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Base Plate Steel TIPS Report

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Dear Mr. Hemstad: Thank you very mch for your input. Especially your mention of late Professor Dexter, who was truly a pillar of knowledge and integrity, ye so down to earth and helpful to all. We all truly miss him.

Your point on Base plate for columns buckling about weak axis is very important and I will pursue it with Lehigh people. Your solution of adding in a way "bracket " plates to sdistribute stresses at the tip of flange and reduce stress concentration is an excellent practice and certainlyI will use it in developing "suggested details". with credit to you. This type of adding brackets to the base of columns you find in many buildings designed prior to 1970's and still is very common , almost standard in bridge engineering. It seems that as i had at the bottom of my first e-mail, we have not listened to Einstein and in our attempts to make things simple, we may have made somthings "simpler". Again, thank you very much for your time and very valuable input.
Hassan


From: Michael Hemstad <mhemstad(--nospam--at)mbjeng.com>
To: seaint(--nospam--at)seaint.org
Subject: Base Plate Steel TIPS Report

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Abolhassan Astaneh-Asl wrote:
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"Dear Friends in Seaint: I am writing a Steel TIPS (Technical Information
and Product Services ) report for SSEC (Structural Steel Educational
Council) on the Behavior and Design of Base Plates for Steel
Concentrically Braced Frames with focus on seismic+gravity effects..."
=

Dr. Asteneh,
A few years ago I designed some big (to me) base plates for some double=
columns acting as cantilevers (flagpole loading).  I talked with the late=
Robert Dexter and a graduate student of his, whose name I unfortunately=
don't remember, at the University of Minnesota.  They had either done=
research, or knew of it, at Lehigh, regarding baseplates and the=
connection of the column to the baseplate.  Among other things, they=
learned that a wideflange column in weak-axis bending is extremely=
dangerous, as there is a large stress concentration in the weld at the=
tips of the flanges.  In their tests, this condition caused brittle=
fracture in a startling percentage of the tests (around 25 percent, if=
memory serves).
=

It seems to me this fact deserves wider dissemination.
=

For what it's worth, my solution was to weld plates across the flange tips,=
and then to the baseplate, eliminating the stress concentration at the=
flange tips due to weak-axis bending.
=

Most of my discussion was with Dr. Dexter's grad student, a very helpful=
and knowledgeable fellow from Korea.  If he is reading this, my apologies=
for not remembering his name, as I appreciated his help greatly.
=

HTH,
Mike Hemstad, P.E.
MBJ
Minneapolis, Minnesota
=

=

=

Michael Hemstad, P.E.
=

=

Meyer, Borgman and Johnson, Inc.
=

12 South Sixth Street
Suite 810
Minneapolis, MN 55402
(612) 338-0713 (main)
(612) 604-3621 (direct)
(612) 337-5325 (fax)
www.mbjeng.com



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