Identification of transient vibration characteristics of pile-group models during liquefaction using wavelet transform
Identification of transient vibration characteristics of pile-group models during liquefaction using wavelet transform
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DOI：
10.1016/j.engstruct.2018.06.028
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发表时间：
2018-09
影响因子：
5.5
通讯作者：
F. Hall;D. Lombardi;S. Bhattacharya
中科院分区：
文献类型：
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作者：
F. Hall;D. Lombardi;S. Bhattacharya
采用基于小波变换的时频分析方法，对2个2 × 2群桩模型的瞬态振动特性进行了研究。模型受到三种不同的记录，包括白色噪声输入和2011年基督城地震的两种不同比例的记录。与传统的傅立叶分析相比，所提出的方法具有的优点，使可视化的时间变化的结构频率和频率含量的地面运动由于液化的有效方式。据发现，液化导致结构频率的减少，其减少取决于超孔隙压力的建立，从而高利率（“快速液化”）导致更大的减少，即高达51%的速度。液化也是延长地面运动的卓越周期和缩小其整体频率带宽的原因。降低结构频率和滤除地震动高频分量的联合作用可能导致移动共振条件，从而导致结构反应放大。液化发生后，有一个重新分配的最大弯矩向更深的海拔，表明运动学土-结构相互作用占主导地位的整体地震反应。
A time–frequency approach based on the wavelet transform is used to examine the transient vibration characteristics of two 2 × 2 pile-group models tested in a shake table. The models are subjected to three different records consisting of white noise input and two differently scaled records from the 2011 Christchurch Earthquake. In contrast to conventional Fourier analysis, the proposed method has the advantage of enabling the visualisation of the temporal variation in structural frequencies and frequency content of ground motion due to liquefaction in an effective way. It is found that liquefaction causes a decrease in structural frequency, whose reduction depends on the rate of excess pore pressure build-up, whereby high rates (“fast liquefaction”) lead to greater reduction, ie, up to 51%. Liquefaction is also responsible for the elongation of the predominant period of the ground motion and narrowing of its overall frequency bandwidth. The combined effect of reduction in structural frequency and filtering of high frequency components of the ground motion may lead to moving resonance condition, resulting in amplification of structural response. After the onset of liquefaction, there is a redistribution of maximum bending moment toward deeper elevations, indicating that kinematic soil-structure interaction dominates the overall seismic response.