Diseño por desempeño aplicado a marcos arriostrados concéntricos en estructura industrial filtro Larox basado en la norma NCh2369:2025.
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Date
2025
Journal Title
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Publisher
Universidad de Concepción
Abstract
En Chile, debido a su particular ubicación geográfica, ha estado expuesto a numerosos sismos de diversas magnitudes en distintas zonas del país. Esta realidad ha impulsado que la industria de la ingeniería desarrolle normativas de diseño con el fin de preservar la estructura principal, asegurando continuidad de operación y protección de los habitantes.
Recientemente ha entrado en vigor la nueva normativa NCh2369 versión 2025, cuyo enfoque es mejorar los requerimientos de diseño asociado a las condiciones de suelos. Entre sus principales cambios destaca el desarrollo de expresiones para suelos tipo D y E, y la incorporación de conceptos como la “aceleración máxima de referencia del suelo” que permiten una mejor interpretación de los espectros de referencias y de diseño, así como la determinación de límites en cortes basales de la estructura.
Por otra parte, en la anterior versión NCh2369:2023, las estructuras de periodo relativamente corto presentaban limitaciones en las generaciones de expresiones espectrales. La nueva normativa NCh2369:2025 (INN, 2025) desarrolla la incorporación del factor R* (factor de modificación de la respuesta estructural), el cual puede evaluarse directamente con los periodos con mayor participación de masa modal, eliminando el factor de corte sísmico mínimo.
Actualmente las estructuras poseen una secuencia de disipadores de energías, tales como los arriostramientos y pernos de anclaje. Sin embargo, el sistema de diseño vigente no siempre garantiza una secuencia de plastificación adecuada o bien no se diseñan explícitamente como fusibles sísmicos, lo que en ocasiones puede derivar a desarrollar fenómenos como el piso blando. Este fenómeno surge debido a diferencias de rigidez lateral en el sistema, aumentando las deformaciones, especialmente en los niveles inferiores.
En este contexto, el presente documento busca verificar una metodología de diseño de pernos de anclajes que logre garantizar que el primer fusible en actuar sea pernos de anclaje y posteriormente el pandeo de arriostramientos en sistemas de marcos arriostrados concéntricos (MAC). El desarrollo de la metodología recae en análisis no lineales tiempo-historia de los elementos mencionados.
La estructura por evaluar corresponde a estructura minera industrial que actúa como soporte de diferentes equipos de filtros y estanques de unidades hidráulicas. Denominada “Estructura filtro Larox”, está compuesta por marcos arriostrados y de momento.
El estudio contempla la evaluación de la estructura bajo distintas amenazas sísmicas, nivel de diseño (SDI) y sismo máximo probable (SMP). La metodología de trabajo consiste, en primer lugar, en evaluar los impactos derivados de la nueva normativa NCh2369:2025 (INN, 2025). Posteriormente, se analizará la distribución de energía disipada entre pernos de anclaje en base de columnas y arriostramientos verticales, examinando las deformaciones de los arriostramientos, viendo su elongación, factores de utilización mediante amplificación sísmica en columnas, y finalmente evaluar los drift entre piso entre la metodología de diseño tradicional y la propuesta.
Chile is unique geographical location has exposed it to numerous earthquakes of varying magnitudes across its territory. This reality has driven the engineering industry to develop design codes aimed at preserving primary structural integrity while ensuring operational continuity and occupant safety. Recently, the new NCh2369:2025 standard came into effect, focusing on improving design requirements related to soil conditions. Among its main updates are the development of expressions for soil types D and E, and the introduction of concepts such as the “maximum reference ground acceleration”, which allow for a better interpretation of reference and design spectra, as well as a more accurate determination of limits in structural base shear. Short-period structures previously faced limitations in generating expressions under the 2023 spectrum version. The NCh2369:2025 standard (INN, 2025) incorporates the R* factor (structural response modification factor), which can be evaluated directly using periods with the highest modal mass participation or by considering each vibration period. Currently, structures include an energy dissipation sequence, such as anchor bolts and bracing systems. However, the current design approach does not always guarantee appropriate plasticization sequences, which can sometimes lead to soft-story effects caused by lateral stiffness differences, increasing deformations, particularly in lower levels. In this context, this study aims to evaluate a design methodology for anchor bolts that ensures the first fuse to act are the bolts themselves, followed by the buckling of bracing members in MAC systems. The methodology is developed through nonlinear time-history analyses of the mentioned elements. The structure under evaluation corresponds to an industrial mining structure that supports various equipment, including filters and hydraulic unit tanks. Known as the “Larox Filter Structure”, it consists of braced and moment-resisting frame. The study examines the structure under different seismic threats: Service Desing Earthquake (SDI) and Maximum Probable Earthquake (SMP). The methodology first evaluates the impacts introduced by the NCh2369:2025 (INN, 2025). Then, the distribution of dissipated energy among anchor bolts at column bases and vertical bracings is analyzed, considering bracing deformations, elongation, utilization factors through seismic amplification in columns, and finally, inter-story drifts are compared between the traditional design methodology and the proposed approach.
Chile is unique geographical location has exposed it to numerous earthquakes of varying magnitudes across its territory. This reality has driven the engineering industry to develop design codes aimed at preserving primary structural integrity while ensuring operational continuity and occupant safety. Recently, the new NCh2369:2025 standard came into effect, focusing on improving design requirements related to soil conditions. Among its main updates are the development of expressions for soil types D and E, and the introduction of concepts such as the “maximum reference ground acceleration”, which allow for a better interpretation of reference and design spectra, as well as a more accurate determination of limits in structural base shear. Short-period structures previously faced limitations in generating expressions under the 2023 spectrum version. The NCh2369:2025 standard (INN, 2025) incorporates the R* factor (structural response modification factor), which can be evaluated directly using periods with the highest modal mass participation or by considering each vibration period. Currently, structures include an energy dissipation sequence, such as anchor bolts and bracing systems. However, the current design approach does not always guarantee appropriate plasticization sequences, which can sometimes lead to soft-story effects caused by lateral stiffness differences, increasing deformations, particularly in lower levels. In this context, this study aims to evaluate a design methodology for anchor bolts that ensures the first fuse to act are the bolts themselves, followed by the buckling of bracing members in MAC systems. The methodology is developed through nonlinear time-history analyses of the mentioned elements. The structure under evaluation corresponds to an industrial mining structure that supports various equipment, including filters and hydraulic unit tanks. Known as the “Larox Filter Structure”, it consists of braced and moment-resisting frame. The study examines the structure under different seismic threats: Service Desing Earthquake (SDI) and Maximum Probable Earthquake (SMP). The methodology first evaluates the impacts introduced by the NCh2369:2025 (INN, 2025). Then, the distribution of dissipated energy among anchor bolts at column bases and vertical bracings is analyzed, considering bracing deformations, elongation, utilization factors through seismic amplification in columns, and finally, inter-story drifts are compared between the traditional design methodology and the proposed approach.
Description
Tesis presentada para optar al título de Ingeniero/a Civil.
Keywords
Diseño industrial, Construcciones antisísmicas, Estructuras de acero