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

使用真实的强地面运动，我们评估的运动中包含的非平稳频率特性，并检查的证据表明，非平稳运动可以产生过大的非弹性反应的结构。主要研究结果如下：1.本文收集了1989年洛马普列塔地震和1993年钏路冲地震的强地面运动记录，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价.通过对洛马普列塔地震的运动分析，将地震的非平稳性分为过渡型、临震型、多优势型、三角形型和平稳型五种类型.在讨论与记录台站的地基剖面相关的非平稳特性时，我们发现在软地基条件下的台站所获得的运动在频率成分上表现出强烈的非平稳特性的趋势。 关于我们 行动。我们可以指出，相关性之间存在的底土条件和观察到的模式的非平稳特性。我们进行非弹性响应分析的结构进行运动具有非平稳频率特性，并检查的意义的非平稳特性的结构响应。为了代表一个结构，我们建立了一个单自由度的振荡系统，具有所谓的双线性，克拉夫，降解三线性和原点为导向的滞后规则与结构的基本周期和强度的变化。我们提出了等效周期，这是确定从最大响应产生的时刻来代表结构的非弹性响应。我们发现，等效周期被拉长，使他们等于主导周期的激励运动，这是可能的机制，具有非平稳频率特性的运动可以产生过大的响应时，满足一定的条件。少

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