Distribute Floor Load/Pressure to Frame

cwharpe

Hello. I am trying to evaluate different non-square Stair frame configurations under a uniform floor load.

How do I transfer the pressure/ distributed loads from a plate to its subframe, without the plate adding stiffness to the overall frame? That is, I just need the vertical (normal) load distribution to each frame member.

I know the line pressures are not uniform along their frame lengths, but I don't know what the variations are. And as model sizes grow, it is quite tedious to first model a flat plate with normal supports along frame members axis, then transfer those reactions to the actual model (beam elements) as distinct nodal loads.

Springs? Plates w/ Node Releases (zero shear transfer in built-up section)?

Any thoughts?

~CWharPE

Victor

One way would be stiff springs or truss elements since these can only transmit force along their direction. Here's an example.

You could also use constraint equations to couple only the translational DOFs in the normal direction, but I think that might be more tedious to set up.

cwharpe

Thanks for the suggestions. Using the springs worked well. Was able to play with spring rate and "Pressure Plate" thickness until solution converged within 3 significant digits.

Frame displacements measured at same node were definitely sensitive to pressure plate thickness. Seemed to me a thinner plate on short springs best followed the frame deflections.

The trade off was how huge deflections in the thin plate dominated the screen graphics. I haven't learned how to filter the screen display results yet, such that it might ignore certain elements and only color display max-mins of selected others. A nice workaround was to create named nodal sets then inspect them in the Solution Table.

~CWharPE

VMH

CWarPE, if you have your elements grouped into components, you can also hide them in the results (see attachments).