Seismic performance of insitu and precast soft storey buildings

Lightly reinforced concrete columns and soft storey configurations are prevalent in many old buildings in regions of lower seismicity. This type of construction is believed to have a very low lateral load and drift capacity from a conventional design perspective. Furthermore, the application of design standards in low and moderate seismic regions such as Australia, results in most of the lightly reinforced structures being deemed unsafe in an earthquake. Therefore, an earthquake damage reconnaissance, experimental field test, and laboratory study of non-ductile columns was undertaken to examine the drift capacity and failure mechanism of such columns. Firstly, a field reconnaissance was conducted in China after the Wenchuan Earthquake in 2008, particularly in regions with similar design intensity MMI VI to VIII experienced in Australia. A comparison between the Wenchuan Earthquake and the characteristics of design earthquakes in Australia was made to provide insight for the development of future design standards and for the assessment of existing buildings in Australia. A unique experimental field testing of a precast soft storey building in Melbourne was then undertaken. Four pull-over tests were conducted to measure the drift capacity and load-deflection behaviour of such buildings. Detailed theoretical models were developed that considered rocking behaviour, connection behaviour, P-Delta effects and ground slab interaction effects. The experimental results together with a comparison with theoretical model predictions showed that the precast columns with weak connection had significant displacement capacity controlled by column rocking irrespective of strength degradation. Finally, a laboratory based investigation was undertaken to understand the collapse behaviour of in-situ lightly reinforced concrete columns. The effect of variation of axial load ratio and longitudinal reinforcement ratio on flexural, yield penetration, and shear displacement as components of the drift capacity were observed. The experimental and analytical results showed that the drift capacity of lightly reinforced concrete columns was considerably greater than the code recommendations. Several analytical models were developed to investigate the lateral load-drift relationship of lightly reinforced concrete columns that included elastic and inelastic flexure, yield penetration and shear deformation effects. In addition, formulae for estimating the drift capacity at lateral load failure and axial load failure were developed from a database of 46 specimens from 12 studies including the experimental work reported in this thesis. The outcomes of this research make an original contribution to the improved understanding of the lateral load---deflection behaviour of lightly reinforced concrete columns and soft storey buildings.