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RE: double angle vs starred (cruciform) angle

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Rainier and Harold:

Actually the engineers I know do know what stitch fasteners are and we do check them. I know Rainier does. But then we're on the left coast.

I've never used starred angles and they might be somewhat difficult to make the end connections. My old Singleton Manual of Structural Design actually has a table of properties for 2 angles in a starred pattern and 4 angles in a starred pattern. And if you were to add in stitch plates, the r value would be higher.

Neil Moore, SE, SECB


At 03:40 PM 6/16/2006, Harold Sprague wrote:
Individual angles in compression have much higher KL/r values than when 2 are together. The way you get 2 angles to act together with a lower KL/r is connecting the 2 angles with stitch fasteners. Normally, engineers do not show stitch fasteners. Few are even aware that they exist. Generally, detailers add them.

There are some old studies indicating the effectiveness of stitch fasteners on back to back angles. I am not aware of any studies that show effective connection of the starred configuration, or how the stitch fastener would work.

Regards,
Harold Sprague





From: raincat1(--nospam--at)aol.com
Reply-To: <seaint(--nospam--at)seaint.org>
To: seaint(--nospam--at)seaint.org
Subject: double angle vs starred (cruciform) angle Date: Fri, 16 Jun 2006 13:33:48 -0400

Using equal leg angles, the slenderness ratio of a starred angle (2 angles joined as a cruciform) is significantly increase (in the weaker axis) compared to double angle (joined at the legs). This should make the starred angle a better compression member than the double angle. However, we don't see the starred angle being used as a bracing member. Is there any reason for this? Thanks!

Rainier C. Catubig
San Diego, California
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