Detection Of Defects Of Concrete-filled Steel Tubes Based On Torsional Mode And Flexual Mode Guided Waves

With the development of modern science and technology, concrete filled steeltubes (CFST) have been widely used in the construction of bridges，high-risebuildings and large-span structures. However, CFST is prone to cavity defects thatpose negative influence on the integrity and mechanical properties of the structures.Therefore, detection of defects in CFST is required. Traditional detection methodsare mostly by single-position measurement at a time, and they tend to be slow andneed extensive labor. While the guided wave detection features fast, efficient andwide-coverage, and has been widely used in the metal structures. This paper aims atdeveloping a guided-wave based defect detection technology for CFST by atheoretical analysis and numerical simulation approach The main contents are asfollows:Firstly, the dispersion equations of guided wave in the torsional and flexuralmodes in CFST are derived. The frequency dispersion curves are obtained bysolving the equation numerically. The dispersion characteristics of guided waves areanalyzed, and mode T(0,1) and F(1,1) are selected for defect detection of CFST. ForCFST with large diameter, appropriate higher torsional modes guided waves aresuggested for defect inspection.Secondly, the procedure of numerical simulation of guided waves in CFST byfinite element software ABAQUS is introduced. Guided waves in CFST arenumerically simulated, and signals are extracted to perform two-dimensionalFourier transformation. Comparison with theoretical results validates the finiteelement simulation of guided waves in CFST.Finally, numerical simulations of guided waves modes T(0,1) and F(1,1) inCFST with defects are conducted, and defects are detected using the two modes.Results show that within the small diameter CFST, defects can be detected by T(0,1)and F(1,1). Defect quantization by reflection coefficients with the area loss ofsection, the radial depth of defect, the longitudinal length of defect and thecircumferential length of defect are studied, and the results shade some lights onthis issue. Furthermore, defect inspection for CFST with large diameter isinvestigated using appropriate higher torsional modes, and numerical results proveits viability.