# Non-Destructive Testing Applications for Steel Bridges
## 6 Summary and Conclusions
\begin{table}
\begin{tabular}{|c|c|l|l|} \hline
**NDT Technology** & \multicolumn{2}{c|}{**Advantages**} & \multicolumn{2}{c|}{**Disadvantages**} \\ \hline \multirow{6}{*}{Magnetic Flux Leakage} & \(\bullet\) & Rapid NDT method & \(\bullet\) & Require access to the element \\  & \(\bullet\) & Simply used for automation & \(\bullet\) & Cannot detect the diagonal defects properly \\  & \(\bullet\) & Requiring little or no surface preparation & \(\bullet\) & Each component needs to be tested twice, \\  & & (cleaning of the surface from oil or grease & & ensuring that the flux travels in \\  & \(\bullet\) & Inexpensive NDT technique & & two directions \\  & & & \(\bullet\) & Its accuracy depends on the size of \\  & & & & the probes \\ \hline \multirow{6}{*}{Chemical and Electrical Testing (CET)} & \(\bullet\) & Fast NDT method & \multirow{6}{*}{\(\bullet\)} & \multirow{6}{*}{\(\bullet\)} \\  & \(\bullet\) & Determine regions susceptible to chloride & & \\  & & penetration & & \\  & \(\bullet\) & It can be implemented to map & & \\  & & corrosion activity & & \\ \hline \multirow{2}{*}{Magnetostriction} & \(\bullet\) & Fast and simple NDT method & \(\bullet\) & Not practical for small defects \\  & & & \(\bullet\) & Requires special training \\ \hline \multirow{2}{*}{Vibration Method} & \(\bullet\) & It is implemented remotely & \multirow{2}{*}{\(\bullet\)} & Time-consuming NDT method \\  & \(\bullet\) & Simple NDT method & \(\bullet\) & Dependent on the ambient condition \\  & \(\bullet\) & No need for surface preparation & & \\ \hline \multirow{6}{*}{Acoustic Emission} & \multirow{6}{*}{\(\bullet\)} & \multirow{6}{*}{Long-term and remote monitoring} & \multirow{6}{*}{\(\bullet\)} & Require surface preparation (removal of \\  & & & thick coatings) \\  & & & \(\bullet\) & Results depend on the arrangement \\ \cline{1-1}  & \(\bullet\) & Portable NDT method & & of transducers \\ \cline{1-1}  & \(\bullet\) & Ability to detect very small cracks & & Require special training and skilled labor to \\ \cline{1-1}  & \(\bullet\) & Ability to locate the source of failure & & test and interpret \\ \cline{1-1}  & & & \(\bullet\) & Requiring noise filtering waveguides in \\ \cline{1-1}  & & & high noises arenasimability to repeat \\ \cline{1-1}  & & & the measurement & \\ \hline \end{tabular}
\end{table} 
Table 3: _Cont._flaws in non-porous surfaces. Magnetic particle testing is a fast and inexpensive NDT method suitable for ferromagnetic materials that requires minimum training for inspectors. The eddy current method is a rapid inspection technique that can be implemented with automation. This method can also be used for the detection of flaws for surfaces with conductive and non-conductive coatings requiring little or no surface preparation. * Acoustic Emission Testing, Infrared Thermography Testing, Ultrasonic Testing, radiographic testing, and laser testing methods are normally used for the detection of subsurface or internal defects in steel bridges, but they can be implemented for the detection of surface damages as well. Care should be taken with radiographic testing methods, as the radiation can pose a health hazard. Despite its slow and costly process, it can detect porosity, cracks, and inclusions in weld interiors with a high accuracy. The Ultrasonic Testing method is practical for the detection of subsurface volumetric flaws. It is very sensitive and accurate but requires relatively expensive equipment. The infrared thermography is cost-effective for the inspection of steel bridges with large areas. However, it cannot be implemented to accurately inspect thick components. Acoustic Emission Testing is a suitable method for the detection of active and incipient cracks, but it cannot be implemented to detect existing inactive defects. * For structural tension elements such as cables, tendons, and ropes, certain NDT methods are more common. These include Magnetic Flux Leakage Testing, Chemical and Electrical Testing, Radiographic Testing (RT), and Acoustic Emission Testing.