UAV Retaining Wall Inspection of a Federal Motorway

23. February 2015
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For a UAV / drone-based retaining wall inspection (structure inspection) besides the Federal Motorway A4 in Thüringen, Germany, the AscTec Falcon 8 took imagery accurate down to few millimeters. The drone’s efficiency was quite impressive: About 12000 qm, with 1.6 millimeters resolution at the object in 24 minutes only.

The UAV retaining wall inspection is one of many successful flying UAV-based inspection and surveying projects of the joint research project “Unmanned Aerial Vehicles (UAV) for State Determination of Structures” of the Forschungsinitiative ZukunftBau from the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety.

The retaining wall at the eastern portal of the Jagdbergtunnel is with over 600 meters length and 20 meters height is this type’s biggest German retaining wall. The goal was to perform two flights that would automatically detect geometrical changes of the wall’s structure on basis of orthophotos and digital surface models (DEM). In comparison of both flights the manipulation should be detected. Indeed the AscTec Falcon 8’s imaging enabled to detect simulated deformation bigger than 7 millimeters at a ground sample distance of 1.6 millimeters per pixel at the object.

Few tachymetric control points are appropriate for complete model’s geo-referencing. From overlapping aerial images dense point clouds and a 3D models can be produced with post-processing software analogously to digital elevation or surface models. The photogrammetric post-production of the aerial images and a point cloud measurement allows the detection of smallest geometric construction changes.

High-tech construction diagnostics made in Weimar

The boutique consulting firm Guido Morgenthal Technologien im Bauwesen is specialized in technology-driven solutions for structural engineering problems. This includes the development and application of cutting-edge numerical simulation tools for problems in dynamics and wind engineering, as well as tailor-made monitoring techniques using smartphones, microcontrollers and Unmanned Aerial Vehicles like the AscTec Falcon 8. Modern numerical simulation techniques allow for a realistic analysis of structural behaviour even for highly complex structures such as long-span bridges. The company is expert in the development and application of simulation, validation and visualisation tools for advanced structural analysis.

„The combination of excellent flight performance and photogrammetry offers maximum potential for inspection, survey and 3D modelling of remote spots. As well as in several other applications of inspection, maintenance and quality control of structures.” Norman Hallermann, Projektleiter, Bauhaus-Universität Weimar (BUW).

Employing cutting-edge technology Guido Morgenthal Technologien im Bauwesen is able to deliver optimised and reliable structural designs as well as robust assessment of existing structures. Our firm has extensive experience in simulations of a wide range of structural systems and loading scenarios, with particular specialisation in bridges and dynamic response phenomena.

The scope includes:

  • Physically nonlinear analysis of concrete, composite and steel structures
  • Geometrically nonlinear systems, including tensile structures and form finding techniques
  • Linear and nonlinear dynamic analysis, e.g. pedestrian-induced vibration of footbridges, seismic analysis, wind-induced vibrations, cable oscillations
  • Analysis of structural damping devices, e.g. Tuned Mass Dampers, cable dampers, active control
  • Stage-by-stage construction analysis, specifically of long-span bridges
  • Soil-structure interaction analysis
  • Analysis of fire resistance of structural members
  • Heating and ventilation simulations.

About UAV retaining wall inspection – project specifications:

Flight system:

  • Type: V-Form Octocopter “AscTec Falcon 8″
  • Flight time: 12–22 Min.
  • Velocity: bis 16 m/s
  • Tolerable wind speed: bis 12 m/s (GPS Mode)
  • Camera mount: actively stabilized

Camera:

  • Type: Sony Alpha 7R – DSLM
  • Sensor: CMOS full-frame (36 × 24 mm)
  • Resolution: 7360 × 4912 Pixels (36,4 MP)
  • Pixel size: 4,89 × 4,89 μm
  • Focal distance: 35 mm
  • Calibration: None, consistent

A project in cooperation with:

Supported by:

  • Chair of Computer Vision in Engineering (Prof. Dr.-Ing. habil. Volker Rodehorst)
  • Regional Authorities for Construction and Traffic in Thuringia (Dipl.-Ing. Wilfried König)
  • Guido Morgenthal Technologien im Bauwesen

Publikationen:

  • Morgenthal G., Hallermann, N.: Quality Assessment of Unmanned Aerial Vehicle (UAV) Based Visual Inspection of Structures. Advances in Structural Engineering, Volume 17 No. 3 2014, pp. 289-302
  • Hallermann N., Morgenthal G. and Rodehorst V.: Vision-based deformation monitoring of large scale structures using Unmanned Aerial Systems 37th IABSE Symposium, Engineering for Progress, nature and People Madrid, Spain, 2014
  • Hallermann N., Morgenthal G.: Visual inspection strategies for large bridges using Unmanned Aerial Vehicles (UAV) 7th IABMAS, International Conference on Bridge Maintanence, Safety and Management Shanghai, China, 2014


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