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,
Poisson&rsquo / s 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 Poisson&rsquo / s ratio make the ultrasonic
testing more complicated.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/1260465/index.pdf |
| Date | 01 February 2004 |
| Creators | Kaynak, Mehmet |
| Contributors | Turer, Ahmet |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
Page generated in 0.0019 seconds