Spelling suggestions: "subject:"tensiones"" "subject:"tension""
51 |
Efficient design of post-tensioned concrete box-girder road bridges based on sustainable multi-objective criteriaGarcía Segura, Tatiana 03 November 2016 (has links)
[EN] Bridges, as an important component of infrastructure, are expected to meet all the requirements for a modern society. Traditionally, the primary aim in bridge design has been to achieve the lowest cost while guaranteeing the structural efficiency. However, concerns regarding building a more sustainable future have change the priorities of society. Ecological and durable structures are increasingly demanded. Under these premises, heuristic optimization methods provide an effective alternative to structural designs based on experience. The emergence of new materials, structural designs and sustainable criteria motivate the need to create a methodology for the automatic and accurate design of a real post-tensioned concrete bridge that considers all these aspects. For the first time, this thesis studies the efficient design of post-tensioned concrete box-girder road bridges from a sustainable point of view. This research integrates environmental, safety and durability criteria into the optimum design of the bridge. The methodology proposed provides multiple trade-off solutions that hardly increase the cost and achieve improved safety and durability. Likewise, this approach quantifies the sustainable criteria in economic terms, and evaluates the effect of these criteria on the best values of the variables.
In this context, a multi-objective optimization is formulated to provide multiple trade-off and high-performing solutions that balance economic, ecologic and societal goals. An optimization design program selects the best geometry, concrete type, reinforcement and post-tensioning steel that meet the objectives selected. A three-span continuous box-girder road bridge located in a coastal region is selected for a case study. This approach provides vital knowledge about this type of bridge in the sustainable context. The life-cycle perspective has been included through a lifetime performance evaluation that models the bridge deterioration process due to chloride-induced corrosion. The economic, environmental and societal impacts of maintenance actions required to extend the service life are examined. Therefore, the proposed goals for an efficient design have been switch from initial stage to life-cycle consideration.
Faced with the large computational time of multi-objective optimization and finite-element analysis, artificial neural networks (ANNs) are integrated in the proposed methodology. ANNs are trained to predict the structural response based on the design variables, without the need to analyze the bridge response. The multi-objective optimization problem results in a set of trade-off solutions characterized by the presence of conflicting objectives. The final selection of preferred solutions is simplified by a decision-making technique. A rational technique converts a verbal pairwise comparison between criteria with a degree of uncertainty into numerical values that guarantee the consistency of judgments. This thesis gives a guide for the sustainable design of concrete structures. The use of the proposed approach leads to designs with lower life-cycle cost and emissions compared to general design approaches. Both bridge safety and durability can be improved with a little cost increment by choosing the correct design variables. In addition, this methodology is applicable to any type of structure and material. / [ES] Los puentes, como parte importante de una infraestructura, se espera que reúnan todos los requisitos de una sociedad moderna. Tradicionalmente, el objetivo principal en el diseño de puentes ha sido lograr el menor coste mientras se garantiza la eficiencia estructural. Sin embargo, la preocupación por construir un futuro más sostenible ha provocado un cambio en las prioridades de la sociedad. Estructuras más ecológicas y duraderas son cada vez más demandadas. Bajo estas premisas, los métodos de optimización heurística proporcionan una alternativa eficaz a los diseños estructurales basados en la experiencia. La aparición de nuevos materiales, diseños estructurales y criterios sostenibles motivan la necesidad de crear una metodología para el diseño automático y preciso de un puente real de hormigón postesado que considere todos estos aspectos. Por primera vez, esta tesis estudia el diseño eficiente de puentes de hormigón postesado con sección en cajón desde un punto de vista sostenible. Esta investigación integra criterios ambientales, de seguridad estructural y durabilidad en el diseño óptimo del puente. La metodología propuesta proporciona múltiples soluciones que apenas encarecen el coste y mejoran la seguridad y durabilidad. Al mismo tiempo, se cuantifica el enfoque sostenible en términos económicos, y se evalúa el efecto que tienen dichos criterios en el valor óptimo de las variables.
En este contexto, se formula una optimización multiobjetivo que proporciona soluciones eficientes y de compromiso entre los criterios económicos, ecológicos y sociales. Un programa de optimización del diseño selecciona la mejor combinación de geometría, tipo de hormigón, armadura y postesado que cumpla con los objetivos seleccionados. Se ha escogido como caso de estudio un puente continuo en cajón de tres vanos situado en la costa. Este método proporciona un mayor conocimiento sobre esta tipología de puentes desde un punto de vista sostenible. Se ha estudiado el ciclo de vida a través de la evaluación del deterioro estructural del puente debido al ataque por cloruros. Se examina el impacto económico, ambiental y social que produce el mantenimiento necesario para extender la vida útil del puente. Por lo tanto, los objetivos propuestos para un diseño eficiente han sido trasladados desde la etapa inicial hasta la consideración del ciclo de vida.
Para solucionar el problema del elevado tiempo de cálculo debido a la optimización multiobjetivo y el análisis por elementos finitos, se han integrado redes neuronales en la metodología propuesta. Las redes neuronales son entrenadas para predecir la respuesta estructural a partir de las variables de diseño, sin la necesidad de analizar el puente. El problema de optimización multiobjetivo se traduce en un conjunto de soluciones de compromiso que representan objetivos contrapuestos. La selección final de las soluciones preferidas se simplifica mediante una técnica de toma de decisiones. Una técnica estructurada convierte los juicios basados en comparaciones por pares de elementos con un grado de incertidumbre en valores numéricos que garantizan la consistencia de dichos juicios. Esta tesis proporciona una guía que extiende y mejora las recomendaciones sobre el diseño de estructuras de hormigón dentro del contexto de desarrollo sostenible. El uso de la metodología propuesta lleva a diseños con menor coste y emisiones del ciclo de vida, comparado con diseños que siguen metodologías generales. Los resultados demuestran que mediante una correcta elección del valor de las variables se puede mejorar la seguridad y durabilidad del puente con un pequeño incremento del coste. Además, esta metodología es aplicable a cualquier tipo de estructura y material. / [CA] Els ponts, com a part important d'una infraestructura, s'espera que reunisquen tots els requisits d'una societat moderna. Tradicionalment, l'objectiu principal en el disseny de ponts ha sigut aconseguir el menor cost mentres es garantix l'eficiència estructural. No obstant això, la preocupació per construir un futur més sostenible ha provocat un canvi en les prioritats de la societat. Estructures més ecològiques i durables són cada vegada més demandades. Davall estes premisses, els mètodes d'optimització heurística proporcionen una alternativa eficaç als dissenys estructurals basats en l'experiència. L'aparició de nous materials, dissenys estructurals i criteris sostenibles motiven la necessitat de crear una metodologia per al disseny automàtic i precís d'un pont real de formigó posttesat que considere tots estos aspectos. Per primera vegada, esta tesi estudia el disseny eficient de ponts de formigó posttesat amb secció en calaix des d'un punt de vista sostenible. Esta investigació integra criteris ambientals, de seguretat estructural i durabilitat en el disseny òptim del pont. La metodologia proposada proporciona múltiples solucions que a penes encarixen el cost i milloren la seguretat i durabilitat. Al mateix temps, es quantifica l'enfocament sostenible en termes econòmics, i s'avalua l'efecte que tenen els dits criteris en el valor òptim de les variables.
En este context, es formula una optimització multiobjetivo que proporciona solucions eficients i de compromís entre els criteris econòmics, ecològics i socials. Un programa d'optimització del disseny selecciona la millor geometria, tipus de formigó, armadura i posttesat que complisquen amb els objectius seleccionats. S'ha triat com a cas d'estudi un pont continu en calaix de tres vans situat en la costa. Este mètode proporciona un major coneixement sobre esta tipologia de ponts des d'un punt de vista sostenible. S'ha estudiat el cicle de vida a través de l'avaluació del deteriorament estructural del pont a causa de l'atac per clorurs. S'examina l'impacte econòmic, ambiental i social que produïx el manteniment necessari per a estendre la vida útil del pont. Per tant, els objectius proposats per a un disseny eficient han sigut traslladats des de l'etapa inicial fins a la consideració del cicle de vida.
Per a solucionar el problema de l'elevat temps de càlcul degut a l'optimització multiobjetivo i l'anàlisi per elements finits, s'han integrat xarxes neuronals en la metodologia proposada. Les xarxes neuronals són entrenades per a predir la resposta estructural a partir de les variables de disseny, sense la necessitat d'analitzar el pont. El problema d'optimització multiobjetivo es traduïx en un conjunt de solucions de compromís que representen objectius contraposats. La selecció final de les solucions preferides se simplifica per mitjà d'una tècnica de presa de decisions. Una tècnica estructurada convertix els juís basats en comparacions per parells d'elements amb un grau d'incertesa en valors numèrics que garantixen la consistència dels dits juís. Esta tesi proporciona una guia que estén i millora les recomanacions sobre el disseny d'estructures de formigó dins del context de desenrotllament sostenible. L'ús de la metodologia proposada porta a dissenys amb menor cost i emissions del cicle de vida, comparat amb dissenys que seguixen metodologies generals. Els resultats demostren que per mitjà d'una correcta elecció del valor de les variables es pot millorar la seguretat i durabilitat del pont amb un xicotet increment del cost. A més, esta metodologia és aplicable a qualsevol tipus d'estructura i material. / García Segura, T. (2016). Efficient design of post-tensioned concrete box-girder road bridges based on sustainable multi-objective criteria [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/73147
|
52 |
DEVELOPMENT OF THE CENTRIFUGALLY TENSIONED METASTABLE FLUID DETECTOR FOR IN-AIR RADON AND ACTINIDE ALPHA DETECTIONMitchell Hemesath (8801069) 21 June 2022 (has links)
This thesis pertains to two R&D objectives associated with deploying TMFD sensor technology for meeting AARST-NRPP metrics for Radon (Rn) in-air detection, as well as for monitoring of ultra-trace actinides in air, amidst other Rn-progeny alpha emitting radionuclides. A challenge has persisted over the past 40+ years for detecting trace actinides in air amidst a 100-1000x higher Rn-progeny background. This thesis had a primary aim for addressing this challenge, and developing and assessing for a novel technology solution. Both objectives were successfully met. Methods, designs, and experimental effects of apparatus are discussed for successful Rn and progeny detection for 1-100 pCi/L concentration levels, as well as for Rn-progeny “blind” spectroscopic detection of 10-12 μCi/cc concentrations of actinides (Pu/U/Am) in air. The resulting CTMFD based technology was compared with the state-of-art “Alpha Sentry” CAM system and found to offer superior performance in multiple categories, and ~18x improvement in time to detect (e.g. at 0.02 DAC in 3 hrs vs ~70 hrs for state-of-art) for actinides while also remaining ~100% blind to ~102x higher Rn-progeny background; and, with 1 keV energy resolution vs ~300-400 keV for Alpha Sentry.
|
53 |
Controlled Damage Rocking Systems for Accelerated Bridge ConstructionWhite, Samuel Lewis January 2014 (has links)
Bridge substructures are generally constructed using cast-in-place concrete and designed to undergo inelastic deformation in earthquake events. Although this construction approach has proven to be economical and provides adequate seismic performance through the formation of ductile plastic hinges, there are downsides relating to construction speed and quality, and post-earthquake repairability.
This thesis explores two categories of Accelerated Bridge Construction (ABC) connection types, which use precast concrete instead of cast-in-place concrete to offer advantages including increased construction speed and quality. High Damage (HD) ABC connection types emulate the seismic behaviour of cast-in-place construction through the formation of ductile plastic hinges.
Controlled Damage (CD) ABC connection types use unbonded post-tensioned precast connections to offer additional advantages including reduced residual drifts, limited and controlled damage and simple repair options. Novel buckling-restrained, fused mild steel energy dissipators suitable for use in CD connections are also developed and tested. These designs utilise 'dry' fabrication to simplify the fabrication process and minimise cost.
Half-scale experimental testing is carried out to demonstrate both the assembly processes and behaviour under reversed cyclic uniaxial and biaxial loading representing an earthquake event. Following benchmark testing, repair strategies are applied to the CD connection types and the columns are tested again, representing a subsequent earthquake event. Good results are obtained from all cases with relatively straightforward construction and repair processes. With further developments and testing, the connection types proposed can provide competitive alternatives to conventional bridge pier design with regard to seismic performance and life cycle costs, with the additional benefits associated with precast construction.
|
54 |
Deformation Capacity and Moment Redistribution of Partially Prestressed Concrete BeamsRebentrost, Mark January 2004 (has links)
Ductility is a measure of the ability of a material, section, structural element or structural system to sustain deformations prior to collapse without substantial loss of resistance. The Australian design standard, AS 3600, imposes minimum ductility requirements on structural concrete members to try to prevent premature non-ductile failure and hence to ensure adequate strength and ductile-type collapse with large deflections. The requirements also enable members to resist imposed deformation due to differential settlement, time effects on the concrete and temperature effects, whilst ensuring sufficient carrying capacity and a safe design. Current AS 3600 requirements allow a limited increase or reduction in elastically determined bending moments in critical regions of indeterminate beams, accommodating their ability to redistribute moment from highly stressed regions to other parts of the beam. Design moment redistribution limits and ductility requirements in AS 3600 for bonded partially prestressed beams are a simple extension of the requirements for reinforced members. The possibility of premature non-ductile failure occurring by fracture of the reinforcement or prestressing steel in partially prestressed members has not adequately addressed. The aim of this research is to investigate the overload behaviour and deformation capacity of bonded post-tensioned beams. The current ductility requirements and design moment redistribution limits according to AS 3600 are tested to ensure designs are both safe and economical. A local flexural deformation model based on the discrete cracked block approach is developed to predict the deformation capacity of high moment regions. The model predicts behaviour from an initial uncracked state through progressive crack development into yielding and collapse. Local deformations are considered in the model using non-linear material laws and local slip behaviour between steel and concrete interfaces, with rigorous definition of compatibility in the compression and tension zones. The model overcomes limitations of past discrete cracked block models by ensuring compatibility of deformation, rather than strain compatibility. This improvement allows the modeling of members with multiple layers of tensile reinforcement and variable depth prestressing tendons having separate material and bond properties. An analysis method for simple and indeterminate reinforced and partially prestressed members was developed, based on the proposed deformation model. To account for the effect of shear in regions of high moment and shear present over the interior supports of a continuous beam, a modification to the treatment of local steel deformation in the flexural model, based on the truss analogy, was undertaken. Secondary reactions and moments due to prestress and continuity are also accounted for in the analysis. A comparison of past beam test data and predictions by the analysis shows the cracking pattern and deformation capacity at ultimate of flexural regions in reinforced and partially prestressed members to be predicted with high accuracy. The analysis method accurately predicts local steel behaviour over a cracked region and deformation capacity for a wide range of beams which fail either by fracture of steel or crushing of the concrete. A parametric study is used to investigate the influence of different parameters on the deformation capacity of a typical negative moment region in a continuous beam. The structural system consists of a bonded post-tensioned, partially prestressed band beam. The primary parameters investigated are the member height and span-to-depth ratio; relative quantity of reinforcing and prestressing steel; material properties and bond capacity of the steels; and lastly the compression zone properties. Results show that the effects of the various parameters on the overload behaviour of partially prestressed beams follow the same trends as reinforced beams. A new insight into the local steel behaviour between cracks is attained. The deformation behaviour displays different trends for parametric variations of the local bond capacity, bar diameter and crack spacing, when compared to past analytical predictions from comparable studies. The discrepancy in findings is traced back to the definition of the plastic rotation capacity and the sequencing of the yielding of the steels. Compared to the other local deformation models, the current model does not assume a linear distribution of strain at a crack. The current findings highlight an important difference between predicted behaviours from different deformation compatibility requirements in local deformation models which has not yet been discussed in the literature. The local deformation model evaluates the relationship between maximum steel strain at a crack and average steel deformation over a crack spacing for the entire loading history. The total steel percentage, hardening properties of the steel and concrete strength are shown by the model to have the greatest effect on these steel strain localisation factors. Section analysis, as currently used in design, can be improved with the proposed simplification of the relationships to identify and quantify the effects of steel fracture on deformation capacity and strength. The numerical effort required to simulate the overload behaviour of practical beam designs with multiple reinforcement elements and a prestressing tendon are currently too great to be used in an extensive numerical study. The numerically more efficient smeared block approach is shown to accurately predict the ultimate carrying capacity of prestressed beams failing by crushing of the concrete. Consequently, this method is adopted to study the allowable limits of moment redistribution in the present investigation, Simplified relationships of the steel strain localisation factors evaluated in the parametric study of deformation capacity is used to predict maximum steel strains and premature failure. The limits of moment redistribution in bonded, post-tensioned partially prestressed band beams are explored by comparing the design load and predicted carrying capacity, for different section ductilities and design moment redistribution. In addition, the effects of different concrete strengths, up to 85 MPa, along with as three reinforcing and prestressing steel ductilities are quantified and compared to current Australian and international design requirements. Limitations in the carrying capacity are investigated for different reinforcement and prestress uniform elongation capacities. More than one thousand beam simulations produce results showing that current design moment redistribution and ductility requirements in the Australian design code for concrete structures (AS 3600) are sufficient for normal strength concretes (less than 50 MPa). A suggestion for design moment redistribution limits, section ductility requirements and steel ductility limits is made for members constructed from higher strength concretes. A special high steel ductility class is proposed for both the reinforcement and prestressing steel to allow moment redistribution in higher strength concrete. No moment redistribution is proposed for members reinforced with low ductility (Class L) steel. An increase of the current elongation limit of Class L steel from 1.5 % to 2.5% is suggested to ensure strength and safety. An increase in the current ductility requirements from fsu/ fsy=1.03 and elongation equal to 1.5% to fsu/fsy=1.05 and 2.5% elongation for low ductility Class L steel is suggested to ensure strength and safety. / Thesis (Ph.D.)--Civil and Environmental Engineering, 2004.
|
55 |
Electrochemical characterization and time-variant structural reliability assessment of post-tensioned, segmental concrete bridgesPillai Gopalakrishnan, Radhakris 2009 May 1900 (has links)
In post-tensioned (PT) bridges, prestressing steel tendons are the major load carrying
components. These tendons consist of strands, ducts, and cementitious grout that fill the
interstitial space between the strands and ducts. However, inspections on PT bridges
have reported the presence of voids, moisture, and chlorides inside grouted ducts as the
major cause of accelerated corrosion of strands. Corrosion of the strands has resulted in
PT bridge failures in Europe and tendon failures in the United States. As most of the PT
bridges have high importance measures and the consequences of failure are significant, it
is important to maintain high levels of safety and serviceability for these bridges. To
meet this goal, bridge management authorities are in dire need of tools to quantify the
long-term performance of these bridges. Time-variant structural reliability models can
be useful tools to quantify the long-term performance of PT bridges.
This doctoral dissertation presents the following results obtained from a
comprehensive experimental and analytical program on the performance of PT bridges.
1) Electrochemical characteristics of PT systems
2) Probabilistic models for tension capacity of PT strands and wires
exposed to various void and environmental conditions
3) Time-variant structural reliability models (based on bending moment
and stress limit states) for PT bridges
4) Time-variant strength and service reliabilities of a typical PT bridge
experiencing HS20 and HL93 loading conditions and different
exposure conditions for a period of 75 years
The experimental program included exposure of strand specimens to wet-dry and
continuous-atmospheric conditions. These strand specimens were fabricated to mimic
void and/or grout-air-strand (GAS) conditions inside the tendons. It was found that the
GAS interface plays a major role in strand corrosion. The GAS interfaces that are
typically located in the anchorage zones of harped PT girders or vertical PT columns can
cause aggressive strand corrosion. At these locations, if voids are present and the
environment is relatively dry, then limited corrosion of the strands occurs. However, if
the presence of high relative humidity or uncontaminated and chloride-contaminated
water exists at these interfaces, then corrosion activity can be high. The strands were
exposed for a period of 12, 16, and 21 months, after which the remaining tension
capacity was determined.
The analytical program included the development of probabilistic strand capacity
models (based on the experimental data) and the structural reliability models. The timevariant
tension capacity predicted using the developed probabilistic models were
reasonably consistent with the tendon failures observed in PT bridges in Florida and
Virginia. The strength reliability model was developed based on the moment capacity
and demand at midspan. Service reliability model was developed based on the allowable
and applied stresses at midspan. Using these models, the time-variant strength and
service reliabilities of a typical PT bridge were determined based on a set of pre-defined
constant and random parameters representing void, material, exposure, prestress,
structural loading, and other conditions. The strength and service reliabilities of PT
bridges exposed to aggressive environmental conditions can drop below the
recommended values at relatively young ages. In addition, under similar conditions the
service reliability drops at a faster rate than the strength reliability.
|
56 |
Avaliação teórica, numérica e probabilística de fundações tracionadas. / Theoretical, numerical and probabilistic evaluation of shallow foundations under tensile loading.Danielle da Silva Arpino 21 December 2012 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A geotecnia constitui uma disciplina relativamente recente na área da engenharia civil, e dessa disciplina faz parte um capítulo ainda menos estudado que trata de fundações submetidas a esforços de tração. O presente trabalho deriva do conjunto de provas de cargas realizado para um importante projeto de linhas de transmissão que permitiu a aferição da teoria de capacidade de carga à tração da Universidade de Grenobel, cujos estudos comparativos mostram bons resultados para fins de aplicações práticas. De posse da extensa documentação técnica produzida e documentada por esse estudo foi possível comparar os resultados obtidos pelas provas de cargas e os resultados teóricos com os resultados das modelagens 2D axisimetricas por elementos finitos. Além dessas análises, foi possível verificar a variação da resistência à tração através de análises paramétricas realizadas a partir da variação da coesão e do ângulo de atrito. Os estudos apresentados reafirmam a confiabilidade das teorias da Universidade de Grenoble, que contemplam a simplicidade desejada às aplicações de cunho prático, com resultados satisfatórios em relação àqueles obtidos nos ensaios de tração. Por outro lado, as análises paramétricas realizadas indicaram a tendência de comportamento que a resistência à tração deve apresentar para diferentes parâmetros do solo. O conhecimento dessas tendências permite ao projetista avaliar os fatores de segurança sob ponto de vista probabilístico, ou seja, permite o emprego de fatores de segurança com o conhecimento da probabilidade de ruína associada. As análises probabilísticas foram traçadas a partir do emprego de funções genéricas de várias variáveis no formato FOSM (First Order Second Moment) que fornecem soluções aproximadas para o cálculo de desvio padrão quando não existe uma amostragem representativa. Ao término das análises, obteve-se como resultado, o mapa comparativo da probabilidade de ruína para os mesmos fatores de segurança empregados com base em resistências estimadas através de diferentes métodos de cálculos (Universidade de Grenoble e modelagem computacional). / Geotechnical engineering is a relatively recent area of civil engineering, which comprises the much less studied topic of foundations under tensile loads. Based on an extensive literature review this paper presents a set of foundation uplift tests carried out for an important transmission line project that allowed to compare the test results with the theory developed at the University of Grenoble, with fairly good results for practical purposes. The test results have also been compared to axisymmetric finite element analysis, also with satisfactory results. This study also presents parametric variations of the soil strength parameters to estimate the variation of the tensile foundation capacity based on sequentially increasing values of cohesion and friction angle. The parametric variation of the soil strength parameters was intended to provide the necessary insight to a complementary probabilistic analysis presented at the end of this dissertation. This work confirms the adequacy and simplicity of the theoretical framework developed at the University of Grenoble comparably to more refined techniques such as finite element analysis, providing a valuable tool for practical design applications. The probabilistic analysis was based on standard FOSM (First Order Second Moment ) approximation, providing estimates of the standard deviation of the tensile foundation capacities to better understand expected variations of the foundation uplift capacity in practical problems.
|
57 |
Avaliação teórica, numérica e probabilística de fundações tracionadas. / Theoretical, numerical and probabilistic evaluation of shallow foundations under tensile loading.Danielle da Silva Arpino 21 December 2012 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A geotecnia constitui uma disciplina relativamente recente na área da engenharia civil, e dessa disciplina faz parte um capítulo ainda menos estudado que trata de fundações submetidas a esforços de tração. O presente trabalho deriva do conjunto de provas de cargas realizado para um importante projeto de linhas de transmissão que permitiu a aferição da teoria de capacidade de carga à tração da Universidade de Grenobel, cujos estudos comparativos mostram bons resultados para fins de aplicações práticas. De posse da extensa documentação técnica produzida e documentada por esse estudo foi possível comparar os resultados obtidos pelas provas de cargas e os resultados teóricos com os resultados das modelagens 2D axisimetricas por elementos finitos. Além dessas análises, foi possível verificar a variação da resistência à tração através de análises paramétricas realizadas a partir da variação da coesão e do ângulo de atrito. Os estudos apresentados reafirmam a confiabilidade das teorias da Universidade de Grenoble, que contemplam a simplicidade desejada às aplicações de cunho prático, com resultados satisfatórios em relação àqueles obtidos nos ensaios de tração. Por outro lado, as análises paramétricas realizadas indicaram a tendência de comportamento que a resistência à tração deve apresentar para diferentes parâmetros do solo. O conhecimento dessas tendências permite ao projetista avaliar os fatores de segurança sob ponto de vista probabilístico, ou seja, permite o emprego de fatores de segurança com o conhecimento da probabilidade de ruína associada. As análises probabilísticas foram traçadas a partir do emprego de funções genéricas de várias variáveis no formato FOSM (First Order Second Moment) que fornecem soluções aproximadas para o cálculo de desvio padrão quando não existe uma amostragem representativa. Ao término das análises, obteve-se como resultado, o mapa comparativo da probabilidade de ruína para os mesmos fatores de segurança empregados com base em resistências estimadas através de diferentes métodos de cálculos (Universidade de Grenoble e modelagem computacional). / Geotechnical engineering is a relatively recent area of civil engineering, which comprises the much less studied topic of foundations under tensile loads. Based on an extensive literature review this paper presents a set of foundation uplift tests carried out for an important transmission line project that allowed to compare the test results with the theory developed at the University of Grenoble, with fairly good results for practical purposes. The test results have also been compared to axisymmetric finite element analysis, also with satisfactory results. This study also presents parametric variations of the soil strength parameters to estimate the variation of the tensile foundation capacity based on sequentially increasing values of cohesion and friction angle. The parametric variation of the soil strength parameters was intended to provide the necessary insight to a complementary probabilistic analysis presented at the end of this dissertation. This work confirms the adequacy and simplicity of the theoretical framework developed at the University of Grenoble comparably to more refined techniques such as finite element analysis, providing a valuable tool for practical design applications. The probabilistic analysis was based on standard FOSM (First Order Second Moment ) approximation, providing estimates of the standard deviation of the tensile foundation capacities to better understand expected variations of the foundation uplift capacity in practical problems.
|
58 |
Most na místní komunikaci / Bridge on a local roadNečasová, Pavla January 2016 (has links)
Graduation thesis deal with the design and assessment of the load-bearing structure of the bridge with four fields. The bridge carries local road Žernov-Přerov over the motorway D1. Thesis include design of three alternative solutions. For detailed treatment was chosen variant of single point supported deskbeam. Graduation thesis include static calculation, general and detailed drawings and visualization.
|
59 |
Most nad místní komunikací / Bridge over a local roadKováč, Daniel January 2017 (has links)
This master thesis is focused for design, respectively for creating counterproposal of existing structure of Motorway Bridge located at D1 motorway between Jánovce and Jablonov in district Levoča in Slovakia. This bridge is over a local road. The main aim of this thesis is design, analysis and assessment of bearing elements of bridge deck. For purposes of this thesis was created three variants of bridge deck. Detailed analysis was performed on bearing construction from post-tensioned precast beam with monolithing concrete slab. Two mathematic models were used for analysis of chosen variant. First model was spatial 3D shell construction. The purpose of this model was determinate cross spreading line of other constant load and live load. Second, flat 2D model, was for determination creep and shrinkage appeared from long-term load. These effects were observed in at advanced defined time nodes. Outcomes from upper mentioned model were used from design and assessment of bearing elements of bridge deck, design prestressed reinforcement cables and concrete reinforcement rods.
|
60 |
A comparative study of the seismic base shear force and story drift ratios using Time History and Modal Spectrum Analysis according to Peru Code E.030 and ASCE 7.16 on high-rise buildingsQuezada Ramos, Eder Nel, Serrano Arone, Yaneth, Huaco, Guillermo 30 September 2020 (has links)
El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / Since the last decade there is an important increase of high-rise buildings in Peru, especially in urban areas. Therefore, it is necessary to assess if the Peruvian Seismic Code is applicable for this type of buildings which have long natural periods as their main characteristic. The main objective of this article is to compare the results of the base shear and story drift ratios of Peruvian seismic design code E.030 with those of the ASCE 7-16 standard to the case of high-rise buildings, this due to the fact that there is limited information for tall buildings in Peru or comparison between national or international code for this type of structures. These high rise buildings have square and rectangular plan floors. Half of them have moment frames and reinforce concrete slab around the rigid core and the others have post-tensioned slab as their vertical load resisting system and central core walls with peripheral columns as the lateral force resisting system. Hence, the response spectrum analysis (RSA) is carried out for every case of the four tall buildings with different configurations using both seismic codes. Then results are compared with the linear response history analysis (LRHA) considering five Peruvian ground motions records, which were scaled to 0.45g PGA. It was verified that generally both the base shear and the interstory drifts calculated using ASCE7-16 are less than that obtained with the seismic code E.030.
|
Page generated in 0.0923 seconds