Elongation of anchors 2

[Mohamed Maher]

Hi all,

I Have question we had anchors 24 mm diamter and grade 8.8 we achieved its Tensile strength and it's passed as per ISO 898 1:2009 P.12&54 as attached But failed as Elongation. We should achieved minimum elongation 12% while it's achieved only 11 and other one 10%.

I believe that design is based only on Tension resistance.. but what is the effect of elongation on design? should we give attention for elongation?

Thanks
Maher

 

[Agent666]

Its there for a reason, elongation is a measure of ductility.

 

[Mohamed Maher]

@Agent what happened if ductility is lower than required by specification , specially this is the ductility at fracture. is that means anchor will not safe?

 

[Agent666]

Possibly means they might not be safe and may fracture and/or not achieve the performance in practice envisaged by those who write the standards. For example you could have stronger bolts than required and pass the tensile strength test, but higher strength 10.9 grade bolts have less ductility and might fail the grade 8.8 elongation requirement.

If the material does not comply, why accept it? What did the material certificate for the bolts say, did they agree with your testing?

There seems to be traditionally a lot of issues worldwide with counterfeit or substandard bolts in the supply chain, so its one area where it pays to act if there are any concerns regarding quality.

 

[Lomarandil]

To answer the question technically, ductility (and hence elongation) is tied to energy dissipation. For structural engineering, this usually means seismic or vibration loads. Elongation might also be important for high pre-tension cases. If you had a bolt loaded statically (especially loaded in shear), you may be not wrong to allow bolts that are near but not quite meeting the specified value.

However, this would be taking on a huge amount of liability for your company. As Agent mentions, it's a growing issue. You'd need to have a really good reason to approve them rather than making the bolt manufacturer supply bolts that meet the specification.

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The name is a long story -- just call me Lo.

 

[Mohamed Maher]

@Agent @Lomarandil thank you very much that was helpful.