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Experimental analysis of the stress-strain state of the passive anchoring of rebar

An important aspect when creating concrete structures is the accurate measurement of the length of the anchors, especially when placing them in the console ledges of walls, eaves and load-bearing structures of buildings. Characteristics of the mounts is especially important due to the transverse load, which vertically falls on the reinforcing bar. Such a radical compression load caused by concentrated and opposing forces.
To study the system nodal anchoring specialists HBM has developed a pilot program to facilitate the efforts of engineers to determine the embedment length of rebar. When testing the analysis of the reaction mounts on the host-based Compression ‒ Compression ‒ Tension (SSR).

The specimen consists of two concrete blocks of different lengths with square cross-section planes: the width of each unit 15 cm, height 24 cm, each unit is equipped with a reinforcing rod at the bottom. The reinforcing rod is attached via screw connections, with a force sensor. With the help of hydraulic cylinder applied force is 1000 kN.
When testing used a PC Pentium III for automatic registration of the measured values in real-time, amplifier and data acquisition software was developed by University employees.
Measured values:

  • Forces on both ends of the reinforcing bar by means of two ring-shaped force sensors C6A/200 kN from HBM.
  • The force on the support structures using a force sensor C2/100 kN HBM and from the other three force sensors.
  • Longitudinal deformation of a reinforcing bar using strain gages LY41-3/120 from HBM glued to the Central part of the test object and diametrically opposed to the reinforcing bar.
  • Longitudinal strain in the concrete using strain gages LY42-50/120 from HBM.
  • Three strain gages is pasted in the locations of outlets on each block, two additional
  • strain gages are under the test object.
  • Move using the four displacement sensors on the front and rear of the blocks.

In previous tests was formed by a longitudinal fissure that had split the test object vertically into two parts. This crack was formed by annular tensile loads arising around the reinforcing bar. The crack starts in the field of fastening and continues in the longitudinal direction. Both lode cell was pasted so that it was possible to fix the moment of formation of cracks. The first test results show that the crack is formed before the fracture of the reinforcing bar. Thus, it was decided not to mount additional rods (supports) in the prototype to avoid any additional restrictive effects.

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