Gamocap & Lognature

Objective of LOGNATURE project was to characterize the response of an experimental wooden wall fixed to the ground to a lateral force.

To evaluate the response of the structure were executed two trials: one applying the force in only one direction, Figure 1 – Trial 1, the other with a periodical lateral one (push pull), Figure 1 – Trial 2. The two trials last respectively 21 and 83 minutes.

Figure 1: Wooden wall in trial 1 and trial 2

A multi-camera vision system, GaMoCap, was used to evaluate the displacements of the surface of the wall and the relative displacements of the planks of wood that compose the surface of the wall.

The multi-camera system is composed by 4 industrial cameras mounted on a aluminum frame Figure 2-a, pointing at the surface to reconstruct Figure 2-b.

frame and cameras used FOV of cameras
Figure 2-a: Aluminum frame on which are mounted the 4 cameras Figure 2-b: FOV of the 4 cameras

Capture frequency was set equal to 2 Hz. Camera resolution was 1600 x 1200 pixels.

To evaluate the displacements of the structure were used color-coded pattern of circular marker, Figure 3-a that covers all the planks to analyze.

A chess marker Figure 3-b was also attached on the head of the actuator to compare displacement results calculated with vision system.

marker employed
Figure 3-a colour coded marker for the planks.
Figure 3-b marker attached to the head of the actuator

In Figure 4 we can observe the 3D points reconstructed (a) and the mesh build on them (b).

points 3d reconcstructed and mesh
Figure 4-a: 3D points reconstructed. Figure 4-b: mesh build on the 3D points.

In Figure 5 we can see the displacement values relative to the first trial of the marker at the top of the grid in the 3 directions.

Trial 1 - traejctories of encircled point
Figure 5: Trial 1 – trajectories of encircled point in X Y and Z directions.

Below the video relative to the first trial. To be notice is the step of X coordinate at ~1200 secs due to the break of the metal bracket that holds down the wall.

In Figure 6 are reported the displacement in Y direction of 3 points, respectively located at the base (A), in the middle (B) and at the top of the grid C, for the trial of alternate trust. The point (M) is the point relative to the marker attached to the head of the actuator.

Lognature Trial 2
Figure 6: Trial 2 – Trajectories A, B, C and M in Y direction

The measurement campaigns were conducted in the framework of the projects LOGNATURE headed by Prof. Piazza Maurizio, with the help of Assistant Professor Ing. Roberto Tomasi, and the Ph.D student Paolo Grossi.

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