Steel Beam Bearing on CMU Repair

[NinerStruct]

I'm working on an addition to an existing building and during demo, the contractor discovered the situation shown in Photo #1. It's an existing W21x44 bearing at the end of a CMU wall and the CMU under the beam bearing has cracking. There's a 1/2" steel bearing plate below the beam with threaded bolts through slotted holes in the beam flange (see photo #2). The core below appears like it may have been grouted, but has also cracked (see photo #3).

The overall reaction at the end of the beam shouldn't be overly large, only about 16 kip, so I don't think it would be caused by overloading. My second thought was that it may have occurred during construction due to temperature shrinkage, but the gap in the head joint is around 5/16", which seems large for shrinkage of the beam.


So I'd love to get others' thoughts on this, and secondly any suggestions for a fix? I'm leaning towards temporary support of the beam, and removing the two courses of block below and replacing, regrouting, and reinforcing with a vertical bar and maybe something horizontal into the existing.

Thanks in advance!

Photo #1
Photo #2
Photo #3

 

[darthsoilsguy2]

is there the same amount of travel left on the bolt other side?

This damage reminds me a lot of an addition that i inspected in 2008. A lot of the masonry embed plate locations looked like this during construction and it all happened between 2 site visits. The steel erector confessed that it all happened because they welded those connections before they plumbed (or perhaps had to re-plumb) the building. no welded connections i'm seeing in yours but maybe it was taken beyond the travel limits during plumbing....

 

[JAE]

Not sure of the cause here - but your repair sounds feasible and appropriate.
If you don't figure out why it happened you might go beyond the vertical rebar and do some additional horizontal strapping back into the main wall to take any potential tension force in the beam back into the meat of the wall.

Check out Eng-Tips Forum's Policies here:
faq731-376

 

[KootK]

I like the construction plumbing hypothesis and the proposed fix. Those LSL movement joints never work worth a damn once loaded unless there is PTFE etc underneath.

I have an alternate hypothesis as well:

While the beam reaction is low, the beam is likely a long member governed by deflection (hence W21x44). That may mean significant slope at the support and possibly a prying mechanism at the connection plate that somehow dumped a ton of compression right into the CMU head shell and caused it to fracture.

I'd consider the use of a neoprene bearing pad in the repaired connection. It just looks way too much like the spalling that you see below improperly detailed corbels at precast beam supports.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[KootK]

Another thought: this beam lacks the pair of bearing stiffeners that you typically see. I feel that the stiffeners help to shift the point of load delivery inwards from the edge a bit.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.