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RE: HHS Rectangular Tube Fabrication Error

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If we were to bend the member to the given curvature, longitudinal strain
strain would be (d/2)/R = 4/4800 = 0.0008, which is about half the yield
strain. But the member must have gone through strain hardening; otherwise it
would revert back to the original straight shape. Now, if it is
straightened, any permanent deformation will remain and rotation ductility
capacity will be reduced. Question is how much ductility is required?

-----Original Message-----
From: Steven Crang [mailto:steven.crang(--nospam--at)hok.com]
Sent: Friday, April 04, 2003 10:40 AM
To: seaint(--nospam--at)seaint.org
Subject: HHS Rectangular Tube Fabrication Error



We provided rectangular HSS members on a project for lateral support of the
curtain wall.  The exterior of the building is 'radiused' as well as the HSS
members behind the curtain wall.  The fabricator curved the HSS members
about the wrong axis.  The sweep was intended to be about the x-x axis but
was fabricated incorrectly about the y-y (weak) axis.  The fabricator is
questioning if they can simply straighten the members and re-roll them about
the correct axis.  The members are HSS 12 x 8 x 3/8, the radius is
approximately 400' and the angle of the circular sector is 4.5 degrees.  The
resulting beam sweep is approximately 3 5/8" and member length is
approximately 31'-4.  I do not think that cold bending the HSS members will
have any adverse affect on their performance based on the relatively low
inelastic deformations even if no thermal stress relief is utilized.  Does
anyone agree/disagree?  Thanks in advance.

Steven Crang, S.E.,P.E. 
HOK Structures 

steven.crang(--nospam--at)hok.com 




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