COMPORTEMENT SOUS CHARGE DES ANCRAGES AVEC VIS D'ANCRAGE

SUMMARY Concrete screws are a relatively new fastening system. Their main advantage compared to traditional post-installed fastening systems is a quick and easy installation. A hole is drilled into the concrete and threads are cut in the concrete by the screw as it is installed. Concrete screws transfer tensile loads into the base material by mechanical interlock of the threads. Due to their load-bearing mechanism, concrete screws with a technical approval of the DIBt can be used for fastenings in cracked and non-cracked concrete. The typical failure mechanism for concrete screws is concrete-cone failure. With increasing embedment depth the ratio of the depth of the concrete failure cone to the embedment depth decreases. The failure load of concrete screws with continuous threads along the entire embedment depth increases proportionally to hef 1,5 (hef = effective embedment depth), but it is about 20 % smaller than the failure load of expansion and undercut anchors with the same embedment depth. In order for concrete screws to function properly, the threads cut into the wall of the drilled hole must not be damaged during the installation. This requirement is achieved by using the embedment depth defined in the Technical Approvals.