Truss Connection Detail
Truss Connection Detail
(OP)
I have a truss, with W14 (Flat)as chord members and TS5x5 as diagonals. Whhich of the following connection is better?
1.) weld a big gusset plate to the web of the W14. Slot through the TS5s and weld to the gusset.
2.) weld a WT to the web of the W14. (Stem of the WT welded to the web of the W14, Flange of the WT welded to the flange of the W14). Then weld all around the TS5s to the flange of the WT directly.
I feel like using the second approach because the web of the W14 is very thin. (3/8") But the first approach is easier to fabricate.
Can anyone give me any advice? Or can you suggest a better
connection detail?
Thanks in advance for your help.
1.) weld a big gusset plate to the web of the W14. Slot through the TS5s and weld to the gusset.
2.) weld a WT to the web of the W14. (Stem of the WT welded to the web of the W14, Flange of the WT welded to the flange of the W14). Then weld all around the TS5s to the flange of the WT directly.
I feel like using the second approach because the web of the W14 is very thin. (3/8") But the first approach is easier to fabricate.
Can anyone give me any advice? Or can you suggest a better
connection detail?
Thanks in advance for your help.
RE: Truss Connection Detail
You might have to provide a thicker gusset for this option but will be easy to fabricate and less expensive than the WT sections.
RE: Truss Connection Detail
If this is a truss for a highway bridge or a very dynamically loaded structure, I would be very leary of welding gusset plates to diagonals and chords. This is because the welds that are in areas of large tension stress or stress reversal are prone to fatigue, if the welds are not designed and detailed properly. In this situation, I would choose a different shape for the diagonals (ie 2 channels or angles, or another wide flange) and utilize a bolted gusset plate connection. Historically, there have been problems with respect to fatigue in slotted tubular connections that are welded.
Dr. John Fisher from Lehigh University has written many articles and a few text books that investigate fatigue and steel connections.
If the truss is for a moderately "static" structure, I feel that Ron's suggestion is a good solution. There are a few books out there that can assist you in these tubular connection. One that comes to mind is from the AWS (American Welding Society) and is written by Omer Bloddet, and I think it is called "Design of Tubular Structures"
RE: Truss Connection Detail
RE: Truss Connection Detail
This will allow you to place gusset plates on either side of the tube and the connection will act in double shear, as civeng has indicated.
This may seem excessive, but I was really suprised to find that this tension in the bolt, even under the turn of the nut method, was enough to crush the walls of the tubes I was using.
If you are ineterested in seeing the bolted details I used, just let me know, and I can also send you a copy of the calculations.
RE: Truss Connection Detail
RE: Truss Connection Detail
I contacted the structural engineer and asked him about the issue of web bending due to the gusset plate connected perpendicular with no stiffener plates. His contention was that the truss was designed conceptually as a pinned jointed frame and wherever a diagonal connected to the chord, there was another diagonal adjacent to it that took away all of the force perpendicular to the chord. Thus, the web never experiences a net force that would cause bending, but only a net longitudinal force.
I'm not sure I agree as the "theoretical" frame is one thing, but the actual behavior of the truss is another. I would suppose, though, that if there was a small net force, the web would distort and the forces would re-distribute.