1992 Fiscal Year Final Research Report Summary
Evaluation of Nonstationary Frequency Properties of Earthquake Strong Ground Motions and Their Significance to Inelastic Responses of Structures
| Project/Area Number |
02452212
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Building structures/materials
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| Research Institution | Nagoya Institute of Technology |
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Principal Investigator |
KUBO Tetsuo Nagoya Institute of Technology Associate Professor Faculty of Engineering, 工学部, 助教授 (20161664)
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| Project Period (FY) |
1990 – 1992
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| Keywords | Earthquake Engineering / Structural Engineering / Ground Motion / Seismic Response / Inelastic Response / Reinforced Concrete / Nonstationary Property / Frequency Contents |
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| Research Abstract |
Using real strong ground motions we evaluate nonstationary frequency properties included in the motions, and examine the evidence that nonstationary motions can generate excessively large inelastic responses of structures. The results obtained are summarized as follows;
1. We collect the strong ground motion records obtained during those such as the 1989 Loma Prieta and 1993 Kushiro-oki earthquakes, and through evolutionary spectral analysis we evaluate nonstationary frequency properties of strong ground motions.
2. Through analysis upon the motions obtained during the Loma Prieta earthquake, we group the nonstationary properties into five patterns that are named herein the transition, advent, multi-dominant, delta-shaped and stationary types.
3. We find the tendency that motions obtained at stations with soft subsoil condition reveal strong nonstationary property in frequency contents when we discuss the nonstationary properties in correlation with the subsoil profile of the recording st
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ations. We can point out that correlation exists between the subsoil condition and the observed pattern of nonstationary properties.
4. We perform inelastic response analysis of structures subjected to motions having nonstationary frequency properties, and examine significance of the nonstationary properties to responses of structures. To represent a structure, we establish a single-degree-of-freedom oscillating system that has the so-called bi-linear, Clough, degrading tri-linear and origin-oriented hysteresis rules associated with a variation of the fundamental period and strength of structures. We propose the equivalent period that is determined from the maximum response generated up to the moment to represent inelastic response of structure. We find the fact that the equivalent periods are elongated so as they equal the dominant periods of the exciting motion, which is the possible mechanism that the motions having nonstationary frequency properties can generate excessively large responses when certain conditions fulfilled. Less
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Research Products
(20 results)
