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mikykas • Apr 30, 2012

Hi guys, a question about EC2

Someone knows maybe if there is any restrictions about mandrel diameters for bent bars in large diameters bars, according to EC2 (else then d>16 --->7*d)?
Nachko • May 13, 2012
EC 1992-1-1: 8.3; 11.8.1
mikykas • May 28, 2012
Thanks for the answer,
I already checked this sections in EC2 , still I coudn't find any special recomandations about mandrel diameters for bent bars in large diameters bars like more then 28 .
In my country the mandrel diameters for bent bars in frame design can get to 20*d .
Maybe the expression 8.1 is the answer although it doesn't speak specifically about the diameter.
Nachko • May 28, 2012
EN 1992-1-1:2004

8.3 Permissible mandrel diameters for bent bars

(1) ...
(2) In order to avoid damage to the reinforcement the diameter to which the bar is bent (Mandrel diameter) should not be less than φm,min .

Note: The values of φm,min for use in a Country may be found in its National Annex. The recommended values are given in Table 8.1N.

Table 8.1N: Minimum mandrel diameter to avoid damage to reinforcement

Bar diameter...........Minimum mandrel diameter for bends, hooks and loops (see Figure 8.1)
φ > 16 mm......................7 φ

(3) The mandrel diameter need not be checked to avoid concrete failure if the following conditions exist:
- the anchorage of the bar does not require a length more than 5φ past the end of the bend;
- the bar is not positioned at the edge (plane of bend close to concrete face) and there is a cross bar with a diameter ≥ φ inside the bend.
- the mandrel diameter is at least equal to the recommended values given in Table 8.1N.

Otherwise the mandrel diameter, φm,min , should be increased in accordance with Expression (8.1)

φm,min ≥ F bt ((1/a b ) +1/(2φ)) / fcd ............................................(8.1)

So, on my opinion it's complex 😀 If you meet the requirements of 8.3 (3), the mandrel diameter doesn't need a check. Otherwise --> exp. (8.1) and 8.3 (2).


Edit: you may open this PDF and read pages 4 & 5:

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