Chord Members

[JedClampett]

Whenever I design a building, I run my numbers, check the walls for wind and seismic, etc. During the diaphragm check, I calculate the global moment on the whole diaphragm and add chord members (reinforcing, angles, overlapping wood plates, etc.) just like the textbooks say.
My question is; Has anyone ever seen a failure due to lack of these chord members? It just seems counter-intuitive that a couple of #5 bars (or angles) at the bearing level in a building are going to do very much. I know the numbers require them and I'll continue to provide them, but they seem pretty cheesy.

 

[BAretired]

I have never seen a failure of that kind even when chord reinforcement is omitted. I suspect the diaphragm usually has enough capacity to carry the chord forces without additional reinforcement.

BA

 

[azcats]

The chord forces are added incrementally to the wall/chord as well. So, especially in masonry, there's plenty of space for those forces to get distributed to other reinforcing throughout the wall.

This got me thinking about diaphragm failures and how I'd never seen one in person or photos. So I head over to google and you can imagine my surprise upon searching for "diaphragm failures".

 

[JedClampett]

It's like doing a search on Red Head anchors.

 

[dhengr]

Azcats:
I didn’t bother to look or Google “diaphragm failures,” but I can just imagine. You’ve just got to bring sex and pregnancies into ever engineering discussion, don’t you?
I’ll bet those weren’t the topics JedC had in mind with his OP.

 

[JedClampett]

Those are always on my mind, but I manage to fit some engineering in occasionally.

 

[frv]

I want to say that there have been some failures in seismic events where the pieces weren't properly tied together, although I can't remember where I read that.. although that may be a load path continuity issue in general more than a chord reinforcement issue in particular.

 

[frv]

ooops.. to clarify: in precast structures.

 

[hawkaz]

The only issues I have seen were at re-entrant corners (diaphragm tearing). Not really related to the chord tie.

Jed- I have made that mistake as well. I was trying to find the required embedment length- not quite what I had in mind.