Seismic Fragility Analysis Of Inverted Lenticular Spatial Pipe-Truss Based On IDA Method

In the recent years, with the development of the economy and culture, the pursuit of the buildings' shape, span and scale is much higher than ever. Because of the unique advantages, large-span spatial pipe-truss is widely used in the public buildings, which are required to a higher safety factor, such as the airports, convention centers, stadiums. Incremental dynamic analysis(IDA) is the most promising method for evaluation of seismic performance of building structures in the recent years. However, the research on performance evaluation of large-span spatial pipe-truss based on IDA method is still in the beginning stage, and it is rarely reported combined with seismic fragility analysis.Given this backdrop, this thesis firstly concluded present situation and existing problems about performance-based seismic on spatial structure, and then introduced the basic theory of seismic fragility analysis on IDA method. After that, Based on a large span inverted lenticular pipe truss in an actual project, selected 10 earthquake waves, studied the failure mechanism of the structure subjected to severe earthquakes with three factors consist of the maximum node displacement, the yield component ratio including the depth of plastic deformation and the displacement curve of the key node. Then applied IDA to the large-span spatial pipe-truss, and the structural fragility curves was achieved in the perspective of probability.The results show that the distribution of three factors keeps consistent while the large-span spatial pipe-truss suffers from different earthquakes. However, the seismic amplitudes are not the same, while the structure appears critical state. So are the other two factors, when the structure collapses subjected to severe earthquakes. The maximum node displacement, the yield component ratio including the depth of plastic deformation and the displacement curve of the key node can efficiently reflect the response of the structure under earthquakes.According to the structural fragility matrix, the probabilities that the pipe truss achieve of the three limit states under the three level of 8-degree earthquake are low. The pipe truss can resist 8-degree rare earthquake with a probability of 99.97%.When the structure is subjected to earthquakes with a certain higher value amplitude, all the three factors(the maximum node displacement, the yield component ratio including the depth of plastic deformation and the displacement curve of the key node) change sharply, and the stiffness of the structure becomes weakened. The pipe truss has a high capacity, but with low ductility. The maximum node displacement is an effective damage measure in the analysis of IDA. IDA combined with seismic fragility analysis can be effectively applied to the seismic performance assessment of large-span spatial pipe-truss.