Structural or Shrinkage Crack in CMU?

[dylansdad]

While visiting a commercial structure I was asked to look at a crack in a CMU wall. The wall is located in an interior wall in the elevator penthouse above the roof. The wall is approximately 20 feet long and was constructed after the original building, mid 1960 to early 1970s. The crack is located in the general vicinity of the hoist beam. It appears to me to be a shrinkage crack but I would welcome others opinions and thanks in advance.

 

[dylansdad]

The walls are approximately 12 feet high. I have come to find out that they are bearing on concrete elevator shaft walls

 

[KootK]

The walls are approximately 12 feet high. I have come to find out that they are bearing on concrete elevator shaft walls

That's the end of the settlement argument then.

The red path would not become loaded until the green path had experienced some strain.

Sure but, then, the green path would always experience some strain. And, even if it didn't, elastic movement in whatever lies below could be the source of the distress.

In my experience, these beams will be grouted for a few cells below the beam but not all the way down like a real pier.

 

[KootK]

The cracks were likely phased in over time to become the shape we see now, because they are not consistent with either a horizontal tension or pure settlement.

In what sense to do you feel that the cracking would not be consistent with horizontal tension? For horizontal tension, I would expect.

1) Crack diminishing towards the bottom as the connection to the roof deck is likely the source of the restraint and;

2) Crack initiating at the beam which acts as stress concentration.

I wouldn't expect a shrinkage crack to be straight up and down, or even the saw toothed version of that.

 

[PMR06]

I have a hard time believing cracks that large would be shrinkage in a 20ft long wall. I would consider looking bigger picture.

Any thoughts on if this is a lateral load issue? What is the lateral system of the rest of that penthouse roof and exterior structure?

Is this a high seismic region of Mississippi? Perhaps it got bounced around a bit in its 50-60yr lifetime?

 

[BAretired]

In what sense to do you feel that the cracking would not be consistent with horizontal tension?

I would not expect a horizontal tension crack to almost close two and a half courses below the steel beam, then open up by a small gap, three large gaps and another slightly smaller gap.



BA

 

[mfrad]

What about steel beam thermal changes perpendicular to the wall. There seems to be some out of plane movement.

 

[1503-44]

The angle indicates a load-deflection-settlement failure.

A black swan to a turkey is a white swan to the butcher.

 

[XR250]

Is the right portion of the wall also sitting on an elevator shaft? If not, maybe that portion settled and the shaft supported section did not.
I see this in houses where the foundation transitions from crawlspace to basement. The deeper soils of the basement are typically stiffer (at least in my market) leading to similar looking cracks.
Seems too big to be shrinkage.