Seismic performance of a steel-frame building isolated with superelastic friction pendulum bearings

Abstract The present study explores the role of nickel–titanium (NiTi) shape memory alloy (SMA) in improving the efficacy of a superelastic friction pendulum (S-FP) system under cyclic and earthquake loading, with emphasis on the effect of the SMA wire diameter (3, 5, and 10 mm) and the geometric arrangement (X-, V-, and W-shaped). The NiTi SMA transformation behaviour and microstructural features are estimated using the differential scanning calorimetry, X-ray diffraction, and field emission scanning electron microscopecharacterisation methods, and by mechanical testing under cyclic loading. The finite element (FE) model of the NiTi SMA bar was verified with the experimental results. 3D nonlinear FE analyses were performed on the FP and S-FP isolation systems and compared with the available experimental data, and also matched through SAP2000 modelling. The proposed SAP2000 model can capture hardening effects in SMA, improving the accuracy of the SMA material model. The results indicate that the integration of SMA improves the isolator efficiency, with the S-FP system enhancing the energy dissipation by 5%–20% for the X and V shapes, and up to 15% for the W shape, while reducing the residual displacement by 5%–95%. Furthermore, the seismic performance of S-FP isolated three-, six-, and nine-storey buildings was evaluated through nonlinear time history analyses in SAP2000. Compared to only building, S-FP isolated building reduce the peak floor acceleration by 65%–85%, the peak interstorey drift ratio (ISDR) by 20%–60%, and the residual ISDR by 30%–95%. Overall, the V-shaped S-FP with 5 mm diameter offers the best control and recentring under intense earthquakes, and acts as a reliable vibration isolation device.