continuous cut-off bar
continuous cut-off bar
(OP)
for continuous cut-off bar in a beam.. is it L/3 or L/4? I saw people using both of them. Which is the correct one and which do you follow and why?
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RE: continuous cut-off bar
What I was saying was this. Do you use L/3 as in:
or L/4 as in:
I was talking about the continuous cut-off bar or the development length. Locally. I saw different group using L/3 and some L/4. Which do you use?
Please reply asap because the plan has to be signed and sealed and I'm deciding whether L/3 or L/4. Thanks.
RE: continuous cut-off bar
The lower drawing you post shows these continuous bars that extend past the cut-off bars. The L/4 or L/3 just affects the areas of steel you need for each.
RE: continuous cut-off bar
RE: continuous cut-off bar
BA
RE: continuous cut-off bar
Ba, it's purely beams above the columns.
Bpstruct, the lower drawing shows both exterior end and interior continious.. the interior is where there is continuous bar just like the top drawing. The standard is that L/4 is for exterior end. But for interior ends that need continuous bar. I think standard is L/3. I wonder if those L/4 used in interior continious bar drawings are just mistakes (the lower drawing is taken from another engineer plan). The top drawing from the ACI.
So guys. What do you actually use... L/4 or L/3 in interior continuous bar cut off. Again. I'm not talking of the exterior one which needs L/4. But the interior, hope you understand what I'm saying.
RE: continuous cut-off bar
The distance to cutoff of SOME of the top bars is purely up to you as the designer.
You can do either L/3 or L/4 or L/whatever as long as you meet the required moment capacity at each section along the beam.
The cutoff bars must extend BEYOND the point where they are no longer needed per code (ACI 318 or whatever your governing code is).
For ACI 318, check out the diagram in Figure R12.10.2. which shows how partial length bars affect the area of steel required to be continuous.
Your top diagram doesn't work very well in my view as there are no continuous bars across the top.
The bottom diagram has the little hooks at the cutoff ends. I've NEVER seen this done this way - only straight bars or the older (not used anymore) bent down "truss" or "crank" bars which your diagrams don't show.
If you don't know how to do this find an engineer who can teach you.
RE: continuous cut-off bar
RE: continuous cut-off bar
RE: continuous cut-off bar
(ACI 315-99)"
http://web.itu.edu.tr/celep/files/y5.pdf
Is there provision in ACI which says L/4 can be used? Some local engineers I asked said L/4 is just wrong in continuous cut-off as it is only for exterior end.. while some engineers use it.. perhaps unaware where they got the diagram.. or just typo in their typical diagram labels. Our local code doesn't state or give details about it because we copy the United States ACI code but only partials of it to minimize thick book so many details are omitted.
RE: continuous cut-off bar
RE: continuous cut-off bar
Every situation is different. The cutoff position is dependent on the load pattern, relative span lenggths, bar diameter, moment diagram, member depth etc.
You must develop the reinforcement required at each point and most codes require an offset of the bending diagram to determine where the bars can be terminated. This means that the reinforcement required at any point and the point of contraflexure are offset normally by D or d in the direction of reducing moment and then the reinforcement must provide necessary developemnt from that offset point.