The main aim of this paper is to describe the results obtained applying a new methodology developed in order to assess the presence of overloaded areas in steel bridges. The methodology is based on the principle that if the load applied (also just once) in a particular area is higher than the yield strength, it changes the residual stress in this area, inducing a different value of stress if compared with the other areas not overloaded. Using X-Ray diffraction it is possible to detect the value of residual stress on the surface of metals, also in small areas, in a non-destructive way. Therefore this technology is used to detect the presence of overloaded areas on steel bridges. As the areas sampled from X-Ray diffraction are very small (1-2 millimeters of diameter) compared with the dimensions of a bridge, it is necessary to know exactly the position of the areas subjected to the maximum load during the life of the bridge. For this reason FEM analysis are previously conducted in order to evaluate maximum load regions. The construction drawings necessary to perform the FEM analysis are not always available, especially for old bridges, therefore reality-based 3D models are created this problem. Such method is also useful by itself, as beside providing suitable drawings for the FEM analysis, it allows to quickly identify possible large deformations of the bridge structure.