Doctorado en Ingeniería - Ingeniería Civil
URI permanente para esta colecciónhttps://repositorio.unal.edu.co/handle/unal/81657
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Item type: Ítem , Propuesta de un índice de condición : Aporte para la gestión del espacio público(Universidad Nacional de Colombia, 2025) Giraldo Ospina, Tania; Galindo Díaz, Jorge; Giraldo Ospina, Tania [0000773131]; Giraldo Ospina, Tania [xRfauUUAAAAJ&hl]; Giraldo Ospina, Tania [0000000276438565]; Giraldo Ospina, Tania [Tania-Giraldo-Ospina?ev=hdr_xprf]; Gestión de la Infraestructura de Transporte y del Espacio PúblicoSe propone un índice de condición del espacio público (ICEP) como instrumento de evaluación objetiva de los elementos que integran su infraestructura para ser incorporado en la gestión del espacio público. Esta investigación tiene un alcance propositivo porque plantea un conocimiento técnico basado en un desarrollo teórico sobre la evaluación de la calidad del espacio público. Esta tesis pretende superar el reto de combinar indicadores de cantidad y accesibilidad con las condiciones físicas, para lo cual se utiliza una calificación ponderada que varía según la escala y los enfoques funcionales. Se adoptaron técnicas y métodos de evaluación del espacio público, que han sido puestos en práctica en contextos no latinoamericanos, como ponderación de elementos y dimensiones, relación entre cantidad y área ocupada de cada elemento, presencia y funcionamiento de los elementos y propósito o función de los espacios públicos. Como resultado, se proporcionó una lista de elementos básicos y complementarios por énfasis funcional y nivel de influencia. El método contó con un proceso de validación mediante la técnica Delphi y se demostró su utilidad en espacios públicos vecinales y zonales de la ciudad de Manizales (Colombia). El ICEP tiene potencial de replicabilidad en diferentes contextos y escalabilidad mediante un software vinculando notificaciones como herramienta participativa digital, que permita a los residentes informar directamente los problemas detectados en la infraestructura. Además, sirve para monitorear la condición, reconocer los daños persistentes o fallos constantes en las técnicas utilizadas para la supervisión y mantenimiento y priorizar la intervención de los problemas detectados (Texto tomado de la fuente).Item type: Ítem , Influence of seismic porewater pressure increase and liquefaction on site response analysis(Universidad Nacional de Colombia, 2024) Moreno-Torres, Oscar Hernando; Mendoza Bolaños, Cristhian Camilo; Salas Montoya, AndresSeismic site response analysis is a technique used to predict the ground’s response to local soil conditions. Recent advancements in understanding the generation of shear-induced excess pore pressure have led to the development and implementation of pore pressure response models in site response analysis that take effective stress into consideration. This research focuses on developing recent approaches to calculate site response analysis using the nonlinear effective stress method. The research specifically examines the impact of Porewater Pressure (PWP) buildup, soil softening, potential liquefaction, and post-liquefaction effects on site response. The study is divided into two stages: (1) The performance of a Porewater pressure generation model coupled with constitutive models is tested to compute stress-strain response during shaking using effective stresses, and to solve dynamic site response problems. (2) A parametric study using 2D elements is conducted to determine the principal variables that affect site response analysis. In the first stage, the study evaluates the performance of nonlinear effective stress constitutive models, commonly known as advanced constitutive models, used in one-dimensional (1D) site response analysis for assessing stress-strain behavior, porewater generation, and liquefaction potential in soft soil deposits at the element level. Three constitutive models are combined with the porewater pressure generation model to develop coupled models called PDMY 02, PM4SAND, and PDMY 03. The study also proposes protocols for selecting model input parameters. This stage of the study provides valuable contributions to the field of site response analysis. It evaluates three coupled constitutive models (PDMY 02, PM4SAND, and PDMY 03) using a comprehensive database of 40 stress-controlled cyclic tests. The findings demonstrate that these models accurately predict stress-strain behavior and pore-water pressure (PWP) response across a wide range of relative densities, with minimal residuals and bias. The improved models exhibit the capability to simulate dilation at high excess PWP (ru) values (greater than 0.75), making them suitable for engineering simulations and enabling precise prediction of dilation spikes during centrifuge tests with accelerated time histories. This research confirms the viability of using these advanced constitutive models for site response analysis in engineering practice. The coupled constitutive models (PDMY 02, PM4SAND, and PDMY 03) show excellent representation of PWP production and stress-strain behavior during validation, particularly when initial liquefaction reaches a value of excess of pore water pressure equal to the vertical effective stress. The small residuals in PWP and stress-strain comparisons, along with minimal bias across different relative density levels, further validate the accuracy and reliability of these models. Overall, this study contributes to the improvement of seismic design and analysis methodologies by demonstrating the effectiveness of these models in accurately predicting soil behavior during seismic events. These findings enhance our understanding of earthquake-induced hazards in geotechnical engineering, facilitating better mitigation strategies and ensuring safer infrastructure design. In the second stage, advanced nonlinear effective stress constitutive models are commonly employed in one-dimensional site response analysis to assess porewater pressure generation and liquefaction potential in soft soil deposits. The focus of the study is on evaluating the performance of a coupled effective stress constitutive model, utilizing a total of 44 input motions to conduct a parametric study with a synthetic soil profile. The study explores four different cases where liquefaction and non-liquefaction can be observed. The findings indicate that the coupled models accurately predict the triggering of liquefaction, showing good agreement with a well-established empirical liquefaction triggering relations database. Additionally, the study identifies several weaknesses in evaluating liquefaction using the cyclic stress method, which is the most widely used method in this context. This stage of the study makes significant contributions to the evaluation of level-ground liquefaction triggering using true coupled constitutive models. The research aims to validate the criteria used to assess the occurrence of level-ground liquefaction and verify the reliability of numerical approximations, specifically the PDMY 03 and DM models, in capturing key liquefaction characteristics observed in field and laboratory tests. A comprehensive parametric study involving 44 ground input motions and 16 synthetic sand profiles was conducted. The analysis focused on evaluating effective stress response and applying established triggering criteria. The results of 2,816 computations consistently demonstrated liquefaction resistance that aligns with established liquefaction resistance curves from the literature. The study highlights the effectiveness of the PDMY 03 and DM models in assessing effective stress site response analysis when significant excess porewater pressures are generated. The PDMY 03 model, in particular, considers post-liquefaction effects, which have a noticeable impact on the results of site response analysis. The research findings reveal that variations in shear stiffness have the most pronounced influence on site response within the effective stress models. Moderate to high ratios of excess porewater pressure, without reaching liquefaction, were observed to have negligible effects on response spectra due to insufficient degradation of modulus. Factors such as drainage, time-dependent behavior, and delayed liquefaction contribute to minimal changes in response spectra. Disparities between the response spectra predicted by the PDMY 03 and DM models were attributed to differences in shear modulus, with notable differences emerging when liquefaction occurred early during intense shaking. The 3D constitutive models incorporated in the PDMY 03 model provide a more comprehensive understanding of soil behavior, capturing multidirectional effects. In contrast, the simplified soil behavior representation of the DM model neglects some intricate mechanisms. The study emphasizes the importance of careful consideration and calibration of soil characterization parameters, input ground motion, and inherent uncertainties to ensure accurate site response analysis. The research also identifies limitations associated with the cyclic stress method for evaluating liquefaction triggering. Variations in groundwater table and bedrock depths were found to have minimal influence on the predicted response. Despite the complexities involved in true coupled effective stress analysis, advancements in computer technology have made calculations more efficient compared to other approaches. The study also indicates that variations in shear stiffness, represented by the change in shear wave velocity (Vs1), have the most significant impact on site response. It further finds that significant differences in nonlinear (NL) total stress and NL effective stress response spectra occur only when liquefaction is triggered or nearly triggered (i.e., excess PWP ratios near unity). Additionally, differences between NL total stress and NL effective stress analyses decrease when liquefaction occurs near the end of strong shaking. Lastly, the soil response is dominated by the higher stiffnesses available prior to liquefaction. Overall, the research shows the legitimacy of using coupled effective-stress constitutive models to evaluate triggering of level-ground liquefaction and the validity of using numerical approximations (PDMY 03 and DM models) as they capture the principal characteristics of liquefaction studied in field and laboratory tests. In summary, this research contributes valuable insights into the evaluation of level-ground liquefaction triggering using true coupled constitutive models. It provides a better understanding of soil behavior during seismic events and emphasizes the need for accurate parameter selection and calibration to improve site response analysis and prediction of response spectra. (Texto tomado de la fuente)