Geometric Nonlinear Synthetic Earthquake Analysis of Base Isolated Tall Steel Buildings Under Site-Specific Seismic Loading: Fid-Bau Portal

Geometric Nonlinear Synthetic Earthquake Analysis of Base Isolated Tall Steel Buildings Under Site-Specific Seismic Loading

Abbas, Rafaa M. / Abdulkareem, Ameer J.

Abstract

The incorporation of base isolation in building construction in the regions of medium to high seismicity is investigated with special emphasis on the geometric nonlinearity response due to the second-order effect. A thorough investigation is carried out by using time history analysis for different building heights located in different seismic design categories with site soil class D. A synthetic earthquake is developed by using spectral matching to adjust reference time series that consisted of available readings from the past earthquake of the 1940 El Centro earthquake adopted as a reference time series to generate time series compatible with the target response spectrum of the selected regions. The superstructure of the adopted tall buildings, with lead rubber bearings, is represented by finite element models. The study reveals that for high-rise building construction, isolation can significantly reduce seismic response in stiff soil (i.e., site class D). Results presented reflect the potential of synthetic time history analysis to assess the dynamic response of base-isolated tall buildings. The results show that site seismic intensity has a negligible effect on the percentage variation in the story shear, overturning moment, and building acceleration values due to the p-delta effect. Generally, story shear and acceleration values reduced, while overturning moment values increased when the p-delta effect is accounted for. The study has shown that geometric nonlinearity due to p-delta increases building flexibility and reduces the pseudo acceleration of the superstructure and hence the earthquake-induced forces in the structure.