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RE: Question on wood Roof Trusses

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Neil:

You can also add a 2x to the web to form a T or an I if need be.and yes
reviewing the truss layouts and calcs are very important no disagreement here

Tarek Mokhtar
structural enginner

>Tarek:
>
>If I remember correctly, one of the TPI publications has an example of how
>ALL of the webs can buckle at once.  If the web bracing isn't anchored to
>something, then this can happen.  Most of the time, the real loads never
>approach the design loads and any buckling problem has moved into the
>factor of safety area.
>
>If people are designing trusses in snow areas, say 160 pcf, then our
>discussions and the possible reprecussions become important.  My original
>involvement in the web bracing responsiblity problem came about 6 years ago
>in a court case.  That's were I found out that the responsibility is kinda
>hidden in the TPI specification, which the UBC refers you too.  How many
>people owned the TPI spec?  Further, it is also difficult to interpret the
>results of the computer output.  That presentation can be, and may already
>have been, improved upon.  I've read where some engineers are going to get
>tough about this and make the truss company provide the web bracing
>anchorage to the building or to the roof or somewhere.  Good luck!.
>
>It still is important to review the truss company's layouts; you might be
>surprised at what you will find.
>
>Neil Moore, S.E.
>
>>Peter:
>>
>>I personally have it in my specs that bracing the truss members is the
>>responsibility of the truss designer for reasons too numerous to
>>recount.this thread was started a while back so check the archives and in
>>particular excellent postings by Roger Turk .
>>
>>I think the bigger problem is getting the framer to actually brace
>>the members that need bracing. and unless somebody shows him where these
>>members are on the framing plan
>>they aint gona walk the building with the little 81/2 x 11's from the
>>truss engineer and do it( all they see is a little astrisk next to said
>>members)
>>incidently every framer that we worked with told me that they have never
>>installed such braces and never knew they were even required .Generally
>>engineers have some sort of a typical detail on their plans that refers
>>back to the truss designer's calcs. good luck getting the framer to
>>comprehend it.
>>it is my opinion that unless the compression bracing is shown on the
>>truss layout sheet with the appropriate details refernced to it nobody
>>will follow
>>my 2 cents
>>Tarek Mokhatr
>>strucural engineer
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