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Masonry Lintels


Bryan
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I know this type of building is not what most of us look at; however, I thought I would ask and maybe we can all learn. The structure is a 90-95 year old multi story commercial build that is now being used for office and studio space. The main components of the building are reinforced concrete columns, beams, elevated floors and roof areas. Between the concrete components are multi wyth masonry brick to construct the exterior walls. The question I have is in regards to the lintels above the masonry windows. In the attached photos the lintels have failed by "bowing" downward with no significant, if any, sings of lintel jacking. Why is this? Is this set up more of a shelf angle vs. a lintel therefore allowing the steel to roll? If so what is the method of correction?

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I've never seen anything like that. It appears that maybe there are hung-plates off I-beams that have failed (bad welds). Usually the welds are stronger than the original steel. If these were sagged and twisted steel angles, you'd certainly see some settlement cracking in the brickwork. I'm guessing the soldier courses are merely hanging from the masonry above, which is still carried by the structural steel beams. It's the only thing that makes sense to me.

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I'd bet a tooth the vertical leg of those angles (in the cavity) is rusted gone. It's just a flat plate, and it's sagging. The miracle of bodacious inertia is what's holding it all in there, but it could suddenly drop some bricks at anytime. I see a fair number of failures like this.

You don't necessarily have to get jacking; it's just one of the common signs of failure.

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I'd bet a tooth the vertical leg of those angles (in the cavity) is rusted gone. It's just a flat plate, and it's sagging. The miracle of bodacious inertia is what's holding it all in there, but it could suddenly drop some bricks at anytime. I see a fair number of failures like this.

You don't necessarily have to get jacking; it's just one of the common signs of failure.

I suppose that's also possible, but it sure happened fast. That's a lot of steel to rust away. And, you'd think the steel wouldn't bend so sharply as it exits the brick jamb, without disturbing the masonry.

Hung-plates never enter the masonry at the jamb. They stop short of it. So, if the outer support hangers were still holding the center would drop like that.

It's a curious occurrence - a new one on me for sure.

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Well, it's 90 odd years old steel. Doesn't sound like it happened fast to me; it happened real slow for a long time. I'd be surprised if there was much iron left. Lots of shards.

There's different quality steel; very different. I don't know what they are exactly, but I can kind of identify them reasonably well visually.

The good stuff has more chrome in it, I know that; it's got more of an ever so subtle bluish tint. That stuff can last. The other stuff, not so much, or not at all.

Warehouses usually had the other stuff.

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Well, it's 90 odd years old steel. Doesn't sound like it happened fast to me; it happened real slow for a long time.

Now that's funny. I zipped through the original post and thought is was a range between 1990 - 1995, and was thinking the windows looked far too old for his assessment to be accurate. Now it makes a bit more sense.

My bad.

Still, I've never seen anything like that. Moisture intrusion must have been a much bigger factor than usual?

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The building has seen its goods days and bad. It was originally built as car factory till all went bust during the great depression. The current owner bought it around 1990 and started cleaning it up and converting it to what it is today.

It is my understanding that when they bought it better than 25% of the window glazing was broken out. Even today with all of the glazing in place the windows are one of the the week points of the building. The morning of the afternoon I was there a big storm a had rolled through and a number of the west facing windows had leaked leaving wet spots on the floor.

On a somewhat related note, the concrete columns appear to be poured around "I" beams and I am assuming the same is true for the overhead beams. Was this just there way of reinforcing the concrete at that point in time, or am I off base?

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Could it be a form of light weight concrete used as a sound dampener and insulator? In other words, the steel is the true structure and the hybrid concrete is merely a surround. I've seen lightweight mixes where perlite was used instead of sand. It's a pretty good sound deterrent and insulator.

Rebar in concrete is one thing, but large slabs of structural steel sounds like a bad marriage, which would eventually crack the heck out of concrete due to their differing flexibility.

I can certainly be wrong, but that's my opinion.

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Could it be a form of light weight concrete used as a sound dampener and insulator? In other words, the steel is the true structure and the hybrid concrete is merely a surround. I've seen lightweight mixes where perlite was used instead of sand. It's a pretty good sound deterrent and insulator.

Rebar in concrete is one thing, but large slabs of structural steel sounds like a bad marriage, which would eventually crack the heck out of concrete due to their differing flexibility.

I can certainly be wrong, but that's my opinion.

No I am sure it was regular concrete, primary due to the large spans involved and the way anchor points were cast in the columns and overhead floor.. What got me thinking down that path was an inspection from a few weeks ago where a base ring of concrete had broken away from the column and I could see the steel base plate at the edge of the concrete. now this building was built around 1950; however it had very similar details. Sorry this is the best photo I have of the detail.

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I assume you are right. But, I believe that, in a case such as you describe: where there are structural steel columns and beams, the steel is the true structure and the concrete is probably more a reinforcement or stabilizer. It's really difficult to imagine the two materials integrated to "be" the structure. Maybe someone out there will be familiar with these installations. I'd love to hear this one nailed down myself.

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On a somewhat related note, the concrete columns appear to be poured around "I" beams and I am assuming the same is true for the overhead beams. Was this just there way of reinforcing the concrete at that point in time, or am I off base?

If you're still talking about the 90-95 year old building, encasing steel beams and columns in concrete was the most common method of fire protection of structural steel.
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