Truss repair

[Canderson]

I'm working on developing repairs for an existing truss. Both of the middle diagonals (in the middle bay) have failed. Their ends were connected in the middle portion of pinned connections and the pin cannot be removed lest the entire structure fail. Of course, this is located high above a stream out in the wilderness and support of the truss to facilitate removal is out of the question. Our office developed a repair attaching a gusset plate to the vertical member and then putting a pin thru that gusset to fasten the new diagonal (both ends). All pins are co-linear.
Our client is concerned about: a) the way this structure will actually work with this offset connection; and b) the hole in the gusset plate getting "reamed" larger thru time and rotation cycles. Any comments? Thanks-
Canderson

 

[bridgebuster]

When you say "both of the middle diagonals" are you describing a panel with X-bracing, i.e. counters?

If so, rather than adding another gusset plate, which I’ve seen done on riveted trusses to repair cracked gusset plates, can you remove and replace the counter with a new one? You would need to design a system with two hairpin bars and splice them in the middle of the truss panel.

The counters would have to be replaced one at a time with the bridge closed to traffic.