Abstract
This study aims to investigate seismic behavior of lead-core rubber elastomeric bearing (LRB) and curved surface friction pendulum slider (FPS) base isolated models considering torsional irregularity for typical reinforced concrete buildings. Nonlinear behavior of structural members was considered in analysis models. Total of 1408 different nonlinear time history analyses of 3-dimensional 3, 5, 7 and 9-story models were performed considering 11 spectrum compatible ground motion record pairs. The results indicate that when the rigidity center of base isolator system is not coincided with mass center of superstructure, highest torsional irregularity coefficients were calculated. Lead-core rubber elastomeric bearing type isolators are more sensitive to torsional effects compared to curved surface friction pendulum slider type isolators. Torsional irregularity coefficient values of lead-core rubber elastomeric bearing models with 20% eccentricity are 47% higher than models without eccentricity in terms of averages. The obtained results indicate that significant scatter exists in displacement values of individual ground motion records for all models. Using limited number of ground motion records may lead to inaccurate predictions of seismic demands.
Highlights
The loss of life and property caused by many large-scale past earthquakes has increased the importance of improving the seismic performance of facilities that contain valuable equipment and must continue to be used immediately after the earthquake such as hospitals, police and radio stations and telecommunication centers, etc
While some studies in the literature indicate that torsional effects due to 10% or 20% eccentricity have significant role on building response, they used very limited building models subjected to a few earthquake records
The use of four different reinforced concrete (RC) frame building model with lead-core rubber elastomeric bearing (LRB) and friction pendulum slider isolators (FPS) type isolators subjected to 11 pairs of ground motion records do not strongly support the abovementioned studies in literature
Summary
The loss of life and property caused by many large-scale past earthquakes has increased the importance of improving the seismic performance of facilities that contain valuable equipment and must continue to be used immediately after the earthquake such as hospitals, police and radio stations and telecommunication centers, etc. Base isolation technology is nowadays used as an option in seismic zones to improve seismic performance of structures subjected to earthquakes. The control of structural movements for such buildings is carried out with a specially designed interface at the level of isolators. The main function of seismic isolators is to reduce the transmission of shear forces to the superstructure by extending the vibration period of the whole system, while providing enough rigidity at service load levels for wind and small earthquakes (Ceccoli et al 1999; Erduran et al 2011). Large displacement problems of isolation system can be eliminated by applying significant damping (Şengel et al 2009). The desirable features of isolators are their low lateral stiffness with good energy dissipation and re-centering ability and vertical stability under the building weight and large displacements. The most common seismic isolator types in practice are lead-core rubber elastomeric bearing (LRB) and curved surface friction pendulum slider isolators (FPS) (Heaton et al 1995)
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