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Transient analysis of floating layer (with gravity)......

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BAP121

Mechanical
Apr 22, 2009
5
Hello sexy eng-tipsters,

I am trying to create a finite element model of a concrete slab with a floating screed layer ontop to try and see the impact on the floating screed layer transient analysis. There is a hard plastic membrane between the two layers so it is as if the screed layer is resting on top of the concrete slab.

To start with, I have modelled the problem in 2D, using PLANE42 elements and CONTAC178 to join the 2 layers together. I ran the problem without gravity, but this gave undesirable effects as gravity is a major factor binding the screed layer to the concrete slab. I therfore need to apply gravity before undertaking the transient analysis. Every time i try this, I end up with far higher displacements from movement under gravity than from the transient impulse i apply.

I know this is probably simple but can someone please simply explain to me how I can apply displacement/stress due to gravity so it is in equilibrium and then do the transient analysis.

Many tanks,

BAPS

:)
 
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I think i managed to solve it by writing a static analysis to LS1 and then applying an impulse and writing a transient analysis to LS2. However when i run it now I get an error message after the static part of the analysis saying "The analysis type must not be changed after the first load step. For a new analysis, FINISH now and reenter /SOLUTION" as well as a couple of other messages befor it continues with the transient part of the analysis.

Is this anything to worry about? The results of the analysis look plausible but just want to check that this sounds OK.
 
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