| More and more surveys of the seismic hazard showed that vertical ground motion decided the final failure of structure. With more and more seismic stations being built, researchers get more and more adequate strong-motion data. And they were surprised to find that sometimes vertical-to-horizontal(PGAV/PGAH) ratios were largely exceeds the commonly(such as Code for seismic design of buildings in China) assumed value of 2/3, even, larger than 1. In this paper, based on 2038 records in total, which were collected while earthquake magnitude M≥5, epicenter distance R≤300km and peak acceleration of horizontal ground motions PGAH≥0.1g, the design vertical acceleration of ground motion are analyzed. The studies of this paper are as following.①The existing studies on vertical ground motions and statistics are analyzed and summarized. And many adequate motion records were gathered, then the earthquake magnitude M≥5, epicenter distance R≤300km and peak acceleration of horizontal ground motions PGAH≥0.1g ones were collected as the base of analysis of this paper.②Based on the summarized study fruits before, the 2038 records are divided into 5 groups on account of earthquake magnitude to screen the outliers.③Based on the records, we can come to a regular of PGAV/PGAH and earthquake magnitude, epicenter distance, characteristic periods. Also, with a detailed analysis, we come to a conclusion: characteristic period has little influence on the relation of PGAV/PGAH and earthquake magnitude, epicenter distance, but has a greater effect on the relation of PGAV/PGAH and earthquake intensity.④Based on the studies about acceleration attenuation curves, some regulars are provided about PGAV/PGAH.⑤Based on the conclusion above, some advises are provided for the seismic design. The values of PGAV/PGAH for seismic design base on earthquake magnitude and epicenter distance are suggested. And the values of PGAV/PGAH for seismic design base on earthquake intensity are suggested, too. |
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