Diseño sísmico de taludes en arena por medio de métodos basados en desempeño
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Fecha
2016
Autores
Viejo Sottorff, Natalia Andrea
Profesor/a Guía
Facultad/escuela
Idioma
es
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Editor
Universidad Andrés Bello (Chile)
Nombre de Curso
Licencia CC
Licencia CC
Resumen
Los taludes constituyen estructuras fundamentales para la construcción y posterior funcionamiento de obras terrestres. Dado que este tipo de proyectos requiere de la ejecución de grandes movimientos de tierra y la formación de cortes y terraplenes, los criterios de diseño a utilizar deben balancear correctamente seguridad, plazos de ejecución, y costos.
En Chile, al igual que en otras regiones sísmicas del mundo, resulta de particular importancia realizar un adecuado diseño de taludes frente a terremotos. Es así como durante las últimas décadas se han comenzado a utilizar los denominados métodos basados en desempeño, los cuales plantean que el diseño puede ser efectuado sobre la base de desplazamientos admisibles que no comprometan la estabilidad global de la estructura y permitan mantenerla operativa luego de la ocurrencia del sismo de diseño. Esta manera de abordar el problema, a diferencia de lo que sucede con el enfoque de diseño tradicional basado en fuerzas y factores de seguridad, permite cuantificar y prever los efectos que puede producir el sismo sobre la estructura; a la vez que entrega soluciones comparativamente más económicas.
Una de las formas comúnmente utilizadas para estimar desplazamientos sísmicos en estructuras de tierra es hacer uso del denominado método del bloque deslizante de Newmark (1965), el cual plantea una analogía entre la masa del talud susceptible de fallar y un bloque rígido que puede deslizar sobre un plano inclinado. Los métodos de diseño actuales basados en desempeño han recogido esta idea para plantear una serie de curvas envolventes que permiten estimar los desplazamientos en un talud cualquiera como función de parámetros característicos de la solicitación sísmica y la estructura propiamente tal.
En el presente trabajo se recopilan métodos basados en desempeño para determinar desplazamientos sísmicos en taludes arenosos, todos ellos desarrollados a partir de terremotos en Estados Unidos, Europa y Asia, y se utilizan registros sísmicos chilenos de 1981, 1985 y 2010 para evaluar su ajuste y aplicabilidad a las condiciones nacionales.
Se utiliza la información de las estaciones acelerográficas ubicadas en suelo tipo arena a lo largo de todo el país. Para cada una de ellas se obtiene una solución de desplazamientos de referencia por medio del método del bloque deslizante de Newmark, la cual se utiliza para evaluar la bondad del ajuste de los métodos basados en desempeño analizados.
A partir de los resultados obtenidos, para el diseño de taludes en arena en Chile, se sugiere el uso de las expresiones propuestas por Richards & Elms (1979), Cai & Bathurst (1996), Jibson (2007) ecuación b y Saygili & Rathje (2008). Se propone además una modificación a la ecuación c de Jibson (2007), basada en la Intensidad de Arias, para su uso en nuestro país.
Slopes are key structures for both construction and operation of earth works. Given this type of projects requires the execution of important earth movements, cuts, and embankments, a design criteria that properly balance safety, deadlines, and costs has to be used. In Chile, as same as in other seismic regions of the world, it is particularly important to provide an adequate design of slopes under earthquake loading. In this sense, during the last decades, the so-called performance-based design methods have begun to be utilized. These methods are intended for design of slopes over the basis of allowable displacements, which does not compromise the overall stability of the structure and keep it operative after the occurrence of the design earthquake. In this way, and in contrast with the traditional design methods based on forces and safety factors, it is possible to quantify and anticipate the effects that the earthquake produce on the structure. In addition, a more economical design-solution can be obtained. One of the commonly used ways for estimating seismic displacements of earth structures is by making use of the sliding block method developed by Newmark (1965), who proposed an analogy between the potentially instable slope mass and a rigid block that can slide on an inclined plane. The current performance-based design methods have followed the Newmark’s idea to generate a series of design envelope curves that allows estimating the displacements on any slope as a function of the main seismic and structural parameters. In this paper, a variety of performance-based design methods for slopes on sand are collected, all of these developed from earthquakes in United States, Europe and Asia. Chilean seismic records from the earthquake events of 1981, 1985 and 2010 are used, in order to apply these methods and evaluate their fitting to the local conditions. The information obtained from the accelerographic stations located in sandy soils throughout the country is utilized. For each station, a reference displacement- solution is obtained by making use of the Newmark’s sliding block method, which is used to evaluate the quality of fit for the performance-based methods analyzed. From the results obtained, for design of slopes on sand in Chile, it is suggested to use the expressions proposed by Richards & Elms (1979), Cai & Bathurst (1996), Jibson (2007) equation b and Saygili & Rathje (2008). In addition, the equation c by Jibson (2007), based on Arias intensity, is modified for its use in our country.
Slopes are key structures for both construction and operation of earth works. Given this type of projects requires the execution of important earth movements, cuts, and embankments, a design criteria that properly balance safety, deadlines, and costs has to be used. In Chile, as same as in other seismic regions of the world, it is particularly important to provide an adequate design of slopes under earthquake loading. In this sense, during the last decades, the so-called performance-based design methods have begun to be utilized. These methods are intended for design of slopes over the basis of allowable displacements, which does not compromise the overall stability of the structure and keep it operative after the occurrence of the design earthquake. In this way, and in contrast with the traditional design methods based on forces and safety factors, it is possible to quantify and anticipate the effects that the earthquake produce on the structure. In addition, a more economical design-solution can be obtained. One of the commonly used ways for estimating seismic displacements of earth structures is by making use of the sliding block method developed by Newmark (1965), who proposed an analogy between the potentially instable slope mass and a rigid block that can slide on an inclined plane. The current performance-based design methods have followed the Newmark’s idea to generate a series of design envelope curves that allows estimating the displacements on any slope as a function of the main seismic and structural parameters. In this paper, a variety of performance-based design methods for slopes on sand are collected, all of these developed from earthquakes in United States, Europe and Asia. Chilean seismic records from the earthquake events of 1981, 1985 and 2010 are used, in order to apply these methods and evaluate their fitting to the local conditions. The information obtained from the accelerographic stations located in sandy soils throughout the country is utilized. For each station, a reference displacement- solution is obtained by making use of the Newmark’s sliding block method, which is used to evaluate the quality of fit for the performance-based methods analyzed. From the results obtained, for design of slopes on sand in Chile, it is suggested to use the expressions proposed by Richards & Elms (1979), Cai & Bathurst (1996), Jibson (2007) equation b and Saygili & Rathje (2008). In addition, the equation c by Jibson (2007), based on Arias intensity, is modified for its use in our country.
Notas
Tesis (Ingeniero Civil)
Palabras clave
Movimientos de Tierras, Taludes (Mecánica de Suelos), Construcciones Antisísmicas, Chile