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广泛地认为强震地面运动的持续时间是影响人造结构反应的重要因素。本项研究的基础是采取和用均方根加速度作为地面运动的一个参数相一致的方式来定义强震地面运动的持续时间。均方根加速度和持续时间是度量强震地面运动强度的一个良好尺度。通过累积均方根(RMS,即root-mean square)函数,研究了均方根加速度对持续时间的依赖关系。均方根的变化率是通过取累积均方根函数的导数而取得的。此导数能够认别出自此以后均方根加速度总是下降的时间。在定义有效持续时间(T_2—T_1)时,这个时间值被用来作为上限截断时间(T_2)。根据反向时间尺度,对记录进行上述运算则可得出下限截断时间(T_1)。文中列出了30个强震地面运动记录水平分量数据(用强震地面运动的均方根加速度),并对按Trifunac-Brady,Bolt以及Vanmarke和Lai方法以及本文所建议的方法所确定的强震地面运动持续时间作了比较。文中还对均方根加速度作为地面运动的一个参数作了讨论。
It is widely believed that the duration of strong ground motion is an important factor that affects the response of man-made structures. The basis of this study is to define the duration of strong ground motions in a manner that is consistent with the rms acceleration as a parameter of ground motion. Root mean square acceleration and duration are a good measure of the intensity of strong ground motion. The root mean square acceleration (RMS) function is used to study the RMS acceleration dependence on duration. The root mean square rate of change is obtained by taking the derivative of the cumulative rms function. This derivative can recognize the time after which the rms acceleration always decreases after that. When defining the effective duration (T_2-T_1), this time value is used as the upper cut-off time (T_2). According to the inverse time scale, performing the above operation on the record results in a lower cut-off time (T_1). The horizontal component data of 30 strong earthquake ground motion records (root mean square acceleration of ground motion with strong earthquakes) are listed in this paper, and are determined by the Trifunac-Brady, Bolt and Vanmarke and Lai methods and the methods proposed in this paper. The duration of the ground motion was compared. The rms acceleration is also discussed as a parameter of ground motion.