Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

Re: Truss permanent bracing. Metal web brace in plane of truss eliminates CLB

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Mitek supplies metal in-plane bracing to their fabricators.
The metal web brace increases the radius of gyration for the web and
eliminates the need for further bracing thereby making it truely a component
supplied to job (similar to GLB or TJI) to be used in a system designed by
others.

When multiple webs need bracing using perpendicular lateral CLB
(continuous lateral bracing), the component truss engineer desires to pass
design responsibility to the EOR because of multiple truss components
acting as a SYSTEM.

The truss fabricator is reluctant to add the metal bracing into a job cost when
they
compete against other fabricators who leave 'bracing by others' to the cost of
the
installer/builder and design responsibility to the EOR.



----- Original Message ----- 
From: "Kestner, James W." <jkestner(--nospam--at)somervilleinc.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Wednesday, August 17, 2005 1:33 PM
Subject: RE: Truss permanent bracing


The options are:

1) Provide lateral bracing which incidently only works well if a) the web
members of adjacent trusses line up and b) the contractor actually installs it.

2) Require the contractor to create a T-section out of each web member that
requires lateral bracing. In fact, this maybe the only practical solution where
web members of adjacent trusses do not line up.

3) Require the contractor to install a metal web brace which does the same as
the T-section. I used to know the name of this product but can't seem to find it
right now. Does anyone know the name or manufacturer?

For those that want to put it back on the truss supplier or contractor, 2) or 3)
sound like possible options.

Jim K.

-----Original Message-----
From: Jordan Truesdell, PE [mailto:seaint1(--nospam--at)truesdellengineering.com]
Sent: Wednesday, August 17, 2005 1:33 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Truss permanent bracing


I've yet to see a shop drawing submission that does not include language
to the effect that the manufacturer adheres to the TPI requirements, aka
no truss bracing. Most show locations of bracing, but no overall plan.
A horizontal bracing member merely insures that all the similar webs in
a line will fail together.  Since slender members are based on the
minimum thickness, and that is universally 1.5", the architectural
design (pitch+span) will tend to force the webs beyond the slender
point.  Aside from going to n-ply trusses all over the building (can you
say "unhappy owner"?), they're limited by the geometry given.  I think
you at least need to give them bracing points and allowable values on
the structure if you expect them to even try to brace.  My guess is that
this is an unwinnable battle for individual firms using notes.  Sadly,
we (SEs) are not nearly as organized as the TPI when it comes to forcing
this issue to the ICC.

Andy Heigley wrote:

>We have talked about this several times in our firm about this topic.  And
>finally resolved to state in our General Structural Notes and specs, to
>specifically state something to these effects:
>
>THE DESIGN OF ALL WEB MEMBER PERMANENT BRACE SIZES AND CONNECTIONS, REQUIRED
>FOR THE STRUCTURAL ADEQUACY OF THE TRUSSES, SHALL BE THE SOLE RESPONSIBILITY
>OF THE TRUSS SUPPLIER.
>ADDITIONAL MEMBER PERMANENT BRACE SIZES AND CONNECTIONS, NOT PROVIDED BY THE
>SHEATHING SHOWN ON THE CONSTRUCTION DRAWINGS, SHALL ALSO BE THE
>RESPONSIBILITY OF THE TRUSS SUPPLIER.  THIS BRACING CAN INCLUDE, BUT IS NOT
>LIMITED TO, TOP CHORD BRACING FOR TRUSSES WITH PIGGY-BACKS, AND INTERMEDIATE
>BRACES FOR GABLE TRUSS WEB MEMBERS.
>
>It is the Truss designer's choice to use a slender member.  If he wants to
>use a slender member and brace it so it works, then he should provide the
>bracing for it.  So far, we've had no arguments from truss suppliers
>regarding this note, and I'll even say I've checked shop drawings that calls
>out the bracing for web members.
>
>So that's my 2 cents.
>
>Andy Heigley, PE
>
>Dublin, Ohio
>
>


******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
*
*   This email was sent to you via Structural Engineers
*   Association of Southern California (SEAOSC) server. To
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
*   send to the list is public domain and may be re-posted
*   without your permission. Make sure you visit our web
*   site at: http://www.seaint.org
******* ****** ****** ****** ******* ****** ****** ********

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
*
*   This email was sent to you via Structural Engineers
*   Association of Southern California (SEAOSC) server. To
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
*   send to the list is public domain and may be re-posted
*   without your permission. Make sure you visit our web
*   site at: http://www.seaint.org
******* ****** ****** ****** ******* ****** ****** ********


******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
* 
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: http://www.seaint.org 
******* ****** ****** ****** ******* ****** ****** ********