Doctorado en Ingeniería - Civil
URI permanente para esta colecciónhttps://repositorio.unal.edu.co/handle/unal/81867
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Ítem Conectores de cortante para secciones compuestas de concreto y perfiles de acero formados en frío(Universidad Nacional de Colombia, 2024-09-25) Hurtado Amézquita, Xavier Fernando; Molina Herrera, Maritzabel; Hurtado Amézquita, Xavier Fernando [https://scienti.minciencias.gov.co/cvlac/EnRecursoHumano/inicio.do]; Hurtado Amézquita, Xavier Fernando [https://scholar.google.es/citations?user=OgNZJaEAAAAJ&hl=es]; Hurtado Amézquita, Xavier Fernando [0000-0002-2950-6019]; Análisis, Diseño y Materiales GiesDesde finales de los años 50’s, hay evidencia del uso de secciones compuestas en edificaciones, siendo Suiza el país pionero en aplicar esta alternativa constructiva. Dadas las ventajas de combinar los perfiles metálicos y elementos de concreto eficientemente, su implementación se difundió rápidamente en Europa y los Estados Unidos, siendo las principales potencias industriales de producción de acero. El adecuado desempeño de los sistemas compuestos depende, en parte, del mecanismo de transferencia de esfuerzos en la interfaz de los componentes, principalmente atribuido a los conectores de cortante. De acuerdo con la normatividad vigente, los únicos dispositivos avalados para tal fin son los espigos, canales, tornillos y placas perforadas, empleando fijación soldada en perfilería laminada en caliente (HRS), sin que esta sea una opción eficiente para perfiles de lámina delgada (CFS), dado que la aplicación de la soldadura puede afectar el perfil con quemaduras y/o perforaciones, reduciendo su capacidad estructural. Aun así, a la fecha, no existe ninguna referencia dentro de las normativas, que especifique el uso de un tipo de conector de cortante en secciones compuestas donde se incluyan perfiles CFS. Los perfiles CFS, provenientes de un proceso de doblado de láminas en frío, potencian la eficiencia de sistemas compuestos debido a su relación resistencia Vs. peso, facilidad de transporte e instalación, considerándose una alternativa sostenible en la construcción. En esta investigación se proponen los conectores de cortante tipo CSC (Confined Shear Connectors), para la adecuada transferencia de esfuerzos en sistemas de entrepiso compuestos, empleando losas de concreto y perfiles en lámina delgada CFS. La configuración del conector CSC propuesta, es el resultado de un análisis de optimización geométrica, basada en el comportamiento mecánico de la sección compuesta, así como la facilidad tanto en la fabricación e instalación del conector como en la construcción del sistema compuesto. El comportamiento del sistema con perfiles CFS y conectores tipo CSC, fue caracterizado a través de los ensayos experimentales alternativos de corte directo (Pry-Out), y ensayos de vigas a flexión, donde se tuvieron como principales variables de estudio la resistencia del concreto, altura de la losa, espesores de los perfiles metálicos y espaciamiento entre conectores. Paralelamente, el comportamiento no lineal del sistema compuesto fue evaluado analíticamente por medio de simulaciones numéricas de los ensayos realizados por el método de elementos finitos (MEF), con las cuales se logró obtener información complementaria del comportamiento de los elementos componentes del sistema, y sus mecanismos de falla. Por último, por medio de análisis estadístico, se plantean las formulaciones de diseño que permiten estimar tanto la resistencia nominal de los conectores de cortante tipo CSC, como el grado de acción compuesta del sistema, condiciones a ser tenidas en cuenta en ámbitos normativos para el diseño entrepisos en sección compuesta por losas de concreto y perfilería CFS. (Texto tomado de la fuente).Ítem Modelo esfuerzo deformación de laminados de bambú-guadua confinados con maderas blandas(Universidad Nacional de Colombia, 2022-11-16) Cruz Guzmán, Alfonso; Takeuchi Tam, Caori Patricia; Cruz Guzman, Alfonso; Cruz Guzmán, Alfonso; Cruz Guzmán, Alfonso; Cruz Guzmán, Alfonso; Análisis, diseño y materiales - GIES; Cruz Guzmán, AlfonsoEl modelo propuesto permite inferir el comportamiento de Laminados de Bambú Guadua Confinados (LBGC) por maderas blandas. El confinamiento es un recurso eficaz para mejorar la rigidez y resistencia de un material, en este caso del bambú laminado. Los materiales empleados para la caracterización fueron Bambú Guadua angustifolia Kunth y pino radiata. Se realizaron 576 ensayos de laboratorio divididos en 4 conjuntos de 144 probetas de cortante, compresión paralela, compresión perpendicular y flexión. Los materiales ensayados fueron madera, bambú laminado y material compuesto de bambú confinado al 20%, 40%, 60% y 80%. El modelo fue validado con probetas adicionales compuestas con pino radiata y pino caribe. Se demostró experimentalmente que hay un incremento en la rigidez del bambú laminado confinado por maderas blandas en la dirección paralela a la fibra. Se propone un modelo estadístico con base en las características individuales y los porcentajes de los materiales (bambú lamiando y madera). Se incluyen análisis numéricos por el método de elementos finitos para contrastar los resultados experimentales. La configuración óptima de material compuesto es de 46%-54% (bambú-madera). El material compuesto presentó una mejora de módulo de elasticidad a flexión (MOE) de 16.6% y una mejora de esfuerzo de rotura por flexión (MOR) de 18.32%. El módulo elástico a compresión paralelo a la fibra presentó una mejora de 10.4%. En elementos solicitados a flexión, el material compuesto presentó una menor deformación por cortante.Ítem A modeling framework for hyporheic flow within hydrodynamics scale(Universidad Nacional de Colombia, 2021) Preziosi Ribero, Antonio; Donado, Leonardo David; Escobar Vargas, Jorge; HYDS Hydrodynamics of the Natural Media Research GroupIn tropical countries, like Colombia and in other parts of the world, free surface streams play a key role either as freshwater supply for human settlements, or as wastewater receivers from households and industrial compounds. Population growth, internal migration of people towards cities and the effects of climate change make that pressure on aquatic ecosystems become a topic of interest for science and public administration. Therefore, understanding different water bodies, their interaction and their integral modelling process are a research topic of great interest in earth sciences and engineering. In fact, in the last 30 years, academia has studied the interaction between free surface streams and aquifers beneath them, focusing on the effects of these type of flows. This milestone marked the beginning of the studies of Hyporheic Flow (HF) and Hyporheic Zone (HZ). Hyporheic Zone (HZ) is defined as "a subsurface flowpath along which water 'recently' from the stream will mix with subsurface water to 'soon' return to the stream''. This place has a great relevance in ecologic, biologic and chemical processes such as contaminant attenuation, nutrient, sediment and heat transport for biota growth, nitrification processes in water bodies and river restoration. These phenomena are closely related with chemical water quality and are modeled usually with conservative and reactive transport equations. Nevertheless, species transport in HZ depends on water flow and the patterns it follows. The flow within the HZ is known as Hyporheic Flow (HF) and its main feature is the wide range of scales in which it acts. Hence, within HZ there is flow from the pore scale and it is controlled by pressure gradients, to the scale of flows controlled by the stream morphology. This wide variety of scales, along with media heterogeneity make the study of processes within the HZ a challenge for the scientific community. Moreover, in countries like Colombia, streams play a key role in society since they are the main freshwater supply and also receive the water disposal. The main goal of this research project is to formulate a methodological frame for HZ modelling from the continuous media perspective. To that end, this work presents the study of HF, starting from different numerical models, proposing simplifications that can portray HF. In the same way, the use of numerical models allows the decomposition of the physical phenomena to characterize their individual contribution to the HF. The models' results are compared with experimental results to validate their practical usefulness and propose their use in different case studies related with biological, chemical and ecological processes. To accomplish the main goal, this document presents three different approaches to HF driven by hydrodynamics, using different numerical tools. These approaches are based in continuum media mechanics, despite using different numerical schemes; each one of the presents pros and cons, but above all, each one of them gives key information about Hyporheic Flow that, in the near future, can be upscaled and used for decision making regarding hydraulic resources. The first numerical model proposed uses Burgers' Equation (BE) to represent HF in a bed with cubical packed spheres. The main goal is to study turbulent velocity decay within uniform media to characterize HF through a simple expression as the BE taking into account the interaction between non linear effects and energy dissipation, characteristic within multiscale flows. For the computational model a Spectral Multidomain Penalty method (SMPM) to avoid numerical errors associated with traditional numerical schemes as finite differences, elements or volumes. The BE model is presented as a first approach of HF in a lab scale. In second place, the use of the Navier-Stokes Equations (NSE) to represent the combination of free surface flow and a sand bed. Again, the main goal is to determine a mean velocity profile representing the transition between free surface flow in a flume and a regular bed. To achieve this goal the Finite Volume Method was used along with an open source code that was modified to include different viscosity values and source/sink terms that are able to capture the velocity decay. The results of flow are compared with different numerical and experimental models. This analysis includes also a conservative transport model that was also compared with experimental results. For the final approach, a numerical particle-tracking model is proposed to assess their influence of HF in fine sediment deposition in river beds. The main goal of this part is to evaluate the process of deposition taking into account different flow scenarios within the HZ. Besides flow in porous media, this model includes particle filtration within the bed to retain particles and show places where deposition is more prone to occur. The results, once again, are compared with flume experiments of kaolinite deposition in a recirculating flume. To wrap up, the three models presented in this work offer a novel vision on Hyporheic Flow within scales driven by hydrodynamical effects. Mainly, the free flow conditions driving flow in porous media and high Reynolds number flows presence within porous media determine hydrodynamics and processes associated with it, such as fine sediment deposition.Ítem Reliability assessment of rock slopes by evidence theory(2020-08-20) Hernández-Carrillo, Rodrigo; Beltrán, Gloria Inés; GRUPO DE INVESTIGACIÓN EN GEOTECNIA - GIGUNEl objetivo de este proyecto de investigación es desarrollar una metodología para efectuar análisis de confiabilidad de la estabilidad de taludes rocosos, teniendo en cuenta la incertidumbre cuando la información sobre los parámetros geomecánicos de entrada es limitada. En mecánica de rocas, los métodos determinísticos y probabilísticos son ampliamente utilizados en el proceso de toma decisiones. No obstante, el primero no considera la incertidumbre y el segundo tiene limitaciones para representar la incertidumbre epistémica y tiene que asumir la distribución de probabilidad de las variables de entrada. Por lo tanto, se recurre a la Teoría de la Evidencia como una herramienta para describir la incertidumbre aleatoria y epistémica de los parámetros geomecánicos y propagarla a través de modelos de equilibrio límite, en los que la geometría es controlada por la orientación de las discontinuidades. Para llevar a cabo una mejor descripción de la variabilidad en el macizo, el proyecto utilizó fotogrametría de corto alcance, lo que permitió obtener series de datos robustas y confiables de la geometría de las discontinuidades, que fue modelada como una variable aleatoria con distribución Kent. Además, se desarrolló un procedimiento para actualizar los análisis de confiabilidad teniendo en cuenta la distribución de probabilidad de la orientación de las discontinuidades. La aplicación de la metodología en un talud rocoso de una mina de arenisca mostró su aplicabilidad a proyectos reales. Consecuentemente, la principal contribución de este trabajo es la generación de un marco de referencia para efectuar la evolución de confiabilidad de taludes rocoso basado en la teoría de la evidencia que permite combinar las series robustas de la orientación de los planos de discontinuidad, con información limitada de sus parámetros de resistencia, que puede ser actualizada a medida que se genera nueva información.Ítem Method for landslides detection with semi-automatic procedures: The case in the zone center-east of Cauca department, Colombia(2020-01-30) Correa Muñoz, Nixon Alexander; Murillo Feo, Carol Andrea; Geotechnical Engineering Knowledge and Innovation - GENKILandslides are a common natural hazard that causes human casualties, but also infrastructure damage and land-use degradation. Therefore, a quantitative assessment of their presence is required by means of detecting and recognizing the potentially unstable areas. This research aims to develop a method supported on semiautomatic methods to detect potential mass movements at a regional scale. Five techniques were studied: Morphometry, SAR interferometry (InSAR), Persistent Scatterer InSAR (PS-InSAR), SAR polarimetry (PolSAR) and NDVI composites of Landsat 5, Landsat 7, and Landsat 8. The case study was chosen within the mid-eastern area of the Cauca state, which is characterised by its mountainous terrain and the presence of slope instabilities, officially registered in the CGS-SIMMA landslide inventory. This inventory revealed that the type `slide' occurred with 77.4% from the entire registries, `fall' with 16.5%, followed by `creeps' with 3%, flows with 2.6%, and `lateral spread' with 0.43%. As a result, we obtained the morphometric variables: slope, CONVI, TWI, landform, which were highly associated with landslides. The effect of a DEM in the processing flow of the InSAR method was similar for the InSAR coherence variable using the DEMs ASTER, PALSAR RTC, Topo-map, and SRTM. Then, a multiInSAR analysis gave displacement velocities in the LOS direction between -10 and 10 mm/year. With the dual-PolSAR analysis (Sentinel-1), VH and VV C-band polarised radar energy emitted median values of backscatters, for landslides, about of -14.5 dB for VH polarisation and -8.5 dB for VV polarisation. Also, L-band fully polarimetric NASA-UAVSAR data allowed to nd the mechanism of dispersion of CGS landslide inventory: 39% for surface scattering, 46.4% for volume dispersion, and 14.6% for double-bounce scattering. The optical remote sensing provided NDVI composites derived from Landsat series between 2012 and 2016, showing that NDVI values between 0.40 and 0.70 had a high correlation to landslides. In summary, we found the highest categories related to landslides by Weight of Evidence method (WofE) for each spaceborne technique applied. Finally, these results were merged to generate the landslide detection model by using the supervised machine learning method of Random Forest. By taking training and test samples, the precision of the detection model was of about 70% for the rotational and translational types.Ítem Integration of Hydrological and economical aspects for water management in tropical regions. case study: middle Magdalena Valley, Colombia(2020-07-15) Arenas Bautista, María Cristina; Donado Garzón, Leonardo David; Hydrodynamics of the natural media Research Group - HYDSWater resources are a determining factor in the economic and social development of communities, given the need that is generated around its use. Over the years, this use has generated pressure on water availability, which were solved by increasing supply, exploring and developing new water sources, and expanding the existing extractions. In Colombia, water concession is the right to the limited use of water, and it is granted to develop economic activity. This concession must be related to water availability to ensure the preservation and efficient water use. However, to allocation water resources efficiently, tools that help to make decisions by analyzing the hydrological regime (surface and groundwater) in areas with lacking reliable data on water availability in an economic context are required. In this context, the main goal of this research was to provide a methodological approximation that allows integrating hydrological, hydrogeological, and economic aspects in water allocation between different users, prioritizing human needs and ecosystem processes, to establish management strategies at a regional scale. In this research performed an integration of diverse hydrological, hydrogeological, and economical aspects, using the Middle Magdalena Valley (MMV) geological basin as a real scale laboratory. Because this area is a primary supply center for the Colombian population, and economic activities related to mining, agriculture, aquaculture, livestock, industrial, services, and O&G exploration and exploitation are developed in conjunction; hydric and economic behavior of the system was analyzed. This analysis was carried out in regards to water availability (surface and groundwater), and its allocation to different stakeholders. For it, three phases were defined: (1.) to characterize the hydrological system, (2.) to characterize the hydrogeological system, and (3.) its integration into an economic optimization model. In the first phase, the hydrologic system behavior was analyzed through a numeric tool, to characterize the water supply, the recharge zones were identified, and the hydrologic alterations affecting the water supply were evaluated. The hydrological modeling allowed to perform an exhaustive interaction analysis between the hydrologic cycle dynamic and the weather condition and land use. Then, it was made an analysis of uncertainty and sensitivity to evaluate the influence of the principal parameters associated with the model. From this analysis, it was validated a methodology allowing to: (i) select proper values for the model parameters, and (ii) evaluate how the model parameters variations influence a simulated response. In the second phase, the geological, hydrological and hydraulic characterization was integrated into a hydrogeological model to estimate the water volume and groundwater flow system description. The result of this phase allowed to consolidate a methodology to assertively restrict a highly parameterized inverse model with lack of information, estimate hydraulic parameters of aquifers and analyze the spatial and temporal variation presented by these parameters at the regional scale. Finally, in the third phase, the hydrological aspects (surface and groundwater) were integrated with an economic optimization framework. This allows them to determine water allocation and water resources quality management. The main objective of this phase was to analyze the water use profit in a regional flow model, integrating multiple water supplies (surface and groundwater) and multiple demands. Here, the allocation model was analyzed from a regional scale in order to consolidate typologies of use by economic sector, and determine management strategies at a regional level. The general results of this research allowed to identify problems and evaluate management strategies, in a tropical basin at the regional level. Additionally, it was concluded that the quantification of water supply affects the allocation process between different stakeholders and this process, in turn, is a function of water quality. As part of the final stage of this research, the water system behavior was analyzed through future scenarios.Ítem Damage probability assessment for adjoining buildings to deep excavations in soft soils(2019-12-30) Sainea-Vargas, Carlos Javier; Torres Suárez, Mario Camilo; GRUPO DE INVESTIGACIÓN EN GEOTECNIA - GIGUNIn densely populated cities, the lack of space on the surface gives rise to the need for utilizing subsoil through different infrastructures, in which deep open excavations are required. However, there are several challenges to face, related to local geotechnical conditions as in the presence of soft soils, or serviceability requirements as potential damages on neighboring buildings may occur. Apart from the unfavorable behavior of soft soils, given its low resistance and high compressibility, their properties are spatially variable. These aspects should be considered in the analyses when assessing potential damages in buildings caused by ground movements during the excavation. In this research, a combination of numerical and probabilistic methods is considered through the use of a random field-based finite element modeling of deep excavations in soft soils. Finite element modeling allows performing tridimensional analysis, simulating staged construction, and including complex soil behavior. Probabilistic methods are useful to address the uncertainty in constitutive parameters related to spatial variability, expressing the response of the models in terms of damage probabilities, and updating initial predictions using information from other sources. Constitutive models Hardening Soil and Hardening Soil Small Strain are considered to model soft soil behavior, and selected parameters E0ref and E50ref were represented as random variables and random fields with different anisotropy in numerical models. Damage probability assessment analyses in terms of damage probability indexes were performed for a synthetic excavation of idealized geometry in Bogotá soft soils, and a real excavation project in Mexico City soft soils. The obtained results indicate a significant increase in assessed probabilities when not considering soil stiffness at small strains. Slight to moderate effects were found when changing the simulated construction sequence, using random-variable based models or changing the anisotropy ratio in random field-based models, except in highly anisotropic random fields. Ground movements and building damage potential distribution depend on boundary conditions, and they are different when changing the constitutive model employed or the simulated construction sequence. Similar results were attained when using the response surface, or the point estimates methods. In the former method, polynomial equations were employed to approximate numerical model performance in order to assess damage probabilities, obtaining similar results when using Gaussian random variables or the distributions found in inferential analyses. The polynomial equation approximation was also useful to update initial damage probabilities employing information from semiempirical methods or a combination of these and actual measurements.