On the intensive impulse ground motion and the quasi-impact failures of civil engineering structure induced during the 1995, Hyogo-ken Nanbu earthquake.

点击翻译按钮获取中文摘要

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 … More 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