Non-destructive testing of columns under axial compression using tranverse vibration technique, and ultrasonic approaches

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2004

Author

Kaynak, Mehmet

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The level of axial compressive load on an existing column is one of the most important parameters to be known. This thesis aims to investigate current state of the art of NDT techniques, their application, and investigate alternative ways of using current technology to estimate the axial compressive load on columns. For this purpose, transverse vibration technique, ultrasonic pulse velocity method, and waveform and frequency content evaluation of ultrasound are investigated and implemented. Analytical and experimental studies on column transverse vibration frequency and axial load relationship are conducted and presented. The measured experimental lateral vibration frequency of the first bending mode decreased under increased axial compressive load as expected from analytical studies. Relationships between axial load and vibration frequency are derived and defined for different boundary conditions. Relationship charts are prepared for complicated solution sets. Numerical calculations, laboratory and field tests revealed that natural frequencies of slender columns are more sensitive to axial load changes. The available ultrasonic methods are investigated and described. Stress wave propagation in anisotropic solids is studied. Previous works have shown that the propogation velocity of stress waves depends on the density, Poisson2s ratio, modulus of elasticity of the medium, and the state of stress. The orientation of the loading direction to the wave propogation direction, the couplant (ultrasonic transmission gel) uniformity, variability in the pressure applied to hold the transducers, alignment of the transmitting and recieving transducers, accuracy and modelling of Poisson2s ratio make the ultrasonic testing more complicated.

Subject Keywords

Columns., Vibration.

URI

http://etd.lib.metu.edu.tr/upload/1260465/index.pdf
https://hdl.handle.net/11511/13993

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

M. Kaynak, “Non-destructive testing of columns under axial compression using tranverse vibration technique, and ultrasonic approaches,” M.S. - Master of Science, Middle East Technical University, 2004.