Efecto del fuego en edificaciones industriales de acero, considerando mortero proyectado como protección pasiva
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Fecha
2023
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es
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Universidad Andrés Bello
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Resumen
Las edificaciones industriales de acero están expuestas a diversos riesgos de incendio debido a la naturaleza de las actividades que se llevan a cabo en su interior. Por lo tanto, es de suma importancia comprender y analizar detalladamente el comportamiento de estas estructuras en presencia de un incendio. La presente investigación tiene como objetivo principal evaluar el comportamiento estructural de una edificación industrial construida en acero bajo los efectos del fuego, considerando un tipo de protección
pasiva, destinada a retardar la transferencia de calor del fuego hacia los elementos de acero, en este caso
en particular se usa una protección conocida como mortero ignífugo proyectado, el cual se caracteriza por su
capacidad de resistir altas temperaturas y reducir la propagación del fuego. Al no considerar en el diseño
estructural tanto el peso adicional del mortero proyectado como el impacto del fuego, se desencadena una
acción conjunta que afecta diversos elementos de la estructura. En primer lugar, el aumento del peso sísmico
provocado por el mortero conlleva un incremento en el corte basal de la estructura, lo que genera aumentos
de daños estructurales ante cargas sísmicas. Además, con la presencia del efecto del fuego, el acero se
degrada rápidamente, lo que trae como consecuencia una disminución de sus propiedades mecánicas y
aumentos de esfuerzos axiales, cortantes y momentos. Por otro lado, se presentan dos metodologías que
permiten determinar los espesores de mortero proyectado para diferentes perfiles de acero, la primera es en
base a masividad del perfil y la segunda es siguiendo AISC Steel Design Guide 19. Además, se lleva a cabo
un estudio de la transferencia de calor que ocurre entre el mortero y el acero. Esta investigación surge a raíz
de afirmaciones contradictorias por parte de proveedores y fabricantes, ya que algunos declaran que el
mortero ignífugo permite un aislamiento integral al elemento de acero o estructura, mientras que otros
sostienen que, hay un traspaso de calor, aunque carecen de documentación respaldatoria. Con el fin de
analizar y comprender el comportamiento de diversas estructuras en situación de incendio considerando
mortero proyectado, se realizan evaluaciones de diferentes casos de estudio, sometidos a distintos gradientes
de temperatura, los cuales demuestran aumentos significativos de esfuerzos axiales en las diagonales de
elevación, aumentando más de un 600% de su valor inicial. En el caso de las columnas, estas presentan
aumentos de esfuerzos cortantes por sobre un 200% y aumento de momento flector sobre un 120%, por lo
que hay que tener en consideración diferentes parámetros a la hora de diseñar una estructura bajo
condiciones de incendio y usando mortero ignífugo proyectado como protección pasiva. Es importante
destacar que el estudio se basa en la capacidad de resistencia al fuego durante un tiempo determinado igual
a 120 min.
Steel industrial buildings are exposed to various fire hazards due to the nature of the activities carried out inside them. Therefore, it is of utmost importance to understand and analyze in detail the behavior of these structures in the presence of fire. The main objective of this research is to evaluate the structural behavior of an industrial building constructed in steel under the effects of fire, considering a type of passive protection aimed at delaying the heat transfer from the fire to the steel elements. In this particular case, a protection known as sprayed fireproof mortar is used, which is characterized by its capacity to resist high temperatures and reduce the propagation of fire. By not considering the additional weight of the sprayed mortar and the impact of the fire in the structural design, a joint action is triggered that affects various elements of the structure. First, the increase in seismic weight caused by the mortar leads to an increase in the basal shear of the structure, generating increased structural damage under seismic loads. Additionally, with the presence of the fire effect, the steel degrades rapidly, resulting in a decrease in its mechanical properties and an increase in axial and shear forces and moments. On the other hand, two methodologies are presented to determine the thicknesses of sprayed mortar for different steel sections. The first one is based on the massiveness of the section, while the second one follows AISC Steel Design Guide 19. Furthermore, a study of the heat transfer that occurs between the mortar and the steel is carried out. This research arises from contradictory statements by suppliers and manufacturers. Some state that the fireproof mortar allows integral insulation to the steel element or structure, while others claim that there is heat transfer, although they lack supporting documentation. In order to analyze and understand the behavior of various structures in a fire situation considering sprayed mortar, evaluations of different case studies are carried out. These structures are subjected to different temperature gradients, which show significant increases in axial stresses in the diagonal elevations, increasing more than 600% of their initial value. For columns, there are increases in shear forces of over 200% and increases in bending moment of over 120%. Therefore, different parameters must be taken into consideration when designing a structure under fire conditions and using sprayed fireproof mortar as passive protection. It is important to note that the study is based on the fire resistance capacity during a given time equal to 120 min.
Steel industrial buildings are exposed to various fire hazards due to the nature of the activities carried out inside them. Therefore, it is of utmost importance to understand and analyze in detail the behavior of these structures in the presence of fire. The main objective of this research is to evaluate the structural behavior of an industrial building constructed in steel under the effects of fire, considering a type of passive protection aimed at delaying the heat transfer from the fire to the steel elements. In this particular case, a protection known as sprayed fireproof mortar is used, which is characterized by its capacity to resist high temperatures and reduce the propagation of fire. By not considering the additional weight of the sprayed mortar and the impact of the fire in the structural design, a joint action is triggered that affects various elements of the structure. First, the increase in seismic weight caused by the mortar leads to an increase in the basal shear of the structure, generating increased structural damage under seismic loads. Additionally, with the presence of the fire effect, the steel degrades rapidly, resulting in a decrease in its mechanical properties and an increase in axial and shear forces and moments. On the other hand, two methodologies are presented to determine the thicknesses of sprayed mortar for different steel sections. The first one is based on the massiveness of the section, while the second one follows AISC Steel Design Guide 19. Furthermore, a study of the heat transfer that occurs between the mortar and the steel is carried out. This research arises from contradictory statements by suppliers and manufacturers. Some state that the fireproof mortar allows integral insulation to the steel element or structure, while others claim that there is heat transfer, although they lack supporting documentation. In order to analyze and understand the behavior of various structures in a fire situation considering sprayed mortar, evaluations of different case studies are carried out. These structures are subjected to different temperature gradients, which show significant increases in axial stresses in the diagonal elevations, increasing more than 600% of their initial value. For columns, there are increases in shear forces of over 200% and increases in bending moment of over 120%. Therefore, different parameters must be taken into consideration when designing a structure under fire conditions and using sprayed fireproof mortar as passive protection. It is important to note that the study is based on the fire resistance capacity during a given time equal to 120 min.
Notas
Proyecto de título (Ingeniero Civil)