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FW: Lateral Restraint for tall column

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If it is available to you, please check Salmon and Johnson, Steel
Structures.  They give an excellent theoretical presentation and also
confirm the 2% rule of thumb.  Keep in mind that bracing requires adequate
strength and stiffness.

Curt La Count, P.E.
Jacobs Engineering
Portland, OR
From: Daniel J. Huntington
To: seaint(--nospam--at)
Subject: Re: Lateral Restraint for tall column
Date: Tuesday, November 24, 1998 5:49AM

When I was in college, I was taught a column bracing point needed to
2% of the downward (vertical) force in order to sufficient act as a brace
against buckling.  Not sure of the origins of the magical 2% number.  Also,
was strongly emphasized the bracing force must be immediately available
no initial flexibilities).  The reason behind this was that is that 2% is a
number which will PREVENT a column from buckling.  By contrast, should the
column begin to buckle (because the bracing stiffness isn't sufficient),
no force will arrest the column from continuing to buckle.  TS6x6 for the
situation you described seems reasonable to me.

Daniel J. Huntington
Structural Designer

KJWW Engineering Consultants, P.C.
623 26th Avenue
Rock Island, IL 61201
PH: (309) 788-0673
Fax: (309) 786-5967


jbotch(--nospam--at) wrote:

> Got a question for all you structural geniuses,
>         I have a column supporting 34k and is also 34 ft high if it is
> unsupported at an intermediate level.  At 9 ft from the base and at 19
> ft from the base are intermediate floor levels framed with 14" TJW and
> plywood sheathing.  With smaller lighter loaded columns I have in the
> past blocked the col. into the floor systems to provide lateral support.
>         The architect on this project has ask if it has to be a full
> column. I am a little nervous using the floor system as restraint for
> this load. A 6x6 tube steel col. works for the full 34', but I would
> like to use something smaller.  What sort of forces would be required
> for restraint, and do any of you have a referece explaining the method
> for arriving at these restraint forces?  Any suggestions for detailing
> the restraint into a system in these floors (without infringing on
> anyones copyrights...)?
> Thanks from high in the Rockies,
> Joseph R. Grill, PE