DETERMINATION OF STRUCTURAL COLLAPSE MARGIN RATIO USING PUSHOVER ANALYSIS

The incremental dynamic analysis (IDA) method suggested in ATC-63 report requires a large amount of time history analyses in determining a structural collapse margin ratio (CMR). It is time-consuming and computationally inefficient, not suitable for a quick assessment on collapse margin during the scheme design stage of structures. A practical method proposed herein to evaluate CMR is on the basis of the pushover analysis procedures, in which the collapse performance points of all selected strong ground motions are determined by the improved Park-Ang global damage model and the combination of the capacity curve obtained from the pushover analysis and the demand curves generated from the response spectra of the motions of concern and Nassar-Krawinkler inelastic spectrum. The proposed method has incorporated the concepts addressed in ATC-63 report and the characteristics of the pushover analysis, as well the consideration of variation in the collapse performance point caused by different motions. The computational efficiency has been substantially improved and reasonably conservative. These have been validated through an 8-story reinforced concrete frame structure.