Ground penetrating radar survey of historic masonry arch bridges of Galicia (Spain)

Abstract

Historical bridges represent an integral part of the tradition architectonic heritage of a region. These ancient structures require sepecial attention because many of them have lost their original utility and now have different functionalities, often supporting special tension conditions such as strong loads and intense vibrations. Therefore, a constant diagnosis of their structure is required to provide information on their preservation and restoration using methods that will not change the historical character of the structure. This thesis presents the results of the application of GPR as non-destructive technique for evaluating the state of conservation of 36 Roman or mediaval bridges selected from around the whole Galician territory (NW Spain). A fiel methodology was proposed in this work to analyze the viability and effectiveness of GPR for obtaining internal información on ancient masonry arch bridges from there points of view: historical, structural and archaeological. As a result, an inventory was developed including the most relevant information obtained for their characterization and diagnosis. This information can be useful for engineers in planning maintenance or rehabilitation tasks as well as in desingning legal regulation for heritage protection. Owing to the heterogeneity of theses structures, the analyisis and interpretation of GPR data can be complex. In such circunstances, a sophisticated numerical modelling was employed to facilitate GPR data interpretation. The GPR numerical modelling allowed the study of the attributes of reflected signals from various targets within the bridge structure. The GPR numerical analysis was undertaken using the finite-difference tiem-domain (FDTD) method and the synthetic models were created from the accurate external geometry of the bridges provided by photogrammetric and 3D laser scanning methods.