Geodetic surface based methods for applications in civil engineering

Abstract

At the Institute for Structural Engineering at the TU Wien a cost and resource efficient concrete shell construction method called "Pneumatic Forming of Hardened Concrete", was invented. A flat hardened concrete plat is transformed into a double curved concrete shell, by inflating a simple air cushion placed under the concrete plate and stressing post-tensioning tendons at the circumference. Basically the stability of a concrete shell is sensitive against geometric imperfections. As part of the quality assurance, the engineering geodesy audits the geometry during the construction process with point and surface-based metrology. The scanned 3D point cloud is approximated with B-Spline surfaces to assess the shape of the shell by means of a static finite element calculation. Three different datum definitions for the 3D cartesian coordinate systems are derived from the requirements of the civil engineers, e.g. to assign geometry impacts to different construction steps. Necessary preparation steps of the approximated geometry as main part of the structural analysis, computed with a finite element model, are shown in the workflow from the point cloud to the static behaviour of the dome. The results of the structural analysis shows no significant changes due to the geometric deviations in the static load behaviour compared to nominal finite element model.