Camila Kleis Rodacki
Owner at WRodacki
Providing maintenance for historical heritage is one of the main means of strengthening the culture of a city. However, old buildings and works of art have highly complex construction details, making it difficult to reproduce or register.
Carrying out an as is project - a project of the structure as it is up to now - is an expensive process that takes many hours of work, but even so, in the end, it is not possible to have all the details recorded faithfully. This happens for different reasons: disorganized or misinterpreted notes, errors in handling the equipment used, measurements obtained at different levels, inclination of elements that are not considered, among other factors that make up the reality of a structure.
For this reason, the use of 3D laser scanning to record these historical elements is increasingly widespread. In addition to capturing geometric dimensions with millimeter precision, it also offers a reflectance feature of the material and a 3D digital replica, increasing the range of studies and analyzes that can be produced.
The Aldo Pereira de Andrade bridge, better known as Ponte de Ferro, located in the city of Blumenau / SC, is one of those historical monuments that become the postcard of the place. The structure was built with steel imported from Germany in 1929, with the function of serving as a passage for the train that connected with the region's port. Between 1971 and 1991, the bridge was deactivated by court order and underwent a restoration and adaptation to be used for the transit of vehicles and pedestrians. Since then, it works normally without major interventions in its structure.
The survey of the bridge, which is 315 meters long and 18 meters high, was carried out with a FARO Technologies scanner that has a range of 150 meters. It was a day in the field to obtain an overall precision of the structure of 4 centimeters and a local precision millimeter. The result obtained is shown in figure 1.
Figure 1: Point cloud vs Photos
Source: WRodacki, 2020.
With just the point cloud, the product of laser scanning, it is possible to view the structure from different perspectives. One of them is the extraction of elevations, longitudinal and transversal cuts, floor plans and simulations that allow the analysis of the structure and its design, as shown in figure 2.
Figure 2 - Floor plans and section
Source: Wrodacki, 2020.
Another possibility is the intensity and elevation maps. One of the information extracted by the scanner is the degree of reflectance of the material: the darker the surface, the lower this value. Through this analysis it is possible to identify different materials, moisture, corrosion, among others. While the elevation map indicates the height of the points in relation to each other, offering an idea of scale. Figure 3 shows the two types of maps.
Figure 3 - Intensity and elevation map
Source: Wrodacki, 2020.
The visualization of the photos obtained with the scanner itself, which is why the point cloud has the real colors of the structure, also offers subsidies for decision making. It is a visual assessment made on the structure with the aim, for example, of analyzing the pathological manifestations present in the structure and planning the necessary interventions.
Image 4 - Visual analysis
Source: Wrodacki, 2020.
One of the great advantages is having the structure in hand with a record so complete that it allows you to view it from different angles, with all the corners and details that compose it, without the need to return to the site to extract new information.
In addition to the applications mentioned, it is also possible to import the point cloud into other software that allow for more advanced and specific studies, according to the need. An example is the modeling of the structure based on the point cloud, which can be used to create a restoration project.
3D laser scanning is a powerful tool that enhances the decision-making power of those involved due to the diversity of studies and analyzes it offers with a single survey, which characterizes it as a strategic agent of great value.
