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"z" limit requirement

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Ah, yes!

The notorious z-limit requirement!

When the z-limit requirement starts requiring what I consider a ridiculous 
amount of reinforcing at a ridiculously close spacing, I calculate the amount 
of Grade 40 reinforcing that would be required and provide only that amount, 
whether or not the reinforcing supplied is Grade 40 or Grade 60.  Z-limit 
does not have to be calculated for grade 40, therefore implying that the 
crack width for reinforcing stressed under service loads up to about 24ksi is 
not a concern.

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

A. M. wrote:

. > Hello Everybody,
. > 
. > For any concrete beam (floor, roof or grade beams), are we REQUIRED by
. > UBC
. > 1910.6.4 to ALWAYS check the "z" (distribution of flexural
. > reinforcement)?
. > Most concrete beam design softwares and beam design examples from books
. > does
. > not check this. When I design a concrete beam (especially a grade beam),
. > most of the time I need a lot more rebar due to the "z" requirement than
. > required by  flexure. Should we ALWAYS check them? Or only on certain
. > conditions? 
. > Thanks in advance for the input.
. > 
. > A.M.
. >