Seismic Drift Demand and Capacity of Non-seismically Designed Concrete Buildings in Hong Kong

Abstract

This paper reviews the seismic engineering research conducted in Hong Kong with special emphasis on the prediction of the seismic drift demand and capacity of existing buildings which have not been designed and detailed to address potential seismic hazards. The paper begins with a comprehensive summary of the local construction and detailing practice of concrete structures, followed by a summary of the drift ratio capacity, ductility capacity, stiffness variation and non-linear damping properties of the non-seismically designed reinforced concrete components. Seismic design response spectra for rock sites developed from Chinese Code GB50011-2001 are compared with the uniform hazard response spectra developed at the University of Hong Kong. The over-conservatism of the Chinese Code particularly in the long period range (T > 2 sec) is highlighted. A direct displacement based method used for the prediction of the maximum drift demands of existing buildings in Hong Kong is also introduced. Phenomena such as stiffness degradation, period shifting, non-linear damping and higher mode effects have been incorporated into the modelling. Lastly, the predicted maximum inter-storey drift demand of 0.3% is compared with the minimum ultimate drift capacity of approximately 1.5%. The capacity predictions were based on results from experimental cyclic load testings of concrete sub-assemblages undertaken in Hong Kong in recent times. The potential risk of damage in Hong Kong buildings under seismic attacks is discussed.