Automatic Identification and Geometrical Modeling of Steel Rivets of Historical Structures from LIDAR Data

Riveting is a joining technique that was widely used in iron and steel structures from the mid-nineteenth to the early twentieth century. Nowadays, many of these riveted structures are still in service around the world, and in many instances, also constitute an important part of the built cultural heritage. The maintenance and conservation of this type of construction is a crucial task for which the HBIM (Historic Building Information Modeling) methodology has recently gained increased attention, postulating itself as the ideal tool for tracking control and conservation-related actions. In the process of data collection and 3D modeling of the structure, the rivets are an important part to be taken into account in the structural safety assessment and health monitoring over time. Any structure of this typology typically presents thousands of rivets, so its measurement and subsequent 3D geometrical modeling is a laborious task and a source of possible errors. Accordingly, this work presents a novel methodology that allows the automatic identification and 3D modeling of rivets in iron and steel structures from LIDAR data. The proposed methodology has been tested with both laboratory specimens and a full-scale real bridge.

Field theory in normal conical coordinates

In the scientific literature, the field theory is most fully covered in the cylindrical and spherical coordinate systems. This is explained by the fact that the mathematical apparatus of these systems is most well studied. When the source of field has a more complex structure than a point or a straight line, there is a need for new approaches to their study. The goal of this research is to adapt the field theory related to curvilinear coordinates in order to represent it in the normal conical coordinates. In addition, an important part of the research is the development of a geometrical modeling apparatus for scalar and vector field level surfaces using computer graphics. The paper shows the dependences of normal conical coordinates on rectangular Cartesian coordinates, Lame coefficients. The differential characteristics of the scalar and vector fields in normal conical coordinates are obtained: Laplacian of scalar and vector fields, divergence, rotation of the vector field. The example case shows the features of the application of the mathematical apparatus of geometrical field modeling in normal conical coordinates. For the first time, expressions for the characteristics of the scalar and vector fields in normal conical coordinates are obtained. Methods for geometrical modeling of fields using computer graphics have been developed to provide illustration in their study.