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FW: 125' long steel truss, connection question

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Simon,

Use the pinned results to check deflections and use the fixed results for
stress.  This should envelope a good solution.

Curt La Count
Jacobs Engineering
Portland, OR
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From: Simon Solorio
To: seaint(--nospam--at)seaint.org
Subject: 125' long steel truss, connection question
Date: Wednesday, June 23, 1999 5:01PM

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.

The architect does not want to see any plates, so I think if the connection
of the web to chord is all welded then the connection has some fixity.
I've check the truss with all the members fixed and the truss with all the
members pinned but i think, with the fillet weld connections, the percent of
fixity is in-between a fixed and hinged connection. The reference books I
have show a welded connection like the one I need to design and seem to
assume the connections are pinned.

Thank you in advance

Simon Solorio, P.E.