TYPES OF ANCHORS
On the basis of the load placed on an anchorage, anchors can be divided into three groups: light anchors, medium anchors and heavy-duty anchors. Light anchors are anchors with a permissible load of up to about 3 kN. The medium anchors group has a permissible load of up to about 20 kN, while heavy-duty anchors can withstand forces up to about 60 kN.
In principle, light anchors include all types of plugs, such as universal plugs, all-around plugs, frame anchors, wall plugs, Aircrete anchors, hammer fix plugs, toggle plugs, panel anchors, self-drilling anchors, molly anchors and expanding plugs, just to name a few. Attaching a cable duct to a plasterboard wall is an example of a light anchorage.
Medium anchors include wedge bolts, wedge shells and wedge screws. For instance, fastening a stair rail or piping in brickwork often results in a medium load. Anchoring steel construction in concrete, however, is an example of an application subject to heavy loads. The appropriate anchors for such situations are safety bolts, fast-building anchors, hammer set anchors, undercut anchors, heavy-duty anchors, wedge anchors and chemical anchors. In fact, whatever the load, an application in the tension zone always requires a heavy-duty anchor.
More information about the tension zone and concrete can be found in the section labeled, “Building materials.” Anchors used before or during the casting of concrete also belong to the category of heavy-duty anchorages. Examples of these are masonry bolts, hook anchors and tube inserts.
When an anchor must comply with strict requirements, the correct calculation of the load is of great importance. Various organizations have drawn up guidelines in this area. The European guidelines for approval have been crafted by the European Organization for Technical Approvals (EOTA). In North America, the American Concrete Institute (ACI), the American Society for Testing and Material (ASTM) and the International Conference of Building Officials Evaluation Services (ICBO ES) are the most important organizations in terms of constructional fastenings. The calculation methods issued by the EOTA and the ACI correspond to one another to a large extent, and they offer the opportunity to affect economical and efficient construction.