Cantilever steel beam at column
Cantilever steel beam at column
(OP)
When you design a cantilever steel beam with moment connections at both sides of the column, do you assume part of the moment goes to the column (due to relative stiffness of the beam and the column) and design the column for that additional moment?? Please advise. For some reasons, we have been assuming the beams are having two pinned connections, and designed columns with vertical load only. Now, I am worried...






RE: Cantilever steel beam at column
RE: Cantilever steel beam at column
RE: Cantilever steel beam at column
Anyway in my opinion you are always safe if you calculate moment connections as if they were pinned, provided you are not in a high fatigue environment and you take the same assumption in all the structural checks performed on the element. However this would of course be a waste of effort in building a moment connection that is not used as such...
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RE: Cantilever steel beam at column
RE: Cantilever steel beam at column
If the cantilever/beam connection to the column is not designed to take moment, then you could assume that all the cantilever moment extends into the beam.
However, very few connections of any kind are truly "pinned" so I would include some column moment in my column design.
RE: Cantilever steel beam at column
I might add, however, that the answer to this question relys primarily upon the connection of the column to the beam. Does the connection allow internal distortion, thus preventing the column from participating in the moment distribution?
RE: Cantilever steel beam at column
I agree with your first statement. If the inner beam is moment-connected with the column, the moment from the cantilever will be shared by the column and the inner beam.
But I am afraid your second statement is not correct. If the column to inner beam connection is a shear connection, the moment will be totally resisted by the column only. The logic is as below.
First of all the cantilever beam has to be moment-connected with the column, as otherwise the cantilever will become unstable. Hence the moment will first get transferred to the column at the joint. If the adjacent beam is not having a moment connection with the column, the inner beam end will tend to rotate and only the bending stiffness of the column will contribute to the resistance.
The inner beam will get the moment only if either the beam has a moment connection with the column or if the cantilever beam is continuous over the column and connected to the column at its bottom flange through a bearing plate. In the latter case, the column will act like a knife-edge without taking any moment from the beam.
RE: Cantilever steel beam at column
But a bolted cap plate to a bottom flange has SOME capacity to accept moment from the cantilevered beam above...just difficult to determine.
RE: Cantilever steel beam at column
RE: Cantilever steel beam at column