# Hybrid Fibres as Shear Reinforcement in High-Performance Concrete Beams with and without Openings
## 2 Experimental Work
### Testing Procedure  
ARAMIS is a non-contact, 3D deformation measuring system. It analyses, calculates and documents deformations of specimens. The graphical report of the results provides the best possible understanding of the tested element behaviour at the process of its loading on the measuring area ranged from 1 to 2000 mm. The surface structure of the measuring object is recognized on the basis of images taken with digital cameras on which each pixel is allocated the appropriate coordinates. The first image represents the undeformed state of the specimen. The next images are taken and recorded sequentially in its different load stages up to failure. With the help of the correlation algorithm and mathematical calculation, the specimen is computed from the radii intersections, camera positions and lens distortion. The specimen coordinates on a part of the surface are set up in a high-resolution grid reflecting the tested specimen. Then, the system compares the 3D coordinates of the specimen and calculates the 3D displacements and strains. Accuracy of the system when measuring displacements is 5 \(\upmu\)m. Strains can be measured in a range of 0.01% up to several 100% [61]. The ARAMIS system is composed of a measuring sensor with two digital cameras with a resolution of 2048 \(\times\) 2048 pixels, and a recording frequency of up to 12 Hz; stand for secure and stable hold of the sensor; sensor controller for the cameras power supply and to control image recording; high-performance computer; software; calibration set for various measurement areas as well as an optical trigger. In this research program, all the beams were whitewashed with lime before the strength tests. Then, one side surface of each beam was randomly covered with a pattern made of black paint so that the system could compute the displacements of characteristic points. The measurement areas for the B-beams defined at the middle part were limited to dimensions (650 \(\div\) 900) \(\times\) 400 mm due to the geometric configuration of the press. In the case of BO-beams, the areas near the openings were defined, Figure 2. Before the tests were carried out, the system was calibrated on the measuring area so that the analysed area was within the measuring space. The size of characteristic points, so-called facets equal to 15 \(\times\) 15 pixels, were found on subsequent compared images. A unique sequence of grey measurement points was assigned to each facet. On the second surface of the beam, it is planned to perform independent measurements of the development and propagation of cracks. Testing of the beams was conducted in a hydraulic machine as shown in Figure 3. All the specimens were examined to failure in four-point bending under static load at a rate of 0.4 mm/min. The beam surface was recognised on the basis of images taken with a frequency 0.2 Hz. In the different load stages, the facets were identified and followed by means of the unique grey level structures and the system determined the 2D coordinates of the facets from the corner points and the resulting centres. In the next stage, the 2D coordinates of the facets, observed from the both cameras lead to a common 3D coordinates using photogrammetric methods. The coordinates were read from the left  
Figure 2: Measurement area. and right sensor cameras taking into account the angle between the camera axes. After the successful computation, the data was processed in order to reduce the measuring noise. Simultaneously, the development and propagation of cracks were monitored and marked on the second surface of each beam to follow up their growth, sequence and pattern of cracking. Measurements of the crack width in a range of 0.01 mm up to 1 mm were performed using the hand-held illuminated optical microscope Optika XC-100L. Visual identification of crack development was assisted by a surface coating of whitewash. A simple unmagnified comparator scale was used to assist in the estimation of crack widths exceeding 1 mm.