Minimum Shrinkage reinforcement in large culvert

[kww2008]

Is the minimum shrinkage reinforcement in the most recent version of large box culvert of 150 mm2/m per face of slab low ?

 

[rapt]

how long is a piece of string?

 

[IDS]

If the culvert is under a road and designed to the bridge code (AS 5100) then it is required to have 500 mm^2/m in each face minimum, so I'd say the answer to your question is yes.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[kww2008]

Thank you Doug. Much difference in minimum requirements from two different Australian standards.

 

[rapt]

kww2008

Maybe one of those standards is talking about something completely different and is not appropriate for the member you are designing!

 

[IDS]

Maybe one of those standards is talking about something completely different and is not appropriate for the member you are designing!

... and maybe they aren't.

The AS 5100 requirement is applicable to "All concrete members" ... "with a thickness greater than 150 mm", and a large culvert is a concrete member with a thickness greater than 150 mm.

There is a get out clause:
"The requirements of this Clause in relation to the quantity of reinforcement in a particular
direction may be relaxed if the member is unrestrained against longitudinal movement in
that direction and the effects of differential temperature and humidity are minimal."
but it is arguable that culverts are restrained in the longitudinal direction, at least at the base, and certainly for structures that are in effect culverts, but do not come under the culvert code (such as buried arches), it is standard practice to provide steel to the AS 5100 requirement.

AS 5100 is applicable to:
"Other structures that are required to support road and railway traffic, e.g., culverts
and structural components related to tunnels, except those covered specifically by
other Standards."
so culverts and cut and cover tunnels that do not come under the culvert codes have a significantly more stringent requirement than those that do.

That's an inconsistency with no logical justification.


Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[rapt]

Doug,

I meant that the AS3600 minimum reinforcement requirements of about .2% were not comparable to the AS5100 requirements and that there might be a logical reason why. And that reason is partly to do with restraint in this case as per the get out clause logic.

The equivalent rule in AS3600 for restrained slabs would require .6% reinforcement!

 

[rowingengineer]

I assume we are talking about precast culverts that are 2.4m long.

http://www.nceng.com.au/

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