Why does concrete reinforcement have deformations?
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- čas přidán 15. 06. 2024
- The tandem of concrete and steel works well in resisting loads since concrete is amazing at resisting compressive loads while the steel bars are great at taking care of the tensile forces. The combination of these two constriction materials gives rise to reinforced concrete that has been a central figure in the construction of modern society. But small details around this composite material have evolved over time. For example, in the early days of concrete construction, the steel reinforcement used to be plain (undeformed). Later on, it was found out that this is not the optimal way to reinforce concrete. This video investigates and points out the effects of using deformed vs. plain rebar on the strength of the reinforced concrete beams.
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References:
[1] J. Maffei, "The Seismic Evaluation and Retrofitting of Bridges," University of Canterbury, Christchurch, New Zealand, 1996.
[2] S. Brzev and J. Pao, "Shear Design of Beams and One-Way Slabs," in Reinforced Concrete A Practical Approach, Toronto, Prentice Hall, 2009, pp. 260-315.
[3] A. P. Clark, "Bond of Concrete Reinforcing Bars," Journal of Research of the National Bureau of Standards, vol. 43, pp. 565-579, 1949. - Věda a technologie
The stirups don't need deformations to prevent slipping because they are bent 90 deg at every corner, so no slipping possible, especially on such small lengths
nope.... ribbed for her pleasure
They are required here in Turkey.
Stirrups in the Philippines are always made from ribbed rebar for good reason. Usually at least 10 mm diameter. We just had multiple magnitude 7 earthquakes with no structural building collapse.
No they should be deformed, it's not accurate to put that in the video. If anyone uses plain bar for stirrups its purely because they are cheap
Great video. Short and to the point. Thanks for quantifying it at the end.
Stirrups are mainly used to for tying your horizontal reinforcing together to create a rigid continuous unit and are typically smaller in diameter bar than the surrounding reinforcing, in a case like you’ve shown, they could be used to gain compressive strength in a column or pier as opposed to a flexural strength ,which many bridge decks an elevated slabs are designed for. I don’t see to many smooth reinforcing in builds, but when I do they are typically smooth dowels, mostly epoxy coated, in control joints to allow for expansion and retraction of the concrete where deformed bar would grip and could cause failure in the joints from the stress of the expansions and retraction cause by weather changes.
Yup, rebar ridges matter coz they increase the bond between the concrete and the reinforcing steel, improving the overall strength and stability of the structure. ☝️👍
I'm more surprised someone ever thought a plain bar would be a good idea
Yeah, it does not sound like a good idea. I wonder if maybe back then deforming the bars was adding too much to the cost. Would be interesting to hear from someone who has worked in a rebar factory.
@@TheEngineeringHub you are probably right. I guess the reasoning for using pain bars was: it's better than nothing and works well the times we tried it.
Same here - sounds like they just winged it on price back in the day but common sense suggests that ridges are going to help hold the concrete to the rebar - much like a screw or ridged nail 🤷♂️
They probably assumed the frictional force was sufficient - after all, steel pilling doesn't have deformations and they work perfectly well.
always watching these video before starting with my job as a structural engineer and it's always super interesting and so well explained :) Good job! It could be nice with some videos that are covering FEM design topic, or maybe they are already there but I somehow overlooked them😃
Excellent presentation. Thank you.
Stirrups are used to tie main reinforcement bars together, so they don't need the increased concrete bonding that deformations provide.
Another great video! thanks for sharing it.
Thanks for your very helpful content.
Excellent presentation
Brother make video on wooden structures, iam studying civil engineering , it will help me to gain good knowledge.
I guess the plain bars in the stirrup, is to prevent the stirrup from gripping more than the rest, causing uneven tensions.
But don't really know
Sounds good to me. I was thinking more along the lines of cost saving, but your theory make more sense. All in all, a stirrup is deformed by the nature of it's shape, so we may both be onto something? I'm sure there's an explanation....
In Poland all steel carrying construction loads should be AIII/AIIIN (deformed). So if there's actually a load across stirrup it should be from a deformed steel bar (which is a factor in some beams), plain stirrups are ok when they are not carrying much of the load and only used as a mounting frame. And even with that we're generally moving towards deformed rebars on all stirrups. Polish Norm is derivative of Euro Code so I guess it should be similar across EU countries.
@@Promilus1984 Thanks for the real answer..
Stirrups do not run horizontally like the structural rebar and are there to keep the rebar in place
Showing strain curves in addition to stress curves would be useful
There were non reported, only mid-point deflections
It’s similar to roughening a cable to have better bond with PU
0:20 how do you retrofit a building or a bridge? maybe make a video on that?
Demolition and rebuilding.
billions of likes for you 👍👍👍
Why is the deformation that exact pattern? I almost always see this exact pattern and sometimes only one other similar pattern
Nice
For her pleasure.
Sir what is steelman
How do they retrofit rebar in concrete?
You won't retrofit the rebar alone, but the whole structural system. It could be adding additional members, strengthening parts of the structure, providing confinment to columns, and so on.
😂😂😂 Crazy never knew that.. 👍🏾👍🏾👍🏾
is it true that rusty rebar is better?
In my concrete lab many years ago we made model beams and columns. We purposely rusted the steel wire used as reinforcement to mimic deformations.
The rust does provide a layer of protection from further oxidation
Far as I've understood it, supposedly much better grip, because it gets increased surface area, and the rust chemically binds more to the calcium (I think it was)
No.
Fake news...
@@m.streicher8286 rust in mostly iron materials is porous, so air can still get in and worsen corrosion
This is one of the things alloys like Stainless try to address, the chromium in the alloy oxidizes when exposed to the air, forming a film that it's nonporous increasing resistance (they're not all actually fully "stainless" like the name implies, most of the "stainless" steels used for knife making and the like are only resistant because the amounts required to make it fully stainless make them not hardenable, but things like Stainless pots and pans and the like can actually be made fully stainless since you don't need to harden them)
really like how your animation style has developed over time. Also enjoying this shorter format--keep em' coming!
also about your stirrup question.. I think you already told us the answer here!
czcams.com/video/KEu7KUpCX0g/video.html
They are not deformed to achieve better bend radiuses
Why does concrete need sand and water? Why do bolts have threads? Why do vehicles have wheels? Why are construction beams not made with cardboard it's obviously cheaper? These are some other awesome videos suggestions. Great stuff keep them coming we need more content like this very useful information
Aren’t you clever ? What’s your engineering channel named ?
“Ribbed - for her pleasure...”
I don't have to watch the video or be an expert to deduce that they are for providing grip to anchor the bar into the concrete. If it was smooth there would be little to lock it in and would be much weaker.
Where does Fiberglass Rebar fit within this loading chart? It was my understanding that while Fiberglass and other composites may not have exact same tensile strength of steel rebar, they do not rust when exposed to water or salts. No rusting means the reinforcement will not swell resulting in early failure. Other reports will state that Fiberglass is actually stronger than steel, but strength to weight might be confusing.
It is possible to use anti-corrosion coatings on steel rebar to prevent or delay rusting. In practical use though I have never found coatings to actually work in the field. Rebar is cut, bent, and tied together. This can cause anti-corrosion coatings to fail and is a waste of money. While Fiberglass rebar might have some additional costs associated with making 'bends' prior to delivery, it is far less expensive in long term.
Are there technologies coming that deliver even higher performance and longevity?
GRFP, CRFP, and AFRP bars, which are glass carbon and aramid fiber composites, behave differently than steel bars. They can have higher yield strengths and they perform better in corrosive environments. The downside is that they can't be bent to shapes. Additionally, their anchorage to the concrete behaves differently because of how the ridges on their shell are created
The most promising corrosion resistance solution on the steel side is stainless. Epoxy coated bars simply do not work due to construction conditions where the coating is harmed nullifying its benefits. Galvanized bars are also becoming more widely accepted but there are issues with the hot dip coating once certain bend radii are made
@@Aquade Using Stainless makes perfect sense. Thanks - appreciate the feedback.
@@Aquade Thanks for comment.
@@Aquade I can still remember pouring concrete in the field. Sometimes we used 'chairs' to hold the rebar up off the ground. But even they can allow water to infiltrate to the rebar. Some old timers said forget chairs, they used rocks... really. Lately have seen nothing used, rebar or welded wire mesh is pulled up by workers with rakes. I have found that to be not very precise. If an engineer has spec'd reinforcement, they also spec where within concrete it must be located for optimal strength.
"..almost tripled" 34k is not more than triple of 11k? huh
True, it's more than tripled. The numbers are read off a hand-drawn chart from the 1940s, so probably give it +/-5%
RRRebars have rrridges.
Key
A smooth bar has nothing for the concrete to adhere to.
Ridges & Dots matter in Condom,
It definitely matters in Rebbar
👍👍👍
Friction
Stirrups must absolutely be deformed bar. This is not accurate and should be removed from the video. The only reason but to is to save money. And then you have another scoan collapse in your hands
That's the point of the video. Have a look at the paper listed in the references
Might cause concrete cancer