Moment Capacity of Composite Floor Girder
Moment Capacity of Composite Floor Girder
(OP)
Hello,
I have a few questions on computing the moment capacity of a composite steel deck + concrete slab beam system as follows:
1) If a girder only has simply supported beams framing into it on one side, are the beams considered as lateral bracing points assuming web shear plate connections are used? My understanding is that decking will not provide adequate lateral bracing to a girder since the ribs typically run parallel to the top of the girder.
2) How is the moment capacity of a beam/girder at an angle computed? For example in plan view if a beam is slanted 30 degrees to the horizontal, what assumptions do you make for the direction of the deck across the top of the beam and how much space you have available for shear studs? Can decking be installed such that it's slanted 30 degrees to match the beam?
3) How is the moment capacity of a beam//girder computed when the decking changes orientation over the top of the member? Do you assume either a parallel or perpendicular deck condition and ignore the other deck condition on the member?
4) Is composite design typically considered for concrete slab + steel decking systems with joists? If so, how is the tensile capacity of the joist taken into account when computing the moment capacity of the combined section? Intuitively I think you could utilize the tensile capacity of the bottom chord to compute the moment capacity, but I'm not sure.
Thanks
I have a few questions on computing the moment capacity of a composite steel deck + concrete slab beam system as follows:
1) If a girder only has simply supported beams framing into it on one side, are the beams considered as lateral bracing points assuming web shear plate connections are used? My understanding is that decking will not provide adequate lateral bracing to a girder since the ribs typically run parallel to the top of the girder.
2) How is the moment capacity of a beam/girder at an angle computed? For example in plan view if a beam is slanted 30 degrees to the horizontal, what assumptions do you make for the direction of the deck across the top of the beam and how much space you have available for shear studs? Can decking be installed such that it's slanted 30 degrees to match the beam?
3) How is the moment capacity of a beam//girder computed when the decking changes orientation over the top of the member? Do you assume either a parallel or perpendicular deck condition and ignore the other deck condition on the member?
4) Is composite design typically considered for concrete slab + steel decking systems with joists? If so, how is the tensile capacity of the joist taken into account when computing the moment capacity of the combined section? Intuitively I think you could utilize the tensile capacity of the bottom chord to compute the moment capacity, but I'm not sure.
Thanks






RE: Moment Capacity of Composite Floor Girder
Once the concrete hardens, it'll be a lot stiffer than your deck. And in order to actually have any lateral movement of the top flange, you'd have to shear off your shear connectors.
RE: Moment Capacity of Composite Floor Girder
This is true after the concrete has hardened, but before the concrete hardens the girder would have to support the dead load + construction live load on the floor without help from the decking + slab; unless the floor is shored.
RE: Moment Capacity of Composite Floor Girder
I'll attach some excerpts from the Ram Steel Beam manual pdf to elaborate on how we handle the other situations you describe.
RE: Moment Capacity of Composite Floor Girder
Just to clarify if you don't consider a girder to be braced by decking, does a beam framing in on one side provide an adequate LTB brace point? Or, do you have to have beams frame in on both sides for the girder to be considered braced?
RE: Moment Capacity of Composite Floor Girder
A beam framing into a girder provides bracing in the program always. Additional brace points can also be user specified. A few more tips here FYI: https://communities.bentley.com/products/ram-staad...
RE: Moment Capacity of Composite Floor Girder
I would not go for much composite action in the edge girder. The studs are prone to to rip out.
RE: Moment Capacity of Composite Floor Girder
RE: Moment Capacity of Composite Floor Girder