Why does concrete reinforcement have deformations?

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.

[sylbou]

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

[tomsko]

Great video. Short and to the point. Thanks for quantifying it at the end.

[davidparks]

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.

[wayneyadams]

Stirrups are used to tie main reinforcement bars together, so they don't need the increased concrete bonding that deformations provide.

[saimandebbarma]

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. ☝️👍

[anitarenic]

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😃

[EntropicTroponin]

I'm more surprised someone ever thought a plain bar would be a good idea

[emlillthings]

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

[weeb]

0:20 how do you retrofit a building or a bridge? maybe make a video on that?

[oligoprimer]

Showing strain curves in addition to stress curves would be useful

[shihabchowdhury]

Brother make video on wooden structures, iam studying civil engineering, it will help me to gain good knowledge.

[davidhiggins]

Stirrups do not run horizontally like the structural rebar and are there to keep the rebar in place

[chang.stanley]

Why is the deformation that exact pattern? I almost always see this exact pattern and sometimes only one other similar pattern

[AlphatecEngineering]

Another great video! thanks for sharing it.

[dragonsdynamite]

It’s similar to roughening a cable to have better bond with PU

[SJR_Media_Group]

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?

[csehszlovakze]

is it true that rusty rebar is better?

[neilgrieve]

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

[britzwickit]

"..almost tripled" 34k is not more than triple of 11k? huh

[joeycheng-sutx]

They are not deformed to achieve better bend radiuses