火灾后结构损伤检测数据小波分析法的研究

Study on Post-fire Structural Damage Detection by Wavelet Analysis

检测缺陷的参数是火灾后混凝土结构受损综合评判的重要依据。火灾对钢筋混凝土结构的影响存在不确定性,判断缺陷的参数困难。超声波穿过混凝土后频谱的变化与混凝土的内部缺陷有关,混凝土的内部缺陷对不同频率的超声波衰减不同,通过混凝土缺陷区的超声波带有缺陷的信息。小波分析可以对指定频带和时间段内的信号成分进行分析,在时域和频域具有良好的局部化性质。可以准确地抓住瞬变信号的特性,对频率成分采用逐渐精细的时域或频域取样步长,从而聚焦到信号的任意细节。运用小波的方法分析接收到的超声波的频谱结构,就能判断缺陷的参数。

To test the parameter at the defective zone is the important basis of integrated judgment of damaged concrete structure after fire. Damage degree of reinforced concrete structures after fire is difficult to be determined accurately because the influence of fire on the reinforced concrete structures can not be precisely evaluated. It is very difficult to estimate the parameter at the defective zone. This paper describes the variations of ultrasonic wave frequency spectrum when it transfers at the defective zone in concrete. The attenuation of the variations of ultrasonic wave frequency after transiting the defective zone in concrete is different. The parameter of the defective zone can be found by analyzing the ultrasonic spectra of echo. Wavelet transform has good time frequency localization and can seize character of instantaneous changing signals accurately and focus any details of signal for frequency through gradually meticulous sampling step of time field and frequency field. We can obtain more information to estimate the parameter at the defective zone by the wavelet method.