# Non-Destructive Testing Applications for Steel Bridges
## 5 Complementary to NDT Methods
### Global Structural Response Testing (GSR)
\begin{table}
\begin{tabular}{|c|c|l|l|l|} \hline
**NDT Technology** & \multicolumn{2}{c|}{**Advantages**} & \multicolumn{2}{c|}{**Disadvantages**} \\ \hline \multirow{4}{*}{Visual Inspection} & \(\bullet\) & Lowest cost of all NDE methods & \(\bullet\) & Dependent on the inspector’s experience and knowledge \\  & \(\bullet\) & Immediate data for viewing and analysis & \(\bullet\) & Limited only to surface defects \\  & \(\bullet\) & No need for equipment and special training & \(\bullet\) & Only able to detect significant flaws \\  & \(\bullet\) & Minimum part preparation & \(\bullet\) & Subjectivity in the identification of the flaws \\ \hline \multirow{4}{*}{Dye-Penetrant Testing} & \(\bullet\) & Simple, less expensive, and rapid NDE method & \(\bullet\) & Limited only to surface defects, unable to determine the depth of cracks \\  & \(\bullet\) & Proper method for detection of & \(\bullet\) & Safety hazard in chemical handling \\  & \(\bullet\) & Proper method for detection of & \(\bullet\) & and disposal \\  & & surface-breaking cracks in metals & \(\bullet\) & Impractical for inspection of the \\  & & & & porous surfaces \\ \hline \multirow{4}{*}{\begin{tabular}{c} Vision-based \\ method/Digital Image \\ Processing \\ \end{tabular} } & \(\bullet\) & Provide better visual appearance of the detected flaws & \(\bullet\) & The cost is dependent on the system used for the inspection \\  & \(\bullet\) & The precise method for rust detection & \(\bullet\) & Can be a time-consuming process \\  & & \(\bullet\) & Need for special training \\ \hline \multirow{4}{*}{\begin{tabular}{c} Eddy Current \\ Testing \\ \end{tabular} } & \(\bullet\) & Rapid NDE method & \(\bullet\) & Its accuracy is dependent on probe size \\  & \(\bullet\) & No need for surface preparation & \(\bullet\) & The probe must be close to the surface of \\  & \(\bullet\) & Detection of hidden defects and estimation & \(\bullet\) & Not suitable for complex geometries, edges; surface conditions affect the test \\  & \(\bullet\) & Low cost and robust sensors, while also & \(\bullet\) & The results are comparative and \\  & & being suitable for automation & \(\bullet\) & not quantitative \\ \hline \multirow{4}{*}{\
\begin{tabular}{c} Radiographic \\ Testing \\ \end{tabular} } & \(\bullet\) & Ability to inspect assembled components & \(\bullet\) & Slow and expensive method; requiring access to the opposite side of a test piece \\  & \(\bullet\) & Minimum surface preparation & \(\bullet\) & Requires handling of radioactive substances and can pose a health hazard \\  & \(\bullet\) & Sensitive to changes in thickness, corrosion, & \(\bullet\) & Not convenient for surface defects and automation unless the system contains specific electronic aid \\  & \(\bullet\) & A permanent record of the inspection & \(\bullet\) & It does not work well with thick sections and is unable to indicate the depth of the flaw below the surface \\  & & & \\  & & & \\ \hline \multirow{4}{*}{Ultra-Sonic Testing} & \(\bullet\) & Portable and lightweight equipment; tests & \(\bullet\) & Expensive compared to other methods \\  & \(\bullet\) & are performed quickly & \(\bullet\) & Special training is needed for the \\  & \(\bullet\) & Inspection data is recorded and can be & interpretation of test results \\  & & accessed easily & \(\bullet\) & It requires surface preparation for coupling \\  & \(\bullet\) & Applicable for thick sections & the transducers to the surface of the \\  & \(\bullet\) & It can be very sensitive (when needed) and & element \\  & & can be fully automated & \(\bullet\) & Difficult for inspection of thin sections \\  & \(\bullet\) & Tests can be performed only from one side & \(\bullet\) & Less effective for brittle materials and \\  & & of the component & \(\bullet\) & irregular geometries \\ \hline \multirow{4}{*}{
\begin{tabular}{c} Infrared Thermography \\ \end{tabular} } & \(\bullet\) & Fast NDE method with the large detection area & \(\bullet\) & Intensive mathematical calculation \\  & \(\bullet\) & The test results are intuitive & & modeling is required for finding the depth \\  & \(\bullet\) & No radiation source; therefore, no health hazard & \(\bullet\) & Not applicable for thick components and \\  & & & cannot detect deep flaws \\  & & No radiation source; therefore, no & \(\bullet\) & Expensive equipment and operational \\  & & health hazard & \(\bullet\) & knowledge are required \\  & & & \(\bullet\) & Moderate accuracy of the results due to \\  & & & & varying emissivity and reflections \\ \hline Laser Technology & \(\bullet\) & Accurate detection of defects & \(\bullet\) & Require special training \\ \hline \end{tabular}
\end{table}