Evaluación del desempeño sísmico de edificio de flotación diseñado según la norma nch2369:2023.
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Date
2024
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Universidad de Concepción
Abstract
Es de conocimiento general que Chile siempre ha sido y seguirá siendo un país que se caracteriza por su alta sismicidad, se tiene larga data de sismos tan devastadores como los ocurridos en Arica el año 1868 con una intensidad estimada de 9.0 en escala de Richter o más recientes los ocurridos en Valdivia el año 1960 con una magnitud en escala de Richter de 9.5 o el último de gran magnitud ocurrido el 27 de Febrero del 2010 con una magnitud en escala de Richter 8.8, lo que impulsa políticas públicas materializadas en normativas como la NCh 2369:2023 que buscan garantizar el buen comportamiento de estructuras de carácter industrial mediante la implementación de estándares cuyo propósito es otorgar a la estructura sobrerresistencia y ductilidad moderada, de la cual se espera no hacer uso.
La primera versión de esta normativa se remonta al año 2003 donde se definieron los primeros lineamientos específicos para afrontar de buena manera los eventos sísmicos dada la recopilación de diferentes códigos y aproximándolos al acontecer nacional, esto generó buenas sensaciones dentro de la comunidad ingenieril hasta que ocurrió el evento sísmico del 27 de Febrero de 2010 donde se evidenciaron errores en la filosofía de diseño como conexiones débiles, pandeo de elementos esbeltos como arriostramientos, problemas en sistemas conexión suelo-estructura, etc. Produciéndose así la necesidad de recopilar estos antecedentes y combinados con los conocimientos estructurales más actualizados para materializar una nueva versión de esta norma, introduciendo parámetros nuevos dentro del acontecer como lo son la incorporación de un factor de amplificación para cargas sísmicas reducidas para elementos no considerados fusibles, aparición de nuevas formas espectrales para diseño y comprobación de elementos y cambios en los límites de compacidad para elementos.
El principal objetivo de este trabajo es realizar el rediseño de un edificio de flotación el cual se proyectó bajo los estándares de la normativa NCh 2369:2003, ahora mediante la actualización del año 2023 cumpliendo las nuevas exigencias de esta para luego proceder con un análisis no lineal de tipo tiempo-historia con la finalidad de determinar el desempeño de este bajo los niveles de sismo de diseño (SDI) y sismo máximo probable (SMP).
El desempeño sísmico arrojó que la estructura presentaba sobrerresistencia, esto debido probablemente al bactor de minoración R utilizado en el diseño de elementos como columnas en los marcos de momento y la existencia de arriostramientos en el otro sentido de la estructura, aún así tanto para niveles SDI y SMP se presentaron fallos en algunos elementos, siendo esto atribuible a la comprobación de la estructura con una baja cantidad de registros y la utilización del parámetro que
maximizó la respuesta en cuestión, aún así se evidenció un uso moderado de la ductilidad de la estructura.
It is common knowledge that Chile has always been and will continue to be a country characterized by its high seismic activity. There is a long history of devastating earthquakes, such as those in Arica in 1868 with an estimated intensity of 9.0 on the Richter scale, or more recent ones like those in Valdivia in 1960 with a magnitude of 9.5 on the Richter scale, or the most recent significant earthquake on February 27, 2010, with a magnitude of 8.8 on the Richter scale. This drives public policies materialized in regulations such as NCh 2369:2023, which seek to guarantee the proper behavior of industrial structures through the implementation of standards aimed at providing the structure with over-resistance and moderate ductility, which ideally should not be needed. The first version of this regulation dates back to 2003, where the initial specific guidelines were defined to properly address seismic events by compiling different codes and adapting them to the national context. This generated positive reactions within the engineering community until the seismic event of February 27, 2010, where errors in the design philosophy were evidenced, such as weak connections, buckling of slender elements like bracings, problems in soil-structure connection systems, etc. This led to the need to gather these findings and combine them with the most updated structural knowledge to materialize a new version of this standard, introducing new parameters such as the incorporation of an amplification factor for reduced seismic loads for non-fuse elements, the appearance of new spectral shapes for design and verification of elements, and changes in compactness limits for elements. The main objective of this work is to redesign a floating building that was designed under the standards of regulation NCh 2369:2003, now updated to the 2023 version, meeting its new requirements, and then proceed with a nonlinear time-history analysis to determine its performance under the design seismic level (SDI) and maximum posible seismic level (SMP). The seismic performance revealed that the structure exhibited over-resistance, probably due to the reduction factor R used in the design of elements such as columns in moment frames and the presence of bracings in the orthogonal direction of the structure. However, failures were observed in some elements for both DSL and MPE levels, which can be attributed to the structure being verified with a small number of records and the utilization of the parameter that maximized the response in question. Nevertheless, a moderate use of the structure's ductility was evidenced.
It is common knowledge that Chile has always been and will continue to be a country characterized by its high seismic activity. There is a long history of devastating earthquakes, such as those in Arica in 1868 with an estimated intensity of 9.0 on the Richter scale, or more recent ones like those in Valdivia in 1960 with a magnitude of 9.5 on the Richter scale, or the most recent significant earthquake on February 27, 2010, with a magnitude of 8.8 on the Richter scale. This drives public policies materialized in regulations such as NCh 2369:2023, which seek to guarantee the proper behavior of industrial structures through the implementation of standards aimed at providing the structure with over-resistance and moderate ductility, which ideally should not be needed. The first version of this regulation dates back to 2003, where the initial specific guidelines were defined to properly address seismic events by compiling different codes and adapting them to the national context. This generated positive reactions within the engineering community until the seismic event of February 27, 2010, where errors in the design philosophy were evidenced, such as weak connections, buckling of slender elements like bracings, problems in soil-structure connection systems, etc. This led to the need to gather these findings and combine them with the most updated structural knowledge to materialize a new version of this standard, introducing new parameters such as the incorporation of an amplification factor for reduced seismic loads for non-fuse elements, the appearance of new spectral shapes for design and verification of elements, and changes in compactness limits for elements. The main objective of this work is to redesign a floating building that was designed under the standards of regulation NCh 2369:2003, now updated to the 2023 version, meeting its new requirements, and then proceed with a nonlinear time-history analysis to determine its performance under the design seismic level (SDI) and maximum posible seismic level (SMP). The seismic performance revealed that the structure exhibited over-resistance, probably due to the reduction factor R used in the design of elements such as columns in moment frames and the presence of bracings in the orthogonal direction of the structure. However, failures were observed in some elements for both DSL and MPE levels, which can be attributed to the structure being verified with a small number of records and the utilization of the parameter that maximized the response in question. Nevertheless, a moderate use of the structure's ductility was evidenced.
Description
Tesis presentada para optar al título de Ingeniero/a Civil.
Keywords
Ingeniería sísmica, Edificios Efectos sísmicos, Análisis estructural (Ingeniería)