Utilização da fotogrametria digital aliada a modelagem numérica para previsão do comportamento mecânico da ponte natural de pedra de Alegrete-RS

Abstract

The main objetive of this work was to analyze the mechanic behavior of a natural stone bridge in Alegrete/RS through the digital photogrammetry combined with finite element method. The complex geometry of the rock mass was obtained through digital photogrammetry coupled with Structure From Motion technique, a three-dimensional reconstruction technology, using the software 3DFlow 3DF Zephyr. The orientation of the geological planar faces of both north and south sides of the natural stone bridge were determined through FACETS, a geological structural plugin incorporated to CloudCompare software. Essential mechanical properties for numerical simulations were estimated through empirical correlations and Schmidt hammer rebound values. The three-dimensional model was imported to ABAQUS, allowing the estimation of the gravitational stress distribution in the rock mass. Through digital photogrammetry combined with Structure From Motion it was possible to obtain photogrammetric products such as the three-dimensional model, digital elevation model and orthophoto. These make it possible to monitor erosive processes, changes in relief and obtain geometric properties. In addition, from the point cloud generated in the three dimensional modeling stage, it was possible to obtain the orientation of the main planar faces of the stone bridge. The average values of diving obtained in this stage affirm the verticality of the discontinuities for both faces. The numerical simulations in finite elements made it possible to estimate the distribution of main stresses in the stone bridge, whose values verified for the minimum and maximum principal stresses are, respectively, 10 and 30 MPa.