ABSTRACT
The assessment of the condition state of historic masonry bridges is a key action regarding their conservation, since only the accurate and precise knowledge of the pathologies present in the bridge can lead to the choice of the optimal restoration actions for each bridge. Given that the purpose of the study is conservation, techniques applied to the study should be non-destructive. The application of visual techniques (photogrammetry and laser scanning) is presented for the acquisition of data from the superficial reality and the geometry of the bridge; infrared techniques, mainly in the thermal infrared, are applied to the detection of pathologies affecting the surface, mainly moisture. Finally, ground penetrating radar is used to study the interior of the bridge (filling material and moisture). These techniques can be applied individually or combined, the latter being the best option regarding the complete analysis of the reality of the bridge.
Masonry bridges are constructions with incalculable value at a local scale for two main reasons. First, they provide transport and travel options, enabling travel that would otherwise take more time and resources. Second, accessibility provided by bridges brings social and economic richness to the area, since exchanges of goods, money, and people are made possible. Existing masonry arch bridges in Spain were built throughout centuries, from the Roman period to modern times. Nowadays, there is still an important legacy of these structures, where around 250 units can be found specifically in the Galician territory (Alvarado et al. 1989), characterizing its landscape and representing a priceless architectural and cultural heritage. Many of these bridges are still in use
within the transportation network and some of them have been modified as necessary to ensure new functionalities related typically with vehicle transportation (Forde 1998). In these cases, the bridges are normally subjected to potentially destructive conditions. Thus, degradation of bridges implies a considerable problem for inhabitants of the areas involved, drastically reducing, or even preventing, their movement.
