SEISMIC BRACING REQUIRMENTS

[steve66]

For a particular installation, seismic bracing is required for all electrical conduits 3" and larger. However, there is an exception that the conduit doesn't require bracing if it is supported by hanger rods that are 12" or less from the top of the conduit to the bottom of the structure where the hanger is attached.

This exception has some additional requirements, one of which is:

"Electrical system must be made of ductile material with ductile connections."

What the heck does that mean? Does it mean the conduits would have to have flexible connections (like FMC) at conduit terminations, such as at a panelboard?

Or does it mean the conduit has to be made of ductile iron, like EMT?

 

[Jraef]

Ductile in this context would mean steel or other metal that retains its strength after being deformed. EMT, RGC, IMC etc.

NOT flexible.

 

[topgone]

Ductile in this context would mean steel or other metal that retains its strength after being deformed. EMT, RGC, IMC etc.

NOT flexible.

Correct.
Ductile - will not flex, as opposed to very malleable.

 

[GoldDigger]

Correct.
Ductile - will not flex, as opposed to very malleable.

Used more in plumbing that electrical, but IMHO both cast iron and fiber cement forumlations would not be ductile.
Wrought iron is malleable, while cast iron can crack easily.

"The definition of ductile is easily stretched out without breaking. ..."
There are other definitions too, and some treat malleable as a synonym.

The key point is that they must not lose strength or crack under tension but must deform while keeping their integrity instead.

 

[infinity]

So for EMT would steel connectors and couplings be required instead of die cast?

 

[GoldDigger]

So for EMT would steel connectors and couplings be required instead of die cast?

Quite possibly.
I have seen die cast couplings crack and tear under stress.
I guess this is another one that may be an AHJ judgement call.

 

[steve66]

OK, that explains it.

Thanks for the replies.

 

[Carultch]

Correct.
Ductile - will not flex, as opposed to very malleable.

Ductile is not the opposite of malleable. In fact, it is very common for a material to be both ductile and malleable.

Ductile refers to tension, malleable refers to compression, and both these concepts mean that the material can be permanently deformed in that particular mode after reaching a certain stress, and retain their strength afterwards. The opposite of both of these terms is brittle, which means that as soon as linear/reversible elasticity ends, the material fails.

Other modes of loading (torsion, bending, shear) will rely on both compression and tension, so if you expect this behavior in these modes, it would have to be both ductile and malleable.