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CMU Crack

CMU Crack

CMU Crack

(OP)
I have a project where the building caught on fire and destroyed a small portion of the roof open-web steel joists. The existing building was constructed in the 70’s or so and as has no vertical reinforcing (although I did see some horizontal ladur joint reinforcing when I was onsite.

I had them demolish the existing damaged joists and a few more for good measure (just in case there were hidden defects). After demolition was completed, I received a call saying that they found a diagonal crack in the corner of the building and needed me to investigate.

The crack (shown in the attached) is diagonal and appears to have been in place for a little while (because it was dirty and appeared to have paint on the inside). However as you follow the crack it appears as if the crack did open up slightly during demolition. However, the building is clad in a brick façade and we found no evidence of the crack reflecting through the façade.

I am wondering how to repair this crack? My repair detail for the roof has the client placing a reinforced bond beam at the top of the wall to attach the new joists to. I am wondering if this is enough or if I should be placing some vertical reinforcing and grout in this location of the wall as well.

RE: CMU Crack

It's already going to be open and accessible, why not throw some rebar and grout down those first 4 or 5 cores. Can't cost that much if you are already bringing in rebar and grout for other repairs.

RE: CMU Crack

It's fine, throw some caulking on there and have 'em call ya when the bricks start popping loose. :P


My boss is the masonry guy around here so I'm entirely out of my element but quite curious. Can one epoxy inject a crack in masonry similar to how you would in concrete?

Maine EIT, Civil/Structural.

RE: CMU Crack

(OP)
I'm not an expert at epoxy repairs, but since the block is hollow I don't think that would be a good idea unless you hat a huge truck with epoxy.

RE: CMU Crack

Looks like a shrinkage crack since it is top down and dies out. Is the wall that is cracked parallel to the open web joists? If so, could have been caused by expansion of the joists during the fire. Add rebar and grout the cells. Don't waste time and money with epoxy for this type of repair.

RE: CMU Crack

Ron: Just out of curiosity, why couldn't a stress crack start at the top and go down?

Maine EIT, Civil/Structural.

RE: CMU Crack

(OP)
Ron,

This is the wall the joists bear on is perpendicular to the exterior wall. Due to a height change in the roof, this wall has another set of josits that frame into the wall 3'-0" below the roof joists that were damaged. That makes the bottom 16' of this wall interior and the to 3'-0" exterior. I was also thinking about a possible temperature difference between the exterior all and the interior bearing wall. Maybe a combination of shrinkage and temperature.

The fire occurred in a RTU dust collection system that was about 50' away from this wall. The fire was under control pretty quickly so I don't think it had anything to do with the fire.

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