Abstract:Choosing the appropriate ground motion as input is the basis of nonlinear dynamic analysis and incremental dynamic analysis of structures.Firstly,20 suites of near-field ground motion records and 20 suites of far-field ground motion records were chosen and modified to match the targeted design spectrum.Then,taking peak ground velocity (PGV) and spectral acceleration corresponding to the fundamental period of the structure S_a(T₁) as intensity measures,dynamic analysis with the single ground motion intensity level and incremental dynamic analysis (IDA) with multiple ground motion intensity levels were conducted on a 5-storey reinforced concrete frame under the aforementioned 4 sets of ground motion records.Engineering demand parameters (EDS_S) such as maximum inter-story drift ratios (θ_max) and maximum residual inter-story drift ratios (RIDR_max) were obtained.The bias indices to represent the spectral matching effect,the variation of EDP_S and the correlation between EDP_S and intensity measures were further analyzed.Finally,seismic fragility analyses corresponding to different damage states were conducted based on IDA results.The analytical results showed that the correlation of EDP_S with PGV is better than with S_a(T₁).Under spectrum-matched near- and far-field ground motion records,the dispersion of EDP_S decreases obviously and there is no obvious biases in θ_max results.If taking PGV as intensity measure,far-field ground motion induces larger θ_max than near-field ground motion.On the contrary,if taking S_a(T₁) as intensity measure,near-field ground motion induces larger θ_max than far-field ground motion.Prior to collapse of the structure,RIDR_max values corresponding to different damage states under near-field ground motion are larger than the values under far-field ground motion.For collapse state,RIDR_max values under near-field ground motion are less than the values under far-field ground motion.