In this ARE 5.0 NCARB-approved Project Planning and Design Exam Prep course you will learn about the topics covered in the ARE 5.0 PPD exam division. A complete and comprehensive curriculum, this course will touch on each of the NCARB objectives for the ARE 5.0 Project Planning and Design Exam.
Instructor Mike Newman will discuss issues related to the generation or evaluation of design alternatives that synthesize environmental, cultural, behavioral, technical and economic issues.
When you are done with this course, you will have a thorough understanding of the content covered in the ARE 5.0 Project Planning and Design Exam including design concepts, sustainability/environmental design, universal design, and other forms of governing codes and regulations.
So SiteCast Construction for medium spans. There's a couple sort of obvious ones that start to jump out. Got commercial scale kind of office buildings schools, things like that. We're probably talking, most of the time, flat plate and flat slab type construction and then we'll go through a couple of more interesting ones of joist slab and waffle slab construction. We'll talk about those in a minute. The flat plate and flat slab are sort of unusual terms which I find a little on the confusing side. Flat plate, if you imagine I have a flat slab of concrete that is of a certain depth and then I have columns also concrete columns and let's say that's a eight-inch depth, maybe it's up to 12 inches, depending on the span but it's just that depth, and then the column and there is no other element in between.
And then if we were looking at the reinforcing bars you would find that there's quite a bunch of reinforcing going on up here at the top, there's quite a bit going on here down at the bottom. There's some that go up and then down there's some that go down and then up but there's also a huge amount of reinforcing that goes down into that column. So there's a lot of action happening with the reinforcing at that one spot and then there's the cage reinforcing for the columns and the reinforcing continues down to the next level.
Which is of course the great thing about the concrete is that everything becomes one structure. It's not individual pieces anymore, it all ties together. So we have quite a bit of stuff happening in these very tight moments here it's just that at that column to slab connection there's a lot of rebar that's happening right in that spot in order to tie all of this together.
The thing you're trying to stop the thing you want to be careful about is you don't want the load on that slab to become something that is pushing down and pushing down and pushing down so much with all of that load kind of per square foot pushing through that the column just sort of pokes its head right up through the system. That would be a disaster. So you need to have that thing not allow for that puncture through the slab.
If you imagine you have a piece of paper and you have a pencil as a column and you're pushing down on the paper the pencil wants to puncture right through that paper slab. Well you're trying to do this in a kind of a similar way right, we have this very thin slab maybe only six or eight inches and then we have this column that's coming right up to it and the load, which is potentially quite a lot of load is pressing down all around it.
It's going to want to let that pencil of a column puncture right up through the slab. So that's one of the reasons there's so much activity in that rebar right there at that point in order to make that not be the case. So this is a demonstration of the flat plate. So I'll call that out as the plate and then the flat slab version. I'm going to have that same slab but then I'm going to have a column capital that is going to help that transition of all that rebar.
So in that situation, instead of having just that really tight space over here in order to fit all that rebar going from the thin slab into that column I now have this extra zone, and so that rebar has sort of opportunity to sort of find its way down.
You get lots of different ways to get that in there and it ends up reducing the span as well. So from a deflection standpoint, our overall span is quite a bit less because you're going from the column capital edge, not from the edge of the top of a straight column. So the flat slab is set up where we have a column capital or possibly what's referred to as a drop panel which is that idea where there's just a little flat panel that doesn't have the angle like the other one but it again provides that opportunity to be able to get that rebar to be able to go a little bit easier angle to have more room to get that stuff through.
So in both of these cases, with the column capital or with the drop panel, or, for that matter with a combination drop panel and column capital which happens quite often these are going to be much stronger and be able to have a lot more load pushing down on these floors, so these are more like industrial-type floors, things you might have a lot of big, heavy equipment on.
You might be having forklifts or things like that kind of driving around, just like that big, heavy equipment. Or possibly, it's just holding up a assembly space and you have lots and lots of people or something.
But you would use these systems in order to reduce the amount of deflection, because I'm changing the span even though the column spacing might be the same I'm changing the span because the column capital reaches out farther, so I'm reducing the deflection which is great thing. I have more capacity to stop the puncturing through of the column through the slab because I have a lot more room to get more rebar back and forth between the column and the slab so it's being helpful from that standpoint.
So I have a lot more load capacity. Typical situation, like typical office space you know, if you're just talking about normal kind of office loading, that flat plate is going to be just fine. If we're talking about the more intense versions for manufacturing and things like that or maybe you just don't know, you're not sure how it's going to be used and so you want to make sure you have that capacity, well then the flat slab would be the more appropriate.
The obvious difficulties with the flat slab is that I no longer have just that flat plate of a concrete slab up there, which means that you know, I don't have to bend plumbing around it. I don't have to push it out, push duct work out of the way of the column capital.
It sort of gives me a lot of freedom and a lot of simplicity. Everything is flat, we can use it as a finish. Once I have these column capitals they potentially start getting in the way you know, if you imagine you have a wall, say, right here. Well that wall comes up, but then it's going to still have this little bit left over and when you're looking at it in plan and you see that that's where the column is and having the wall right there seems perfectly reasonable but then you forget that oh, in fact that column capital goes out much farther.
And so that happens all the time with these. And so it can be a little funny from a planning stand point that you've kind of got to deal with these big drop panels or these big column capitals. But, like I said, if you're looking in order to have this be very heavy loads, that's a great way to do it.
It provides much more capacity and doesn't deflect as much. If you're doing just sort of normal loads flat plate's going to be just fine. So in our typical situations, these are the two most likely ways that you would be using concrete in these middle span types. If we're going to start talking about kind of the next level up of distance a little bit farther in the terms of spanning capacity but also maybe a little bit more kind of heavy-duty if you really want to get beyond even the flat slab then we're going to start talking about the joist slab and the waffle slab.
So let's do an example of that next.
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From the course:
ARE 5.0 Project Planning & Design Exam Prep
Author: Mike Newman