Torsional Response of a Building Isolated with Triple Friction Pendulum Bearings under Stochastic Ground Motion Excitation

A Triple Friction Pendulum (TFP) base-isolated building is designed to reduce displacement during an earthquake. However, the appropriate torsional response of multi-storey RCC buildings under stochastic ground motion is still unclear. This paper proposes a new mathematical model to study the torsional response of a TFP base-isolated RCC building subjected to stochastic ground motions. Stochastic ground motions are generated by the Monte Carlo simulation technique. The study examines the torsional response of the base-isolated building through base eccentricity (eb/d), super-structure eccentricity (es/d), uncoupled torsional to lateral frequency ratio of super-structure (Ωs), uncoupled torsional to the lateral frequency of isolator (Ωb) and base shear. The displacement attained as a result of eccentricity is compared with the design-bearing displacement recommended by the China Building Code (GB-2005). The study reveals that the torsion caused by eccentricities significantly influences the torsional behaviour of base-isolated buildings. The TFP base-isolated building with Ωs> 1 is torsionally more stable and potential displacement is not more complex by increasing the value of eb/d. In contrast, the building with Ωs< 1 is torsionally elastic and potential displacement becomes more complex by increasing the value of eb/d. The effect of superstructure eccentricity decreases almost linearly when isolation eccentricities take place. As the time of the superstructure increases, the torsional response of the building also increases. The study concludes that the GB-2005 Standard's design isolator displacement is traditional for the isolation eccentricities.