Abstract
Multiple earthquake damages show that the long-period ground movements have an amplification effect on the dynamic response and seismic damage of long-period structures. To form an improved code design spectrum suitable for long-period ground movements, the standard response spectra consisting of four segments for near-fault pulse-like (NFPL) and far-field harmonic (FFH) ground movements are proposed. Firstly, two types of special long-period ground movements with reliable information are selected for this research. Then, the fundamental period of a single-degree-of-freedom (SDOF) system is extended to 16 s with the damping ratio of 5 %, and the seismic response spectrum and the normalized response spectrum are analyzed. Next, the normalized acceleration spectrum of long-period ground movements is calibrated to the standard response spectrum of regular variation. Finally, the parameters of standard response spectrum about long-period ground movements and the ones of the current code design spectrum are discussed. The results show that the current code design spectrum overestimates the structural seismic response in the short period under NFPL and FFH ground movements, while it underestimates the structural seismic response in the long period. The fundamental period of a SDOF system of china’s current code design spectrum should be extended to consider the influence on long-period structures acted by a long-period earthquake. Further, it accounts for the resonance effect of long-period ground movements which ensures the seismic design safety of long-period structures.
Highlights
The database expansion of recording ground movements demonstrates that there is significant long-period components lying in recent great earthquakes, such as Wenchuan earthquake, Chi-Chi earthquake, Great East Japan earthquake, and so on [1,2,3,4,5]
The normalized acceleration spectrum under common ground movements reaches the peak at 0.18 s, while those under Near-fault pulse-like (NFPL) and far-field harmonic (FFH) long-period ground movements reach the peaks at 0.52 s and 1.48 s respectively
The normalized acceleration spectra under long-period ground movements are relatively dispersed throughout the fundamental periods, and they are not concentrated in the period range of T < 1 s as that under common ground movements
Summary
The database expansion of recording ground movements demonstrates that there is significant long-period components lying in recent great earthquakes, such as Wenchuan earthquake, Chi-Chi earthquake, Great East Japan earthquake, and so on [1,2,3,4,5]. The selected value of long-period segment of seismic design spectrum plays an important role in the seismic design of long-period structures. Digital Seismograph has created many strong earthquake records with reliable long-period components, and many researchers have discussed the reasonable value of long-period segment [17, 18]. Zhou et al, who studied the value of the long-period segment of seismic design spectrum by collecting high-quality acceleration records and related data in different regions, suggested the long-period segment of design response spectrum should not be segmented and the attenuation index should be taken as 0.9 [20]. The statistical response spectra of long-period ground movements are compared with code design spectrum, so as to provide a reference for seismic response analysis of long-period structures and value revision of long-period segment about code design spectrum in China
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