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RISAFloor slab edge fixity?

RISAFloor slab edge fixity?

RISAFloor slab edge fixity?

Is there a way to pin the edge of a slab (such as where attached to a wall, to avoid attracting seismic moment) in RISAFloor?

I have a concrete structure with 3 sides and a roof. I want to test it without the moment function attracting seismic loads.


RE: RISAFloor slab edge fixity?

I assume you're talking about a semi-rigid slab (which gets automatically created out of plate elements). If so, then not really.... There should be ways to fudge it, however.

My suggesting would (if it's an exterior wall) to terminate the slab edge just shy of the wall.... say 3". Then you can add in plate element (with corner pins) or rigid links with end releases into the RISA-3D model to limit whatever forces or moments you don't want to transfer.

If it's an interior wall that's continuous through the slab, there doesn't seem to be a clear way to do it. Maybe some variation of the suggestion above. Or, you create a dummy floor to create a gap in the wall just above or below the floor and use a similar modeling technique (rigid links or plate elements) to better control force transfer.

RE: RISAFloor slab edge fixity?

Thanks Josh. I considered a dummy floor. I was concerned about seismic load distribution, but now that I think about it I think as long as I don't have a diaphragm at the dummy floor the load distribution would be identical.

One method I tried was to change the slab cracked section to 0.99 but of course I can't combine load cases if I do that. I think the dummy floor may be the easiest and most reliable over the course of the design.


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