Impact Acoustic Detection Methods And Techniques For Interface Debonding Defects Of Concrete-Filled Steel Tubes

Concrete-filled steel tube(CFST)is widely used in super high-rise structures and longspan bridges due to their superior mechanical qualities and effective construction efficiency.Debonding of the interface between steel tubes and concrete can arise as a result of improper mix design,building methods,and core concrete creep,directly reducing the bearing capacity of the structure and posing a threat to structural safety.An effective technique for identifying interfacial debonding between steel tubes and concrete is impact acoustics.Yet,several limitations,such as unclear detection mechanisms and unscientific diagnostic for traditional impact acoustic methods,and the lack of portability of detection equipment for novel impact acoustic techniques,have an impact on the quality and efficacy of detection in real-world engineering applications.The main research contents are as follows:(1)This paper proposes a vibration energy ratio(VER)algorithm based on wavelet transform for the debonding detection of CFST interfacial,based on the differences in energy distribution between the flexural vibration mode and the thickness mode.In addition,to suppress the impact of wind noise on the acoustic signals during outdoor detection,a wind noise suppression algorithm based on wavelet denoising combined with bandpass filtering is proposed.(2)This paper has developed a portable impact acoustic detection instrument for detecting interfacial debonding of CFST.The tests of the instrument’s acoustic signal collection ability and the optimal distance between the impact source and microphone have shown that the developed detection instrument has great acoustic signal acquisition performance and the optimal distance for impact acoustic detection is maintained between5-20 cm between the impact source and microphone.In addition,this paper has developed a CFST debonding impact acoustic detection system software that is compatible with the detection instrument,which incorporates the proposed VER detection algorithm.This has enabled the preliminary realization of the integrated real-time detection of the CFST interfacial bonding status.(3)This paper verified the accuracy of the proposed algorithm and developed the instrument through laboratory model experiments.The experimental results of three groups of tests,including debonding qualitative detection,debonding thickness detection,and twodimensional scanning imaging,show that by setting a reasonable VER threshold,it is possible to distinguish between debonding and bonding,and a higher VER value indicates a more severe debonding in the area.In addition,compared with the traditional spectral peak frequency method,the VER algorithm provides a more precise location of defects.(4)Moreover,to further validate the practicality of the algorithm and instrument proposed in this paper,they were applied to the actual debonding detection of the SEG Building in Shenzhen and the Sanshanxi Bridge in Foshan.The detection results showed that the CFST columns of the SEG Building and the CFST arch ribs of the Sanshanxi Bridge suffered from severe debonding and required timely maintenance.In addition,although the impact acoustic method cannot provide a quantitative evaluation of the debonding condition,it has a high detection efficiency and shows good prospects for preliminary engineering detection applications.