Thank you very much for your videos! They are extremely detailed in a good way. Could you pls refer what clause of EC2 states about the distance that shall not be accounted for the shear design (2.5*z in your example)? Is 6.2.2(6) the one: "For members with loads applied on the upper side within a distance 0,5*d
Hi 1sH.B, sorry for the late response. I believe (but am not sure) that the two figures relate to the shear strength of the concrete in the RC beam and are based on empirical testing carried out. VED min is the shear capacity of the RC beam if it is reinforced with the minimum shear reinforcement allowed. Probably too late now for you but perhaps, this answer will help someone else.
Thank you Mike. Very good instructional video. I notice that the characteristic value of the steel reinforcement is not modified by its materials safety factor, 1.15, in the link spacing formula - or is this factor built into the 0.08 factor?
Hi Keith Spears, yes you are right. The formula comes from EC2 amended by our NA. No need to consider the materials factor of safety here - a minor relief! Hope this helps, Mike
Hi Mike You didn't calculate the minimum area of shear reinforcement Asw (only the spacing), how do you know that your initial proposed H12 links satisfy Asw? Also is this method a simplification? As I have come across another more complicated method in the codes were concrete strut angle and capacity are calculated to find shear reinforcement.
Hi James Birchall, yes this method is a simplified method that only really represents one stage of the entire design and detailing of an RC beam. However, if you are lucky enough to have a beam that only needs minimum shear reinforcement, then this simple approach is just fine. As for the link design, you can vary the diameter of the legs and their spacing. Bigger links can have larger spacings and smaller links need closer spacings. I think that the H12 size of links suggested at the start of the example was OK and so I then I worked out the spacing from there. The calculation is only a short one and so you could go back and try different link diameters. Hope this helps, sorry about the delay in replying. Mike
When calculating minimum shear enforcement ratio according to Eurocode 2, 9.5N (calculocivil.com/eu/ec2/tran_reinforcement/base) I cant get the units right. Square root of N/mm^2 divided by N/mm^2 makes no sense unit wise. The mm's become mm^2 / mm which is fine and are used in many tables, but the extra sqrt(N)/N makes no sense.. Can you help? You used the same formula in the video.
Hi valter stenback, good point. The units do look wrong. I believe that the shear strength of concrete is proportionate to its compressive strength and the formulae in the Eurocode are derived from experiments. So the purpose of the square root of fck is to find the shear strength. The idea is not to find the square root of the units but to make use of this proportionality. For example, if the two strengths were related exactly by the square root, then a 25 N per sqmm compressive strength concrete would have a shear strength of 5 N per sqmm. Another different empirical formula for the shear strength of concrete makes use of the cube root of the compressive strength. I hope that this helps, Mike
+Javed Shaah Hi Javed Shah, around 40 seconds into the video I mention the support widths as 400mm. The beam width is however 350mm. Hope this helps, Mike
Hi Javed Shah, yes, RC beams are generally supported in columns and in this example I have just assumed that the column was that width. No reason why especially.
Hi again, the tutorial is based on EN 1992 which is a European code of practice. In the UK, this tends to be called Eurocode 2 or EC2. I suspect that other countries may have similar approaches to this.
next time always refer to clauses of the Eurocode. This is not the design approach given in the Eurocode. The Eurocode uses the variable strut inclination method. The strut angle MUST be checked to see if its 21.8 degrees then one continues to find the spacing and area of shear links required.
Hi Patrick, the design method in the video is not based directly on the Eurocodes but it produces a design that accords with the Eurocodes. It is based on the IStructE document ("Manual for the design of concrete building structures to Eurocode 2"). This is partly written for structural engineers who prefer a different and more direct approach to RC design, Mike
10:56. 226 is the area of 2 links not a single link I think! Thanks for your videos, very clear and very helpful
Great tutorial,many thanks,always up to date! Carry on please good job! Could you make one on punching shear?
Thank you very much for your videos! They are extremely detailed in a good way.
Could you pls refer what clause of EC2 states about the distance that shall not be accounted for the shear design (2.5*z in your example)?
Is 6.2.2(6) the one: "For members with loads applied on the upper side within a distance 0,5*d
Thank you so much. Now i know where the minimum shear come from
Very helpful, thanks a lot for these videos! most appreciated.
hi, sir just want to ask about constants you are using "0.15" & "0.08"
and whats VED1 min, thanks SIR
Hi 1sH.B, sorry for the late response. I believe (but am not sure) that the two figures relate to the shear strength of the concrete in the RC beam and are based on empirical testing carried out. VED min is the shear capacity of the RC beam if it is reinforced with the minimum shear reinforcement allowed. Probably too late now for you but perhaps, this answer will help someone else.
Thanks sir
Thank you Mike. Very good instructional video.
I notice that the characteristic value of the steel reinforcement is not modified by its materials safety factor, 1.15, in the link spacing formula - or is this factor built into the 0.08 factor?
Hi Keith Spears, yes you are right. The formula comes from EC2 amended by our NA. No need to consider the materials factor of safety here - a minor relief! Hope this helps, Mike
Hi Mike
You didn't calculate the minimum area of shear reinforcement Asw (only the spacing), how do you know that your initial proposed H12 links satisfy Asw?
Also is this method a simplification? As I have come across another more complicated method in the codes were concrete strut angle and capacity are calculated to find shear reinforcement.
Hi James Birchall, yes this method is a simplified method that only really represents one stage of the entire design and detailing of an RC beam. However, if you are lucky enough to have a beam that only needs minimum shear reinforcement, then this simple approach is just fine. As for the link design, you can vary the diameter of the legs and their spacing. Bigger links can have larger spacings and smaller links need closer spacings. I think that the H12 size of links suggested at the start of the example was OK and so I then I worked out the spacing from there. The calculation is only a short one and so you could go back and try different link diameters. Hope this helps, sorry about the delay in replying. Mike
Great video thanks for your time!
hi mike, can you do a video on Slender column please?
Do more questions with udl
When calculating minimum shear enforcement ratio according to Eurocode 2, 9.5N (calculocivil.com/eu/ec2/tran_reinforcement/base) I cant get the units right. Square root of N/mm^2 divided by N/mm^2 makes no sense unit wise. The mm's become mm^2 / mm which is fine and are used in many tables, but the extra sqrt(N)/N makes no sense.. Can you help? You used the same formula in the video.
Hi valter stenback, good point. The units do look wrong. I believe that the shear strength of concrete is proportionate to its compressive strength and the formulae in the Eurocode are derived from experiments. So the purpose of the square root of fck is to find the shear strength. The idea is not to find the square root of the units but to make use of this proportionality. For example, if the two strengths were related exactly by the square root, then a 25 N per sqmm compressive strength concrete would have a shear strength of 5 N per sqmm. Another different empirical formula for the shear strength of concrete makes use of the cube root of the compressive strength. I hope that this helps, Mike
always my goat
.4/2? Isn't the width of your support 350mm?
+Javed Shaah Hi Javed Shah, around 40 seconds into the video I mention the support widths as 400mm. The beam width is however 350mm. Hope this helps, Mike
Hi Mike, first of all thanks for your help. Do you mean the width of our columns (supports) are of 400mm?
Hi Javed Shah, yes, RC beams are generally supported in columns and in this example I have just assumed that the column was that width. No reason why especially.
Very helpful. Thanks!!
How do you get the 2.5z?
Hi Jay-r Salvatierra, thanks for the question. 2.5z comes from the code, which in turn comes from a model derived from research. I hope this helps.
thank you for the response. What code do you use? is it ACI?
Hi again, the tutorial is based on EN 1992 which is a European code of practice. In the UK, this tends to be called Eurocode 2 or EC2. I suspect that other countries may have similar approaches to this.
z.cotg(teta), cotg(teta) limit is 2.5. see cl. 6.2.3(2) from Eurocode 2-1-1.
next time always refer to clauses of the Eurocode. This is not the design approach given in the Eurocode. The Eurocode uses the variable strut inclination method. The strut angle MUST be checked to see if its 21.8 degrees then one continues to find the spacing and area of shear links required.
Hi Patrick, the design method in the video is not based directly on the Eurocodes but it produces a design that accords with the Eurocodes. It is based on the IStructE document ("Manual for the design of concrete building structures to Eurocode 2"). This is partly written for structural engineers who prefer a different and more direct approach to RC design, Mike