Materials for Structures - Masonry - Part 5

So, again, this is one of those interesting things. The structural system is, in fact, the finished system. And so, it really is important to kind of keep in mind how that structural system, how the details are being played out, because you are literally playing with the structure of the building when you're assembling these different components together. So one other masonry element that's worth talking about is the CMU block itself. So as we said, the CMU is eight by eight by 16.

So we've got couple holes in here, now there's a lotta different specifics to how these things work, different proprietary systems, there's different setups. Some are a little bit heavier than others. So sometimes you'll see it looks a little different than this, but the idea is that I have a stretcher face and then the other sides are ready to be buttered together, so we can get some mortar in there.

And I have these holes which both lighten up the overall element, but also allow me to put rebar moving right through that whole system. I can grout the whole thing together, and have multiple pieces stuck together, and this becomes a structural wall as it sort of builds up with this rebar going all the way through. That rebar might be every cavity, it might be every other cavity, might be every third cavity. Depends on how much structural capacity we're looking for.

But it creates this opportunity for making this a contiguous structural wall out of a bunch of individual pieces, so it's kind of interesting right? It's unlike doing a concrete wall, where I'm making a contiguous element. I'm actually using a bunch of individual pieces and then finding a way to make them act like a contiguous wall structure. So that's a sort of great system. It allows you to pick it up with two hands fairly easily put it into place.

It's light enough that you can move them around fairly simply. Obviously I would have ones that have finished faces on two sides, if I'm doing a corner piece or something. So you have to be very careful about the numbers when you're ordering them. And equally if I imagine, a big wall going up, I can put an opening in that wall and kind of just like what we talked about over here, I can use a steel angle or something like that to hold up these elements that are over the actual opening.

Maybe I, if it's a bigger opening and it's kind of chunkier CMU wall, it might not be a little tiny steel angle, I might use a wide flange or something. But I can hold it up in very much the same way. Or, from a structural standpoint, I could also choose to use what's referred to as a bond beam. Which is gonna look exactly like a regular CMU from the outside.

And it's just this U-shaped CMU. And the whole point of the U-shaped CMU is I can put some rebar down at the bottom, sort of thin little rebars that are gonna shoot right through it, and then I'm gonna fill it with grout, and that's gonna grout that rebar all together.

And it's gonna make that function like it's a beam. So I could then have another one right next to it. And I could have 10 of these all in a row, and that rebar is just going right along and I'm filling it with the grout.

And all of these, even though they're individual elements which should just fall down, could span right across an opening because we've effectively, by putting this grout and this rebar in that little U-shaped space, we've effectively made these act as one piece, they become one beam that's going to span right across our opening. But at the same time, if I'm standing outside, looking up, I'm gonna see this as a series of individual elements that are just like any of the other CMU.

I won't even be able to tell how it's all standing up there above an opening. Because all the structure is actually on the inside. So that's a bond beam. And that's one of those concepts that seem important to me to make sure you feel comfortable with because that is very likely to show up on the exam. In terms of the way the CMU works, well it's gonna be pretty much, as we talked about with the brick, it's gonna have stretcher courses, it's gonna have different wythes, potentially, usually one, maybe two wythes.

It's going to need to have coping over the top. We don't wanna get moisture in. It's gonna have issues about how much water can penetrate in, so we're probably gonna want to find a way to do a rainscreen or cavity or something like that. It's gonna have all the same basic issues that the brick masonry does, it's just that it's made out of concrete, so as I said it will always be shrinking slightly.

It will have this bigger quality. So it's physically larger, so the cavities are bigger, therefore it's easier to put rebar through and to fill those cavities with grout. So this thing can very easily become a full structural wall again out of these individual elements, we can make one single big structural wall. Which is kind of an amazing thing. And we have to worry about the same set of tooling like we did in the brick.

So we have to think about, is it a concave tooling? Is it single strike tooling? Probably not gonna wanna do a raked, just the same reason why we didn't wanna do it in the brick and probably be very careful about having moisture get into these walls as best we can. So now we've started talking about how all these different pieces and the terminologies and how all these things work and we've looked at some of these things in some of the other exams as well.

Now you can pretty simply see well, there's a million possibilities about how all these things can start getting put together. So we'll have to look at some examples of that as we go along, but the gist of it should be pretty straightforward. There's, like I said, a million possibilities. Don't worry about that so much. As long as you feel like you understand the sort of way and why things are being put together. It's mostly about structure, and it's mostly about water. Those are the two basic things going on. I'm trying to keep the water out or at least let it in and then get it out.

And I'm trying to make it so that I can take individual tiny pieces, and make great big structural, pretty massive quality walls out of these materials. So from a structural standpoint in terms of the everyday use, the masonry very common, very easy to work with, but there's a lot of variation and a lot of sort of possibility out into the future about how these things are gonna be made up as we go along. It's of course, also possible to start thinking about arches and domes and all kinds of other ways.

I don't think those are gonna show up on the exam to the same level, so we're probably gonna keep that sort of simple for now. But, this kind of terminology, this sort of set of ideas you should absolutely feel comfortable with.

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