Floor-to-3D composite beams
Floor-to-3D composite beams
(OP)
We have an office building type with perimeter brick veneer above and below bands of windows. Thus, the brick will have to be supported by ledge angles hanging off of the floor beams above.
The ledge angles will also have to be diagonally braced back up to a point under the floor, just inside the perimeter floor beam - perhaps to another parallel or perpendicular interior floor beam.
The question is - while in RISA Floor we can model this gravity load from the brick to the perimeter beam - the brick is actually eccentric a bit to the perimeter beam and will also impose some level of
torsion on it. Also, the lateral wind forces on the exterior wall will have to be resisted by diagonal braces. If we have diagonal braces - these don't show up in the RISA Floor model. So if we make the perimeter beams "lateral" they will come into the RISA 3D module and we can then model the angles an braces and put the brick load in there.
But in 3D we are not sure that it can do composite beam design. The lateral/diagonal braces impose torsion on the perimeter beam and lateral wind forces (from the exterior wall/windows) to the interior beams.
Does 3D perform composite beam design based on the info provided by RISA Floor?
The ledge angles will also have to be diagonally braced back up to a point under the floor, just inside the perimeter floor beam - perhaps to another parallel or perpendicular interior floor beam.
The question is - while in RISA Floor we can model this gravity load from the brick to the perimeter beam - the brick is actually eccentric a bit to the perimeter beam and will also impose some level of
torsion on it. Also, the lateral wind forces on the exterior wall will have to be resisted by diagonal braces. If we have diagonal braces - these don't show up in the RISA Floor model. So if we make the perimeter beams "lateral" they will come into the RISA 3D module and we can then model the angles an braces and put the brick load in there.
But in 3D we are not sure that it can do composite beam design. The lateral/diagonal braces impose torsion on the perimeter beam and lateral wind forces (from the exterior wall/windows) to the interior beams.
Does 3D perform composite beam design based on the info provided by RISA Floor?
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RE: Floor-to-3D composite beams
Personally, I don't have a good concept of how to include torsion and weak axis bending and such in combination with a composite beam. For that reason, I can't give you too much guidance. If I were stamping the drawings, I'd probably lean towards doing the design in RISA-3D as a non-composite steel beam.
That being said, if you have an idea about how best to combine those effects together you are certainly free to do so. You're just going to do it manually. You can still use the program results, of course. You just have to determine how to combine them together.
RISAFloor will give you a really good representation of the composite beam capacity and demand and such. Then RISA-3D should give you a good idea of the weak axis capacity (of the naked steel beam) and the effects of torsion on the member demand. It's a little trick to interpret, but it's there (be sure to review the Member Torsion Results spreadsheet). You just then have to figure how best to combine these together into a combined stress code check.
RE: Floor-to-3D composite beams