Ús de tecnologies geomàtiques avançades per seguiment de desplaçaments en assajos a escala reduïda de pòrtics metàl·lics

Nowadays laser scanning is one of the most popular techniques in modern surveying, it is very useful in different work cases. Laser scanning (also known as LIDAR) uses the laser beam to determine the distance to the points, which has the ability to generate pointclouds. This enables us to create different types of mesh, depending on where it is pointing. This project aims to support with laser scanning and total station data acquisition, to different tests under development at the Structural Laboratory (UPC). This includes amont other tasks: - to design the data collection with both devices; - raw data processing (cleaning outliers, noise filtering and so on); and, finally, - the transformation of the coordinates to a common reference system in order to get the displacements of the key points in the frame along time. There are several types of laser scanning modes, depending which is the objective (Balsavias, 1999). Aerial Laser Scanning (ALS) can determine different ground surfaces from a small plane, it covers more surface than terrestrial laser scanning. Aerial laser scanning data is used for topographic and cartographic surveys and for the creation of 3D terrain models, and also 3D city models (modelling of buildings and constructions). In other words, to analyse, built up territories. Terrestial Laser Scanning (TLS) determines surfaces of single objects or small surfaces from the ground, is closer to objects than aerial laser scanning so it have more resolution and accuracy. Structural load tests are done in a laboratory to check designs and validate calculation codes. Classically, linear unit deformations are measured in a timely manner, with strain gauges, displacement transducers (LVDTs for instance) and micrometers. During the tests that are carried out at DECA Laboratory of Structures and Materials Technology (Departament d’Enginyeria Civil i Ambiental, C1 building, Campus Nord, UPC, Barcelona, Spain) on 4 stainless steel frames, the measurement with Terrestrial Laser Scanner has been tested to track the global (3D) changes during the application of progressive loads. Measurements with Total Station to several targets on the frame have been carried out also to achieve more accuracy. For this purpose, several reflective targets were placed on the steel, which had good visibility for the Total Station and for the TLS. This project is also based in inserting both data collected in the same coordinate system, which gives the possibility to compare the two data collected and find results. It is interesting to know how digital information can vary from one device to the other, laser scan generates millions of points while total station generates hundreds but with more accuracy. All these tasks aim to the exploration of the new techniques which, eventually, may lead to an improvement in the structural test performance. It is worth to say that the measuring approach developed in this TFG in a non-contact or remote technique, in contrast with the classical sensors (strain gauges, LVDTs and so on). The main objective of this project is to assess the performance and contribution of the total station and the terrestrial laser scanning during testing of steel frames. With Terrestrial Laser Scanning, the objective is to collect data before, during and after the load tests, processing the resulting data with some-pointcloud softwares in order to generate the frame displacement field. The objective with the Total Station is to determine the initial state of the steel frames, highlighting their geometrical irregularities (if any). The frame final state is measured as well. The expected net results for each load tests are 8 to 10 3D models of each frame (TLS), corresponding to different times. On the other hand, by means of the Total Station we will get an accurate frame geometry at the beginning and at the end of each test (20-30 select points for each steel frame). As previously stated, all these results will help in identifying any possible geometrical irregularity in the shape and surface of the steel beam: initial defects produced during the frame manufacturing, and/or dents or sags resulting from the loading tests itself. As secondary objectives, this project wants to show the contribution of the non-contact, masive and remote geomatics techniques to complement traditional systems (Total Station) in this type of testing and environment (small scale testing of structures), working out the achievable resolutions and precisions. Additionally, the integration of total station and terrestrial laser scanning results in the same coordinate system is envisaged; the behaviour of the targets for this purpose will be assessed