Дисертації з теми "GROUP OF PIERS"
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1
Ozkeskin, Asli. "Settlement Reduction And Stress Concentration Factors In Rammed Aggregate Piers Determined From Full- Scale Group Load Tests." Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/2/12605153/index.pdf.
Повний текст джерелаАнотація:
Despite the developments in the last decades, field performance information for short aggregate pier improved ground is needed for future design and to develop a better understanding of the performance of the short (floating) aggregate piers.
A full-scale field study was performed to investigate the floating aggregate pier behavior in a soft clayey soil. Site investigations included five boreholes and sampling, four CPT soundings, and SPT and laboratory testing. The soil profile consisted of 8m thick compressible clay overlying weathered rock.
Four large plate load test stations were prepared. A rigid steel footing having plan dimensions of 3.0m by 3.5m were used for loading. Four 65cm diameter reaction piles and steel cross beams were used to load the soil in each station.
First test comprised of loading the untreated soil up to 250 kPa with increments, and monitoring the surface settlements. Moreover, distribution of settlements with depth is recorded by means of deep settlement gages installed prior to loading.
Other three tests were conducted on clay soil improved by rammed aggregate piers. In each station, seven stone columns were installed, having a diameter of 65cm, area ratio of 0.25, placed in a triangular pattern with a center to center spacing of 1.25m. The length of the columns were 3m, 5m in the two station resembling floating columns, and 8m in the last station to simulate end bearing columns to observe the level of the improvement in the floating columns. Field instrumentations included surface and deep settlement gages, and load cell placed on a aggregate pier to determine distribution of the applied vertical stress between the column and the natural soil , thus to find magnitude of the stress concentration factor, n , in end bearing and floating aggregate piers.
It has been found that, the presence of floating aggregate piers reduce settlements, revealing that major improvement in the settlements takes place at relatively short column lengths.
It has been also found that the stress concentration factor is not constant, but varies depending on the magnitude of the applied stress. The magnitude of stress concentration factor varies over a range from 2.1 to 5.6 showing a decreasing trend with increasing vertical stress.
2
Lemme, Nathan A. "Effectiveness of Compacted Fill and Rammed Aggregate Piers for Increasing Lateral Resistance of Pile Foundations." BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2393.
Повний текст джерелаАнотація:
Compacted fill and rammed aggregate piers (RAPs) were separately installed adjacent to a 9-ft by 9-ft by 2.5-ft driven pile foundation founded in soft clay. The compacted fill used to laterally reinforce an area of 11 ft by 5 ft by 6 ft deep adjacent to the pile cap was clean concrete sand. The thirty-inch diameter RAPs were installed in three staggered rows to a depth of 12.5 ft below the ground surface adjacent to the pile cap to test the increase in lateral resistance afforded by their installation. The foundation was laterally loaded and load, displacement, and strain readings were recorded. The results of this testing were compared with similar tests performed with virgin soil conditions. The total lateral capacity of the pile foundation increased by 5 percent or14 kips due to compacted fill placement against the face of the pile cap. The passive force acting only on the pile cap decreased from 54 kips in the virgin case to 30 kips after installation of the compacted fill, a decrease of about 45 percent. The total lateral capacity of the pile foundation that was retrofit with RAPs was increased by 18 percent or 52 kips as compared to an identical pile cap in virgin clay. The passive force acting on the pile cap at 1.5 inches of pile cap displacement was determined to be approximately 50 kips, showing a slight decrease in passive resistance as compared to the tests performed on virgin soil. Both reinforcement techniques reduced pile head rotation and the bending moments in the shallow portions of the piles.
3
Metsänen, Toni Tapio [Verfasser], Martin [Akademischer Betreuer] Oestreich, Martin [Gutachter] Oestreich, and Warren E. [Gutachter] Piers. "Metal-catalyzed generation of main-group electrophiles : mechanisms and applications / Toni Tapio Metsänen ; Gutachter: Martin Oestreich, Warren E. Piers ; Betreuer: Martin Oestreich." Berlin : Technische Universität Berlin, 2016. http://d-nb.info/1156012031/34.
Повний текст джерела
4
Andersen, Paul Joseph Walsh. "Performance of a full-scale Rammed Aggregate Pier group in silty sand based on blast-induced liquefaction testing in Emilia-Romagna, Italy." BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8530.
Повний текст джерелаАнотація:
To investigate the liquefaction mitigation capability of Rammed Aggregate Piers® (RAP) in silty sand, blast liquefaction testing was performed at a soil profile treated with a full-scale RAP group relative to an untreated soil profile. The RAP group consisted of 16 piers in a 4x4 arrangement at 2 m center-to-center spacing extending to a depth of 9.5 m. Blasting around the untreated area induced liquefaction (ru ≈1.0) from 3 m to 11 m depth, producing several large sand boils, and causing settlement of 10 cm. In contrast, installation of the RAP group reduced excess pore water pressure (ru ≈0.75), eliminated sand ejecta, and reduced average settlement to between 2 to 5 cm when subjected to the same blast charges. Although the liquefaction-induced settlement in the untreated area could be accurately estimated using the CPT-based settlement approach proposed by Zhang et al. (2002), settlement in the RAP treated area was significantly overestimated with the same approach even after considering RAP treatment-induced densification. Analyses indicate that settlement after RAP treatment could be successfully estimated from elastic compression of the sand and RAP acting as a composite material. The composite reinforced soil mass, surrounded by liquefied soil, transferred load to the base of the RAP group inducing settlement in the non-liquefied sand below the group. This test program identifies a mechanism that explains how settlement was reduced for the RAP group despite the elevated ru values in the silty sands that are often difficult to improve with vibratory methods.
5
Szydlik, Linda (Linda L. ). "The Effects of Career Group Counseling on the Self-Concept of At-Risk High School Students as Measured by the Piers-Harris Children's Self-Concept Scale." Thesis, University of North Texas, 1995. https://digital.library.unt.edu/ark:/67531/metadc277630/.
Повний текст джерелаАнотація:
The purpose of this study was to determine the effectiveness of career group counseling in raising the self-concept of at-risk high school students. The following subgroups were represented in the sample: male and female students, white and non-white ethnic groups, and students from sophomore, junior, and senior classifications. Two groups of students in the Lewisville Independent School District meeting the criteria for at-risk as defined by House Bill 1010 were administered a pretest and posttest using the Piers-Harris Children's Self-Concept Scale. The experimental group was from the Lewisville Learning Center. The control group was students enrolled in the Coordinated Vocational Academic Education (CVAE) classes at Lewisville High School. A treatment sample of 25 students received career group counseling. A nontreatment sample of 25 students did not receive any group counseling. The t-test for independent samples was used to analyze the data. The pretests for the experimental and control groups showed no significant difference at the .05 level. The treatment sample received 30 hours of group counseling in the Fall semester of 1994. At the end of 30 hours of counseling a posttest was administered to the treatment sample and to the control sample. The t-test for independent samples was used to analyze the data. While career group counseling appeared to impact the students in the experimental group, the limitations of sample size and population may have effected the results. The treatment was significant at the .05 level and the null hypothesis was rejected. The findings showed that career group counseling was not an effective tool for increasing positive self-concept. It is concluded that self-concept was not effectively enhanced through group interaction conducted by the school system in this study. Further research is recommended.
6
Kuruoglu, Ozgur. "A New Approach To Estimate Settlements Under Footings On Rammed Aggregate Pier Groups." Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609733/index.pdf.
Повний текст джерелаАнотація:
This study uses a 3D finite element program, calibrated with the results of a full scale instrumented load test on a limited size footing, to estimate the settlement improvement factor for footings resting on rammed aggregate pier groups. A simplified 3D finite element model (Composite Soil Model) was developed, which takes into account the increase of stiffness around the piers during the ramming process.
Design charts for settlement improvement factors of square footings of different sizes (B = 2.4m to 4.8m) resting on aggregate pier groups of different area ratios (AR = 0.087 to 0.349), pier moduli (Ecolumn = 36MPa to 72MPa), and with various compressible clay layer strengths (cu = 20kPa to 60kPa) and thicknesses (L = 5m to 15m) were prepared using this calibrated 3D finite element model.
It was found that, the settlement improvement factor increases as the area ratio, pier modulus and footing pressure increase. On the other hand, the settlement improvement factor is observed to decrease as the undrained shear strength and thickness of compressible clay and footing size increase.
After using the model to study the behaviour of floating piers, it was concluded that, the advantage of using end bearing piers instead of floating piers for reducing settlements increases as the area ratio of piers increases, the elasticity modulus value of the piers increases, the thickness of the compressible clay layer decreases and the undrained shear strength of the compressible clay decreases.
7
Kfoury, Dimitry. "Calcul de Schubert affine et formules de Pieri." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0215.
Повний текст джерелаАнотація:
Les formules de Pieri sont des formules qui permettent de comprendre la structure d'algèbre de cohomologie de la Grassmannienne (affine) ou même celle des variété de Drapeaux. Plusieurs sont déjà établies dans quelques types et cas particuliers. Cependant ce problème reste encore ouvert pour la plupart des cas affines, en particulier pour trouver des formules de Pieri dans "H^*(\mathcal{G}r_G)" en types "B", "C" et "D".Dans cette thèse, même si on généralise quelques résultats pour un groupe de Weyl affine non-tordu général, on explore principalement les types A et C.Dans la variété de drapeaux de type A affine, on trouve une formule pour la multiplication, dans l'algèbre de cohomologie d'une variété de drapeaux, d'un élément de la base "\xi^w" par un autre (spécial) qu'on appellera ''crochet''. On montre ce résultat en utilisant la formule de Pieri donnée par Lam et al dans \cite{insertion}.En type C affine, on propose une conjecture pour une formule de Pieri en Cohomologie, en montrant qu'elle est valide en degré 1 et ''presque'' tous les cas du degré 2. On la vérifie aussi, en testant de nombreux exemples à l'aide de l'ordinateur.En Homologie, on redémontre, en utilisant une nouvelle stratégie simplifiée, la formule de Pieri en type C \cite{lam2010schubert}. Cette nouvelle approche pourrait éventuellement être utilisée dans le but d'établir des formules en types exceptionnels.Dans les variétés de drapeaux de dimension finie, on trouve aussi une majoration des coefficients de Littlewood-Richardson et on la généralise, en tout type, pour des classes particulières qu'on appellera ''petites classes de Schubert''Pieri's formulas are a gateway to understanding the algebra structure of the (affine) Grassmannian or even that of Flag varieties. Several are already established in a few particular types and cases. However, this problem remains open for most affine cases, especially to find Pieri formulas in "H (\mathcal{G}r_G)" in types "B", "C" and "D".In this thesis, even if some results are generalized for non-twisted affine Weyl groups, we mainly explore types A and C. In the flag variete of affine type A, we find a formula for multiplying, in the cohomology algebra of a flag variety, one element of the base "\xi^w" by another (special) element that will be called ''crochet''. This result is shown using the Pieri formula given by Lam et al in \cite{insertion}. In the affine Type "C", we propose a conjecture for a Pieri formula in Cohomology, showing that it is valid in degree "1" and "almost" all cases of degree "2". It is also checked, by testing many examples using the computer.In Homology, the Pieri formula in type C \cite{lam2010schubert}, is re-demonstrated, using a new simplified strategy. This new approach could eventually be used to establish formulas of exceptional types.In the finite dimensional flag varieties, we find an upper bound for the littlewood-Richardson's coefficients and generalize it, in all types, to particular classes that will be called ''small Schubert classes''
8
Ozalp, Murat Can. "Experimental Investigation Of Local Scour Around Bridge Pier Groups." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615594/index.pdf.
Повний текст джерелаАнотація:
It is an important task that design engineers in practice predict the local scour around bridge piers as accurately as possible because excessive local scour around bridge piers unbalance and demolish the bridges. Many equations have been proposed previously by various researchers, based on their experimental findings, but no general method has been developed so far due to the complexity of the topic. In the present study two new bridge pier groups were employed to investigate the inclination effect of the most upstream and downstream piers on the local scours around all piers. Total of 72 experiments have been conducted with 3 inclination angles, one of which representing the vertical case, each experiment lasting 6 hours, under uniform flow and clear-water conditions for a range of water depths and flow velocities on the uniform bed material. It is clearly observed and measured that the amount of local scour reduces substantially by the effect of inclination in the group piers, especially the reduction in the scour around the most upstream pier is found notable. Based on the experimental data, regression analyses are made and an empirical scour depth equation is developed for each individual pier in the pier groups studied. Comparisons with the similar studies performed by other researchers have been made and the results discussed.
9
Leclerc, Marc-Antoine. "Homogeneous Projective Varieties of Rank 2 Groups." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23558.
Повний текст джерелаАнотація:
Root systems are a fundamental concept in the theory of Lie algebra. In this thesis, we will use two different kind of graphs to represent the group generated by reflections acting on the elements of the root system. The root
systems we are interested in are those of type A2, B2 and G2. After drawing the graphs, we will study the algebraic groups corresponding to those root systems. We will use three different techniques to give a geometric description of the homogeneous spaces G/P where G is the algebraic group corresponding to the root system and P is one of its parabolic subgroup. Finally, we will make a link between the graphs and the multiplication of
basis elements in the Chow group CH(G/P).
10
Nazariha, Mehrdad. "Design relationships for maximum local scour depth for bridge pier groups." Thesis, University of Ottawa (Canada), 1996. http://hdl.handle.net/10393/9989.
Повний текст джерелаАнотація:
An investigation of local scour at pier groups has been conducted with the aim of developing design recommendations and scour depth prediction equations for the bridge pier groups. A comprehensive series of steady uniform flow experiments was performed on groups of 2, 3, 4, and 6 model piers. All tests were conducted under clear-water scour conditions. Parameters governing local scour depth around bridge piers include: flow characteristics, sediment properties, and pier size and shape. The effects of these parameters on the maximum local scour depth for a single pier (D$\sb{\rm s}$), have been thoroughly investigated in the past. However, when design criteria developed for single piers are applied directly to pier groups, this approach ignores the following important group effects: (1) sheltering, (2) reinforcement, and (3) horse-shoe vortex (HSV) compression. Furthermore, the group effects will alter with changes in pier spacing, S, and flow angle of attack, $\beta$. This study, which investigates the local scouring process for the aforementioned groups of model bridge piers, and presents design relationships for predicting the corresponding maximum local scour depths, is an attempt to address this limitation in current design practice. Initially the local scour was examined for five different single pier diameters (0.0127 m, 0.018 m, 0.025 m, 0.033 m and 0.05 m). Having established single pier relationships, groups of 2, 3, 4, and 6 equally spaced piers were examined, while altering alignment to the flow and separation distances. For piers in line with the flow direction, downstream piers are sheltered by the upstream ones resulting in reducing scour depth around downstream piers. This effect diminishes with the increasing $\beta$ if there is only one row of piers i.e., 2 and 3 pier groups. In the case of 2 rows of piers aligned to the flow direction (i.e., 4- and 6-pier groups), there is a specific range of $\beta$ in which downstream piers are exposed to the flow. As $\beta$ increases, depending on pier spacing, the piers of one row may shelter the downstream piers of the other row. The reinforcement effect is significant only for small ratios of pier spacing/ pier diameter (S/d) when $\beta \le$ 10$\sp0$. In these ranges of S/d and $\beta$, the front piers are scoured more than that of a single pier. Moreover, the score depth of downstream piers, which are less than that of a single pier, increases with increasing S/d. The compressed (HSV) arms affect the local scour depth significantly if piers are staggered and S/d $\le$ 5. In this range of S/d, the HSV arms are intensified, resulting in a deeper scour hole. However, this effect also becomes insignificant with increasing S/d. The data obtained for each pier group were analysed, using a multiple regression model, to develop local scour depth prediction equations for the front, middle, and rear piers. The regression model includes two important dimensionless parameters ($\beta$ and S/d) associated with group effects, as regressors. The proposed prediction equations estimated the observed data and similar-type published data reasonably well, within marginal errors. From a general practical view-point, the number of prediction equations was reduced to two equations for all pier groups: one for the front piers and the second one for the downstream piers (i.e. combined middle and rear piers).
11
Duveau, Jérémy. "Les empreintes de pieds du Rozel (Manche) : Instantanés de groupes humains au Pléistocène supérieur. Approche combinée morphométrique et expérimentale." Thesis, Paris, Muséum national d'histoire naturelle, 2020. http://www.theses.fr/2020MNHN0004.
Повний текст джерелаАнотація:
Les empreintes de pieds d’hominines représentent des vestiges uniques ouvrant une fenêtre sur de brefs moments de vie de groupes disparus. Leur étude donne des informations directes sur la taille et la composition de ces groupes, paramètres essentiels à leur succès adaptatif mais rarement accessibles à partir du registre fossile. Toutefois, l’étude des empreintes est rendue complexe par le nombre de facteurs (caractéristiques corporelles et biomécaniques, nature du substrat, taphonomie) impactant leur morphologie et leur relative rareté au sein du registre fossile. Depuis 2012, plusieurs centaines d’empreintes de pieds potentielles attribuables à des néandertaliens ont été découvertes associées à un riche matériel archéologique dans 5 niveaux datés à 80 000 ans de la paléodune du Rozel (Manche, France). La découverte de ces empreintes offre l’opportunité de s’intéresser à la taille et à la composition des groupes sociaux néandertaliens, problématique centrale de ce doctorat. Dans un premier temps, l’analyse des empreintes potentielles découvertes entre 2012 et 2017 a permis d’identifier 257 empreintes de pieds et 8 empreintes de mains ce qui représente à ce jour le plus gros corpus ichnologique associé aux Néandertaliens. Puis, grâce au développement d’une approche combinant morphométrie et expérimentation, la taille et la composition des groupes a été estimée à partir des empreintes numérisées en 3D. Les empreintes de pieds étudiées reflètent ainsi différentes classes d’âge allant du très jeune enfant (à partir de 1 an) à l’adulte. Les empreintes issues du niveau le plus dense ichnologiquement représentent un groupe de petite taille, probablement composé de 10 à 13 individus, dont 90% étaient des enfants et des adolescents. Les empreintes de pieds du Rozel fournissent ainsi des informations uniques sur la taille et la composition des groupes néandertaliens permettant de mieux comprendre les occupations paléolithiques au Rozel il y a 80 000 ansThe hominin footprints represent unique remains that open a window on brief moments in the lives of extinct groups. Their study provides direct information on the size and composition of these groups which are essential to their adaptive success but rarely accessible from the fossil record. The study of these footprints is complex because several factors (body and biomechanical characteristics, nature of the substrate, taphonomy) impact their morphology and because they are relatively rare within the fossil record. Since 2012, several hundred potential footprints attributable to Neandertals have been discovered associated with a rich archaeological material in 5 levels from the Le Rozel paleodune (Manche, France) that are dated of 80,000 years. The discovery of these footprints offers the opportunity to focus on the size and composition of Neandertal social groups, which is the central issue of this doctorate. First, the analysis of the potential footprints discovered between 2012 and 2017 allowed identifying 257 footprints and 8 handprints; this sample represents the largest ichnological assemblage associated with Neandertals to date. Then, thanks to the development of an approach combining morphometry and experimentation, the size and composition of the groups were estimated from 3D digitized prints. As a result, the studied footprints reflect different age groups ranging from very young children (from 1 year old) to adults. The footprints from the ichnologically densest level represent a small group, probably composed of 10 to 13 individuals with 90% of young individuals. The Le Rozel's footprints thus provide unique information on the size and the composition of Neandertal groups to better understand Paleolithic occupations in Le Rozel 80 000 years ago
12
Bonfiglioli, Marco. "Riprogettare l'offerta di Retail Marketing: il caso I.C.A.S." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
Знайти повний текст джерелаАнотація:
Oggi le imprese di produzione affidano sempre più spesso la copertura del mercato a imprese commerciali intermediarie che svolgono il ruolo di raccordo fra l’offerta dei produttori e la domanda del cliente finale. In questo contesto il luogo dove si materializzano le vendite dei prodotti è il punto vendita che può assumere forme diverse a seconda delle dimensioni, dell’assortimento e del mercato di riferimento.
Il Retail Marketing costituisce la disciplina che studia come orientare e stimolare le scelte del cliente all’interno del punto vendita. Attraverso la scelta del giusto mix di leve sulle quali intervenire si crea vantaggio competitivo nei confronti della concorrenza. Lo scopo è di rispondere al maggior numero possibile di esigenze dei clienti nel settore di competenza per incrementare i loro acquisti, concentrandoli in un’unica shopping expedition.
All’interno dell'elaborato verranno approfondite le leve di Retail Marketing da utilizzare come linee guida per riprogettare l’offerta di un’attività commerciale. In particolare si analizzerà il caso del Cash & Carry “I.C.A.S.”, punto di vendita all’ingrosso di proprietà di Pieri Group S.r.l., dove ho svolto il tirocinio da giugno a settembre del 2017. Durante la mia esperienza ho avuto la possibilità di raccogliere direttamente informazione sull’attività: dall’evoluzione del fatturato negli ultimi anni fino all’analisi del comportamento di acquisto della clientela. Questi dati sono stati utilizzati per elaborare alcune proposte concrete di marketing con l’obiettivo di migliorare il posizionamento di ICAS sul proprio mercato di riferimento.
13
Garnier, Edwige. "Territoire et migration : le rôle de la territorialisation dans la construction identitaire et culturelle d'un groupe social se vivant en exil : les Pieds-Noirs aujourd'hui." Université Joseph Fourier (Grenoble), 2005. http://www.theses.fr/2005GRE10194.
Повний текст джерелаАнотація:
Cette recherche doctorale est consacrée à la population française d'origine européenne et chrétienne, établie en Algérie puis rapatriée, appelée ici la population pied-noire. Ce groupe social revendique, le plus souvent, une culture et une identité particulières. Il se présente également comme déraciné. Le départ d'Afrique du nord est toujours considéré comme un exil par de nombreux membres de cette population, en dépit du fait qu'il s'agisse d'un rapatriement au sein de l'Etat-nation. Le rapatriement est ainsi intégré dans la construction identitaire de ce groupe. Il semble, de ce fait, que les particularismes identitaires et culturels de la population pied-noire aient été conservés, bien que modifiés, suite à sa migration. Qu'en est il de ses rapports à l'espace? Quels sont ses liens actuels avec son territoire perdu ? Ce groupe s'est-il, parallèlement, approprié certains espaces et lieux en métropole ou à l'étranger? Ces questionnements concernent donc à la fois la culture et l'identité du groupe mais aussi sa territorialisation et sa territorialité à l'heure actuelle. Il s'agit avant tout d'appréhender à quel point culture, identité et territoire interagissent et quel est l'impact d'une migration, de la mobilité de manière plus générale, sur ces interrelations. Une reterritorialisation semble être une nécessité pour la sauvegarde du groupe social, mais aussi pour une transmission culturelle et identitaire aux générations n'ayant pas ou peu connu l'Algérie coloniale. La forme prise par la recomposition territoriale pose tout de même question. La conception d'un territoire de forme aréolaire parait devoir être dépasséeThis doctoral research is devoted to the french population of european and christian origin, established in Algeria, then re-patriated, called here the pied-noir population. This social group asserts a particular culture and identity. It also presents itself as uprooted. The departure from north Africa is still experienced as an exile by many members of this population, despite the fact that it truly was a repatriation within the nation-state. Re-patriation is thus integrated, generally, in the identity construction of this group. It seems that identity and cultural particularisms of the pied-noir population were preserved, although modified, following its migration. What happened to its rela tionship to space ? What are its current bonds with its lost territory? ln parallel, did this group take possession of certain spaces and places in france or abroad ? These questions concern at the same time the culture and the identity of the group but also its territorialisation and its territoriality at the present time. It is a matter, firstly, of taking stock of the extent to which culture, identity and territory interact with each other, and of the impact of a migration, and of mobility (more generally), upon these interactions. A reterritorialisation seems to be a necessity for the safeguard of the social group and also for a transmission of culture and identity to the generations who knew little or not at all of colonial Algeria. The form taken by territorial recombining raises questions. The concept of a territory as a limited area appears to be exceeded
14
DEVI, GEETA. "SCOURING AROUND A GROUP OF PIERS." Thesis, 2023. http://dspace.dtu.ac.in:8080/jspui/handle/repository/19770.
Повний текст джерелаАнотація:
Scour is caused by the erosive action of flow of water, which erodes and takes away
sediments from the river bed, as well as from the area of bridge piers and abutments. This
process of scour is well-known for its complicated behaviour, and this process becomes
more complex for the group of piers. As per the literature available, scour is a major
contributor for the collapse of the bridge structures. Hence it becomes essential for the
researches to predict the scour depth accurately. To fulfill this necessity, the deep
understanding of the flow-field around the piers and factors affecting the scour depth is
important. Numerous studies are available in the literature on the flow-field and local scour,
but majority of them are focused only on single pier. However, multiple piers are more
common in the bridge designing due to economical and geotechnical considerations.
Engineers across the world are predominately considering single pier characterization for
the group of piers, although all bridge structures are laid on the group of piers. The design
considerations developed for a single pier mostly ignores the most significant group effects
for multiple piers such as: pier sheltering, pier spacing and mutual interference effect. It is
demonstrated by the fact that inadequate research and development for the multiple piers
have been observed. Therefore, it is utmost important to investigate the factors affecting
the multiple piers and develop an equation by considering all the variables for accurate
prediction of scour depth.
The primary aim of this research is to investigate the effect of the pier spacing (Ps) between
the piers and temporal scour development on scour depth and propose a new equation for
scour depth estimation. In order to meet the objectives of this research, detailed
experimental study has been conducted for, single pier, two piers, and three piers. In total,
232 experiments have been carried out for various pier spacing and pier arrangements on
uniformly graded sediment in the Hydraulic Engineering Laboratory of Delhi
Technological University, Delhi, India. Pier arrangements studied in this research are:
single pier, two piers in tandem arrangement, two piers in side-by-side arrangement, two
piers at an angle of 15 and 30 degrees to the direction of flow, three piers in tandem
arrangement, three piers in side-by-side arrangement and three piers in staggered
viii
arrangement. The instantaneous 3-D velocity measurement is conducted by utilizing
SonTek 16-MHz Micro-ADV (Acoustic Doppler Velocimeter) has been used. For
profoundly understanding and continuous monitoring of scour evolution SeaTek
Ultrasonic ranging system have been used.
The Experimental observations for the temporal scour evolutions and scour hole
development pattern for all the pier arrangements under various pier spacing has been
presented in the graphical and pictorial form. The findings of this research shed light on
the factors that causes scour: pier spacing, flow depth, Froude number, and scour
development pattern. These are all important variables, which needs to consider in order to
accurately predict the maximum scour depth. Results shows that, the flow-field around the
group of piers is much more complex than single pier and pier spacing plays a major role
in the scour depth estimation. The results also exemplify that non-dimensional scour depth
increases with the increase in the Froude number and velocity of flow. The effect of pier
spacing shows that the scour depth increases as the pier spacing increases at a certain Ps
range, then it decreases. Furthermore, two semi empirical equations has been proposed for
the tandem and side-by-side arrangements by using GEP, and the comparison of the
proposed GEP equation with the well-known equation and experimental results shows that
the GEP is better prediction tool for scour depth. Lastly, to evaluate the influence of various
parameters on the scour depth sensitivity analysis has been conducted, and concluded that
pier spacing plays an important role in scour estimation. The findings of this study can be
further used for the evaluation of the research data.
15
Zhang, Rong-Tai, and 張榮泰. "Shaking Table Study on Bridge Piers with a Scoured Pile-Group Foundation." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/898z4s.
Повний текст джерелаАнотація:
碩士國立臺灣科技大學
營建工程系
106
In this study, the impact of scouring on the seismic performance of bridge pier with pile-group foundation was investigated under multi-hazard circumstances. The model bridge pier with pile-group foundation comprised a lumped mass, a steel pier, and a footing supported by a aluminum group pile within dry soil. The shaking table test was carried out to study the dynamic response of the bridge pier with pile- group foundation model at different bare depths. Conducting dynamic system identification to the bridge pier with pile- group foundation model to realize dynamic characteristics. The test results show that the soil contribute most of the damping ratio. As the exposure depth deepens, the basic vibration period of the specimen is prolonged, but the system damping ratio didn’t change significantly. During the time history, the basic vibration period and damping ratio of the model would increase in the ground motion with high acceleration. When the ground motion is moderated, the basic vibration period and damping ratio of the model will decrease. As the exposure depth deepens, the maximum bending moment of the pile increases and the position distribution of the bending moment changes. The maximum bending moment of the bridge piers may decrease after exposure to a certain depth. Soil-structure interaction behavior is simulated by nonlinear soil spring (p-y curves) and establishes three different numerical models for simulation. The first way is the simulation of soil-structure interaction behavior using relevant domestic research formula, which is modeled by SAP2000. The second way is the simulation of soil-structure interaction behavior using API formula, which is modeled by SAP2000. The third way is the simulation of soil-structure interaction behavior using soil spring with elastic, plasticity and gapping behavior, which is modeled by OpenSees. The results show that simulation of soil-structure interaction behavior using API formula modeled by SAP2000 and simulation of soil-structure interaction behavior using soil spring with elastic, plasticity and gapping behavior modeled by OpenSees can effectively predict the behavior of the test model.
16
Lança, Rui Miguel Madeira. "Clear-water scour at single piers and pile groups." Doctoral thesis, 2013. http://hdl.handle.net/10400.6/3603.
Повний текст джерелаАнотація:
The major damage to bridges at river crossings occurs during floods. Damage is caused for various reasons, one of the main reasons being the riverbed scour at bridge foundations. Local scour is induced by the flow field generated around piers typically inserted in movable bed rivers. In Portugal, the tragic accident of Entre-os-Rios was mostly due to scour at one of the bridge piers.
Physical and economic reasons lead to bridge foundations composed of a pier column founded
on a pile cap, supported by an array of piles. Piers of this configuration are known as complex piers. Frequently the pile cap is completely buried, or in opposition, above the water, being the column or the pile group respectively the only structural element interacting with the flow and causing local scour. In modern bridges it is also common to find structural solutions where the deck is supported directly by pile groups composed of only one alignment, without pile cap. For scouring proposes the structural elements may be considered as single piers, pile groups and pier alignments.
The construction of new bridges and the maintenance of thousands of bridges built before the main developments in local scour prediction, amount to costs of billions of Euro and justifies a rigorous prediction of the scour depth, both for economic and safety of human lives reasons.
The present study develops an extensive research to systematically map equilibrium scour at single cylindrical piers and pile groups and relate the observations with the characteristic variables of the tests. Special attention is given to the effect of time, relative sediment size and relative approach flow depth at single cylindrical piers and spacing, skew-angle, number
of columns and time at pile groups. The pertinence of considering the effect of viscosity it is also assessed.
Using dimensional analysis, the following major conclusions are achieved. Regarding single cylindrical piers, it is discussed the required duration of the laboratory tests to render reliable equilibrium scour depths and it is confirmed that equilibrium scour depth decreases with the relative sediment size. It is suggested a predictor for the equilibrium scour depth at single cylindrical piers, function of relative sediment size and relative approach flow depth. The parameters of the equation suggested by Franzetti et al. (1982) are fully characterized rendering a predictor of the scour depth time evolution. Regarding pile groups and pier alignments, it is assessed the effect of the test duration on the equilibrium scour depth and it
is confirmed that the spacing factor and the factor for the number of aligned rows
recommended in the predictors commonly used in engineering practice are reliable since the scour depth at single cylindrical piers and pile groups remain essentially self-similar in time. The prediction of the equilibrium scour depth at pile groups is improved by the suggestion of a aggregate pile group factor, function of the pile spacing, skew-angle and number of parallel pile alignments. Finally it is revealed that the viscosity may affect scouring in laboratory tests.
17
Pieris, Martin. "The ˙43 Group and its Legacy in Sri Lanka." Thesis, 2022. http://hdl.handle.net/1959.13/1446929.
Повний текст джерелаАнотація:
Research Doctorate - Doctor of Philosophy (PhD)This research project examines the birth of ‘Ceylonese modernism’1 through the formation of the ˙43 Group in Sri Lanka in the period just before independence in 1943. Their contribution to art practice in the country’s post-independence and independent eras is explored and, parallel to this, the Group’s influence on the development of my own practice as a contemporary artist is posited.
18
yu, kuo wen, and 郭文郁. "Analysis of the response of group pile foundation pier under earthquake." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/89903824725759781924.
Повний текст джерелаАнотація:
碩士國立中央大學
土木工程研究所
86
There are many earthquake occurring in Taiwan.The effect of soil layer acting on structure should be considered in the dynamic response of bridge under earthquake.By the great advances of capacity of microcomputer,the analysis of soil-structure interaction(SSI) is accessible.When foundation was established on weak soil layer,the pile is required to transmit the loading to the rock base and the battered piles are used if larger lateral force was applied. Therefore,the response of battered pile of pier suffering earthquake is necessary to be studied. This paper adopts the three dimensional finite element to evaluate the response of group pile foundation of bridge pier consider SSI under earthquake by direct method in time domain.This paper used eight node linear element to simulate soil and beam element to simulate pile and pier.The Mohr-Coulomb failure criteria of elastoplastic material is applied to describe the stress strain behavior of soil. Three cases are discussed in this paper.First,evaluate the response of bridge pier with different spacing which varying from one to six time of pile spacing.Second,discuss the differences of dynamic responses of bridge pier with same length of piles planted in different depths of soil layers.Third,compare the dynamic responses of bridge pier with different angles of battered piles. From the results of analysis,corresponding to the increasing of pile spacing the maximum top and bottom displacements of pier and maximum acceleration decrease.The maximum bending moment and shear force in the bottom behave in the same manner.The maximum bending moment,maximum shear force,maximum acceleration,maximum displacement in the bottom of the pier decrease with the increasing angle of battered piles.In the contrast,the maximum displacement,maximum acceleration in the top of bridge pier decrease with the increasing angle of battered piles.
19
lu, Chi-lun, and 呂其倫. "Application of Ring Column Groups to Pier Scour Prevention." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/00031120032574790661.
Повний текст джерелаАнотація:
碩士逢甲大學
水利工程與資源保育研究所
99
Heavy rainfall frequently occurs in the summer in Taiwan due to the effects of the stationary fronts and typhoons. In recent years, the climatic anomalies tend to induce more extreme weather. For example, record-breaking heavy rainfall induced by Typhoon Morakot (2009) caused an unprecedented disaster in Taiwan. High flow caused scouring of the river bed around the piers, resulting in the exposure of the pier foundation and threatening the safety of bridge. To protect the bridge foundation, the use of Ring column groups as a pier scour countermeasure is reported. In this study, hydraulic model experiments with Ring column groups are carried out to search for the ideal arrangements to reduce the bridge scour. It can be served as a reference of design for relevant engineers in future. A series of experiment was conducted with uniform sediment under the clear-water steady flow conditions. Various parameters including relative distance, angle between the Ring column groups, angle of attack with flow of the Ring column groups, and distance between the Ring column groups and bridge pier are considered. Laboratory data are used to assess the influence of each parameter on reducing the kinetic energy of the flow. When the Ring column groups are installed, the scour depth decreases obviously, and both the downflow and horseshoe vortex are guided effectively downstream far away from the bridge pier structure. The Ring column groups can extend the range of protection due to the Ring columns special irregular and porous surface, not only increase the protective efficiency on the pier foundation but also reduces scour depth itself. The result shows that scour depth reduction of the pier could reach 55.8% of the original value, which is the best set type among the experimental conditions conducted in this study, when the Ring column groups settings at a distance of 6 times the pier diameter, 50 degrees for the angle between the Ring column groups, spacing of 2 times the pier diameter, and zero degree for the angle of attack with flow.
20
Ju, Hong-Yi, and 朱宏翊. "The protective effect of Porous Structure groups for pier scour." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/14044072027015120780.
Повний текст джерелаАнотація:
碩士國立成功大學
水利及海洋工程學系碩博士班
95
Because the establishment of the pier of the bridge makes the area of water cross-section reduce on the natural river, flow field change, and then change primitive sediment transport characteristic, therefore result in local scour phenomenon around the pier. When protective structure is set up upstream of pier will begin to effect pier scour. So this paper uses mainly the Porous Structure groups to reduce local scour around the pier. This paper research into the protective effect of Porous Structure groups for pier scour mainly, through experiment change Porous Structure groups set up distance, height, Porous Structure and Porous Structure set up interval, then change Porous Structure different arrangement the way and different Porous Structure set up the quantity in addition, perform for a series of discussions. (1) Scouring processes, (2) Bottom bed height around the pier, (3) Bottom bed height around the Porous Structure, (4) Pier the minimum and maximum scour depth position and (5) Protective effect. According to the results of experiment, the Porous Structure groups set up 5 times diameter of the pier from the pier and Porous Structure groups bottom is set up 0.15 times of depth of water from the sediment of the bottom bed above, Porous Structure groups can provide for protective effect of pier to attain to 85.88%, for Porous Structure set up the way best in the experimental condition range of this paper.
21
Jan, Yuan-Haur, and 詹元豪. "Local Scouring to Single Pile and Pile Groups of Bridge Pier." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/79241168101427856530.
Повний текст джерела
22
Hsu, Shu-Nu, and 徐淑女. "Experimental Study On Triangle Arrangement Of Porous Cylinder Groups for Pier Scour Countermeasures." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/32862052957856010725.
Повний текст джерела
23
Teng, Chueh-Ming, and 鄧爵明. "A study of piled pier and scoured groups of piles under statically lateral cyclic loading." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/ztbsws.
Повний текст джерелаАнотація:
碩士國立臺灣大學
土木工程學研究所
105
This study investigated the structure behavior and soil-structure interaction of single-column pier and the group piles model through lateral cyclic loading test. A large biaxial laminar sand box was used to set the model specimen and sand. The upper part of the structure is a single-column pier consisting of a 120 mm×120 mm×20 mm joint face connected with actuator, a solid steel pier with a diameter of 40 mm, 200 mm high and a 150 mm×150 mm×15 mm base plate made by steel. The lower structure is a group pile foundation specimen, consisting of 200 mm×200 mm×15 mm aluminum bottom adapter plate, 150 mm×150 mm×15 mm aluminum base plate with d25 mm×8.25 mm ×800 mm 2 × 2 group pile composition. The experiment divide into pure structure model and model of scouring. The pure structural model is fixed to the shear box and experiment with no sand. The scouring model also fixed the specimen in the shear box and the model with specified exposed length of pile foundation, as a ratio of pile diameter D, from 0D, 3D to 6D to explore the foundation of different depth of exposure. The sand property of dry fine silica sand is controlled by relative density of 50%. In the course of experiment, the lateral displacement of the different sizes is ±1 mm、±5 mm、±10 mm、±15 mm、±20 mm、±30 mm、±40 mm and ±50 mm. In the ±1 mm ~ ±20 mm for three cycles and ±30 mm ~ ±50 mm for two cycles. Among the experiment, the displacement, angel and strain response are recorded. Furthermore, the strain gauge can calculate the value of bending moment and axial force. The results of the experiment. Displacement: With the depth of the soil exposed, the displacement of the base plate is more obvious. Angle: the angle variation of the actuator elevation is different from that of the base plate, indicating that the pier is not a rigid body. Under the same displacement, as the depth of scouring increases, the rotation angle decreases. Strain: It can be observed that the position of the strain is large at the top and bottom of the pile. In the large strain area, the strain gauge is easy to slip, loose and even damage in the experiment process, so that the strain value of the large position is more prone to abnormal. Axial force: As the souring increase, the axial force of the pile will decrease. Moment: Pure structure, the maximum bending moment is generated at the base of the foundation. The maximum moment of the scouring model appears at the top of the foundation. Hysteresis loop: As the exposed depth increase, the force will decrease.
24
Therrien, Andréanne. "Efficacité d'un plan d'activation des intentions sur l'examen quotidien des pieds de personnes atteintes de diabète de type 2 inscrites dans un programme d'enseignement de diabète en groupe." Thèse, 2017. http://depot-e.uqtr.ca/8084/1/031624529.pdf.
Повний текст джерела