1997 Fiscal Year Final Research Report Summary
Effects of soil-structure interaction on the design spectra for buildings
| Project/Area Number |
07458082
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Natural disaster science
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| Research Institution | University of Tokyo |
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Principal Investigator |
MINAMI Tadao Earthquake Research Inst., University of Tokyo, Professor, 地震研究所, 教授 (10012923)
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| Co-Investigator(Kenkyū-buntansha) |
SAKAI Yuuki ERI,Univ.of Tokyo, Assist.Prof., 地震研究所, 助手 (10235129)
KUDO Kazuyoshi ERI,Univ.of Tokyo, Asso.Prof., 地震研究所, 助教授 (50012935)
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| Project Period (FY) |
1995 – 1997
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| Keywords | soil-structure interacting system / school buildings / dynamic impedance / apparent shear wave velocity / swaying and rocking springs / earthquake response spectra |
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| Research Abstract |
In addition to the soil-structure interaction effects, this year we introduced elastic-plastic behaviors of the buildings into the practical procedure for evaluating the soil-structure interaction effects which had been developed in the previous years, since the buildings fall down after undergoing a considerable amount of plastic deformation. As a consequence, the apparent natural periods of the building elongate and the damping constants increase thus making the spectral shape shift to the short period side and spectral values decrease.
Numerical analyzes on the typical accelerograms revealed that this phenomenon was often emphasized too much and canceled the soil-structure interaction effects, i.e., the response in the short period range being greatly suppressed. This coincides with the damage observation made in the 1995 Kobe earthquake ; damage to 1-4 storied buildings was much slight as compared to the surprisingly heavy damage to middle height buildings (with around ten floors). The interaction effects was recovered when we introduced a suitable reduction factor for the apparent shear wave velocity of the ground during an extremely strong ground shaking. For instance, if we reduce the shear wave velocity by applying the well known shear rigidity-amplitude relations having been derived from the soil dynamic laboratory tests, the response spectra for the Kobe earthquake records were feformed to be more consistent to the observed damage. Practical procedures for evaluating the apparent shear wave velocity should be studied in more detail in relation with the damage investigation in the past strong ground motions.
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