Determination of the State of Strain of Large Floating Covers Using Unmanned Aerial Vehicle (UAV) Aided Photogrammetry

Abstract

Floating covers used in waste water treatment plants are one of the many structures formed with membrane materials. These structures are usually large and can spread over an area measuring 470 m × 170 m. The aim of this paper is to describe recent work to develop an innovative and effective approach for structural health monitoring (SHM) of such large membrane-like infrastructure. This paper will propose a potentially cost-effective non-contact approach for full-field strain and stress mapping using an unmanned aerial vehicle (UAV) mounted with a digital camera and a global positioning system (GPS) tracker. The aim is to use the images acquired by the UAV to define the geometry of the floating cover using photogrammetry. In this manner, any changes in the geometry of the floating cover due to forces acting beneath resulting from its deployment and usage can be determined. The time-scale for these changes is in terms of weeks and months. The change in the geometry can be implemented as input conditions to a finite element model (FEM) for stress prediction. This will facilitate the determination of the state of distress of the floating cover. This paper investigates the possibility of using data recorded from a UAV to predict the strain level and assess the health of such structures. An investigation was first conducted on a laboratory sized membrane structure instrumented with strain gauges for comparison against strains, which were computed from 3D scans of the membrane geometry. Upon validating the technique in the laboratory, it was applied to a more realistic scenario: an outdoor test membrane structure and capable UAV were constructed to see if the shape of the membrane could be computed. The membrane displacements were then used to calculate the membrane stress and strain, state demonstrating a new way to perform structural health monitoring on membrane structures.

Remote Monitoring of Floating Covers Using UAV Photogrammetry

“…UAV-aided photogrammetry is a safe and time-efficient assessment technique [11,12], which can be remotely operated to conduct UAV RTK mapping survey without coming into contact with the asset. This paper will report the series of UAV surveillances conducted on one of the floating covers at WTP.…”

Application of UAV in Topographic Modelling and Structural Geological Mapping of Quarries and Their Surroundings—Delineation of Fault-Bordered Raw Material Reserves

“…The UAV technique itself is capable of detecting rapid changes in the morphology of rivers [13,14] and erosion processes [15], or stream restoration [16]. Ong et al [17] used UAV and GPS to map floating covers in wastewater treatment plants and evaluated the strain level and health of the structures. UAV was also used for the environmental modelling of an open-pit gravel mine and for measuring the volumetric change [18].…”

The Use of Precise Survey Techniques to Find the Connection between Discontinuities and Surface Morphologic Features in the Laže Quarry in Slovenia

“…Technological developments in unmanned aerial vehicles (UAVs) and data processing technology have led to the extensive use of these techniques in various fields [13][14][15][16][17][18][19]. Remotely piloted systems are able to support numerous mapping applications [20][21][22][23][24][25][26][27]. UAV techniques can detect rapid changes in morphology and topography [19,[28][29][30][31][32][33][34].…”