The best-known and most used cast-in fastenings are anchor plates of steel to which system components are welded. Where fastening points are already known at the construction stage, the anchor plates used are mainly headed stud anchorings which are built in along with the reinforcement, before pouring concrete (Figure 7.1).

Headed stud anchorings have a general approval issued by the German Institute for Construction Technology (in German; Deutsches Institut fur Bautechnik — DIBt), for general building construction, but not for accidental actions such as earthquakes.

Fig. 7.1 Anchor plate with headed stud anchorings (source: www. halfen. de)

Cast-in fastenings must be planned precisely before construction starts, defining the load to be absorbed and where the fastening points are to be positioned.

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7.1.1 Post-mounted fastenings

Post-mounted fastenings are used to transmit loads wherever detail design has not provided for any cast-in fastening points before construction has started or where new fastenings become necessary in the course of refitting work. However, there are also design challenges here: although loads, dimensions and positions of system compo­nents are known precisely, high density of reinforcement, poor access and closeness to other fastening points or structural section edges may make planning, designing and installing fastening points extremely complex. The options available for post-mounted fastenings are basically as follows:

— run-through anchors

— spreading anchors

— undercut anchors

— composite anchors

— cast-in anchors.

For safety-related fastenings, only fastenings with sufficient mechanical grip should be used [63]. With metallic anchors, this can be achieved very well by using form-locking undercut anchors, so that a general authoritative approval only exists for undercut anchors, although work is underway to achieve an approval for composite anchors in the near future.