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Evaluation of Nonstationary Frequency Properties of Earthquake Strong Ground Motions and Their Significance to Inelastic Responses of Structures

地震强地震动非平稳频率特性评价及其对结构非弹性响应的意义

基本信息

批准号：
02452212
负责人：
KUBO Tetsuo
金额：
$ 2.75万
依托单位：
Nagoya Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1992
项目状态：
已结题

项目摘要

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 … More 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

使用实际的强地面运动，我们评估了运动中包含的非平稳频率特性，并检验了非平稳运动可以产生结构过大的非弹性响应的证据。主要研究结果如下：1.收集了1989年洛马普里埃塔地震和1993年久路秋木地震的强地面运动记录，并通过演化谱分析对强地面运动的非平稳频率特性进行了评估。通过对洛马普里塔地震的运动分析，将非平稳性质分为过渡型、临界型、多显性、三角型和平稳型五种类型。通过对记录的st…的非平稳特性进行讨论，发现软土地基条件下测站的运动在频率成分上表现出较强的非平稳性。更多信息。我们可以指出，地基条件与观测到的非平稳特性模式之间存在相关性。对具有非平稳频率特性的结构进行了非弹性响应分析，并考察了非平稳特性对结构响应的影响。为了表示结构，我们建立了一个单自由度振动系统，它具有与结构的基本周期和强度的变化相关的所谓的双线性、Clough、退化的三线性和面向原点的滞后规则。我们提出了由最大反应到时刻确定的等效周期来表示结构的非弹性反应。我们发现，等效周期被拉长，使得它们等于激励运动的主导周期，这是具有非平稳频率特性的运动在满足一定条件时能够产生过大响应的可能机制。较少