] [Thread] [Date] [Author]

["James Hannah" <jvhannah1(--nospam--at)insightbb.com>]

Method 1.  For purlins of medium length there would be two angles centered
about the midpoint and approximately 5' apart.  For longer purlins another
pair of angles are added with one each 5' outside or the previously
installed pair or braces.  Normally in situations which require bottom
flange purling bracing the braces which brace the top flange have already
been located above the bottom flange purling brace.  These braces are
located an inch or two down from the top flange and an inch or two up from
the bottom flange.  You could end up with 4 pairs of braces approximately
evenly spaced across the purlin.

Method 2. Strapping which is located at third, quarter, or fifth points,
runs across 3, 4, or 5 purlins and then X's to the opposite flange while
strapping which is on the opposite flange crosses this strapping and moves
to the first flange being braced.

Method 3.  Sheet the inside flange of the purlin with an adequate panel
screwed to the bottom flange and take out the bottom flange forces by a
diaphragm.

Naturally all connections and purlin anchorage's must be checked for
strength and stability.  A load path for the purlin brace forces must be
provided to get the forces into the frames and/or structural bracing and to
the foundation.

In cases which require bottom flange bracing there will normally be other
load combinations which also control in other situations that will require
top flange bracing usually due to gravity loads.  Also check continuity
defections which can cause bottom flange compression and require bracing.

There are probably many other solutions and situations as well.

Jim Hannah, EIT


----- Original Message -----
From: Bill Polhemus <bill(--nospam--at)polhemus.cc>
To: <seaint(--nospam--at)seaint.org>
Sent: Wednesday, June 12, 2002 11:32 AM
Subject: "Zee"-Shape Purlins Resisting Uplift Loads


> Has anyone here (maybe you who work in the metal building world) had
> experience with resisting uplift on zees used as purlins? I'm wondering
> about the "usual and customary" method of bracing the bottom flange of the
> zee against lateral torsional buckling due to wind uplift.
>
>
>
> William L. Polhemus, Jr. P.E.
> Polhemus Engineering Company
> Katy, TX, USA
> Phone (281) 492-2251
> FAX (281) 492-8203
> email bill(--nospam--at)polhemus.cc
>
>
>
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