Seismic vulnerability and pounding hazard of asymmetric buildings with transfer system: Experimental and analytical modeling

Historically there is no provision for seismic design of building structures in Hong Kong. However, previous studies suggest Hong Kong should be regarded as a region with moderate seismic risk. The main objective of this study is to investigate the seismic vulnerability of existing wind-designed tall buildings in Hong Kong. It remains a big issue on how such non-seismic-designed buildings will perform under the strike of earthquakes.;In this study, a 1:25 scaled model was fabricated to simulate an asymmetric 21-story building with transfer plate in Hong Kong and tested on shaking table. The test results reveal that the transfer plate and stories above are most susceptible to severe damages under earthquakes. The model damages were evaluated quantitatively through various seismic damage indices, including ductility, inter-story drift ratio, frequency ratio, final softening, and Park and Ang damage index. A new algorithm was developed to estimate the overall Park and Ang index of the whole structure from measured data. Utilizing Park and Ang index as a benchmark, the other damage indices are correlated explicitly with damage states for the first time. This correlation provides a practical approach to assess seismic damages rapidly and is expected to be applicable to similar buildings in Hong Kong.;In the second part of this thesis, seismic torsional poundings between adjacent structures (another possible earthquake-induced damage) were studied from both theoretical and experimental aspects. Theoretically, seismic pounding was modeled using the nonlinear Hertz contact. Numerical simulations were conducted to study the poundings between two single-story towers as well as between a tower and a barrier. An analytical solution is obtained for the latter case. The results show torsional pounding is much more complex than translational pounding and most of them are chaotic or group periodic impacts. From experimental aspect, two 1:45 steel models were fabricated to simulate two adjacent 21-story buildings in Hong Kong, and pounding tests were conducted between them as well as between a model and a rigid wall. It is found that seismic pounding may induce an unplanned period shift to adjacent buildings, which makes their seismic responses more unpredictable than a stand-alone-building.