Technical information

Because much research takes place internationally in the field of "fastenings" it was decided to have the calculation rules for short anchors in concrete in the Netherlands better match the state of the art. Because CUR recommendation 25 ("short anchors in concrete" -1991) has in the meantime become an established norm it was decided to keep this number. For the method of calculation CEB Bulletin 233 "Design of fastenings in concrete" - 1997 and the ETAG "Guideline for European Technical Approval of Metal Anchors for use in Concrete" is used as the starting point.

 

The method is applicable to concrete strength classes C20/25-C53/65 and various failure mechanisms are taken into consideration:

• steel failure 
• pull out
• concrete cone failure
• concrete splitting failure
• concrete blowout failure
• concrete pry-out failure
• concrete edge failure

After determining the characteristic strength of an anchor (for the applicable failure mechanisms) calculation takes place with partial safety factors to obtain a calculation value. The calculation rules of the CUR 25 recommendation are applicable without supplementary tests to DEMU anchors:

• 1985 and 1988 galvanised,
• 1980 with connector A1 quality
• 1988 with connector A4-80 quality,
• 1980-P with galvanised connector, with connector A1 quality and connector A4-80 quality.

To calculate the 1988 with connector A4 quality, the calculationresults can be taken from the 1988 with connector A1 quality.

 

The consequences of the new calculation rules for these products are:

• The formerly used edge and centre-to-centre distances of 5 x d and 10 x dnom are no longer valid. Besides minimum distances to be used according to the CUR recommendation, calculation will have to take place with various factors with the consequences of small edge and centre-to-centre distances having an effect on the calculation value.
• The type 1980 bolt anchors were supplied with bolts of quality 4.6, where steel failure was normative in a number of cases. Partly further to the new method of calculation DEMU has decided to start using bolts of quality 8.8, so the calculation values in a number of cases will be considerably higher.
• With the combination of bolts of quality 8.8, and our special A4-80 connectors (yield stress 640 N/mm²) an anchor is formed that "concretefailure" is nearly always normative. This also results in much higher calculation values compared to the old 1980 anchors.

This version replaces version 2.0. More constructive information with respect to the use of suspension reinforcement: At present there is too little information in the current literature to extend version 2.1 with specific information with regard to suspension reinforcement. To be able to make optimal use of suspension reinforcement in the next version DEMU will supplement the current information after an investigation so optimal use can be made of pre-applied anchors in combination with suspension reinforcement.