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RE: EOR review of truss calcs

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Steve,
You only need to confirm in a letter (at least this is how it works in the four or five building departments in my area) that the trusses conform to the intent of your design for the specific job. In other words, the calcs were designed using the live and dead loads provided by you, the trusses match the roof layout on your roof plan and that drag trusses have been provided where you specified on the plans. Beyond this, you are required to complete the load path after the placement of the trusses to the foundation.
Here is a sample of a letter I provided a few years ago - since then I have shortened them whenever possible:
 
"I have reviewed the truss calculation package from <deleted> for the projects located at <address of job>. The trusses conform to the intentions of the architectural and structural design as noted on sheet S2.1 of the structural drawings drawing. The only discrepancy lies with the indicated plate height which is specified on the truss package as 10’-1” but is actually 8’-1”. This does not change the design of the trusses nor does it impact the project in any manner.

The T-3 truss is correctly designed for the drag load of 5,200 pounds. This can be verified on the structural analysis package.

The live load of 16 psf is consistent with a 4:12 pitched roof and is in compliance with table 16-C of the 1994 Uniform Building Code. The roof dead load  including the ceiling load is consistent with mission tile roofing. The structural analysis uses a 20 psf dead load but includes a miscellaneous load. The 19 psf load used by <truss manufacturer>  is within a reasonable range for this roof material.

Please accept this letter as my authorization for acceptance of the truss calculations submitted by <truss manufacturer>."
 
This is generally all that has been required. It does not establish any more responsibility upon the EOR for the actual design of the roof system which remains with the truss manufacturer's engineer. It does however, place responsibility on the EOR to insure that the total system meets the minimum or greater live and dead loads applied to the rest of the structures and which were used to evaluate the lateral load resisting system. It also places responsibility on the EOR for the connection of the roof to the structure below and for all lateral load path ties.
 
I'm sure there are more conservative engineers out there that will disclaim much more, but this seems to be in line with what other engineers in my area are providing. If you do, however, note a problem with the trusses (I've discovered girder trusses where the loads were distributed incorrectly based upon the truss designers layout) you must address it and require correction of the package. In short even though you may not be responsible for the design of the truss system, you are ethically responsible to check it thoroughly to find faults that can be problematic and to bring them to the attention of the truss designer.
 
Regards,
Dennis S. Wish, PE
 
-----Original Message-----
From: SCHFUN(--nospam--at)aol.com [mailto:SCHFUN(--nospam--at)aol.com]
Sent: Saturday, May 26, 2001 7:11 PM
To: seaint(--nospam--at)seaint.org
Subject: EOR review of truss calcs



What is the standard of practice for the design engineer's review and
stamping of pre-fab trusses?  Building departments in Southern California
often require this, and some engineers are uncomfortable with the practice of
stamping the work of another engineer (the truss designs are typically
prepared using a proprietary computer progaram and reviewed and stamped by
the truss engineer).

Is the engineer-of-record expected to check the truss calculations? Or just
verify that the proper loading criteria was used in the truss design?


Steve Helfrich. P.E.