Dynamic structural analysis of a high-rise building using simulated intra-plate earthquake : case study for Queensland

Records from intra-plate earthquakes demonstrate that they have particular characteristics, such as frequency content, peak ground acceleration and duration, which may vary throughout the continent. The lack of quality strong motion records of large Queensland earthquakes at short distances necessitates the use of synthetic seismograms for testing of structural behaviour. In this study the structural effects of a moderate magnitude earthquake was simulated from a magnitude 4.4 sub-event recorded in 2004 at the Four Seasons station near Bundaberg, Queensland, using Green's Function method. Previous validation studies for similar events in Australia have shown that synthetics produced by this method are comparable with the Building Code AS 1170.4, and can be used to represent ground motion during typical earthquakes in the study area. A set of spectral curves derived from the synthetics was first compared with the Design Spectrum recommended in tbe Australian Loading Code. A dynamic analysis of a modelled high-rise building was then undertaken, to simulate vibration caused by the passage of seismic waves from a typical moderate size earthquake at close distance. The results of the structural response indicate that the design code may overestimate the design base shear, and the distribution of seismic forces over the height. This is especially evident for buildings over storeys, with width less than 25m, for which cases the earthquake forces govern structural design. The results of this case study emphasise the need for evaluation of location specific spectral curves and their usage in the structural design of high-rise buildings.