Post installed Anchor Bolts Min. Pretension and Torque

The Pretension and torque in post install anchors are defined in the ETA/ESR of the respective anchor . Please refer to the attached example.

Here we have defined the installation torque required and we should adhere to these values for following reasons :

1. When tightening the anchor. Pre-tension is created when we apply the torque to the anchors. Overtime this pretension will relax to a certain degree. Some anchors such as HST, HSL-3, or HIT-Z require an applied torque to properly set the anchoring mechanism while other anchors such as RE500 or HY200 with HIT-V rods include an installation torque primarily related to a relative clamping or pre-stress on the fixture. Installation torque can also affect the minimum edge and spacing distances of an anchor. As we have defined the spacing criteria for the anchors in our ETA’s hence this should be followed accordingly .
2. In our technical data, the recommended tightening torque is linked to the minimum spacing and edge distance: If an anchor is very close to the edge, the concrete cover will split at a relatively low tightening torque; with large edge distance you can tighten much more. Thus the recommended tightening torque is a compromise between desirable pre-tension load and the also desired possibility to go close to the edge.

According to ETAG001 Annex A, anchors shall be installed in accordance to the standard instructions supplied by the manufacturer. Torque moment, where appropriate, shall be applied to the anchor by a torque wrench having calibration traceable.

Hence we should follow the installation torque as per the ETA/ESR values.