User Guide

10
anchor and during service life. In summary, we can say a product sensitive to these
circumstances may have comparable test loads during on-site testing compared to a
non-sensitive product. However, if all circumstances would be tested (involving
hundreds of tests, as carried out during the approval process) the differences could
be significant or it could even happen that such a product would never get an
approval.
Another buzzword for scenario C is “long term behavior” and we should remember
that the expected life-time of an anchor or rebar is at least 50 years.
The long-term behavior of anchors or post-installed rebars is also checked within the
approval process with the most relevant tests named below.
- Functioning under sustained loading (creep test)
- Crack movement test (mechanical and bonded anchors)
- Functioning under freeze/thaw conditions (bonded anchors only)
- Tests for checking durability (bonded anchors only)
This behavior can also never be checked by a “simple on-site test” and value
comparison.
Therefore, the wrong conclusion of Scenario C may lead to reaching a critical
displacement value of the anchor or post-installed rebar during the working life
by means of pullout failure.
Let’s have a deeper look into the crack movement test mentioned above. It may
seem surprising, but this test is the decisive one for most anchoring products.
Products showing highest load values in a pullout test may fail in the crack movement
test.
Without going into detail on the exact procedure, the tests are conducted as follows:
After installing the anchors in cracked concrete, the anchors are under sustained
load based on the characteristic load evaluated in a short-term test/pullout test.
While the anchors are loaded under tension, cracks are opened between 0.1 mm and
0.3 mm 1000 times and the displacement of the anchor under tension is measured.
During these tests the measured displacement should be below the constant value of
3 mm.