【摘要】 研究液化场地和非液化场地上地表地震加速度记录的时频曲线,提出频率下降率概念和计算方法,给出液化场地和非液化场地频率下降率的分界值。加速度时频曲线采用零交法进行分析,非液化场地包含软土场地和除去软土场地后的一般非液化场地。结果表明:①所定义的频率下降率的概念和计算方法,能够反映液化和非液化场地地表加速度时频响应特征和变化规律;②峰值前,在平均意义上液化场地与一般非液化场地平均频率相差不大,软土场地上的平均频率远小于一般非液化场地和液化场地;③峰值后,在平均意义上一般非液化场地加速度平均频率最高,软土场地居中,液化场地最低;④软土场地与液化场地峰值后平均频率范围有交叉,如以加速度时频曲线绝对变化量为判断标准,软土场地和液化场地会出现混淆;⑤液化场地和非液化场地的加速度频率下降率的分界值为0.5,以此可正确区分出液化场地与非液化场地以及液化场地与软土场地。更多还原

【Abstract】 The time-frequency histories of acceleration records on liquefied and non-liquefied sites are analyzed.The concept and the calculation method of frequency decreasing ratio are proposed;and the division between the liquefied and non-liquefied sites is presented.The zero-crossing method is employed to analyze the time-frequency curves of acceleration records.The non-liquefied sites include the soft sites and the ordinary non-liquefied sites.The results indicate:① The concept and calculation method of frequency decreasing ratio proposed in this paper can describe the characteristics and regulations of time-frequency on liquefied and non-liquefied sites.② Before PGA,the difference of the average frequencies of acceleration on liquefied and non-liquefied sites is not obvious;and the average frequency of acceleration on soft sites is smaller than that either on liquefied or non-liquefied sites.③ After PGA,the average frequency of acceleration on ordinary non-liquefied sites is the highest of the three types of sites,that of soft sites is the middle and that of liquefied sites is the smallest.④ If the absolute change of the time-frequency is used as the criteria,it will be confused between soft sites and liquefied sites.⑤ The threshold of frequency decreasing ratio is 0.5 between liquefied and non-liquefied sites,which can distinguish the liquefied sites,non-liquefied sites and soft sites correctly.更多还原