The technique utilizes a camera fixed on a tripod facing the structure of interest. The camera may be placed as far as 10 meters away from the facility. Specialized devices that emit and direct light towards the camera are also placed in certain locations in the facade of the building. The camera then detects whether the light sources move towards or away from each other. Each light source image is analyzed and filtered to remove potential noises and reduce the uncertainties of the measurement.
The technique may be applied in infrastructure facilities including buildings, bridges or other structures. The endeavor is under a large project which aims at creating infrastructure adaptable to external conditions. “Our new approach to detect building deformations could be used to continuously monitor movements. For bridges, the measured deformations could be used to counteract external loads such as a truck traversing the bridge, thereby increasing the lifetime of the bridge. Because it operates in real-time, it could be used to set off an alert the moment any new deformations – which can lead to cracks – were detected," Flavio Guerra, lead author of the study and a Research Assistant at the University of Stuttgart, stated.
According to Guerra, the ultimate purpose of the project is to create lightweight buildings that would present different behavior based on the applied external forces. For example, future buildings would sustain deformations when high winds strike but would also stand still during a seismic shock. To achieve this, measuring the deformation patterns is of high importance.
Structural displacements can also be measured using fiber optic sensors which, however, are installed during the construction works. Nevertheless, the new method proposed is applicable even to an existing building. Moreover, it is more cost-efficient.
The research team applied the new technique in a 9-meter tall, steel-framed prototype building. Typical techniques including vibrometry and strain gauge sensors were also utilized to derive the applied deformation of the tested building. The data collected showed that the new method is accurate and efficient.
The team's future plan is to further evolve the developed software so they can obtain continuous measurements for a long time period. Moreover, there are also plans to utilize the new method to derive the deformation of existing buildings.
Source: The Optical Society