Displacement spectrum model incorporating period characteristics of ground motions

The unique period characteristics of long-period ground motions pose significant seismic threats to high-rise and super-tall structures, making the incorporation of these characteristics into response spectrum models essential for accurate seismic assessment. The ratio of peak ground velocity to peak ground acceleration (PGV/PGA) was introduced as a key indicator to characterize the period characteristics of ground motions. Based on the observed spectral features, a displacement spectrum model incorporating PGV/PGA effects was established. Statistical methods were then employed to determine the model's amplification factors. Following model verification, the effects of PGV/PGA, PGA, PGD/PGV, and damping ratio on the displacement spectra were systematically investigated. Subsequently, the proposed model was compared with the design displacement spectra specified in the code for seismic design of buildings (GB/T50011-2010), leading to relevant design recommendations. The results indicate that, in the acceleration-sensitive region, displacement spectra are positively correlated with PGA, while the influence of PGV/PGA is negligible, suggesting the period characteristics of ground motions have minimal effect here. In the velocity- and displacement-sensitive regions, for a given PGA, displacement spectra increase almost linearly with increasing PGV/PGA, highlighting the significant influence of period characteristics of ground motions. As the damping ratio increases, the displacement spectra decrease, albeit at a diminishing rate. This increase in damping ratio effectively mitigates the influence of period characteristics of ground motions. In the displacement-sensitive region, the predicted displacement spectra for long-period ground motions are consistently lower than the design values prescribed by the Chinese code GB/T50011-2010, indicating that the code's provisions are relatively conservative in this region. However, for sites with characteristic periods less than 0.45 s subjected to long-period ground motions, the code may underestimate spectral demands in the acceleration- and velocity-sensitive regions. These nuanced findings highlight the need for region-dependent design considerations that account for both period characteristics and site conditions.