Diseño de pernos de anclaje basado en desempeño sísmico aplicado a marcos arriostrados concéntricos.
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Date
2025
Journal Title
Journal ISSN
Volume Title
Publisher
Universidad de Concepción
Abstract
En Chile, el diseño sísmico de estructuras industriales se basa en las disposiciones establecidas en la norma NCh2369. Dentro de este marco normativo, el diseño de elementos estructurales en los cuales se acepta plastificación, como arriostramientos y pernos de anclaje, se realiza considerando cargas sísmicas reducidas por el factor de modificación de la respuesta, R.
El comportamiento ideal de una estructura ante un evento sísmico es aquel en el cual la fluencia de los pernos de anclaje precede al pandeo de los arriostramientos, ya que esto favorece que los pernos asuman un rol predominante en la disipación de energía, disminuyendo la probabilidad de pandeo de los arriostramientos y el riesgo de formación de un piso blando. Sin embargo, la forma tradicional de diseño no garantiza esta secuencia de plastificación, comprometiendo la estabilidad de la estructura.
Ante esta problemática, se plantea una nueva metodología de diseño de pernos de anclaje, la cual garantiza la secuencia de plastificación deseada. Esta propuesta está desarrollada para edificios industriales estructurados en base a marcos arriostrados concéntricos (MAC) y tiene como principal objetivo mejorar su desempeño sísmico. Para evaluar su eficacia, se realizan análisis dinámicos no lineales del tipo tiempo-historia, considerando la no linealidad de los anclajes y arriostramientos. Los análisis se efectúan en primera instancia en un espacio arquetipo plano de 16 estructuras con períodos comprendidos entre los 0.15 s y 0.90 s. Posteriormente, se realizan en dos estructuras tridimensionales, correspondientes a edificios industriales reales emplazados en las zonas centro y norte de Chile.
El objetivo de los análisis es comparar el desempeño sísmico de las estructuras mediante la aplicación de ambas metodologías. Para los análisis se utilizan 15 registros sísmicos considerando dos niveles de amenaza sísmica, correspondientes al sismo de diseño (SDI) y sismo máximo posible (SMP). Los parámetros analizados incluyen: distribución de la energía disipada por pernos y arriostramientos; factor de reducción de la respuesta por ductilidad; elongación de pernos de anclaje; factor de utilización de columnas sísmicas; drift de entrepiso y deformación de arriostramientos verticales. Los resultados obtenidos evidencian que la aplicación de la metodología propuesta mejora significativamente el desempeño sísmico de las estructuras en comparación con el diseño tradicional. Los análisis realizados respaldan la aplicabilidad de la metodología propuesta como una alternativa eficiente para optimizar el desempeño sísmico de estructuras industriales de tipología MAC.
In Chile, the seismic design of industrial structures is based on the provisions established in the NCh2369 standard. Within this regulatory framework, the design of structural elements in which plasticization is allowed, such as bracing systems and anchor bolts, is carried out considering seismic loads reduced by the response modification factor, known as R. The ideal behavior of a structure during a seismic event corresponds to a scenario in which the tensile yielding of the anchor bolts precedes the buckling of the bracing members. This mechanism ensures that the anchor bolts play a predominant role in energy dissipation, reducing their likelihood of buckling and thus mitigating the risk of soft-story formation. However, traditional design methods do not guarantee this plasticization sequence, compromising the stability of the structure. To address this issue, a new design methodology for anchor bolts is proposed, which ensures the desired plasticization sequence. This methodology is specifically developed for industrial buildings structured with concentrically braced frames (CBFs) and aims to enhance their seismic performance. To evaluate its effectiveness, nonlinear time-history analyses are conducted, considering the nonlinearity of both anchor bolts and bracing members. Initially, the analyses are performed on a planar archetype space consisting of 16 structures with periods ranging from 0.15 s to 0.90 s. Subsequently, the analyses are extended to two three-dimensional structures, which correspond to real industrial buildings located in northern Chile. The objective of the analyses is to compare the seismic performance of structures through the application of both methodologies. These are conducted using 15 seismic records, considering two levels of seismic hazard: the design-level earthquake (SDI) and the maximum considered earthquake (SMP). The analyzed parameters include the distribution of energy dissipation between anchor bolts and bracing members, the response reduction factor due to ductility, anchor bolt elongation, seismic column utilization factor, interstory drift, and deformation of vertical bracing members. The results demonstrate that the proposed methodology significantly improves the seismic performance of structures, compared to the traditional design approach. The conducted analyses support the applicability of the proposed methodology as an efficient alternative for optimizing the seismic performance of industrial structures of the CBF typology.
In Chile, the seismic design of industrial structures is based on the provisions established in the NCh2369 standard. Within this regulatory framework, the design of structural elements in which plasticization is allowed, such as bracing systems and anchor bolts, is carried out considering seismic loads reduced by the response modification factor, known as R. The ideal behavior of a structure during a seismic event corresponds to a scenario in which the tensile yielding of the anchor bolts precedes the buckling of the bracing members. This mechanism ensures that the anchor bolts play a predominant role in energy dissipation, reducing their likelihood of buckling and thus mitigating the risk of soft-story formation. However, traditional design methods do not guarantee this plasticization sequence, compromising the stability of the structure. To address this issue, a new design methodology for anchor bolts is proposed, which ensures the desired plasticization sequence. This methodology is specifically developed for industrial buildings structured with concentrically braced frames (CBFs) and aims to enhance their seismic performance. To evaluate its effectiveness, nonlinear time-history analyses are conducted, considering the nonlinearity of both anchor bolts and bracing members. Initially, the analyses are performed on a planar archetype space consisting of 16 structures with periods ranging from 0.15 s to 0.90 s. Subsequently, the analyses are extended to two three-dimensional structures, which correspond to real industrial buildings located in northern Chile. The objective of the analyses is to compare the seismic performance of structures through the application of both methodologies. These are conducted using 15 seismic records, considering two levels of seismic hazard: the design-level earthquake (SDI) and the maximum considered earthquake (SMP). The analyzed parameters include the distribution of energy dissipation between anchor bolts and bracing members, the response reduction factor due to ductility, anchor bolt elongation, seismic column utilization factor, interstory drift, and deformation of vertical bracing members. The results demonstrate that the proposed methodology significantly improves the seismic performance of structures, compared to the traditional design approach. The conducted analyses support the applicability of the proposed methodology as an efficient alternative for optimizing the seismic performance of industrial structures of the CBF typology.
Description
Tesis presentada para optar al título de Ingeniero/a Civil.
Keywords
Diseño antisísmico, Anclaje (Ingeniería de estructuras)