the term Pu in ACI 318-08 21.5

[jenofstructures]

Hello everyone

I would like to enlighten myself on a certain chapter of ACI 318-08

The ACI 318-08 section 21.5.1.1 stated that the factored axial compressive force on the member, Pu, shall not exceed Agf'c/10

but this part of the code is about flexural members for special moment frames. Can you please explain to me the meaning of this?

In my understanding, the axial load Pu for a compression must be greater than Agf'c/10 (it is in the 21.6), and if the force transformed axially to the column is lower than Ag f'c/10, chances are, the rebars we are getting is minimal, although we have a minimum provision for column. So the ACI 21.5 is just stating that once the column force is lower than said computation, we can compute its dimensions and rebar like a flexural member, so we can see if this one governs (Using a horizontal load i.e. earthquake load). This is just my opinion here.

Can you please explain this?
Thank you in advance

Poems are made by fools like me, but only God can make a tree. engineers creates wonderful buildings, but only God can creates wonderful minds

 

[ishvaaag]

Yes, that seems the right interpretation, once under 10% of brute capacity compression you can proportion the member as flexural; otherwise go to 21.6, Firs paragraph in the commentary makes this clear.