• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 24
  • 11
  • 4
  • 2
  • 1
  • 1
  • Tagged with
  • 53
  • 12
  • 9
  • 9
  • 9
  • 8
  • 8
  • 7
  • 7
  • 7
  • 7
  • 7
  • 6
  • 6
  • 6
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Children's Influence -Regarding Home Delivery Grocery Bags with Familyfood Optima AB in Focus.

Haglund, Josefin, Stenberg, Sophie January 2012 (has links)
Background Children are influencing the family’s decision making process regarding food products. The children’s spending power is increasing and they become consumers in an early age. By influencing the parents, the children make them buy products that they had not planned to buy or make the parents avoid products that they usually would have bought. Online food shopping is increasing in Sweden and the home delivery grocery bag is the category of online food that has increased the most from 2010 to 2011. Familyfood Optima AB is one of the home delivery grocery bags companies that deliver grocery bags in the south of Sweden. Purpose The purpose of this thesis is to find how children affect their parents’ behavior of purchasing home delivery grocery bags. Method To understand how children affect their parents in the decision of home delivery grocery bags a qualitative approach was used where twelve semi-structured interviews were held. Seven of the interviews were held with customers to Familyfood Optima AB. Four interviews were held with non-customers that had been customers to Familyfood Optima AB and one interview was held with a respondent that never had been a customer of a home delivery grocery bag company. Conclusion Children are influencing their parents in the decision to purchase home delivery grocery bags. They also influence the parents in the decision of whether or not to continue purchasing the home delivery grocery bag. The decision of purchasing a home delivery grocery bag depends on the children’s influence and the extent of the parent’s yielding. To influence their parents, the child use both direct and indirect influence techniques and three of the five bases of power. The children’s influence is also dependent on the child’s age and the influence from peers.
12

Integrity and Fracture Response of Offshore Pipelines Subject to Large Plastic Strains

Nourpanah, Nikzad 11 March 2011 (has links)
Steel pipelines are widely used in offshore oil/gas facilities. To achieve economically feasible designs, regulatory codes permit utilization of the pipelines well past their elastic response limit. This requires thorough integrity check of the pipeline subject to large scale yielding (LSY). Engineering criticality assessments (ECA) are used to justify the integrity of a cracked pipeline against fracture failure. The currently used ECA crack driving force equation was developed for load-controlled components subject to very limited crack-tip plasticity. Moreover, fracture toughness data are extracted from deeply-cracked laboratory specimens that produce the lowest margin of toughness values. Therefore, the current framework can be overly conservative (or include non-uniform inaccuracies) for ECA of modern pipelines that undergo LSY and ductile crack growth prior to failure. The two main goals of this thesis are: (i) Development of an alternative crack driving force estimation scheme, (ii) Justification of the use of use of shallow-cracked single edge notch tensile (SENT) specimens for the ECA. Strain concentration in concrete coated pipelines, and effect of Lüders plateau on the fracture response are also investigated. A new reference strain J-estimation scheme is proposed and calibrated to 300 nonlinear parametric FE models, which takes advantage of the linear evolution of the J with LSY bending strains. The scheme is hence strain-based and needless of limit load solutions, providing additional accuracy and robustness. The near-tip stress and strain fields of cracked pipelines were also investigated and compared to those obtained from a K-T type formulation. It is shown that the J-Q constraint theory can satisfactorily characterize these fields up to extreme plastic bending levels. Similar J-Q trajectories were also observed in the SENT and pipeline models. Subsequently, FE models utilizing a voided plasticity material were used to parametrically investigate ductile crack growth and subsequent failure of pipelines subject to a biaxial stress state. Plastic strain and stress triaxiality fields ahead of the propagating crack, along with R-curves, were compared among SENT and pipeline models. It is concluded that the SENT specimen could be a viable option for ECA of such pipes based on the observed crack tip constraint similarity.
13

Dynamique critique à la transition d'écoulement et comportements de fluage des systèmes amorphes : modélisation mésoscopique / Critical dynamics at the yielding transition and creep behavior of amorphous systems : mesoscopic modeling

Liu, Chen 10 November 2016 (has links)
Les systèmes amorphes "mous", loin de leur transition vitreuse, comprennent les verres colloïdaux de hautefraction volumique, les émulsions concentrées, les mousses, etc...L’échelle de temps pour leur relaxationmicroscopique est divergente, et ils ne se mettent en écoulement que lorsque la contraint appliquée estsuffisamment grande. Cette transition dynamique d’un état apparemment solide à un état apparemmentliquide, suivant la contrainte imposée, est appelé transition d’écoulement. Cette transition est étudiéedans cette thèse par l’intermédiaire d’une modélisation mésoscopique, basé sur un modèle d’élémentsélasto-plastiques en interaction.Après une brève introduction à la transition vitreuse et aux systèmes réels supposés être décrit parle modèle élast-plastique, une formulation du modèle différente de celle qui est habituellement présentéedans la littérature est introduite, pour à la fois incorporer les protocole à taux de cisaillement fixé et leprotocole à contraint fixée. A travers des approximations, un modèle mésoscopique de type champ-moyen(à l’origine décrit par Hébraud et Lequeux) est déduit à partir du modèle elasto-plastique qui contient lesinformations spatiales.En appliquant le protocole à taux de cisaillement fixé, le transition d’écoulement est dans un premiertemps étudiée à travers la dépendance de la statistique des avalanches (chutes de contrainte) en taux decisaillement. Une transition d’un comportement de champ moyen à un comportement corrélé est observéen variant le taux de cisaillement. Les lois d’échelle observées dans la limite des petits taux de cisaillementsupportent l’idée que la transition d’écoulement appartient à une certaine classe d’universalité de transitiondynamique. L’étude de la symétrie de la forme moyenne des chutes de contrainte en fonction de leur durée,de la taille de système et du taux de cisaillement appliqué, conduit à l’interprétation que les chutes decontrainte résultent d’une superposition d’avalanches individuelles possédant une longueur coopérative etun temps coopératif.En étudiant les fluctuations de contrainte macroscopique, la longueur coopérative l_c est identifiéepar un crossover en taille de système en-dessous de laquelle le loi d’échelle avec la taille de système1/L^d impliquée par la théorème de limite centrale, ne fonctionne plus. En complément, une échelle detemps de saturation T_c est trouvé dans le séries temporaire de taux de cisaillement plastique, tempsen-dessous duquel la dynamique de la contrainte peut être décrite par un mouvement Brownien. Le tempsde saturation, pour les systèmes de taille plus petit que l_c obéit à une loi d’échelle avec la taille de systèmeT_c~(l_c)^z. Cette dernière peut être interprétée comme la loi d’échelle entre la longueur coopérative et letemps coopératif des avalanches individuelles.En appliquant le protocole de contrainte imposée, la transition d’écoulement est étudiée en simulantdes expériences de fluage sur les systèmes amorphes. Les modèles mésoscopiques (le modèle elasto-plastiqueet le modèle champ moyen de Hébraud-Lequeux) sont capables de reproduire la réponse du taux decisaillement macroscopique pour une contrainte imposée légèrement au-dessus de la contrainte, et ceciqualitativement en accord avec les expériences. A travers cette étude, il apparaît que le condition initialeinfluence significativement le comportement de fluage des systèmes amorphes. / Amorphous systems deep blow the glass transition, as well as colloidal glasses at high packing fractions,concentrated emulsions, foam systems, etc. exhibit divergent microscopic relaxation time scales and flowonly upon a large enough external loading. This dynamical phase transition of amorphous systems fromthe apparent solid state to the apparent liquid state mediated by the external loading, is called theyielding transition. This transition is studied throughout this thesis by a mesoscopic modeling approach,specifically versions of the so-called elasto-plastic model.After introducing a general background of the glass transition and experimental systems, that are thetarget of the elasto-plastic model description, a formulation of the elasto-plastic model, slightly differentfrom the conventional ones used in the literature, is introduced for incorporating both the shear ratecontrol and the stress control protocols. It is also shown that the mean-field Hebraud-Lequeux model canbe derived from the spatially resolved elasto-plastic model by assuming some approximations.Using the shear rate control protocol, the yielding transition is firstly probed by studying the shearrate dependence of the avalanche statistics close to criticality. A crossover from a non mean-field behaviorto an apparent mean-field behavior with respect to an increasing shear rate is evidenced. Scaling laws in thezero shear rate limit, support the idea that the yielding transition belongs to a non mean-field universalityclass of a dynamical phase transition. The dependence of the symmetry of the average shape of the stressdrops on the stress drop duration, the system size and the shear rate, leads to the interpretation that stressdrops at finite shear rates result from the superposition of individual avalanches possessing a cooperativelength and time scale.By studying the macroscopic stress fluctuation, the cooperative length scale l_c is identified as thecrossover size below which the scaling relation with the system size 1/L^d implied by the central limittheorem breaks down. Further a saturation time scale T_c can be defined in the analysis of the timeseries of macroscopic plastic strain rate. Below this time scale one observes the manifestation of Browniandynamics. The saturation time for systems of sizes smaller than the cooperative length l_c scales withthe system size as a power law T_c~(l_c)^z, which can be interpreted as the scaling relation between thecooperative time and the cooperative length of individual avalanches.Further using the stress controlled protocol, the yielding transition is studied by simulating typical creep experiments of the amorphous systems. The mesoscopic models (the elasto-plastic model aswell as the mean-field Hébraud-Lequeux model) are shown to be capable to reproduce the response ofthe macroscopic shear rate to an imposed stress slightly above the yielding point in qualitatively goodagreement with several experiments. Within the mesoscopic modeling approach, the results reveal thatthe creep behavior depends strongly on the initial condition of the amorphous system submitted to creepexperiments.
14

Comportamento mecânico de um solo cimentado curado sob tensão em ensaios triaxiais / Mechanical behaviour of a cemented soil cured under stress in triaxial tests

Dalla Rosa, Francisco January 2006 (has links)
O comportamento de solos estruturados por cimentação é fortemente influenciado pelo estado de tensões existente durante a deposição do agente cimentante. Procedimentos rotineiros de extração e preparação de amostras em laboratório geralmente causam danos à estrutura natural do material, impedindo, muitas vezes a observação do comportamento real do ponto de vista de rigidez e de deformabilidade. A simulação, em laboratório, das condições de confinamento durante a formação da estrutura cimentante, torna-se uma condição necessária para o estudo do comportamento desses materiais. Seguindo essa linha, o trabalho busca avaliar a influência da tensão de confinamento (tensão de cura) existente durante a formação da cimentação no comportamento deste material, a partir de ensaios triaxiais drenados consolidados isotropicamente. Assim, neste estudo propõe-se a utilização de um solo artificialmente curado sob tensão, observando em conjunto a essa variável a influência do nível de cimentação bem como os efeitos oriundos da tensão confinantes utilizada na fase de cisalhamento. Procurou-se avaliar características de deformabilidade e resistência, através de uma análise do comportamento dos materiais. A avaliação das superfícies de plastificação foi realizada a partir da análise de pequenas deformações do solo cimentado. A análise tensãodilatância se desenvolveu com base no exame do comportamento do material a deformações relativamente grandes. Os resultados mostraram, no geral, que o comportamento do material cimentado foi fortemente influenciado pela variação da tensão de cura, tanto a pequenas bem como a deformações relativamente grandes. / The behavior of cemented structured soils is strongly influenced by the existing stress state during the addition of the cementation agent. The common procedures for laboratory sampling usually cause damage to the natural structure of the materials, hindering, many times, the identification of the real behavior in regard to deformability and stiffness properties. The simulation, in laboratory environment, of confining conditions during the cement structure formation turns to be a mandatory circumstance for the study of the material’s behavior. Inside this context, this work aims to evaluate the influence of the existing confining stress (stress cure) during the cement formation in the behavior of the material, through isotropic drained triaxial tests. Thus, it suggested in this study the usage of artificially cemented soil cured under stress, with parallel observation of the influence of the cement degree, as well the effects from the confining stress used during the shearing stage. It was also evaluated deformability and strength characteristics through behavior analyses of the materials. An assessment of the yield surfaces was carried on from soil cemented small deformation analysis. The evaluation of stress-dilatancy was developed based on the exam of relatively large deformation behavior. The results showed that the general behavior of this material was strongly influenced by the variation of the stress curing both at small strains and at relatively large strains.
15

Comportamento mecânico de um solo cimentado curado sob tensão em ensaios triaxiais / Mechanical behaviour of a cemented soil cured under stress in triaxial tests

Dalla Rosa, Francisco January 2006 (has links)
O comportamento de solos estruturados por cimentação é fortemente influenciado pelo estado de tensões existente durante a deposição do agente cimentante. Procedimentos rotineiros de extração e preparação de amostras em laboratório geralmente causam danos à estrutura natural do material, impedindo, muitas vezes a observação do comportamento real do ponto de vista de rigidez e de deformabilidade. A simulação, em laboratório, das condições de confinamento durante a formação da estrutura cimentante, torna-se uma condição necessária para o estudo do comportamento desses materiais. Seguindo essa linha, o trabalho busca avaliar a influência da tensão de confinamento (tensão de cura) existente durante a formação da cimentação no comportamento deste material, a partir de ensaios triaxiais drenados consolidados isotropicamente. Assim, neste estudo propõe-se a utilização de um solo artificialmente curado sob tensão, observando em conjunto a essa variável a influência do nível de cimentação bem como os efeitos oriundos da tensão confinantes utilizada na fase de cisalhamento. Procurou-se avaliar características de deformabilidade e resistência, através de uma análise do comportamento dos materiais. A avaliação das superfícies de plastificação foi realizada a partir da análise de pequenas deformações do solo cimentado. A análise tensãodilatância se desenvolveu com base no exame do comportamento do material a deformações relativamente grandes. Os resultados mostraram, no geral, que o comportamento do material cimentado foi fortemente influenciado pela variação da tensão de cura, tanto a pequenas bem como a deformações relativamente grandes. / The behavior of cemented structured soils is strongly influenced by the existing stress state during the addition of the cementation agent. The common procedures for laboratory sampling usually cause damage to the natural structure of the materials, hindering, many times, the identification of the real behavior in regard to deformability and stiffness properties. The simulation, in laboratory environment, of confining conditions during the cement structure formation turns to be a mandatory circumstance for the study of the material’s behavior. Inside this context, this work aims to evaluate the influence of the existing confining stress (stress cure) during the cement formation in the behavior of the material, through isotropic drained triaxial tests. Thus, it suggested in this study the usage of artificially cemented soil cured under stress, with parallel observation of the influence of the cement degree, as well the effects from the confining stress used during the shearing stage. It was also evaluated deformability and strength characteristics through behavior analyses of the materials. An assessment of the yield surfaces was carried on from soil cemented small deformation analysis. The evaluation of stress-dilatancy was developed based on the exam of relatively large deformation behavior. The results showed that the general behavior of this material was strongly influenced by the variation of the stress curing both at small strains and at relatively large strains.
16

Comportamento mecânico de um solo cimentado curado sob tensão em ensaios triaxiais / Mechanical behaviour of a cemented soil cured under stress in triaxial tests

Dalla Rosa, Francisco January 2006 (has links)
O comportamento de solos estruturados por cimentação é fortemente influenciado pelo estado de tensões existente durante a deposição do agente cimentante. Procedimentos rotineiros de extração e preparação de amostras em laboratório geralmente causam danos à estrutura natural do material, impedindo, muitas vezes a observação do comportamento real do ponto de vista de rigidez e de deformabilidade. A simulação, em laboratório, das condições de confinamento durante a formação da estrutura cimentante, torna-se uma condição necessária para o estudo do comportamento desses materiais. Seguindo essa linha, o trabalho busca avaliar a influência da tensão de confinamento (tensão de cura) existente durante a formação da cimentação no comportamento deste material, a partir de ensaios triaxiais drenados consolidados isotropicamente. Assim, neste estudo propõe-se a utilização de um solo artificialmente curado sob tensão, observando em conjunto a essa variável a influência do nível de cimentação bem como os efeitos oriundos da tensão confinantes utilizada na fase de cisalhamento. Procurou-se avaliar características de deformabilidade e resistência, através de uma análise do comportamento dos materiais. A avaliação das superfícies de plastificação foi realizada a partir da análise de pequenas deformações do solo cimentado. A análise tensãodilatância se desenvolveu com base no exame do comportamento do material a deformações relativamente grandes. Os resultados mostraram, no geral, que o comportamento do material cimentado foi fortemente influenciado pela variação da tensão de cura, tanto a pequenas bem como a deformações relativamente grandes. / The behavior of cemented structured soils is strongly influenced by the existing stress state during the addition of the cementation agent. The common procedures for laboratory sampling usually cause damage to the natural structure of the materials, hindering, many times, the identification of the real behavior in regard to deformability and stiffness properties. The simulation, in laboratory environment, of confining conditions during the cement structure formation turns to be a mandatory circumstance for the study of the material’s behavior. Inside this context, this work aims to evaluate the influence of the existing confining stress (stress cure) during the cement formation in the behavior of the material, through isotropic drained triaxial tests. Thus, it suggested in this study the usage of artificially cemented soil cured under stress, with parallel observation of the influence of the cement degree, as well the effects from the confining stress used during the shearing stage. It was also evaluated deformability and strength characteristics through behavior analyses of the materials. An assessment of the yield surfaces was carried on from soil cemented small deformation analysis. The evaluation of stress-dilatancy was developed based on the exam of relatively large deformation behavior. The results showed that the general behavior of this material was strongly influenced by the variation of the stress curing both at small strains and at relatively large strains.
17

On the Seismic Design of Structures with Tilting Located within a Seismic Region

Valenzuela-Beltrán, Federico, Ruiz, Sonia, Reyes-Salazar, Alfredo, Gaxiola-Camacho, J. 07 November 2017 (has links)
A reliability-based criterion to estimate strength amplification factors for buildings with asymmetric yielding located within a seismic region presenting different soil conditions is proposed and applied. The approach involves the calculation of the mean annual rate of exceedance of structural demands of systems with different levels of asymmetric yielding. Two simplified mathematical expressions are developed considering different soil conditions of the valley of Mexico. The mathematical expressions depend on the ductility of the structural systems, their level of asymmetric yielding, their fundamental vibration period and the dominant period of the soil. In addition, the proposed expressions are compared with that recommended by the current Mexico City Building Code (MCBC). Since the expressions are developed with the help of simplified structural systems, the validity of such expressions is corroborated by comparing the expected ductility demand of multi-degree of freedom (MDOF) structural systems with respect to that of their equivalent simplified systems. Both structural representations are associated with a given annual rate of exceedance value of an engineering demand parameter. The expressions proposed in this study will be incorporated in the new version of the MCBC.
18

Computational Code for Optimization of Thermal Treatment of Fine Grained Soils as a Method of Expediting their Load Induced Consolidation

Abeysiridara Samarakoon, Radhavi 29 June 2016 (has links)
Construction in soft soils has been a challenging task for engineers due to the excessive time taken for dissipation of construction induced pore water pressure and the ensuing postconstruction settlement. Use of vertical drains has proven to be an effective and economical method for soft ground improvement and hence extensive research has been carried out to further improve its efficiency. Effect of temperature on radial consolidation is one aspect of such research among many others that have been pursued. Elevated temperature certainly has a pronounced effect on the hydraulic conductivity due to the reduction it causes in the viscosity of water. Furthermore, temperature also generates excess pore water pressure due to the tendency for differential volumetric expansion between the soil grains and pore water. Thermally induced volumetric strains can have an effect on the magnitude of settlement as well. A numerical methodology based on the NavierStokes equations of flow and thermoelasto-plastic soil compressibility relationships was developed to model transient fluid flow in a clay under thermal treatment. Experimentally verified soil compressibility relationships coupling the loading and thermal effects obtained from literature were employed in this model. The transient temperature distribution within the consolidation soil was modeled using the Fourier’s equation of heat transfer. The effect of temperature on consolidation of clay was investigated by a parametric study involving different maximum temperatures, surcharge loads and initial porosities of clay. It was concluded that the improvement in the magnitude and rate of settlement at elevated temperature is more significant at relatively smaller surcharges and low initial porosities. Since there is a possibility for thermally induced volumetric expansion even in normally consolidated clays, an optimum combination of surcharge and thermal treatment should be employed for given initial conditions of the soil, in order to achieve the maximum improvement in settlement. The developed numerical model will provide the framework to carry out further investigations and determine the viability of the practical implementation of coupled thermomechanical consolidation using prefabricated vertical drains.
19

Experimental and numerical investigation of panel zone behavior and yielding mode classification for steel beam-column joints / 鋼構造柱梁接合部におけるパネルの挙動と降伏モードの分類に関する実験的・解析的研究

Wang, Yandong 23 March 2020 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22431号 / 工博第4692号 / 新制||工||1732(附属図書館) / 京都大学大学院工学研究科建築学専攻 / (主査)教授 大崎 純, 教授 西山 峰広, 准教授 聲高 裕治 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM
20

Experimental Evaluation of Replaceable Shear Fuse Moment Connections

Oh, Shannon Shun 01 December 2018 (has links)
Steel special moment frames (SMFs) are known to be highly ductile seismic force- resisting systems. The performance of an SMF relies on the ability of the connections to accommodate large inelastic deformations. After the brittle failure of some steel moment frame connections during the 1994 Northridge Earthquake, experimental tests were used to investigate the ductility and strength of these connections. An experimental study was performed to investigate the seismic performance a new connection called the Replaceable Shear Fuse (RSF) connection. The RSF connection uses shear-yielding fuse plates to prevent beam and column yielding. A total of 7 test specimens with varying fuse plate sizes and configurations, a W14×48 column, and a W14×38 beam were created. The connections were loaded laterally and cyclically at increasing displacements until the connection failed. The results show that RSF connections have the capability to prevent beam and column damage by focusing inelastic rotations to shear fuse yielding and bolt slip. Specimens with 14 in. deep beams achieved rotations ranging from 0.06 to 0.10 rad without excessive degradation and local buckling. Stable yielding was also achieved for all test specimens. Hysteretic responses for Specimens A1.3 and A1.4 were similar to typical responses from welded moment connections. The behavior of Specimen A1.16 was similar to that of a bolted flange plate connection, whereas the other remaining specimens had responses that were a combination of welded moment and bolted flange plate connections. Peak responses from tests indicated that inelastic rotations were accommodated by both fuse plate yielding and bolt slip. The first observation of major bolt slip occurred in the fuse plates as early as the 0.05 rad drift cycle. The early occurrence of bolt slip allowed for a higher rotational capacity. While the top and bottom fuse plates were replaced for each test, no repairs were needed for the beam and column. The RSF connection proved to be a more resilient alternative SMF connection.

Page generated in 0.3454 seconds