results for meshed or not meshed plate

[popabf]

Hi.
I have o problem with an uniformly distributed force over the surface of a plate restrained only at the

corner nodes. The plate is a quadratic 1mx1m and the force is 2KN/m2.

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! ! Sorry about the drawing.
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I made 3 examples of this plate:
a) unmeshed plate;
b)(assign->areas->automatic mesh) automatic meshed plate 4x4;
c)(edit->mesh areas) meshed plate 4x4 --> I obtain 16 new plates.

As reactions results I obtained:
a) U1,U2,R1,R2,R3=0 and U3=0.5 KN;
b) U1,U2,R3=0 and R1,R2=-0.0441 KN and U3=0.5 KN;
c) U1,U2,R3=0 and R1,R2=-0.0441 KN and U3=0.5 KN;

As displacements the results are:
a) all 0;
b) all 0;
c) small displacements for the nodes that are not supports (-it is corect-).

My 1st question is why aren't the reactions the same for all the plates? It seems that when I mesh the plate, some moment reaction appear. Why?

The 2nd questions reffers to the distribution of the force over the plate: the 2KN/m2 is multiplied with

every new plate area (from the meshing)? Because when right click over a such plate I get the same 2 KN/m2 as load.

Thanks!
Bogdan

 

[Wrightguy]

I hope someone can answer this because I have the same problem with a floor slab design.

Please help someone??

 

[masomenos]

The reason moment appears is because after you meshed your shell, you now have unsupported shells/joints which have load that are offset from support locations whereas before all joints were supported. this moment is expected after you mesh. Vertical load should remain the same on all 4 restraints

If you assigned as an area uniform load, SAP keeps track of the load assignment even if you mesh.. so yes, 2KN/m2 would be correct on every plate, only now after meshing you have more numerous, smaller plates (ie smaller load per plate, but same total vertical load)