| Co-Investigator(Kenkyū-buntansha) |
NATANI Seiichiro Osaka City University, Faculty of Engineering, Research Assist., 工学部, 助手 (20047369)
KOBAYASHI Harutoshi Osaka City University, Faculty of Engineering, Associate Prof., 工学部, 助教授 (40047395)
SONODA Keiichiro Osaka City University, Faculty of Engineering, Professor, 工学部, 教授 (70047108)
TOHDA Jun Osaka City University, Faculty of Engineering, Associate Prof., 工学部, 助教授 (90128744)
TAKADA Naotoshi Osaka City University, Faculty of Engineering, Professor, 工学部, 教授 (50047239)
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| Research Abstract |
Information on the evidence of the impulsive seismic strong motion, especially, relating to the vertical motion have been collected and examined to clarify the mechanisms on quasi-impacted failure of civil engineering structure by 1995 Hyogo-ken Nanbu earthquake. One of the interests was pointed to revealing the fracture mechanism of reinforced concrete (RC) structures, especially yiaduct piers, due to strong vertical ground motions at the earthquake. For the sake of this, quasi-impact failure phenomena observed in this earthquake are first described. Second, stress propagation characteristics within a multi-layred ground model excited by vertical ground motions are discussed through a one-dimensional wave reflection theory. Third, a stress amplification phenomenon in the cross section of column in a viaduct pier under a pulse-like vertical stress induced at the bottom face of footing slab is examined by 3D FEM analyzes. Fourth, a possibility of quasi-impact failure of a reinforced con
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crete column is examined through 3D FEM analyzes for a viaduct pier model supported by a multi-layred ground model, and it was made clear that high frequency characteristics of vertical ground motions during earthquake gave the most significant effect on an axial impulsive failure of RC column due to strong tensile and compressive forces. Lastly, to verify the results obtained from the above numerical simulation, model tests by an underwater explosion method were carried out. As results, we could also pointed out the importance of high frequency characteristics of vertical ground motions for failure problems of viaduct piers.
On the other hand, a mechanism on the generation of intensive impulse ground motion was discussed based on the laboratory test for model ground. The experimental results showed the remarkable non-linear effect on not only S-wave but also P-wave velocity and those waveforms depending on the amplitude. A possibility of the intensification of high frequency vertical strong motion within sub soli layrs was pointed under the consideration on the characteristics of dynamic behavior of the ground material and the deep geologic structure resulting in focusing rays of the body wave. Less
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