Effectiveness of Seismic Isolation Technique as a Retrofit Solution in the Case of an RC Building with Corroded Reinforcement

This paper aims to quantify the change in seismic response of a reinforced concrete (RC) building retrofitted by the seismic isolation technique when reinforcement corrosion is considered. In this regard, an 8-story RC building that possesses the characteristics of the existing fixed-base building stock in Türkiye has been identified and hypothetically retrofitted with lead rubber bearings (LRBs). In the numerical models, four different corrosion scenarios to represent the spatial distribution of corrosion on the frame elements of the superstructure and three different corrosion levels considering the mass losses (5, 10 and 20%) due to corrosion are considered; the corresponding reductions in (i) the cross-sectional areas of both the longitudinal and transverse reinforcements and (ii) the mechanical properties of steel and concrete are taken into account. Code-based bidirectional nonlinear response history analyses (NRHAs) are performed by considering the nonlinearity not only in the seismic isolation system but also in the superstructure. Furthermore, LRBs are represented by a force–displacement relation that enables modeling of the deterioration in strength of isolators due to lead core heating during cyclic motion. The results revealed that the spatial distribution of the corrosion is highly effective in amplification of inter-story drift ratios (ISDRs), which can be in the order of 2-fold depending on the level of mass loss. It is found that the seismic isolation technique is still effective in protecting the superstructure against earthquakes even though there is a corrosion problem in frame members.