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• To: <seaint(--nospam--at)seaint.org>
• From: Christopher Wright <chrisw(--nospam--at)skypoint.com>
• Date: Thu, 3 May 2007 11:13:49 -0500

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On May 3, 2007, at 8:15 AM, 남윤호 wrote:

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In generally steel check for combined bending and axial stress interaction is as follows:
```  fa/Fa + fbx/Fbx + fby/Fby < 1.0            -----------(1)
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However, the old calculation used the steel check formula under 2 directions horizontal seismic loading(1g each) as follows:
```  fa/Fa + root(fbx^2+fby^2)/Fbx < 1.0     -----------(2)

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Is it reasonable using equation (2) that steel code checked under 2 directions horizontal seismic loading? If it is reasonable, why do you think using Eq. (2)?
I've never seen your eq 2 specified before, but it's the correct relationship for round sections like pipe. (1) is correct for a section with a rectangular envelope but if you were to use it with pipe you'd get the stress at a 'corner' that doesn't exist. You should work out the algebra for yourself, so you understand what's going on.
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Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw(--nospam--at)skypoint.com   | this distance" (last words of Gen.
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.......................................| John Sedgwick, Spotsylvania 1864)
```http://www.skypoint.com/~chrisw/

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