Detection of grout sleeve defects based on the time domain dimensionless indicators of component signals

In recent years, precast concrete structures have been widely used in building and bridge engineering. Grouted sleeve connectors (GSC) are extensively applied to connect vertical rebars between precast concrete members. In practical construction, defects, such as no grouting, insufficient grouting, and missing rebar, often exist in the GSC, which reduces the load-bearing capacity. Therefore, detecting GSC defects is important for the safety of precast concrete structures. In this paper, a numerical model of meso-scale GSC concrete was developed. The model was verified by test data from existing literature. The ultrasonic wave signals in the GSC with and without defects were compared in detail. The signals were decomposed based on wavelet packet transform and empirical mode decomposition. Then the time domain dimensionless indicators were extracted to examine the GSC defects. The proposed method was shown to be superior in detecting the GSC defects with high sensitivity.