Truss Bending
Truss Bending
(OP)
We are currently load rating a truss where the connections are welded with gusset plates. When we input the truss into STAAD we assumed fully fixed connections at the ends. The resultant moments in the members were small, but since the members bend in the weak axis, the load rating is very low. Is there any information out there that discusses partial fixity of such connections?





RE: Truss Bending
This approach is sometimes called "secondary stress level" analysis. Some of the codes and authors calls for the increase in the allowable stresses (approx.25% range) in such case, with yours definitely qualifying. I would strongly advise to re-analyze the truss using true truss model, likely in 2-D, as the presence of portal frames tends to complicate the 3-D model and could lead to instability. One should also remember that self-weight generates moments too, but at the nodes they should be zeroed.
RE: Truss Bending
Regards,

Qshake
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