Top Rebar Lap length CSA 2

[palk7 EIT]

Hi All,

Is there a provision in CSA 23 for considering that a horizontal re-bar is considered as A TOP bar only if it has 300 mm fresh concrete beneath it? Its for the LAP LENGTH cuz the top bar lap length is more than the other bars.

 

[skewl]

It appears to be related to the development length factor k1 in A23.3-19.

 

[dik]

The provision is to cover the situation where you may have air working it's way up, reducing the bond on the bottom of top bars... hence the requirement for having 12" of concrete below.

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-Dik

 

[palk7 EIT]

Thank you it makes sense, in ACI I think straight away top bars have increased LAP length they dont give a provision of 12" of concrete has to be below for considering it as Top bars (More conservative)

 

[ProgrammingPE]

ACI uses ψt in the formula for ld which goes from 1.0 to 1.3 when there's more than 12" of concrete below horizontal reinforcement, so it looks like it is the same as k1.

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