Here is a short list of manufacturers who make undercut anchors. Fortunately, undercut anchors tend to fare well in these stringent tests.
Keil anchor cracked#
One of the concerns is how these anchors perform in cracked concrete. The American Concrete Institute has added new testing requirements for post-installed mechanical anchors, which is to say all anchors that are not cast into place in the concrete. The second type is called a self-drilling anchor, which doesn't require the additional bit. The standard type requires drilling the hole, followed by drilling the undercut with the special bit.
When in place, the anchor uses the compressive strength of the concrete to resist the load, unlike a wedge anchor, which relies on the concrete's tensile strength. The bottom of the hole has a notched opening, or undercut, made either with a special drill bit or with an anchor that has a drilling device at the end of the bolt. Undercut anchors are not your typical anchors.
From an engineering point of view, steel failure is more predictable and reliable than concrete failure, so it is preferred by engineers, says Bob Sayer of Liebig International, a German manufacturer of anchors for the past 30 years. The anchorage is so strong that the steel in the anchor will often break before the concrete. They are well suited for dynamic loads and are frequently employed in seismic retrofitting. That is why they are commonly used on roller coasters, nuclear power plants, and other structures where human safety is paramount. Undercut anchors are the strongest you can buy, and you put them in places where you want to avoid problems no matter what the cost. The undercut anchor can sometimes require additional drilling, and often can be three times the cost of other post-installed mechanical anchors. Post-installed mechanical anchors come in several styles: wedge, sleeve, drop-in, stud, and undercut.