Doctorado en Ingeniería - Ingeniería Civil
URI permanente para esta colecciónhttps://repositorio.unal.edu.co/handle/unal/82554
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Ítem Freight-Transit tour synthesis(Universidad Nacional de Colombia, 2023-12) Moreno Palacio, Diana Patricia; González-Calderón, Carlos Alberto; Posada Henao, John Jairo; López-Ospina, Héctor Andrés; MORENO PALACIO, DIANA PATRICIA; https://scholar.google.com/citations?user=eXCDGeIAAAAJ&hl=en; Moreno Palacio, Diana Patricia [eXCDGeIAAAAJ&hl=en]; https://orcid.org/my-orcid?orcid=0000-0002-9697-7646; Moreno Palacio, Diana Patricia [0000-0002-9697-7646]; https://www.researchgate.net/profile/Diana-Patricia-Moreno-Palacio; Moreno Palacio, Diana Patricia [Diana-Patricia-Moreno-Palacio]; Vias y Transporte (Vitra); https://www.scopus.com/authid/detail.uri?authorId=57199156747; Moreno Palacio, Diana Patricia [57199156747]This research introduces a multi-class demand synthesis model for transit and freight, utilizing entropy maximization and fuzzy logic. The model incorporates traffic data and fuzzy parameters to accommodate uncertainty. The use of fuzzy logic enhances classical modeling by providing flexibility and addressing data uncertainty, a critical aspect in resource-constrained decision-making scenarios. Finite resources such as road capacity necessitate optimal decision-making. Flexible models are essential, as not all constraints can be fully met. Fuzzy logic excels in handling variability and uncertainty, improving results' reliability. It aids in estimating congestion patterns, emissions levels, and accidents, thereby providing valuable insights to decision-makers. Fuzzy logic's flexibility is crucial for real-world adaptability. It enhances transportation planning, benefiting urban mobility. Results' accuracy directly impacts decisions, and fuzzy logic incorporates real-world variability into models. The research focuses on triangular membership functions, a commonly used approach. Fuzzy logic's adaptability is compared with deterministic models, demonstrating superior performance. It helps in finding satisfactory solutions when full constraint satisfaction is unfeasible. Pareto frontiers indicate multi-objective optimization. Decision-makers can use this frontier to choose the right model based on accomplishment versus entropy trade-offs. Fuzzy logic accommodates partial solutions when strict constraints cannot be met. Trials with a developed model show that capacity and cost significantly influence outcomes. Sensitivity analyses reveal the model's robustness. The model's application is promising for shared lanes and infrastructure optimization, handling data variability and uncertainty. It aids in decision-making for urban transportation planning and infrastructure development. Government agencies must strategize mobility elements. Accurate data are crucial for decisions related to routes, traffic management, and infrastructure. Fuzzy logic can guide decisions about shared lanes and resource allocation, enhancing urban transportation planning and development.Ítem Los modelos híbridos de elección de modo de transporte en la planeación urbana incluyendo la variable latente seguridad(Universidad Nacional de Colombia, 2019-07-31) Agudelo Vélez, Laura Inés; Córdoba Maquilón, Jorge Eliécer; Sarmiento Ordosgoitia, Iván Reinaldo; Vias y Transporte (Vitra)Los desplazamientos que realizan las personas en su vida cotidiana demandan recursos como: espacio urbano, modos de transporte, tiempo y dinero, entre otros. Atender las necesidades de desplazamiento de la población es uno de los temas que más espacio ocupa en los planes de ciudades. Se busca la solución a un problema en crecimiento, que dada su condición dinámica requiere de estudios amplios que enriquezcan los modelos convencionales. La heterogeneidad de la vida cotidiana le imprime un carácter especial a los estudios que se encargan de modelar los patrones de viaje y con ello definir políticas de planeación urbana y de transporte. Lo que demanda una lectura amplia que genere una completa aproximación a la realidad cambiante producto de la subjetividad de la elección. Las condiciones particulares de cada sujeto lo alejan de ser ese individuo homogéneo que se ha considerado en los modelos tradicionales de elección de modo de transporte. En esta investigación se abordan modelos que con la inclusión de la variable latente seguridad permitan al sujeto tomar un rol activo en la elección de modo de transporte. Dicha variable es entendida y estudiada desde tres elementos que la conforman: el entorno, el sujeto y el modo de transporte. Se desarrolla una investigación mixta en la que, a partir de técnicas cuantitativas y cualitativas, se dimensiona integralmente el problema complejo de la elección del modo de transporte. Así se obtiene un espectro más amplio que permite una mejor identificación de las diversas mixturas que envuelven la elección y que los modelos tradicionales, e incluso los híbridos actuales, no logran captar dado lo limitado de sus planteamientos y metodologías. Constituyendo con ello un aporte en la modelación de transporte. Los datos para los análisis se obtuvieron a través de técnicas cuantitativas (encuestas de preferencias reveladas y preferencias declaradas, al igual que cuestionarios de indicadores de seguridad) y cualitativas (grupo focal y cartografía social). Además de las encuestas que convencionalmente se utilizan en transporte, se efectuó un ejercicio de realidad virtual para vivir un recorrido real recreado a través de videos 360°. A partir de esa experiencia multisensorial, los sujetos eligieron y calificaron, en función de la percepción de seguridad, los diferentes modos de transporte utilizados en ese viaje. Se recrearon diferentes escenarios urbanos de la ciudad de Medellín que fueron sometidos a evaluación por parte de distintos sujetos. Con la finalidad de evaluar el impacto de la percepción de seguridad del sujeto sobre la elección del modo de transporte, se utilizó un instrumento validado de autoeficacia. Previamente, con el objetivo de depurar la variable de confusión de psicopatología de trastornos de ansiedad, se aplicó el instrumento MINI (MINI Entrevista Neuropsiquiátrica Internacional). Ser un sujeto seguro implica ser auto eficaz. La autoeficacia es uno de los elementos constitutivos de la seguridad y bajo esta premisa fue abordada la variable latente en esta investigación. Como resultado se obtuvo que la elección de modo de transporte está fuertemente relacionada con el entorno por el que se realiza el desplazamiento. A partir del análisis estadístico, se obtuvo asociación y significancia entre la elección de modo y el entorno recorrido. Con el análisis de contenido, se reafirmaron las categorías de análisis que fueron definidas a partir de la cartografía social y el grupo focal; encontrando que: lugares activos, iluminados, recorridos en el día, entre otros aspectos, incrementan la percepción de seguridad. Por el contrario, lugares solitarios, con presencia de habitantes de calle, con muros o cercos, recorridos en la noche, disminuyen la percepción. Así mismo, a través de los modelos híbridos se encontró que las variables seguridad del entorno, del sujeto y del modo son significativas. De otro lado, se obtienen los pesos que tienen los modos de transporte sobre la percepción de seguridad en función de los diferentes entornos recorridos. Los sujetos con bajos niveles de autoeficacia puntúan para trastorno de ansiedad, lo que apoya la premisa en esta investigación. En el caso de quienes tienen niveles medios de autoeficacia en un menor porcentaje (7%) resultaron calificados como ansiosos, mientras que el 93% restante hacen parte del grupo de los no ansiosos. Adicionalmente, los sujetos con altos niveles de autoeficacia califican como seguros los diferentes modos de transporte. A modo conclusivo, cuando se efectúa una elección de modo de transporte teniendo en cuenta la percepción de seguridad, los participantes eligen de manera predominante el auto. De acuerdo con esto, y con el fin de avanzar en la implementación de modos sostenibles, será necesario evaluar la seguridad ya que se trata de una variable significativa. Los resultados de este trabajo permiten concluir que para una movilidad sostenible específicamente en el contexto latinoamericano debe incluirse un pilar fundamental como es la seguridad. Los resultados de la investigación muestran el potencial que tiene el bus, dado que las calificaciones asignadas en la mayoría de los entornos evaluados se encuentran en el costado de la seguridad, lo cual lo convierte en un modo potencial para trabajar en pro de ganar usuarios y con ello aportar en la construcción de una movilidad sostenible. (Texto tomado de la fuente)Ítem Estimation of dynamic parameters in residual soils derived from crystalline rocks based on geophysical multichannel analysis of surface waves tests(Universidad Nacional de Colombia, 2020) Galeano Parra, Diego Iván; Zapata Medina, David Guillermo; Monsalve Mejía, GasparResidual soils are preferentially formed at inter-tropical latitudes where climate conditions favor in situ weathering actions. The tropics constitute approximately 40% of the Earth's surface area and are home to approximately 40% of the world’s population, which is expected to reach 50% by the late 2030s in these zones. Consequently, numerous urban centers and associated infrastructure has been built, or is projected, over residual soil masses. Conversely, these soils are less often studied and published literature dealing with their fundamental behavior is scarce. This research work presents a field and laboratory testing program designed to investigate the: i) performance of the Multichannel Analysis of Surface Waves, MASW, and Cross-correlation, CC, techniques for the determination of dynamic parameters in residual soil masses; ii) in situ state of stresses of the residual soil masses and the ability to reproduce those in a laboratory environment; iii) yield stresses and 1D stress-strain characteristics; and iv) yielding and stiffness degradation characteristics of residual soils at different strain levels. Four residual soil masses were selected to conduct seismic tests with different array configurations and geophone-source offset separations. The frequency-domain cross-correlation technique was also implemented to extract Rayleigh wave phase velocities from passive data. At each sampling site, results of Electrical Resistivity Tomography, downhole and/or seismic dilatometer tests were used to evaluate the plausibility of the Vs profiles obtained using surface wave methods. Additionally, an advance laboratory testing program consisting of Constant Rate of Strain consolidation, pseudo Ko-triaxial, and monotonic and dynamic cyclic triaxial tests equipped with Bender Elements was conducted. Drained and undrained stress probe tests were conducted on specimens reconsolidated to their in situ stress state employing the Ko-recompression technique. Despite the large horizontal and vertical soil heterogeneity, the surface wave techniques succeeded in detecting major interfaces and in providing a reasonable first of soil stiffness. Based on in situ measurements of Ko-values, the Ko recompression technique was found to be adequate for reproducing the in situ stress state of the tested residual soils. A linear variation between small strain shear modulus, Go, and mean normal effective stress, p', was observed. The experimental results indicate that the tested soils exhibit incrementally nonlinear responses, which were adequately described in terms of the successive yield surfaces Y1, Y2, and Y3, proposed by Jardine (1992, 1995). The influence of the pre-shear stress paths on stiffness degradation characteristics and yielding behavior was also investigated. Additionally, for a soil of sedimentary origin and a loose sand treated with Microbially Induced Carbonate Precipitation (MICP), the compressibility characteristics were evaluated. The experimental results show a significant reduction in compressibility of the biotreated material with respect to untreated control samples. Very low Ko-values were obtained for stress levels before the initial cementation bond breakage. Empirical relations for the elastic shear modulus, Go, were developed as a function of the mean normal effective stress, p', and void ratio for clean and MICP-treated sands.Ítem Modelo de comportamiento de conductores y la generación de accidentes de tránsito.(Universidad Nacional de Colombia, 2021) Arias Rojas, Wilson; Córdoba Maquilón, Jorge Eliecer; VIAS Y TRANSPORTE (VITRA)Esta investigación doctoral, presenta el resultado del análisis del comportamiento de conductores en un escenario controlado, en un simulador de conducción, en el cual, mediante la medición de ondas cerebrales, se determinó el grado de concentración al conducir y por medio del uso de Machine Learning, se planteó un modelo de comportamiento de los conductores al someterse a un efecto distractor mientras se conduce, el cual permite analizar los factores más relevantes que se reflejan en errores y malas prácticas al momento de conducir. En esta investigación se analizó una muestra poblacional desde los 16 hasta los 90 años, compuesta de hombres y mujeres, a partir de un universo obtenido de una base de datos de fatalidades durante 7 años, se construyó un simulador de conducción con un software para la simulación que permite diferentes escenarios de conducción. Se elaboró un programa de captura de ondas cerebrales el cual midió el grado de concentración de los participantes del experimento mientras eran sometidos al efecto distractor de envío de mensajes de Whatsapp mientras conducían en el escenario escogido. Posteriormente se hizo un análisis de la información obtenida por medio de redes neuronales, obteniendo los resultados del comportamiento de los conductores y errores más comunes durante el experimento, se planteó un modelo de comportamiento de conductores ante los efectos distractores Finalmente se clasificaron conductas riesgosas de conductores al ser sometidas a un efecto distractor, observando el comportamiento de conductores mayores de 50 años, los cuales son más cautelosos ante efectos distractores, y se planteó un modelo matemático que depende del grado de concentración de usuarios y varía de acuerdo con el escenario escogido por cada uno de los participantes del experimento (Texto tomado de la fuente)Ítem Model-based real-time monitoring of large-scale urban traffic networks for decision making.(Universidad Nacional de Colombia, 2021-09) Portilla Caicedo, Christian Roviro; Espinosa Oviedo, Jairo José; Sarmiento Ordosgoitia, Ivan Reinaldo; Grupo de Automática de la Universidad Nacional GAUNALThis thesis proposes and implements a real-time urban traffic monitoring system for decision-making as an alternative to classical solutions based on on-road sensors, which often implies a large installation, operation, and maintenance cost. The main purpose of this system is to improve the mobility and environmental conditions of cities. This solution takes advantage of data generated by Waze (Free Community-based GPS, Maps, and Traffic Navigation App) through smartphones carried by users traveling in the cities. FLEXI (Flow Estimation based on Collaborative Information) was developed as part of the monitoring system and is based on a mathematical model that transforms the mean speed and delay given by Waze into more usable traffic variables such as demand and queues. Moreover, the monitoring system fuses online, offline, and collaborative information to improve estimation accuracy. The monitoring system was implemented in real-time in Medell´ın - Colombia, including 38 signalized intersections. To this end, FLEXI was calibrated using data collected in the field, achieving a mean relative error of 15 % and a mean absolute error less than 1 veh/min/lane for the estimation of the flow and queue of vehicles.Ítem Measuring bicycle accessibility with spatial effects evaluation(Universidad Nacional de Colombia, 2020-12) Ospina Zapata, Juan Pablo; Botero Fernández, Verónica; Duque Cardona, Juan Carlos; López , Víctor Ignacio; Brussel, Mark; Grigolon, Anna; Montoya, AlejandroThis research seeks to understand how the accessibility measure can be explained by the sociodemographic characteristics of cyclists, the built environment at the origin and destination, and the built and natural environment along the route. We first conducted a bicycle route survey to collect information about the characteristics of cyclists and the routes they take in Medellin city. Second, we developed an econometric model, which aimed at understanding how the natural and environmental factors of origin, destination, and along the route, affect cyclists’ travel distance. Such an understanding is essential to know about cyclists' preferences, which may affect their potential space of interaction in the city. Third, we solved an optimization problem which involved making investment decisions to build a cycling network that was aimed at maximizing the coverage of cyclists, while maintaining a minimum total network cost at its minimum. Fourth, we analyze the accessibility for cyclists, which takes into account the results derived from the econometric model and the optimization model. Our results reveal the importance of built and natural characteristics along the road in explaining cycling travel distances while controlling for socioeconomic and built environment measures at origins and destinations. All these results suggest that cyclists’ behaviors are diverse and therefore, including cyclists’ preferences will allow a more sensitive assessment of individual variations in accessibility measures.Ítem Experimental assessment of rutting in permeable asphalt mixtures(2020-08-20) Senior Arrieta, Vanessa; Graciano Gallego, Carlos Alberto; Vega Posada, Carlos Alberto; Universidad Nacional de Colombia - sede Medellín; VIAS Y TRANSPORTE (VITRA)This study presents an experimental investigation on the rutting resistance of permeable asphalt mixes (PAM). In practice, PAM, also referred to as Open-graded friction courses (OGFC) or permeable friction courses (PFC), are prone to permanent deformation due to heavy vehicle traffic loads and a weak mineral skeleton caused by their high air void contents. Consequently, the draining capacity of the PAM is diminished making the roads unsafe particularly in wet conditions. Hence, the rutting mechanism of PAM is evaluated through three laboratory tests: dynamic modulus, flow number, and Hamburg wheel tracking test (HWTT). The laboratory samples were prepared and compacted considering four air voids (AV) contents: 18%, 20%, 22% and 25%. From the HWTT, a comparative analysis was conducted using X-ray computer tomography (X-ray CT) images obtained before and after the tests in order to investigate AV distribution due to rutting. Results from the tests indicated that an increase in AV content reduced the rutting performance of PAM, as well as higher AV content led to larger mix densification and thus a deeper rut was achieved. Similar results were attained from the analysis of the X-ray CT images, nevertheless, a larger AV densification was observed in the upper part of the samples beneath the developed rut, which can lead to further weakening the mineral skeleton and progress of other several distress that typically develop for PAM.Ítem Airline choice model: the role of satisfaction latent variable.(2020-08-14) Muñoz Hoyos, Claudia Helena; Córdoba Maquilón, Jorge Eliecer; Laniado Rodas, Henry; Sarmiento Ordosgoitia, Ivan; Universidad Nacional de Colombia - Sede Medellín; VIAS Y TRANSPORTE (VITRA)Understanding and modeling travelers’ decisions on air transportation by correctly analyzing passengers’ satisfaction and their airline choice are essential elements in air transportation planning. However, the relationship between passengers’ satisfaction with airlines and their airline choice behavior has been developed in each area independently from the other. This research reduces the gap between air traveler satisfaction assessment and airline choice by analyzing how air traveler satisfaction influences the air carrier choice process. This research focuses on understanding how travelers choose airlines for international round-trip flights, identifying the relevant factors that passengers take into account and quantify the impact of traveler satisfaction has on their preferences. For this purpose, three different databases were collected and used. First, we study the role of service quality perceptions in determining passengers’ satisfaction. Traveler perception of service quality was evaluated, considering it as a chain of services related to departure airport service, airline service, and arrival airport service. Thus, a new scale for assessing passenger experiences in air travel is proposed. We apply a second survey to find a robust customer satisfaction index for air journeys. In which, structural equation modeling was applied to validate the theoretical model by examining the relationship between service quality stages, perceived value, passenger satisfaction, and behavioral intentions. Finally, we use the third survey for analyzing air passengers’ demand for international round-trip flights. With this survey, we found models without latent variables, and subsequently, they were included to find a hybrid discrete choice model. Thus, this study hypothesizes that the airline choice process depends not only on a set of measurable factors but also on passenger satisfaction with the airline which, in turn, is influenced by travelers’ personality traits. Results indicate that passenger's personality traits, which were measured through a personality test, allow explaining the passenger satisfaction with the airlines. Furthermore, passenger satisfaction with each airline service is associated with airlines’ utilities. Therefore, by incorporating traveler satisfaction with airline into an airline choice model, choice behavior can be modeled more precisely. Hence, the service quality scale for air travel, the customer satisfaction index for air journeys and the hybrid choice model found in this research provide useful information for developing effective operational and marketing strategies for successful air transportation management. Keywords: Service quality, passenger satisfaction, satisfaction index, airline choice model, personality traits, round-trip flights.Ítem Stiffness matrix and loading vector of a two-layer Timoshenko composite beam(2020-02-01) Areiza-Hurtado, Mauricio; Aristizabal-Ochoa, Jose Dario; Universidad Nacional de Colombia - Sede Medellín; ESTABILIDAD ESTRUCTURALEste trabajo presenta un resumen de los resultados obtenidos de la investigación realizada durante los estudios de doctorado. Inicialmente la propuestra del trabajo de grado consistía en la obtención de la "Matriz de rigidez y vector de carga de una viga de Timoshenko de dos capas" (ver Capítulo 5), sin embargo se ha adjuntado a este documento otros capítulos que se encuentran intimamente relacionados y que fueron también fruto del trabajo de investigación. Los capítulos 1 y 2 presentan la formulación teórica y la verificación con ejemplos, respectivamente, de la matriz de rigidez y el vector de carga de una viga pretensada incluyendo los efectos de largo plazo. El capítulo 3 presenta el análisis de segundo orden de una viga columna sobre fundación elástica con deflección inicial y conexiones semirrigidas. Los capítulos 4, 5 y 6 presentan el análisis de una viga de Timoshenko de dos capas. En el capítulo 4 se presenta la formulación para un sólo elemento, en el capítulo 5 se presenta la derivación de la matriz de rigidez y se hace la verificación con aplicaciones al diseño de vigas mixtas de acero y concreto. Finalemnte en el capitulo 6 se usa la formulación desarrollada en el capítulo 5 para realizar el análisis de nudos adhesivados. Los capitulos 3 al 6 cuentan con el identificador único y permanente para las publicaciones electrónicas (DOI) en el encabezado de cada capítulo para una fácil referencia.Ítem Effect of longitudinal stiffening on the ultimate resistance of plate girders subjected to patch loading(2019-06) Loaiza Ramones, Nelson Adolfo; Graciano Gallego, Carlos Alberto (Thesis advisor)Several investigations have shown that the ultimate resistance of plate girders subjected to patch loading is increased when a longitudinal stiffener is placed at the web panel of the steel girder. However, the influence of factors such as the patch loading length and the configuration of the longitudinal stiffener has received little attention. Therefore, this thesis is aimed at studying the effect of longitudinal stiffening on the ultimate resistance of plate girders subjected to patch loading. At first, the influence of the patch loading length on the critical buckling coefficient is investigated by means of linear finite element analysis. The effect of the panel aspect ratio, the position, and size of the longitudinal stiffener was also addressed. Additionally, the influence of a second stiffener located at the web panel was studied (multiple stiffening). Results indicate that buckling coefficients increment when the patch loading length is increased. Currently, in the Eurocode 3 Part 1-5 the ultimate resistance of girders subjected to patch loading is obtained by calculating the slenderness parameter, a dimensionless factor that depends on the yield resistance and the critical buckling load. The critical load which expression is derived from numerical modelling shows that critical load rises with an increasing distance between the stiffener and the loaded flange. However, at ultimate load level experiments had shown that ultimate resistance rises when the longitudinal stiffener is placed near the loaded flange. With the purpose of obtaining the same behavior described at ultimate load level, new hypothesis of boundary restrictions at the stiffener location are presented to model the elastic buckling behavior of webs subjected to patch loading. From these results a new approach that corrects the calculation of the slenderness parameter and harmonize the behavior between critical load and ultimate load level is proposed. The last edition of the AISC Specifications presents a formulation to calculate the ultimate resistance of unstiffened girders subjected to patch loading. This formulation is based on a four plastic hinges mechanism that considers crippling effect produced in the web panel of slender girders. Considering that the flange-to-web yield strength ratio has no influence on the ultimate resistance for hybrid girders subjected to patch loading, a closed-form solution to predict the ultimate resistance for stiffened girders is proposed by modifying a previously developed mechanism. International code provisions suggest use a longitudinal stiffener at one-fifth of the girder height as the best position for flexural resistance (b1 =0.20hw), nevertheless results indicate that the optimum position to increase the ultimate resistance of a girder subjected to patch loading is different (b1 0.20hw). It has also been demonstrated that when the slenderness of the directly loaded panel b1/tw decreases the ultimate resistance increases. Since bending governs the in-service girders behavior, a check for steel bridges girders erected by incremental launching was performed using nonlinear finite element analysis. In this case two strategies to study the impact of the slenderness ratio b1/tw on the ultimate resistance were evaluated, the first by changing the web thickness tw while maintaining the stiffener at b1 =0.20hw, and the second by changing the position of the stiffener b1 for various web thicknesses. Results show that the contribution of a stiffener placed at b1 =0.20hw is only significant for thinner webs. Finally, the results derived from the theoretical predictions are compared against the test experimental results available in the literature, in order to discuss the goodness and limitations of the approaches developed herein.