Reply to a reader question on IBC vs ACI minimum reinforcements + New URL / Web Address

This RONJIE.COM Civil Engineering website has a new URL (or web address): engg.ronjie.com.

A reader read through my article about the UBC and IBC seismic provisions, and posted a question-comment not related to seismic provisions though, and this time talking about ACI and IBC minimum reinforcement provisions for concrete.  My reply and the original comment is shown below.
jojitsan said...

a querry, not for IBC seicmic but for over-over-sized axial concrete, ACI says p min of 0.01(Ag/2), IBC says 0.0025, is it ok then to use 0.0025Ag min ?

11:25 AM

RONJIE.COM said...

@jojitsan: Can you be more specific where IBC specifies such? And which IBC specifically. The IBC of today (2006 or 2009) that I know refers to ACI (318-05 or 318-08), and therefore there should be no conflict. In some older codes, the "General Requirements" or earlier sections of the code could have some conflicting information with later sections (such as the Concrete Design section). The more onerous provision should govern. Anyway in this case you mentioned, I remember from 8 years ago when I took up advanced concrete design in grad school that there is a good, rational basis for the 1% minimum set by ACI. I would think the 0.0025 you are talking about could be for something else. That minimum value appears very close to that use for slabs - which are over-over-sized for axial loads (because flexure governs). Please read the codes carefully and look at the bigger context of such provisions. But as mentioned, I am not 100% familiar with all "new" provisions in the IBC.

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