軟かい地盤上における中層建築物の地震時における振動性状について
スポンサーリンク
概要
- 論文の詳細を見る
The characteristics of vibration of a building which rests on a soft ground such as clay, were investigated in comparison with the ground movement observed at the same time during Matsushiro earthquake swarm. The displacement records were both outside and inside a four-story reinforced concrete building in the campus of the Faculty of Engineering, Shinshu University. Earthquakes cited in this paper, occurred from April to June, 1967, and were found to be at a distance of about 10 to 20 k m. and in the range of magnitude 2.8 to 4.5. A comparison of spectra of the building with those of the ground surface shows that there is no significant difference between them excepting the spectral component of the periods which corresponds to the predominant period attributed to the surface layer of ground. In the spectra of the ground surface some peaks appear in the period of 0.30 to 1.0 sec. for both the N-S component (the direction of large dimension of the building) and the E- W component. Among those the frequency of the maximum spectral amplitude is found to be about 0.55 to 0.65 sec. , which agree with the periods of the surface waves. But this frequency component does not bring about the effect so as to magnify the vibration of the building, because the wavelength of the seismic waves is relatively larger than the horizontal dimensions of the building. Accordingly, in view of the relationships among the spectra of the building and those of the ground surface, it may be evident that a portion of the larger amplitude found in the period of about 0.25 to 0.30 sec. is effective to the vibration of the structure. This period coincides with the predominant period of the microtremor on the ground surface near this site. From the maximum spectral amplitude in the period of 0.25 to 0.30 sec., a treatment is shown on how well the magnification of the movement of the first floor to the ground surface or that of the fourth floor to the first floor depends on the earthquake magnitude. For this purpose, the normalized amplitude is used in dividing the spectral amplitude of the first floor by that of the ground surface, or the spectral amplitude of the fourth floor by that of the first floor. As a result, the difference due to the direction of vibration is obtained from the N-S and the E-W components. The normalized amplitude of the first floor for the E-W component varies more abruptly with the earthquake magnitude than that for the N-S component, and vice virsa of the fourth floor. It seems reasonable to consider that the horizontal translation would predominantly occur along the direction of large dimension of the building, while the rocking motion inversely along the direction of the short dimension. Theoretical investigation was made for the period of the horizontal translation in considering the interaction of the soil, the foundation and the upper structure of the building. If it is assumed with much plausibility that the shear velocity of the ground surface is about one quarter of that of the building, the observation may be well explained, though only qualitatively at present.
- 1972-07-25
論文 | ランダム
- 米国企業の文化・社会貢献活動
- ナツミカン及びヒュウガナツの雌ずいの成熟度による受精能力
- ステロイドと免疫抑制剤の併用が効を奏した多発性筋炎1例
- 血胸を合併したマイコプラズマ肺炎の1例
- 軍事化を許容する政治構造--抵抗弱い高度成長の陰の地域 (防衛費突出と軍拡の行方)