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RE: 3-D Loading

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Hmmmm...sounds similar to tower design. In the UBC the Cq for diagonal
loading is 4.0. For normal loading, it's 3.6. and the forces in the legs are
higher due to Mc/I.

Thx,

Bill Allen, S.E.
ALLEN DESIGNS
Laguna Niguel, CA


||-----Original Message-----
||From: Michael Valley [mailto:mtv(--nospam--at)skilling.com]
||Sent: Thursday, November 18, 1999 4:30 PM
||To: seaint(--nospam--at)seaint.org
||Subject: RE: 3-D Loading
||
||
||It makes perfect sense.  Scott described an analysis done for wind
||loading which does not specifically require consideration of
||orthogonal effects.  The building in question is the Citicorp Center.
||The engineer is Bill LeMessurier.  An interesting article was
||published in The New Yorker, May 29, 1995.
||
||In this case diagonal loading was more severe than either of the
||orthogonal loads because of the unique characteristics of the
||building.  (In case you don't remember what's unique, see the sketch
||below.)  Unlike normal square buildings with four columns at the
||corners, the four columns in the lowest story are at the middle of
||the sides.  The available moment arm is much smaller for diagonal
||loading than for orthogonal loading.  Therefore the forces in the
||columns and superdiagonals are larger.
||
||-----o-----
|||              |
||o            o
|||              |
||-----o-----
||
||
||> From:          "Bill Allen" <Bill(--nospam--at)AllenDesigns.com>
||> Subject:       RE: 3-D Loading
||> Date:          Thu, 18 Nov 1999 17:00:08 -0800
||
||> This doesn't make any sense at all, unless I am missing
||something. If you
||> design a building for loads at 45* (assuming a square
||building), then that's
||> like designing for 71% concurrently in each direction. Is
||that more severe
||> than 100% in one and 30% in the other? It would seem to me
||that the only
||> elements that are critical in these conditions are those who are
||> participating in the lateral force resisting system for
||both directions,
||> i.e., common columns, etc. in which case it would appear to
||me that 1.3 is
||> greater than 1.0. But maybe, once again, I am
||oversimplifying the problem.
||>
||> Regards,
||>
||> Bill Allen, S.E.
||> ALLEN DESIGNS
||> Laguna Niguel, CA
||>
||>
||> ||-----Original Message-----
||> ||From: Scott Maxwell [mailto:smaxwell(--nospam--at)engin.umich.edu]
||> ||Sent: Thursday, November 18, 1999 3:28 PM
||> ||To: seaint(--nospam--at)seaint.org
||> ||Subject: Re: 3-D Loading
||> ||
||> ||
||> <snip>
||> ||Either during
||> ||construction or after occupied (I can't remember), he for
||some reason
||> ||decided to look at it with wind at 45 degrees and ALL the
||> ||lateral braces
||> ||were overstressed...to the point that there was a concern of
||> ||a collapse
||> ||that could result in several blocks being destroyed...so a
||> ||fix was developed.
||> ||
||> ||I guess that is what I get for watching too much
||Discovery channel...I
||> ||actually learn interesting things.
||> ||
||> ||Scott
||>
||> <snip>
||
||- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
||- - - - - -
||Michael Valley                                   E-mail:
||mtv(--nospam--at)skilling.com
||Skilling Ward Magnusson Barkshire Inc.
||Tel:(206)292-1200
||1301 Fifth Ave, #3200,  Seattle  WA 98101-2699          Fax:
||      -1201
||
||