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RE: Section 1633.2.6 and 1612.4

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Now I understand where you are coming from but I still disagree.  Eh is
defined in section 1630.1.1 and in its definition it refers to Section 1632.
The bottom of Section 1632 refers to back to 1612.2 and 1612.3.  1612.3 is
for ASD and allows E/1.4.

Furthermore, it makes no sense to have to design a memer or connection for
exactly the same for whether you use ASD or Ultimate.

Mike O'Brien


> -----Original Message-----
> From: Swingle, Mark [mailto:Mark.Swingle(--nospam--at)dgs.ca.gov]
> Sent: Friday, September 10, 1999 5:18 PM
> To: 'seaint(--nospam--at)seaint.org'
> Cc: 'mswingle(--nospam--at)earthlink.net'
> Subject: RE: Section 1633.2.6 and 1612.4
>
> Mike O'Brien wrote:
>
> <If you multiply back through with the 1.4 factor, you have
> <reconverted your forces to ultimate levels.  Could you
> <explain further why you think that 1.4 factor is necessary
> <if you are designing to ASD?
>
> (MS) The short answer is: that's what the code says.
>
> The long answer follows: In the example I gave, the base
> shear at ultimate levels is V=0.196W, but the collector
> force was derived from V=0.196/1.4W=0.14W.  Saying V=0.14W
> really is not correct, and is misleading.  Really what I
> should say is E/1.4=0.14W since E=rhoEh+Ev reduces to
> E=Eh=V when rho=1 and one is using ASD (see the
> definitions in 1630.1.1).  Am I sufficiently confusing?
>
> Here's another way: My collector force F was based on
> E/1.4, not on E.  The definition of Em is omega times Eh,
> but Eh=E as I said above, so with omega = 2.2, and
> F=E/1.4=Eh/1.4, the winner is....
>
> Em=2.2(1.4)(F)
>
> I also think this is correct because in this example,
> the old 3Rw/8 would have been 3 (since Rw=8 for steel
> ordinary braced frames), and the new value is
> 2.2(1.4)=3.1 which is approx the same.  (Of course,
> not all systems happen to match the previous code as
> this one did, but we can talk more about that later.)
>
> Thanks for your patience.
>
> Mark Swingle, SE
> Oakland, CA
>
> Disclaimer:  These are my own opinions.  They are
> subject to change due to the ravages of time and
> after being subjected to reasoned criticism.
>
>