Bridge inspection with drones

With the passage of time, the existing structures suffer the deterioration of their components due to the action of loads, the weather, polluting elements, seismic movements, impacts, explosions, misuse, lack of maintenance, etc.

With this premise, it is advisable to know the current state of a structure almost permanently, which is complicated and expensive.

Since the range of possibilities in the amount of damage is so wide, it is not possible to apply a single methodology to solve the pathology currently studied. According to the magnitude of each case, an immediate diagnosis can be made, up to cases in which specific (special) analyzes and tests must be carried out due to the complexity of the bridge inspection standards.

The magnitude and complexity of the damage that can occur to a bridge and civil works structures in general, make the inspection and diagnosis mechanics not so easy to select.

One of the best ways to obtain information about the state of a structure is to perform a visual inspection. The purpose of the structural inspection is to determine the condition of the service. Upon inspection, it will be necessary to:

Identify the causes that caused or caused this deterioration.
Know the extent of the deterioration.
Study the variation over time of the conditions to which the work is subject.
In the main inspections, it is requested to inspect all the elements of the bridge, which makes sense since some of them do not reach 100 years of the bridge's useful life. Among them are support devices, with an approximate useful life of between 25 and 40 years.

Not all bridges are designed for ease of maintenance, and some items may be in really difficult access sites.

The current possibilities to carry out the inspection of difficult to access structural elements are limited:

Stairs, up to a height of about 5 m. The range for low heights and with a high risk factor.
Telescopic boom truck with basket, up to a height of about 15 m. It requires an adequate access path and the positioning time is considerable.
Truck with articulated arm and gangway, which allows working at lower levels than parking. Especially for bridge inspection, it requires a partial or total traffic cut, depending on the location of the structure. The positioning time is considerable.
Work at height with specialized mountaineers.
Eye inspection with binoculars. Due to the distance, the degree of detail is low, there are difficulties in recording inspection images and the field of vision is limited.

A new inspection tool, the use of drones, has recently been introduced. In recent years, significant progress has been seen in the development of drones, particularly quadcopters, powered by electric motors, with microelectromechanical systems, GPS, and microcontrollers. These systems are relatively inexpensive, strong enough to support additional loads (cameras), and sufficient autonomy for small inspection missions.

Structural aerial inspection is a complex activity, which must be carried out in an organized and systematic manner. It consists of obtaining high quality images using RPAS (drones), which allow a detailed analysis of the structure to be carried out, especially in those elements that are difficult to access and which until now required high costs and time in their inspection.