Use of UAS for damage inspection and assessment of bridge infrastructures

The present work focuses on the use of Unmanned Aircraft System (UAS), commonly known as drones, for the inspection and assessment of bridge infrastructures. Recent events, in Italy and abroad, have not only brought into question infrastructure behaviour but also reminded that many ordinarily used bridges and viaducts are reaching the end of their design service life. Lack of appropriate maintenance and monitoring could worsen the situation in many circumstances, further calling for cost-effective countermeasures and tools. With this in mind, a comprehensive UAS-based methodology for the inspection and damage assessment of bridges is proposed. Such approach is applicable not only in the aftermath of a disaster (e.g., after a seismic event) but also routinely, to support disaster risk reduction strategies towards resilient bridge infrastructures. In addition to routine inspections, fast UAS-based evaluation procedures of the extent and severity of damage are described with the objectives to determine whether the transportation infrastructure systems are safe and suitable to use or reopen. Thanks to aerial data acquired by means of remote-controlled multirotor UASs equipped with high-resolution cameras, data processing in the form of a 3D virtual model, as an example, allows useful virtual inspections and provides key input in-formation to structural/numerical modelling and analysis, the latter being part of any quantita-tive risk analysis and loss assessment framework. The abovementioned aspects of the methodology are examined in detail with the support of in-situ applications and corresponding results meant to showcase lessons learnt and issues still open.