Seismic isolation is a design strategy adopted for the protection of structures, based on the premise that it is possible and feasible to uncouple a structure from the ground and thereby protect it from the damaging effects of the earthquake motions. The most common systems are the elastomeric-based isolation ones, which consist of alternating rubber layers and reinforcing metal sheets, connected by vulcanization of the elastomeric compound, with the insertion of 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 isolator system and the quantification of their loss of efficiency after a fire event. At this purpose, a case study of an r.c. existing structure with multi-storey frames was analysed, for which, after a seismic vulnerability assessment, two possible adaptation 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 insulators. 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-hazard assessment of the system of seismic isolation at the base of an existing reinforced concrete building / DE SILVA, Donatella; Bilotta, Antonio; Ruggiero, Marco; Tomeo, Romeo; Nigro, Emidio. - In: STRUCTURAL. - ISSN 2282-3794. - 243:(2022). [10.12917/STRU243.23]
Multi-hazard assessment of the system of seismic isolation at the base of an existing reinforced concrete building
Donatella de Silva;Antonio Bilotta;Romeo Tomeo;Emidio Nigro
2022
Abstract
Seismic isolation is a design strategy adopted for the protection of structures, based on the premise that it is possible and feasible to uncouple a structure from the ground and thereby protect it from the damaging effects of the earthquake motions. The most common systems are the elastomeric-based isolation ones, which consist of alternating rubber layers and reinforcing metal sheets, connected by vulcanization of the elastomeric compound, with the insertion of 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 isolator system and the quantification of their loss of efficiency after a fire event. At this purpose, a case study of an r.c. existing structure with multi-storey frames was analysed, for which, after a seismic vulnerability assessment, two possible adaptation 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 insulators. 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.