Seismic isolation is a design strategy adopted for the protection of both new and existing structures, based on the assumption that it is possible to uncouple a structure from the ground and thereby protect it from the damaging effects of earthquakes. The most common isolators are the elastomeric ones, which consist of alternating rubber layers and reinforcing metal sheets, connected by vulcanization of the elastomeric compound, and a lead central core. In case of a fire, this compound can suffer permanent damage which can seriously compromise the functionality of the isolation system. This study is focused on the assessment of the fire effect on the elastomeric isolators and the quantification of their loss of efficiency after a fire event. At this purpose, a case study of an existing r.c. structure with multi-storey frames was analysed, for which, after a seismic vulnerability assessment, two possible interventions with seismic isolation were designed. The evaluation of the isolator thermal response for 30 and 60 minutes of exposure to the ISO 834 standard fire curve was used for quantify the damage induced by the fire in terms of degradation of vertical and horizontal stiffness and vertical load-bearing of the isolators. This damage level was defined starting from the thermomechanical properties of the elastomeric layer damaged by fire which, in particular, reached temperatures greater than a critical temperature threshold (70, 200 and 320°C). The estimated degradation was used to evaluate the seismic performance of both isolators and structure in different design configurations, also in a multi-risk scenario that foresee the occurrence of a seismic event after a fire. Finally, in order to mitigate the fire effect on the elastomeric isolators, the effectiveness of a passive fire protection system consisting of plasterboard gypsum boxes was evaluated, ensuring that the critical temperature of 70°C on the outer surface of the isolator was not exceeded even after 60 minutes of exposure to standard fire.
Multi-risk assessment of a base isolated structure / de Silva, D.; Bilotta, A.; Tomeo, R.; Nigro, E.. - (2023). (Intervento presentato al convegno 9th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering tenutosi a Athens (Greece) nel 12-14 June 2023).
Multi-risk assessment of a base isolated structure
de Silva D.;Bilotta A.;Tomeo R.;Nigro E.
2023
Abstract
Seismic isolation is a design strategy adopted for the protection of both new and existing structures, based on the assumption that it is possible to uncouple a structure from the ground and thereby protect it from the damaging effects of earthquakes. The most common isolators are the elastomeric ones, which consist of alternating rubber layers and reinforcing metal sheets, connected by vulcanization of the elastomeric compound, and a lead central core. In case of a fire, this compound can suffer permanent damage which can seriously compromise the functionality of the isolation system. This study is focused on the assessment of the fire effect on the elastomeric isolators and the quantification of their loss of efficiency after a fire event. At this purpose, a case study of an existing r.c. structure with multi-storey frames was analysed, for which, after a seismic vulnerability assessment, two possible interventions with seismic isolation were designed. The evaluation of the isolator thermal response for 30 and 60 minutes of exposure to the ISO 834 standard fire curve was used for quantify the damage induced by the fire in terms of degradation of vertical and horizontal stiffness and vertical load-bearing of the isolators. This damage level was defined starting from the thermomechanical properties of the elastomeric layer damaged by fire which, in particular, reached temperatures greater than a critical temperature threshold (70, 200 and 320°C). The estimated degradation was used to evaluate the seismic performance of both isolators and structure in different design configurations, also in a multi-risk scenario that foresee the occurrence of a seismic event after a fire. Finally, in order to mitigate the fire effect on the elastomeric isolators, the effectiveness of a passive fire protection system consisting of plasterboard gypsum boxes was evaluated, ensuring that the critical temperature of 70°C on the outer surface of the isolator was not exceeded even after 60 minutes of exposure to standard fire.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
