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对现代建筑中广泛使用的混凝土桩的检验,本文提出一种比传统的所谓负载试验法更为可靠和经济的新方法——振动分析法。首次以声管模型来估计桩的形伏,实验结果表明该方法是可行的。 在圆柱形桩的上端,用小锤敲击以产生发射脉冲,用加速度计以接收反射信号。把整根桩看成是由多节圆往相接而成,如图1所示。假定:(1)每节圆柱的长度等于声波在半个取样周期内的传播距离。(2)每节的横向尺寸小于波长,故可认为柱中传播的是平面波。(3)忽略传播损耗。(4)截面积的变化仅发生于节与节之间的界面处。
In order to test the widely used concrete piles in modern buildings, this paper presents a new method of vibration analysis that is more reliable and economical than the traditional so-called load test. For the first time, the shape of the pile is estimated by the acoustic tube model. The experimental results show that this method is feasible. At the upper end of the cylindrical pile, a small hammer is struck to generate a launch pulse and the accelerometer is used to receive the reflected signal. Think of the entire pile as being connected by multiple joints, as shown in Figure 1. It is assumed that: (1) The length of each cylinder is equal to the propagation distance of the sound wave in a half sampling period. (2) The transverse dimension of each section is less than the wavelength, so that the propagating plane in the column is a plane wave. (3) ignore the propagation loss. (4) Changes in cross-sectional area occur only at the interface between nodes and sections.