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RE: TRUSS QUESTION

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See comments below.

-Juan José Treff De la Mora [mailto:jjtreff(--nospam--at)hotmail.com] wrote:

>I was asked to design a 110 ft span roof truss. The truss will only carry 
>the standing seam roof and some lamps inside. No snow, medium risk seismic 
>zone and a 75 mph wind. 

First, include at least an extra 5 kip at the worst panel points due to
lifting.  People just cannot resist tossing a chain up to the truss to pick
up something heavy.  They will do it whether you design for it or not.  They
only way to stop it is to encase the truss.

>The supporting columns will be made of concrete. The owner wants to 
>use equal leg angles (L) and tubes (HSS) in A36 steel for price reasons.

First, tubes do not come in A36 steel.  They have been A500 (46ksi) for at
least the last 25 years.
I don't know where you are at but in the US and Mexico, A36 is not commonly
available anymore.  The standard is 50ksi steel (A992, I think).  A36 can be
ordered but at a premium and/or you will get 50 ksi anyway.

Mark Jones
Jacobs Engineering


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