RC Slab Design EC2 - Worked example - Shear and deflection checks
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- Опубликовано: 23 окт 2024
- A short tutorial showing how the shear capacity of a simply supported slab is checked using EC2. Also its deflection is managed by checking its span/depth ratio. This is the second of two videos. The first shows how the main bending reinforcement of the slab is calculated.
ERRATUM: The shear resistance of the slab using the second equation amounts to 124.9 kN (not 69.4 kN as shown in the video)
Hi Hon Tin Chin, Vrdc1 & Vrdc2 are two different methods of finding the resistance of the RC slab and they can be used at any position along the length of the slab. In this example, I have used the formulae to find the resistance of the slab adjacent to the support. I hope that this helps, Mike
If we were doing the shear check for a flat slab, do we just use the reaction in the columns like you did here or it depends on whether it’s an edge, internal or corner column. I have been looking for an example all over the internet but couldn’t find anything tackling this point in particular.
Hi Mike, lovely video....clear and concise.......is the reaction/shear force value suppose to be 18.125kn?? And not 17.3kn?
very well explained, Sir. and very helpful. i really hope that you will upload a video on t-beams, Sir. Your explanations are crystal clear :)
Very clear and helpfull, what if the designed shear is greater than the resistant oncrete capacity how the procedures will be and also for the span/effective depth ratio >30
Hi, if the applied shear force exceeds the resistance of the concrete, it is best to start again with a larger beam. Not sure what you mean about the span/d ratio.
Great video, really good explanation
could you do a two-way slab or flat slab video?
Very helpful ,could you do detailing drawing!Thanks Mike.
Hi Mike,
its very noble of you to deliver these short lectures on youtube.
In a skew deck slab usually one gets bigger shear values in obtuse corners. Is this ok if we increase the the size of the main reinforcement locally or add some vertical bars locally (links or bent up bars ) ?
We have minimum shear reinforcement for the beams in EC2. Is there a concept of minimum shear reinforcement for slab with reference to high shear in skew slabs.
Thanks
very clear - well explained- excellent
Hi S Fara, thanks for taking the time to let me know.
from where did you get this table? is it from the ACI CODE?
Excellent. Could have done with RUclips back when I went to Uni....:)
Is there a mistake in the Vrdc2 calculation?
Hi Robert, Thanks for the comment. Unfortunately there is a mistake in the arithmetic and the answer is actually 124.9kN. Please see the ERRATUM above. Mike
+Mike Bather Thanks for that Mike. I was using your very helpful videos to design a similar slab so that clarifies that discrepancy.
@@mikebather yes, 124.9 kN right answer
Hi Mike,
Thanks for the great video. Btw, is there any thumb rule for determining the
lap length for main and curtailment r/f? Thank you
Hi Pabodha Kannangara, thanks for the comments. For small scale work, laps of 40 d (d is bar diameter) were commonly used with the old British Standards. This figure could still be used with the Eurocodes but for larger jobs really an RC detailer would be able to calculate lap lengths more accurately using EC2 and this could lead to a more sustainable design (i.e. less material used). I hope that this helps, Mike
Tks Mike. I got it.
hi Mike. Thank you for your videos, very useful. But what is the next step if my deflection is not ok, as in my actual span/depth ratio is greater then my allowable span/depth ratio?
Hi Kapalesa Katjomuise, unfortunately there is not much you can do. Increase the depth or decrease the span are the simplest things to do. If these are not possible then you could consider increasing the steel reinforcement. Many engineers begin their calcs with the span/depth check to prevent this. I hope this helps.
it does help, thank you very much Mike.
why the Vradc2 is 69.4kN？I got different results
Hi, Thanks for the comment. Unfortunately there is a mistake in the arithmetic and the answer is actually 124.9kN. Please see the ERRATUM above. Mike
thank you .Really appreciate your help.
Hi sir, may I know where is Vrdc1 & Vrdc2 located?
Hi @Mike can you do one similar worked example for two way slab? Or is there already in your channel? I did not find it. Hope to see it soon. Thanks
Hi James Beckson, thanks for the suggestion. I have not done a video (for 2 way spanning slabs) yet, but hope to do so one day, Mike
Thanks for the response Mike.. Hope to see more videos in future. They are really helpful.
Brilliant video, you teach it so much better than what I was taught.
very good explanation. Do you have any video about precast concrete design?
Hi Bernard, sorry but no video at present, although it is part of the course that I teach at the University. So, if I ever get some spare time one day...
Is there any tutorial for continuous slab design
Hi, how would you design a T-beam for short-term and long-term deflection?
Hi GriffithGrey, Sorry but I have no plans for dealing with T beams in the very near future. These videos are just a little bit of support for our first year students, Mike
still my goat
Please do a two way slab deflection check. Thanks.
thank you sir.
how did u come with the curtailment of H8
Hi John Lee Baelon, I think that you are referring to the curtailment of the H12 mid-span reinforcement. The bending moment that these bars are designed to resist only exists at the mid-span of the slab. This bending moment decreases to zero at the supports and so the bending reinforcement here (at the supports) can be greatly reduced. I have used some old guidance from the UK, however this should be appropriate for anywhere really as concrete is concrete. "50% of the mid-span bars can be stopped short of the support at a certain distance from the centre line of the supporting wall (i.e. within 0.08 x span)".The final dimensioning of reinforcement is generally done by a detailer - who has detailed knowledge of this kind of thing. I hope that this helps, Mike
Wow awesome
hello, could you make a video of how to design a two way concrete slab?
Hi, my current plans are to do some more analysis videos with frames and beams. Thanks for your suggestion. I may get around to two way slab design in the future but please don't wait for this as it may be quite a while.
Very clear and helpfull, what if the designed shear is greater than the resistant oncrete capacity how the procedures will be and also for the span/effective depth ratio >30
Almost all slabs are designed so that their shear resistance is greater than the design shear forces applied to them. When the design shear forces exceed the resistance, most engineers redesign the slab as it is a relatively unusual and expensive business increasing the shear resistance of a simply supported slab. Using large span to effective depth ratios is really outside the focus of this little video. You would need to check out the actual stresses in the reinforcement and then in some circumstances, EC2 permits larger span to depth ratios.