Concrete structures are ubiquitous in the infrastructure of the country. Bridge decks, roadways, parking structures and more require condition assessment and diagnosis to ensure safety. Currently bridge decks are inspected using visual inspection augmented by chain dragging or hammering to detect changes in sound reverberations. These protocols result in subjective, highly variable, and unreliable information. They also require that traffic be rerouted during evaluation. Ground Penetrating Radar (GPR) is an evaluation protocol being used more and more due to its greater quantitative evaluation. The current 2-D evaluation systems require significant amounts of skilled operator labor for setup and measurement and evaluation and can also result in subjective evaluations.


The HERMES bridge inspector is an ultrawideband-based nondestructive evaluation (NDE) system. The LLNL-developed system provides 3-D ground penetrating radar information. An array of micropower impulse radar (MIR) sensors is mounted under a trailer. Reflected radar data is gathered by driving the trailer over a bridge at 55 mph and 3-D image maps of the internal structure of the bridge deck are created.



  • Compactness, low weight, and low power requirement of the MIR sensors allows for arrays to be created.
  • High resolution data is obtained from array of sensors.
  • Image mapping software creates unambiguous 3-D images.
  • Evaluation can be performed at highway speeds so that traffic is not slowed or rerouted.
  • Concrete can be penetrated up to 30 cm.


Potential Applications

The HERMES system was designed for bridge inspection-detecting delaminations, cracks, voids, etc.-as they age, but construction also requires evaluation of structures. Assessment of other concrete structures would benefit from the 3-D images HERMES provides.

Development Status

The HERMES system and its successor, PERES, are being tested by the Federal Highway Administration (FHWA) for further validation of its bridge inspection capabilities compared to current GPR techniques. LLNL scientists and engineers are experts in nondestructive evaluation techniques and have the capability to transfer this knowledge to numerous commercial applications.

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