How to Provide Crank Bar in Slab

Added: 2026-05-30

[00:00:01]Welcome back to Civil Engineers YouTube channel. In this practical video, I will guide you for steel reinforcement details in the construction of this RCC slab which you can see practically.

[00:00:13]If you see guys at the distance of L by 4, already we provided crank bar to resist negative bending moment because this is two-way slab. Therefore, you can see bent up bar or crank bar on both directions.

[00:00:29]The length between two column is here 16 ft at the distance of L by 4.

[00:00:36]We have extra We have crank bar not extra steel rods. If you see guys, the main bars and distribution bar spacing is 6 by 6 in and and we used here 12 mm die of steel rod, guys. You can see this is crank bar section in this practical video which are bent on 45°.

[00:00:59]The spacing is 6 by 6 in. And This is at the distance of L by 4 on on the top of the floor beam where we have negative bending moment. There we have more chances of cracks. To resist cracks, the extra steel rods or crank bar should be provide. As you can see in this practical video, this is crank bar which is very economical to resist negative bending moment at the distance of L by 4. Specially we can provide where we have negative bending moment.

[00:01:31]At the middle we have positive bending moment. So there you can use also extra steel rods, but not in RCC slab, but you can provide it in RCC floor beam or plain beam.

[00:01:46]Guys, you can see.

[00:01:52]In two-way slab, the crank bar should be provide on both direction.

[00:01:57]But in one-way slab, you can provide only in main side.

[00:02:09]Guys, you can see.

[00:02:11]This is on 45°.

[00:02:19]On the other side, guys, they provided lapping length at the distance of L by 4 or you can see at the bottom section of this crank bar.

[00:02:27]So, this is not good.

[00:02:29]Already they did. So, this is a technical terms you should know about this that the lapping should not be provided at the distance of L by 4.

[00:02:36]There we have more chances of cracks. To resist cracks, so provide extra steel rods or crank bar, but don't provide lapping length which can you weak the especially this zone where we have negative bending moment.

[00:02:51]This point is already weak compared to its middle. So, therefore, if you provide the lapping length, so you are making more danger at steel structure.

[00:03:08]Guys, you can see.

[00:03:10]This is at the distance of L by 4 on each side. We have the length 5 ft crank bar. That's why because here the span is 20 ft here. On the other side, that is 16 ft, so we have crank bar at the distance of 4 ft.

[00:03:27]If the span is more than 20 ft, so we are providing crank bar or extra steel rods at the distance of L by 3.

[00:03:34]Total length divide by 3 or if the span is up to 20 ft, so you can provide it at the distance of L by 4.

[00:03:42]Guys, you can see also the cantilever slab or you can say the cantilever beam.

[00:03:51]At the distance of or the span 7 ft. You can see already they did the steel reinforcement on the top of this, but they didn't provide any extra steel rods specially in cantilever beam or slab.

[00:04:02]So, these are very important to know before starting steel structure design.

[00:04:06]If you are going more than two stories, so you should hire the structure engineer to give you the structural design. Otherwise, you will face more problems in steel structure specially for any structure if that is residential building or commercial building.

[00:04:20]So, this is a short video to guide you for technical terms crank bar, extra steel rods, lapping length in RCC two-way slab.

[00:04:28]Thanks for watching. See you in next video. Goodbye.