Secrets of Reinforcement | How to design reinforced concrete

did you know the greatest reinforced concrete structures today wouldn't exist without broken flowerpots my name is Tyler la I'm a concrete freak and this videos for you Joseph Monier a French gardener go France developed reinforced concrete in 1867 Monier was tired of his clay pots breaking so what did he do he tried something new tried something different and it worked he filed for a patent for reinforced concrete for combining steel and concrete together to help hold his pots together they would still crack but he would keep those cracks small he had big pot small pots all kinds of water buckets and look at this long crazy thing that dudes a visionary I've never even seen a pot like that but Monier was already investigating and developing it so many years ago so when you see a crack like this think like Monier I'm just gonna keep those cracks small I'm gonna put reinforcement across it there are all kinds of different ways to do this I'm not gonna talk about all of them but I've got videos on most of them you should check it out but how do we know where the cracks are gonna form in our concrete and the simple answer is where is the concrete trying to get longer longer yeah where is it trying to get longer this is called tension make sure what I'm talking about if I have concrete and I pull on it now she doesn't take a lot of load to make a crack but if I have reinforcement inside of it those cracks they still form but they're small and we'd like those cracks ideally to be less than point zero zero four inches that's what a CI 350 says that water or fluids won't penetrate it we don't have to have them that size but that's what's ideal if you don't learn more this and how to control cracks you can watch this video but how do we figure out where the tension is well to do this we have to become the structure and we have to imagine the structure deflecting under load and then put that reinforcement where there's tension and have you seen cracks on previous projects that means they didn't have enough reinforcement there because we'd like those cracks to be so small we could barely see them we should I'm talking about if we have a beam that's on support so we idealize if gravity starts loading it it's gonna make it move like this or deflect and at the top it's gonna be getting shorter at the bottom it's gonna be getting longer we tall the top it's in compression and the bottom its intention so what do we need to steel the bottom of course we're gonna put it near the tension face so how much reinforcement do I need well it depends yeah depends aren't just diapers it depends on lots and lots of different things and that's why we have engineers they help us figure out these problems and calculate and see exactly how much we need bill engineers but ideally we have closely spaced reinforcement that's placed very close to the surface not too close because we don't want to have corrosion but close enough to help keep those cracks small and that's why I'm a big fan of deformed bar mats they're really small bars that are closely spaced that are deformed so they're still gonna grab on on the concrete I'm also a fan of combining reinforcements and fibers together you will get improved performance with them both together I talked about this in this video you should check it out now if we have another type of beam cantilever beam one that's kind of hanging off a cliff if we do our job to think about how is it gonna move its like this and there's gonna be tension at the top so that's where we need our reinforcements now we have a really long beam with lots of different supports let's think about it deflecting it's gonna look like this where's their tension there there there there there there there there like all over the place right but what happens here well it's getting smaller there right it's compressing but when we put reinforcement in it we usually at least in my country put it almost everywhere why why would we put rebar where we know there's compression well there's a couple good reasons well one is it decreases labor cost if I'm already extending the bar I might as well keep it going and - the theory is not always right we don't always know where the tension is going to be and sometimes especially in elevated slabs we need to protect ourselves from surface cracking so we put our steel in a lot of different places how about on the ground now you look at this and say it can't deflect right think about it where's it gonna move but as concrete dries it shrinks it's like a sponge it's gonna shrink and the ground underneath it is gonna restrain it or hold it it's gonna keep it from moving freely and this is why people sometimes put plastic underneath their slabs usually two sheets with at least 15 mils here's a whole table of different friction coefficients that a CI 360 has put together this is how hard it is to get your slab to move over these different surfaces and we'd like the lowest number hence the two sheets of plastic but if the concrete dries more at the surface than at the bottom it's gonna curl it's gonna move up and curl and if there's load on the edges oh no it's gonna crack I hate corner cracking how do we stop this reinforcement right we'd like to put this deal near the surface to help keep the crack small that's what people are gonna see them a good number is about one and a half inches on an interior floor slab are there other places we need steel yeah sometimes on reentrant corners crack is gonna want to form there when we're about to pour the concrete you'll see these diagonal bars there and you would get them as close as we can to that surface maybe an inch away just so concrete coats it so in summary find the tension then use the reinforcement to stop the cracks and learn from your past projects if you've seen cracks other places then you know how to stop them and remember the cracked pots remember what Joseph Monier did he had a problem and he came up with the solution the world needs your ideas don't be satisfied with the status quo don't be satisfied with the problems you put up with every day don't give up come up with innovative solutions we need you and maybe you will be the next Joseph Monier viva la concrete baby thank you so much for watching this video give me a thumbs up if you liked it leave me a comment in the area below tell me about your concrete ideas I want to hear them and check me out on instagram at concrete Tyler take everybody pues you

Channel: Tyler Ley

Views: 222,230

Keywords: Tyler Ley, #simpleconcrete, reinforced concrete, reinforcement, reinforcement design, concrete, simple reinforced concrete, durability, crack, concrete cracks, civil engineering, civil engineering (field of study)

Id: vbrQaQltVRA

Length: 8min 11sec (491 seconds)

Published: Mon Oct 28 2019