Seismic Vulnerability Analysis Of Steel Reinforced Concrete Frame-core Tube Structure Based To IDA

Steel Reinforced Concrete Frame-core tube structure is one of the main structural systems of super high-rise buildings.In engineering applications,the traditional elastoplastic time-history analysis method is widely used in seismic design of structures,but which is unable to accurately consider the ground motion uncertainty and structural uncertainty.Hence,It is of great significance to research on the probability-based seismic fragility analysis of super high-rise buildings.Incremental Dynamic Analysis（IDA）is an important method for structural seismic fragility analysis.Different ground motions,intensity measures and structure types produce different IDA analysis results.It is necessary to seek a reasonable and effective intensity measure for IDA analysis and seismic fragility assessment.At present,the Peek Ground Acceleration（PGA）and Spectral acceleration S_a（T₁）at the fundamental period of the structure are used to evaluated the seismic performance in seismic fragility analysis of the most super high-rise structures.In this paper,taking Steel Reinforced Concrete Frame-core tube structure for example,seismic fragility analysis carried out achieves structural fragility performance of each intensity measures under different earthquake levels,selected the intensity measures of Spectral acceleration S_a（T₁）and average spectral acceleration S_a.avg.（1）Based on the nonlinear analysis software SAP2000,the numerical model of a 35-storey steel reinforced concrete frame-core tube structure is established in this paper.First,modal analysis is carried out and the accuracy and reliability of the model is verified.Then,the IDA analysis is implemented by selecting 10 ground motion records and the maximum inter-story displacement angle as the structural demand measure for obtaining the IDA curves of 19 different one-dimensional scalar and multidimensional vector intensity measure,which combine fundamental scalar intensity measures PGA,S_a,S_a.avg.avg with Peek Ground Velocity（PGV）,Peek Ground Displacement（PGD）and time holding（T_d）.The differences in the spectrum and other characteristics of the ground motions make the IDA curves diversity.The results show that the IDA curve obtained by using the average spectral acceleration S_a.avg.avg is more concentrated in distribution than the spectral acceleration S_a,but they generally perform a softening mode and some curves perform a transitional softening mode with“hardening”characteristics.（2）In accordance with the result of IDA,the Effectivity evaluation on intensity measures is carried out as well as Correlation,Practicality and Proficiency evaluation on intensity measures,which the Effectivity as the core index is measured by the sum of the squares of residuals.And ultimately determine to select S_a.avg,<S_a,PGD>,<S_a.avg,T_d>,<S_a.avg,PGA*T_d^1/3>for the subsequent seismic fragility analysis and PGA,Sa for the comparative analysis.（3）Seismic fragility analysis and structural fragility comparison under the different earthquake levels are carried out with the six selected intensity measures.The collapse probability of each intensity measure under the action of frequent,fortified and rare earthquakes is less than 1%,4%and 9%respectively,which indicate that the Frame-core tube structure can achieve the three-level seismic design requirement of buildings and it has a good seismic performance.Under the rare earthquake,the collapse probability of S_a.avg、<S_a,PGD>、<S_a.avg,T_d>and<S_a.avg,PGA*T_d^1/3>is4%,while the collapse probability of the traditional intensity measures PGA and S_a is 7%and 9%,which show that the traditional intensity measures PGA and S_a for seismic fragility analysis results are relatively conservative.It is suggested that S_a.avg.avg measure is used for probabilistic seismic fragility analysis on super high-rise buildings.