Thousands of skyscrapers have been built everywhere in Hong Kong and other metropolis throughout the world. To maximise the lettable space, residential or commercial buildings are often arranged to sit on the companion facilities such as, shopping malls, car parks and mass transit infrastructures. To serve for the multi-purposed architectural arrangement, transfer structures are well recognised as an effective mean of facilitating the complicated architectural layout. However, a major deficiency of using transfer structures is the abrupt changes in the structural systems. This may result in soft storeys which are vulnerable to earthquakes....[ Read more ]

Thousands of skyscrapers have been built everywhere in Hong Kong and other metropolis throughout the world. To maximise the lettable space, residential or commercial buildings are often arranged to sit on the companion facilities such as, shopping malls, car parks and mass transit infrastructures. To serve for the multi-purposed architectural arrangement, transfer structures are well recognised as an effective mean of facilitating the complicated architectural layout. However, a major deficiency of using transfer structures is the abrupt changes in the structural systems. This may result in soft storeys which are vulnerable to earthquakes.

In this thesis, the incremental substitution procedure (ISP) is analytically developed and verified as a suitable method of analysis for day-to-day assessment on the seismic vulnerability of tall buildings with transfer structures. Through introducing incremental ground excitations and irreversible objective damage measurements to the classic substitute-structure method (Shibata and Sozen 1976), ISP is consistent with a special, yet rational class of cases in the conventional nonlinear time-history analysis. This enables the three dimensional multi-modal nonlinear seismic responses of irregular tall buildings to be captured from a series of equivalent linear systems and ordinary elastic response spectra. The procedure is successfully linked with the commercial finite element analysis programme SAP 2000 [CSI 2001]. Applications to large-scale complex building structures are presented as case studies.

Further studies on the effects of vertical irregularity on the performance of tall buildings under earthquake excitations are conducted using simplified benchmark models. By incorporating the variables of the benchmark models with the current design limits for conventional low-to-medium rise shear beam buildings, a universal design chart specifying the desirable maximum core stiffness ratio is developed for design and quick assessment purposes.

Conclusions and recommendations based on the research findings are presented for references to the practising engineers for seismic design and vulnerability of tall buildings assessment in low-to-moderate seismicity regions.