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Re: 125' long steel truss, connection question

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In a message dated 99-06-23 20:00:25 EDT, you write:

<< Simon Solorio >>
I'm designing a 125' long steel truss, a section view of the truss is a 
triangle. The top chords (2 top chords) are pipes and the bottom chord (1 
bottom chord) is also a pipe. The web members are pipes.
Questions;
1. the top and bottom chords are going to be a continuous pipe, so when I 
analyse the truss should I assume the connection at the node intersections 
(at the chords only) fixed or should I analyse it assuming the the chords are 
pinned between each node of the truss?

2. the pipe web members are going to welded to the pipe chord members with 
fillet welds, where can i find information on how much fixity i should design 
this connection.

Thank you in advance

Simon Solorio, P.E

Simon,

A quick question on your computer model.

If you model your chords as pin at the connection node then doesn't one of 
the web members needs to be fixed to provide some rotational rigidity.  If 
all the members (chords and webs) framing into a node are pinned(no 
rotational rigidity) the analysis program should give you a warning or error. 
 Is this not the case?

Or maybe I misunderstood. 


The two cases you want to check are:
  
The first you consider the chord continuous and have all the web members     
pinned at the node.  

The second is you have the chord pinned at the connection and want the web 
members to exhibit some rotational rigidity, maybe with a torsional spring.

David Guerrero