The inelastic displacement ratio spectra of pulse-type ground motions always have higher spectral values than ordinary ground motions. And the inelastic strength reduction factor spectra of this type motions are usually less than those of ordinary ground motions. That will result in higher displacement and strength demands for building structure when the structure is subjected to pulse-type ground motions. This article attempts to investigate the influence of different frequency components on the amplitude parameters and inelastic response spectral characterizations of pulse-type ground motions. In total, 53 pulse-type ground motions selected from 12 large earthquakes are utilized in this study. And multi-scale decomposed method is adopted to obtain different frequency ground motion components. The frequency content of the ground motion component obtained by the multi-scale decomposed method is very simple. So this type of ground motion component is termed as simple component. To investigate the influence of the ground motion components in different frequency ranges on the original ground motion (OGM), high frequency component (HFC) and low frequency component (LFC) are defined. The HFC is the linear summation of the simple components with the period less than is, and the LFC is the linear summation of the simple components with the period no less than is. To compare with the results obtained by traditional methods, the predominant component (PC) which can be used as the representation of the dominant velocity pulse and the residual component (RC) which is obtained by removing the PC from original ground motion are analyzed. To explore the reasons for the special characterizations of the inelastic response spectra for pulse-type ground motions, a harmonic ground motion model is used in this study. This article first studies the relationship of the three kinds of amplitude (PGA, PGV and PGD) between original ground motion and the four kinds of ground motion components (LFC, HFC, PC, and RC). Analyses show that the velocity amplitude of PC is less than that of LFC and RC, but the correlation coefficient of the PGV between PC and OGM is more significant. There is a weak relationship of the displacement amplitude between HFC and OGM. Both of the correlation coefficients for PGV and PGD between LFC and OGM are larger than 0.9, but the correlation coefficient of PGA between LFC and OGM is still very large. And then the comparison of the inelastic response spectra between original ground motions and four kinds of ground motion components (HFC, LFC, PC, and RC) is performed. Analyses indicate that the inelastic displacement ratio spectra (IDRS) of HFC and RC are less than those of OGM which is consistent with previous analysis results. The IDRS of LFC and RC is significantly larger than that of OGM. The inelastic strength reduction-factor spectra (ISRS) of PC and LFC are less than those of OGM, and the difference between PC and LFC is not significant. The ISRS of RC and HFC is larger than that of OGM in short-period regions, and the ISRS of LFC is more approximate to that of OGM in long-period regions. The results show that low-frequency component is the major factor that influences the velocity and displacement amplitude of pulse-type ground motion. And it can also cause considerable influence on the acceleration amplitude of original ground motion. Besides, low-frequency component is the immediate causes of the larger inelastic displacement ratio and the smaller inelastic strength reduction factor for pulse-type ground motions.
