“…Conveniently and effectively detecting the fullness of sleeve grouting has always been a difficult problem in prefabricated concrete buildings. The ultrasonic wave method (Feng et al, 2020), the impact-echo method (Chou, 2019), the X-ray CT method (Zelelew et al, 2013;Gao et al, 2017), the damped vibration method (Zhu et al, 2018), the X-ray method (du Plessis and Boshoff, 2019), and the embedded wire-drawing method (Gao et al, 2019) are relatively mature detection technologies, but they are expensive and labor intensive, which means they are not conducive to the full detection of sleeve grouting. Because such defects are typically local, traditional global-based non-destructive dynamic testing methods also face great challenges when used with complex structures, because these technologies are unable to obtain effective local feature information from global dynamical data (Yoon et al, 2010).…”