Terminology "Slab Band"; "Continuous Drop"

[ajk1]

Is a continuous drop exactly the same as a "slab band"? My opinion is that a "continuous drop" is more specific and clearer in meaning than a "slab band", if continuous drop is what is meant. To me a "continuous drop" in a span means that the drop panel extends right across the span at a location (rather the just to span/6), whereas "slab band" refers more to the width into which rebar is placed. Do you agree?

 

[ajk1]

Thanks! I decided to leave "slab band" on the typical details that I am reviewing, because it occurs in so many places on them, and seems to be an acceptable term that is defined in the CSA Standard. Thanks again for the help.

 

[slickdeals]

I want to ask a tangential question on this topic. This pertains to the requirement of minimum reinforcement in a system with slab bands. See attachment.
The way the code is interpreted by many (including the software programs RAM, ADAPT) is as per the attachment, which may be correct with the way the code is written but appears to be excessive.

I am not sure if the other codes have any language in them that's different from how ACI spells it out.

 

[rapt]

slickdeals,

You will probably know my opinion seeing I write one of the programs mentioned.

If you look at the reason in the code, it is because of development of 1st crack and requiring sufficient reinforcement to ensure that the tension force required to crack the concrete can be carried by the reinforcement post cracking. So yes, it is logical.

If you look beyond the code and look at reinforcement strain, which none of the major codes limit for some illogical reason, this is a defacto limit on the maximum strain, albeit a not very efficient one for anything other than rectangular sections.

For reinforcement with a maximum strain of 5%, you will find that with minimum reinforcement the strain will still be slightly over the breaking strain at ultimate strength. If you have less ductile reinforcement (eg Australian Class L or Eurocode class A, USA WWF and probably some other reinforcement types) then the actual strain could be 3 - 4 times the breaking strain. So minimum reinforcement really should be much higher for the lower ductility reinforcements.

Where the logic breaks down for T sections is the minimum reinforcement rule gives higher requirements as Z of the section increases (flange in tension for a T beam) where a proper strain calculation has higher minimum requirement where the compression face is widest (flange in compression for a T beam). If you used this logic for the section across the beam in your diagram, minimum would be much higher than the codes currently say in the beam direction at +ve moment sections.