How to determine load path in concrete 2-way flat plate? 1

[snipit]

I'm not talking about simple buildings with typical bays. I was wondering how to get the correct load path for slab with columns placed in very random locations, no pattern.

Any resources/helps would be appreciated!

 

[Greenalleycat]

I see this as analogous to designing a suspended slab over piles (e.g. driven timber or blade piles)

In this case I would model a plate element in SpaceGass and apply supports (could make them spring supports to be real fancy, if you have sufficient information to estimate this)
Then run the model and see what comes out
Make sure your plate mesh is sufficiently fine to give reasonable results, and I recommend playing around with flexural stiffnesses to see how sensitive the reactions are to variations in slab stiffness

 

[KootK]

You want a setup that pays as much homage to stiffness as possible. I'd start by drawing lines that rationally connect your various columns to create something akin to column strips. Obviously, FEM has a lot to offer in this regard as well.

 

[ggcdn]

A finite element analysis software that has shell elements is usually used these days.

You can also get a pretty good sense of tributary areas by just drawing lines between nearest neighboring supports, marking the midpoints, and connecting them into polygons (with a little judgement).

And you can compare the two by analyzing the finite element model with a unit load (1psf) - the support reactions are then equal to the tributary area.


-JA
try [link calcs.app]Calcs.app[/url] and let me know what you think

 

[snipit]

You can also get a pretty good sense of tributary areas by just drawing lines between nearest neighboring supports, marking the midpoints, and connecting them into polygons (with a little judgement).

HA!! I tried this before, adopted from Thiessen Polygon Method from Hydrology measuring precipitation. However, I don't know the validity of the result so I stopped.

 

[snipit]

I'd start by drawing lines that rationally connect your various columns to create something akin to column strips.

Column strip is actually what I'm trying to to get to finally. This is also what I did and finally ending up with so many lines from one column at the center to all neighboring columns. That was when I started to think if I'm doing this thing correctly or just randomly drawing lines.

 

[Tomfh]

Finite element is common as you can sidestep all that business of "column strips". Column/middle strips are just a design concept that allow you to analyse and design your slab as a series of beams.

 

[CovertShear]

If you want an exact result, use FEM.

My FEM has a nice "principal stresses with trajectories" result option. It gives you a good idea how a slab works near supports.