Nonlinear response analyses of a 2-storey RC building with fibre-reinforced elastomeric isolators

Abstract

Base isolation (BI) is one of the most promising techniques for seismic risk mitigation. How-ever, the high cost of traditional isolators undermines the systematic implementation of BI sys-tems in both new and existing buildings. In the last decade, fibre-reinforced elastomeric isolators (FREIs) have been developed as a promising low-cost alternative to steel reinforced elastomeric isolators. This study presents a numerical investigation on a three-dimensional, two-storey reinforced concrete (RC) frame designed for gravity loads only, which is representa-tive of a recurrent situation in many existing European buildings even in earthquake-prone areas. The specimen was base isolated with innovative FREIs and was subjected to shaking table tests at LNEC, Lisbon, Portugal, within the ERIES-FREISUST research project. This pa-per presents the main outcomes of the numerical modelling of the building specimen. In a first stage, the building was analyzed through a pushover analysis in fixed-based configuration to identify the global seismic capacity, damage progression, and collapse mechanism. The influ-ence of infill walls along one horizontal direction was also addressed by the model, showcasing its significant contribution to the lateral resistance. The FREI BI system was designed to achieve a target isolation period lower than 2 s. Assuming a Bouc-Wen hysteretic model of FREIs, which was calibrated based on experimental tests, the specimen response was investi-gated via nonlinear time history analysis (NLTHA). Based on the expected displacement ca-pacity of the BI devices, both ordinary and pulse-like ground motion records were selected to be representative of medium-to-high seismicity regions and to finely tune the performance level of FREIs. Both horizontal components of ground motions were imposed to the model. NLTHA demonstrated adequate filtering effect of the isolation system with no damage to both structural and non-structural building components, confirming the experimental observations from the shaking table tests and the effectiveness of FREIs for applications to housing projects.