und zweiaxial mit jeweils konstantem Verhältnis der Beanspruchung in Zug–Zug Richtung belastet, um den Versuchstand zu erproben und auszutesten. Die Gedanken, Ergänzungen und Erkenntnisse der Autorin im Zusammenhang mit dem textilbewehrten Beton und die hier auftretenden Effekte werden auch in diesem Kapitel behandelt. Das Schlusskapitel der Arbeit beinhaltet die Zusammenfassung und den weiteren Ausblick. Aus diesem Anlass werden die wissenschaftlichen Erkenntnisse der vorliegenden Arbeit zusammengefasstThis doctoral thesis pertains to the conception for Bi–axial Tension–Tension Tests of thin textile reinforced concrete plates. This dissertation contributes to the application of mechanical engineering knowledge into the specific area of Material–Construction Engineering; all results obtained from experimental conditions will be released to the public. The conception of this testing regime is presented, as well as the manner in which an experimental Tension–Tension Test can optimally ascertain and accurately predict and describe load-bearing behaviour of textile reinforced concrete (TRC). This thesis is generally subdivided into two parts –“Test Preparation” and the detail of Bi-axial Tension-Tension testing on AR-Glass TRC plates. The “Test Preparation” component of this document includes the following four principal points. The first point is concerned with the assembly of testing equipment. Problems stemming from framework or lack of control over the testing machine are examined here. Negative effects on test results induced by the Hydraulic cylinder and related oil pressure are investigated and complemented in this section. The second point focuses on the numerical simulation used in order to determine the Bi–axial Tension–Tension Test samples. The specimen geometry given the testing boundary conditions was copied and optimized by means of a Finite–Element–Program (ATENA). The third point is concerned with the notion of “load application”. It was necessary to develop a premise for the loading transmission and connection between steel plates (steel mounting plates) and concrete cogs. The final point takes into account the methods used for measuring the Bi–axial Tension–Tension–test of this work. The second component present in this thesis describes in detail the five Bi–axial Tension–Tension–Tests conducted on AR–Glass TRC plates utilized to prove and ensure the accuracy of the experimental equipment. The TRC plate was built on frame of the bi-axial testing machine and received tensile loading in both directions. This loading relationship was held constant in both directions during the test. Furthermore, the author presents her own thoughts, as well as supplemental commentary, associated with textile reinforced concrete and the resulting experimental outcomes. The last chapter closes this doctoral thesis and includes the abstract of and further prospects for this study. All scientific cognitions are summarised in this chapter
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Michler, Le. "Entwicklung eines Versuchsstandes zur zweiaxialen Beanspruchung von textilbewehrtem Beton." Doctoral thesis, Technische Universität Dresden, 2008. https://tud.qucosa.de/id/qucosa%3A25142.
Full textAbstract:
Im Rahmen der vorliegenden Arbeit wird das Versuchskonzept für zweiaxiale Zug-Zug-Versuche an textilbewehrten Betonscheiben behandelt. Diese Arbeit soll einen Beitrag leisten, die Kenntnisse aus
dem Maschinenbau, der Mechanik in den Bereich der Bauingenieure und Baustoffe umzusetzen, um alle Effekte, die vom Versuchstand verursacht werden, öffentlich zu machen. Es ist ein Versuchskonzept zu erarbeiten, wie ein experimenteller Zug-Zug-Versuch optimal zu gestalten ist, um das Tragverhalten des textilbewehrten Betons genau zu ermitteln. Die Arbeit ist hauptsächlich in zwei Teile gegliedert.
Der erster Teil befasst sich mit dem Thema „Versuchsvorbereitung“. Es beinhaltet folgende Hauptpunkte:
• Der erste Punkt beschäftigt sich mit der Auswertung durchgeführter Versuche und deren Versuchsaufbauten. Hier werden Aspekte von der konstruktiven Auslegung der Rahmen bis zur Steuerung der Prüfmaschine behandelt. Es wird diskutiert, welche Effekte auf das
Versuchsergebnis vom gewählten Hydrauliksystem bzw. von den Hydraulikzylinder und der Steuerung des Öldrucks ausgehen können.
• Im zweiten Punkt wird eine Finite–Element–Simulationen durchgeführt, um die zweiaxialen Zug-Zug-Versuchskörper zu konzipieren. Mit Hilfe von einem Finite–Element– Programm, hier
ATENA, wird die Probengeometrie mit den Randbedingungen des Versuchs nachgebildet und optimiert.
• Der dritte Punkt beschäftigt sich mit dem Thema „Lasteinleitung“. Ein Konzept für die Verbindung und Kraftübertragung von Stahlplatten (Stahllasche) zur Lasteinleitung in „Beton“ soll entwickelt werden.
• Der vierte Punkt beschreibt die gewählte Messmethode der Versuchsdurchführung, und wertet deren Potenzial und Möglichkeiten .
Der zweiter Teil der vorliegenden Arbeit beschreibt detailliert die fünf durchgeführten zweiaxialen Zug–Zug–Versuche an mit AR-Glas textilbewehrten Betonscheiben. Die textilbewehrten Betonscheiben werden am Rahmen der zweiaxialen Prüfmaschine eingehängt und zweiaxial mit jeweils konstantem Verhältnis der Beanspruchung in Zug–Zug Richtung belastet, um den Versuchstand zu erproben und auszutesten. Die Gedanken, Ergänzungen und Erkenntnisse der
Autorin im Zusammenhang mit dem textilbewehrten Beton und die hier auftretenden Effekte werden auch in diesem Kapitel behandelt.
Das Schlusskapitel der Arbeit beinhaltet die Zusammenfassung und den weiteren Ausblick. Aus diesem Anlass werden die wissenschaftlichen Erkenntnisse der vorliegenden Arbeit zusammengefasst.This doctoral thesis pertains to the conception for Bi–axial Tension–Tension Tests of thin textile reinforced concrete plates. This dissertation contributes to the application of mechanical engineering knowledge into the specific area of Material–Construction Engineering; all results obtained from experimental conditions will be released to the public. The conception of this testing regime is presented, as well as the manner in which an experimental Tension–Tension Test can optimally ascertain and accurately predict and describe load-bearing behaviour of textile reinforced concrete (TRC). This thesis is generally subdivided into two parts –“Test Preparation” and the detail of Bi-axial Tension-Tension testing on AR-Glass TRC plates. The “Test Preparation” component of this document includes the following four principal points. The first point is concerned with the assembly of testing equipment. Problems stemming from framework or lack of control over the testing machine are examined here. Negative effects on test results induced by the Hydraulic cylinder and related oil pressure are investigated and complemented in this section. The second point focuses on the numerical simulation used in order to determine the Bi–axial Tension–Tension Test samples. The specimen geometry given the testing boundary conditions was copied and optimized by means of a Finite–Element–Program (ATENA). The third point is concerned with the notion of “load application”. It was necessary to develop a premise for the loading transmission and connection between steel plates (steel mounting plates) and concrete cogs. The final point takes into account the methods used for measuring the Bi–axial Tension–Tension–test of this work. The second component present in this thesis describes in detail the five Bi–axial Tension–Tension–Tests conducted on AR–Glass TRC plates utilized to prove and ensure the accuracy of the experimental equipment. The TRC plate was built on frame of the bi-axial testing machine and received tensile loading in both directions. This loading relationship was held constant in both directions during the test. Furthermore, the author presents her own thoughts, as well as supplemental commentary, associated with textile reinforced concrete and the resulting experimental outcomes. The last chapter closes this doctoral thesis and includes the abstract of and further prospects for this study. All scientific cognitions are summarised in this chapter.
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Benzaria, Omar. "Contribution à l'étude du comportement des pieux sous chargements cycliques axiaux." Phd thesis, Université Paris-Est, 2012. http://tel.archives-ouvertes.fr/tel-00809269.
Full textAbstract:
Dans le cadre du Projet National SOLCYP, le présent travail avait pour but d'étudier la réponse des pieux sous chargements axiaux pour les phases avant, pendant et après cycles. Pour atteindre cet objectif, une étude expérimentale étendue a donc été réalisée par le moyen de deux compagnes d'essais de chargements cycliques sur différents types de pieux instrumentées (battus, forés, vissés) dans deux sites expérimentaux : le site de Merville dans l'argile surconsolidée des Flandres et le site de Loon-Plage près de Dunkerque dans les sables denses des Flandres. Les essais cycliques comportaient des essais en compression, en traction et alternés avec des séries de cycles à forte amplitude conduisant à la rupture cyclique et des séries d'amplitude modérée à très grands nombres de cycles (N>5 000 cycles).L'interprétation de ces essais a englobé, d'une part, une analyse globale du comportement des pieux sous chargements cycliques notamment (i) la réduction de la capacité du pieu; (ii) le nombre de cycles que le pieu peut support avant la rupture (iii) l'évolution du déplacement en tête des pieux (rigidité cyclique). D'autre part, elle a intégré une étude locale en particulier sur la dégradation du frottement latéral et l'évolution de la résistance de pointe du pieu. Cette thèse, basée sur l'étude expérimentale, a permis la formulation des conclusions pratiques sur le comportement des pieux sous chargements cycliques axiaux et a proposé des perspectives pour bien cerner cette problématique
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Štaffa, Jiří. "Ztráty jednofázového asynchronního motoru s trvale připojeným kondenzátorem." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2015. http://www.nusl.cz/ntk/nusl-221263.
Full textAbstract:
This project deals with increasing efficiency of one phase induction motor with permanent split capacitor. We can whole thesis divide into two parts, the first one is basic and the second is interested in analysis and measurement. First part handles with construction of single phase induction motor, explanation of function principle, start and run of motor. Calculating of efficiency including type of losses, which reduce efficiency. Second part concerns analysis losses including moment load characteristic, motor measurement while rotor is locked, with no load operation, measuring mechanical and additional losses. Further there will be measured useful values for creation model for simulation (reactance of windings etc.). Than will be the model created in ANSYS Maxwell with module RMxprt. After analytic calculation in RMxprt and using Finite Element Method (FEM) load characteristics will be compared together. This comparison gives us information about accuracy of model for simulation. Simulation and measurement will be carried out on another engine with high quality ferromagnetic material used for magnetic circuit of motor. Further will be done simulation of motor with modifications shown in previous chapter for high efficiency.
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IrenePang and 彭艾琳. "Axial capacity degradation of jacket foundation under cyclic axial tension loads." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/4m3w48.
Full textAbstract:
碩士國立成功大學
水利及海洋工程學系
106
In recent years, Taiwan has been actively developing renewable energy and offshore wind power is one of the key projects in Taiwan's Renewable energy development. Jacket foundation which has high stiffness and is well suited for the deeper water depth in Taiwan. The piles of jacket foundation are subjected to highly cyclic tension and compressive loading and the design of jacket type foundation for offshore wind turbine is mainly controlled by axial tension loading. Cyclic axial tension loads may cause degradation of pullout capacity due to the reduction of pile shaft resistance. This study presents a numerical model to simulate the behavior of pile under cyclic axial tension loads. The numerical model calibration was done by using the data from the field test results of Jardine and Standing(2000). The results from the field test and predictions made by the calibrated model based on the effect of pile driving and the calculation method of soil volume strain degradation were generally in agreement and simulated axial capacity degradation of piles under cyclic tension loads. This thesis used the methods of EAP (2012) along with the interaction diagram produced from this numerical method to evaluate the axial capacity of pile under cyclic axial tension loads and the result of this analysis showed that the increase of pile diameter, pile length and relative density of sand increased the pile capacity. The ratio of axial cyclic load amplitude had a more significant effect on the pile capacity which decreased with the number of loading cycles compared to the ratio of mean axial cyclic load.
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Lam, Dennis, and K. K. Y. Wong. "Axial Capacity of Concrete Filled Stainless Steel Columns." 2005. http://hdl.handle.net/10454/5549.
Full textAbstract:
NoConcrete filled steel columns have been used widely in structures throughout the world in recent years especially in Australia and the Far East. This increase in use is due to the significant advantages that concrete filled steel columns offer in comparison to more traditional construction methods. Composite columns consist of a combination of concrete and steel and make use of these constituent material's best properties. The use of composite columns can result in significant savings in column size, which ultimately can lead to significant economic savings. This reduction in column size can provide substantial benefits where floor space is at a premium such as in car parks and office blocks. The use of stainless steel column filled with concrete is new and innovative, not only provides the advantage mentioned above, but also durability associated with the stainless steel material. This paper concentrates on the axial capacity of the concrete filled stainless steel columns. A series of tests was performed to consider the behaviour of short composite stainless steel columns under axial compressive loading, covering austenitic stainless steels square hollow sections filled with normal and high strength concrete. Comparisons between Eurocode 4, ACI-318 and the Australian Standards with the findings of this research were made and comment.
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Giakoumelis, G., and Dennis Lam. "Axial Capacity of Circular Concrete¿filled Tube Columns." 2004. http://hdl.handle.net/10454/5652.
Full textAbstract:
noThe behaviour of circular concrete-filled steel tubes (CFT) with various concrete strengths under axial load is presented. The effects of steel tube thickness, the bond strength between the concrete and the steel tube, and the confinement of concrete are examined. Measured column strengths are compared with the values predicted by Eurocode 4, Australian Standards and American Codes. 15 specimens were tested with 30, 60 and 100 N/mm2 concrete strength, with a D/t ratio from 22.9 to 30.5. All the columns were 114 mm in diameter and 300 mm in length. The effect due to concrete shrinkage is critical for high-strength concrete and negligible for normal strength concrete. All three codes predicted lower values than that measured during the experiments. Eurocode 4 gives the best estimation for both CFT with normal and high-strength concrete.
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Lam, Dennis, and N. Testo. "Axial Capacity of Concrete-Filled Steel Elliptical Hollow Sections." 2007. http://hdl.handle.net/10454/5569.
Full textAbstract:
NoConcrete filled steel tube (CFST) columns are becoming increasingly popular due to the advantages they offered. They are not only considered aesthetically pleasing but can also offer significant improvement in axial capacity without increases in crosssectional area being required. Elliptical steel hollow sections represent a recent and rare addition to the range of cross-sections available to structural engineers, however, despite widespread interest in their application, a lack of verified design guidance is inhibiting uptake. The use of elliptical steel hollow section with concrete infill is new and innovative, not only provides the advantage mentioned above, but also on the basis of both architectural appeal and structural efficiency. The aim of this paper is to investigate the behaviour of the elliptical CFSTs under axial loading. A total of 12 specimens were tested with wall thicknesses of 4 mm, 5 mm, 6.3 mm and concrete core strength of 30 MPa. This paper reported on the behaviour of concrete filled elliptical hollow sections under axial load. The effect of the wall thickness of the steel section, the bond between steel and concrete and the concrete confinement are presented.
32
Lam, Dennis, and C. Roach. "Axial capacity of concrete filled stainless steel circular columns." 2006. http://hdl.handle.net/10454/5793.
Full text
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Tian, Chunn-Hua, and 田淳華. "Investigation on Analysis Models for Axial Capacity of DrilledShafts in Multiple Strata." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/16261525527684955421.
Full textAbstract:
碩士國立暨南國際大學
土木工程學系
101
Drilled shafts have been the preferred foundation system for infrastructure and buildings. Significant advances in drilled shaft research have been made over the past few decades, where many scholars have suggested analysis models. Most past models were developed based on data of drilled shafts in a predominate type of geomaterial, such as clay, sand, gravel, or rock. Ground profile with multiple layers is often encountered in several metropolises around the world. It is warranted to assess the applicability of existing models on shafts in a ground profile with multiple layears. In this study, a database of load test case histories for drilled shafts in multiple strata is compiled. Two commonly used analysis models that can considere all types of geomaterials along the depth of drilled shafts are evalauated critically, namely (1) approaches given by the drilled shafts design guidelines by the Federal Highway Administration (FHWA(2010) method) and (2) design recommendations given by the Taiwan Buildings Foundation Design Specification (TBFSD (2001) method). Tip and side ressitances were first evaluated separately. On average, both models overpredict the side and tip resistances with significant scatter. For side resistance, prediction is better for shafts in a single soil (sand or clay) profile than that in a mixed profile. The model bias or model factor was computed and analyzed for each analysis equation. For the compression capacity, a consistent evaluation can be resulted with consideration of these model factors.
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Kim, Kyung Jun. "Development of resistance factors for axial capacity of driven piles in North Carolina." 2002. http://www.lib.ncsu.edu/theses/available/etd-11092002-125104/unrestricted/etd.pdf.
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Liu, Yu-Chun, and 劉玉純. "The Study of Load-Carrying Capacity of Light-Gauge Steel Wall Studs under Axial Loads." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/05236766574312335550.
Full textAbstract:
碩士朝陽科技大學
建築及都市設計研究所
90
This investigation is concentrated on the study of load-carrying capacity of light gauge steel wall studs under axial loading conditions. The design strength of wall studs is computed based on the “Specification for the Design of Cold-Formed Steel Structural Members” published by the American Iron and Steel (AISI). The experimental program is mainly focus on the test of silicate boards. The parameter “ 0” obtained form the test was adopted in the use of calculation of wall stud strength. In the analysis of light-gauge steel wall studs, two different approach were adopted: (1)all steel design; (2)sheathing braced design. In addition, the comparisons between the light-gauge steel wall studs and brick wall/3D wall were
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Chen, Chan-Hsien, and 陳湛弦. "Performance of Axial Capacity Analysis Models for Drilled Shafts- Critical Evaluation of Two FHWA Approaches." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/9pv263.
Full textAbstract:
碩士國立暨南國際大學
土木工程學系
103
Drilled shafts are popular deep foundation systems used to support many important superstructures. Significant advances in drilled shaft research have been made over the past few decades, where most previous researches have focused on drilled shafts in a single predominate type of geomaterial such as clay, sand, gravel, or rock. In practice, drilled shafts in a generalized profile that two or more types of geomaterials encountered over the depth are not uncommon. Whether it is rational using combined recommended correlation models calibrated against data of shafts in a single type of geomaterial for those in a generalized ground condition shall be properly explored. To critically evaluate existing analysis models for drilled shafts capacity, two models both proposed by Federal Highway Administration (FHWA) were selected for study. These two analysis models include: (1) approaches given in the drilled shafts design guidelines published by FHWA in 1999 (denoted as the FHWA 1999 method) and (2) approaches given in the drilled shafts design guidelines published by FHWA in 2010 (denoyed as the FHWA 2010 method). Both models can consider drilled-shafts in a single or multiple geo-strata. To conduct this study, databases of axial compression load test case histories for drilled shafts were compiled. As a result, four databases of tests in different types of groud profiles were put together. Characteristics of load transfer for drilled shafts in axial compression were first studed, and schemes that can rationally separate butt load into side and tip resistances were proposed. Effectiveness of side and tip resistances using the two selected models were then examined. Although consistence prediction of the measured resistances can be reached using approaches given by the original guidelines, there are considerable scatter in the predicted results. Further investigation found that the capacity evaluation can be improved when uses of the type of undained shear strength fpr cohesive soils and limit of the beta factor for chesionless soils were changed. Useful design recommendations for capacity evaluation using the FHWA approaches also are given.
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CHEN, YEN-LIN, and 陳彥霖. "Performance of Selected Analysis Models for Axial Compression Capacity of Drilled Shafts in Multiple Strata." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/xcynpr.
Full textAbstract:
碩士國立暨南國際大學
土木工程學系
105
The drilled shaft has been the preferred foundation system employed in projects involved with use of deep foundation owing to its beneficial features of low noise and vibration during installation. Significant advances in drilled shaft researches have been made over the past few decades. Most previous researches have focused on drilled shafts in a single predominat geomaterial. However, it is not uncommon for a drilled shaft to encounter multiple geomaterials over the depth. For rational evaluation of axial compressive capacity, approaches that can taking account contributions from various types of geomaterial are needed. In this study, three analysis models that can be applied for computing axial capacity of drilled shafts in multiple strata were selected for critical evaluation of their performance on capacity evaluation. The selected models include : (1) The Kulhawy Approach, which is a generalized capacity evaluation model that can be applied for various types of drilled foundation in several differernt gomaterials developed by Prof. Kulhawy and his associated researches, (2) The TGS (2001) Approach, which is the computation model prescribed in the Taiwanese Foundation Design Spectification for Building, and (3) the CFEM (2006) Approach, which is the computation model given in the Canadian Foundation Engineering Manual. The groud profiles can be categorized into four different types, including (1) pure clay profile, (2) pure sand profile, (3) interbededly clay and sand profile, and (4) profile with multiple starta. Evaluation ofperformance of the selected models were carried out through analyses using a compiled database consisting of load test case histories from all over the world. A total of 165 load test case histories were obtained. The diameters of shafts range from 0.3 m to 2.5 m, the depthes range from 4.6 m to 76 m, while the diameter over depth ratio for these shafts range from 0.018 to 0.25. The measured failure loads were interpreted from the load test results. Compariosn were made between the interpreted loads and those predicted from the analysis models. For drilled shafts in clay profile, the axial capacity can be better predicted by the Kulhawy and the TGS (2001) approaches. For shafts in sand profile, all three approachs can result in consistent predictions. However, all three approaches tend to underestimate slightly the side resistance and overestimate the tip reistance. The predicted results are somewhat scattered for shafts in multiple strata. In this study, model factors for shafts in different ground profiles were computed for all approaches. The model factors characterized the mean bias for the prediction model and can be used as the corrections for capacity evaluation. Satisfactory results can be obtained when corrections were applied for evaluation of the compression capacity for drilled shafts in various profiles. Based on results of this study, recommendations are made for consideration on analyses of axial compression capacity for drilled shafts.
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Chu, Tsu-Hung, and 朱祖宏. "Evaluation of Interpretation Criteria and Capacity for Drilled Shafts in Gravelly Soils under Axial and Lateral Loading." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/02626300806742460847.
Full textAbstract:
碩士中原大學
土木工程研究所
97
This study is a critical evaluation of drilled shafts under axial and lateral loading in gravelly soils. Both interpretation criteria and analysis methods are examined using field load test data. Available interpretation criteria are used to establish a consistent axial and lateral interpretation criterion. The β method, general bearing capacity equation, and SPT-N empirical equation are evaluated for axial capacity, while the simple Chang method is used for lateral capacity. Based on these analyses, QL1 is close to load at 0.31%B with 2.6 mm and QL2 is close to load at 18.4 mm for uplift loading. QL1 is close to load at 0.54%B with 7.2 mm and QL2 is close to load at 52.1 mm for compression loading. Among all axial interpretation criteria, the Davisson method gives the lowest results and Chin method has the highest results. For lateral loading, QS&W is close to Q0.75%B and Q10.0mm, while QL is close to Q1.2%B and Q11.4mm. For the analysis of axial capacity, the side resistance of β method is generally underestimated and the general bearing capacity equation is overestimated. The suggested SPT-N empirical equations were also evaluated using measured results. For lateral capacity, the statistical data show that the larger the lateral displacement, the closer the results between measurements and simple Chang method. Finally, specific design recommendations for the interpretation and capacity analysis are given.
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Chiu, Yi-Jen, and 邱益仁. "The Study of Load-Carrying Capacity of the Steel Wall Frames With Calcium Silicate Board Under Axial Loads." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/haak48.
Full textAbstract:
碩士朝陽科技大學
營建工程系碩士班
92
This study is concentrated on the strengths and behaviors of cold-formed steel wall frames with silicate board. By changing the distance between self-drilling screws and the thickness of sheathings, steel wall frames were tested in this research. In addition, relative parameters were obtained from a series of silicate board tests in order to adopt in the computation of the strengths of wall specimens. The comparisons were made between the tested results and the predicted values calculated based on AISI and AS/NZS specifications. The recommended effective length factor (K) was also proposed for the design purpose. By using 0.6 times the ultimate strength and its displacement from each individual board test, the sheathing parameter was found between 175.795 and 268.341 kN, and the values of sheathing shear strain varies from 0.0028 to 0.0052. The sheathing material affected the strength and failure mode of walls. It was found that the strengths of steel walls with silicate board are 1.83 to 2.27 times greater than the strengths of steel walls without sheathing. It was also observed that the strengths of steel walls with silicate board computed according the AISI specification are underestimated as compared to the tested values.
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Ren, Q.-X., C. Hou, Dennis Lam, and L.-H. Han. "Experiments on the bearing capacity of tapered concrete filled double skin steel tubular (CFDST) stub columns." 2014. http://hdl.handle.net/10454/10283.
Full textAbstract:
noTapered concrete filled double skin steel tubular (CFDST) columns have been used in China for structures such as electricity transmission towers. In practice, the bearing capacity related to the connection details on the top of the column is not fully understood. In this paper, the experimental behaviour of tapered CFDST stub columns subjected to axial partial compression is reported, sixteen specimens with top endplate and ten specimens without top endplate were tested. The test parameters included: (1) tapered angle, (2) top endplate thickness, and (3) partial compression area ratio. Test results show that the tapered CFDST stub columns under axial partial compression behaved in a ductile manner. The axial partial compressive behaviour and the failure modes of the tapered CFDST stub columns were significantly influenced by the parameters investigated. Finally, a simple formula for predicting the cross-sectional capacity of the tapered CFDST sections under axial partial compression is proposed.
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Mahgub, Munir, Ashraf F. Ashour, Dennis Lam, and Xianghe Dai. "Tests of self-compacting concrete filled elliptical steel tube columns." 2016. http://hdl.handle.net/10454/10317.
Full textAbstract:
YesThis paper presents an experimental study into the axial compressive behaviour of self-compacting concrete filled elliptical steel tube columns. In total, ten specimens, including two empty columns, with various lengths, section sizes and concrete strengths were tested to failure. The experimental results indicated that the failure modes of the self-compacting concrete filled elliptical steel tube columns with large slenderness ratio were dominated by global buckling. Furthermore, the composite columns possessed higher critical axial compressive capacities compared with their hollow section companions due to the composite interaction. However, due to the large slenderness ratio of the test specimens, the change of compressive strength of concrete core did not show significant effect on the critical axial compressive capacity of concrete filled columns although the axial compressive capacity increased with the concrete grade increase. The comparison between the axial compressive load capacities obtained from experimental study and prediction using simple methods provided in Eurocode 4 for concrete-filled steel circular tube columns showed a reasonable agreement. The experimental results, analysis and comparison presented in this paper clearly support the application of self-compacting concrete filled elliptical steel tube columns in construction engineering practice.
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Lam, Dennis, Jie Yang, and Xianghe Dai. "Finite element analysis of concrete filled lean duplex stainless steel columns." 2019. http://hdl.handle.net/10454/16821.
Full textAbstract:
YesIn recent years, a new low nickel content stainless steel (EN 1.4162) commonly referred as ‘lean duplex stainless steel’ has been developed, which has over two times the tensile strength of the more familiar austenitic stainless steel but at approximately half the cost. This paper presents the finite element analysis of concrete filled lean duplex stainless steel columns subjected to concentric axial compression. To predict the performance of this form of concrete filled composite columns, a finite element model was developed and finite element analyses were conducted. The finite element model was validated through comparisons of the results obtained from the experimental study. A parametric study was conducted to examine the effect of various parameters such as section size, wall thickness, infill concrete strength, etc. on the overall behaviour and compressive resistance of this form of composite columns. Through both experimental and numerical studies, the merits of using lean duplex stainless steel hollow sections in concrete filled composite columns were highlighted. In addition, a new formula based on the Eurocode 4 was proposed to predict the cross-section capacity of the concrete filled lean duplex stainless steel composite columns subjected to axial compression.
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Burkett, Terry Bryce. "Resistance analysis of axially loaded drilled shafts socketed in shale." 2013. http://hdl.handle.net/2152/21935.
Full textAbstract:
An investigation into the load-settlement behavior of two drilled shafts, founded
in shale, is presented. The motivation for this research is to advance the understanding
on how drilled shafts react under loading in stiff clays and shales. The objectives of the
study are to measure the strengths within the subsurface material at the test site, estimate
the unit side shear and unit end bearing of the shale-shaft interaction by running two axial
load tests, and compare the results to the current design methods that are used to predict
the axial capacity of drilled shafts.
A comprehensive field investigation, performed by Fugro Consultants, provided
strength profiles of the subsurface material at the test site. Through the cooperation of
the Texas Department of Transportation (TxDOT), the Association of Drilled Shaft
Contractors, and McKinney Drilling Company, two drilled shafts were installed at a
highway construction site in Austin, Texas. The load tests were performed by Loadtest,
Inc.; using the patented Osterberg-Cell™ loading technique to axially displace the shafts.
Ensoft, Inc. installed strain gauges at multiple levels within the shafts, making it possible
to analyze the shaft mobilization during loading.
Ultimate end bearing values of about 100- and 120-ksf were measured for Test
Shafts #1 and #2, respectively. The current methods for estimating unit end bearing,
developed by TxDOT and the Federal Highway Administration, provide fairly accurate
predictions when compared to the measured information. The ultimate side resistance
obtained near the O-Cell™ in each test was about 20-ksf, however, the measured ultimate
side resistance steadily decreased nearing the tip of the shaft. For the zones where the
side resistance was believed to be fully mobilized, the TxDOT design method accurately
predicts the side resistance. A limited amount of information is currently available for
load tests performed in soils with TCP values harder than 2-in per 100 blows. Additional
load test information should allow for a stronger correlation between TCP tests and unit
resistances for very hard clay-shales, as well as, allowing for further evaluation of the
shale-shaft interaction near the shaft tip. The results presented herein demonstrate the
effectiveness of the current design methods for drilled shafts and the non-uniformity of
side resistance within one- to two-diameters of the shaft tip.text