Foundation elasticity

[mgaafar]

I am trying to model a raft slab. if I use the planer support the model runs, but when I remove the supports and replace that with "parameters of foundation elasticity" from FE thickness, the model give me warnings saying that there are "no supports"!

my question is that option working? and if it is working , what are the proper steps for that?

Thanks

[Artur.Kosakowski · Accepted solution]

In such case you can just ignore this warning In case it is a shell model make sure that you also restrained horizontal d.o.fs in addition to the vertical displacements.

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[mgaafar]

Thanks very much for the clarification

[dimogrec]

Artur in case of a plate on elastic foundation which is the better way to restrain horizontal degrees of freedom? Linear support on contour or setting up Ky and Kx (tangent elasticity on parameters of  foundation elasticity)?

If set a Kz (on thickness properties) then on map results I see soil reactions (in KN/m2). Am I right that soil reaction is actually the soil pressure?

In case we use a shell on planar support we can see only nodal reactions in KN/m (on FE nodes)

On calculation note of a panel I see no info about the foundation coefficient (and/or soil properties assumed on calculations. Is there a way to include those properties in case of raft foundation? If finally the soil reaction is actually the soil pressure I would also like to include min/max values in the plate calculation note. Always on calculation note point 1.5.2. Maximum moments and reinforcement for bending why Mx (+/-) My (+/-) are always 0.00?

[Artur.Kosakowski]

Artur in case of a plate on elastic foundation which is the better way to restrain horizontal degrees of freedom? Linear support on contour or setting up Ky and Kx (tangent elasticity on parameters of  foundation elasticity)?

I'd say that if there are no horizontal loads either is good. If they are I would use the prior option.

If set a Kz (on thickness properties) then on map results I see soil reactions (in KN/m2). Am I right that soil reaction is actually the soil pressure?

Correct.

On calculation note of a panel I see no info about the foundation coefficient (and/or soil properties assumed on calculations. Is there a way to include those properties in case of raft foundation?

You can see them in the Panels table (see the attached picture). Mind that you need to add these columns to the default display of the table (RMB click to access Table columns) 

 If finally the soil reaction is actually the soil pressure I would also like to include min/max values in the plate calculation note.

You can copy and paste this info from the FE Results table.

 Always on calculation note point 1.5.2. Maximum moments and reinforcement for bending why Mx (+/-) My (+/-) are always 0.00?

Thank you for pointing this out. We will investigate why this happens.

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[athurD]

Hi. I is prolem. Please help me. Thanks

Thanks

[Anonymous]

Hello,

The right solution is 1'st point.

[athurD]

Hi. thanks

please see picture.

So 1 or 2 is true or right.

[kamlinmoodley]

Hi Artur,

You mention " In case it is a shell model make sure that you also restrained horizontal d.o.fs in addition to the vertical displacements.".

Can you provide some more details on how to do this? ie, would you advise using a pin, spring or gap support? Where would you advise we place this support, ie in the middle of foundation, on edges or throughout the entire panel?

Regards

Kamlin

[Artur.Kosakowski]

Assuming that the lateral displacements is limited by friction you may just apply surface support with UX and UY blocked.

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[kamlinmoodley]

Hi Artur,

Thanks. But where would you advise we block the Ux and Uy? (see attached image for my raft foundation.

Also, Where would you suggest I block rotations , Rx, Ry, Rz? The position of these boundary conditions have an effect on the moment at the slab at that position and hence the steel reinforcement. 

kindly adise

[Artur.Kosakowski]

But where would you advise we block the Ux and Uy? (see attached image for my raft foundation.

You may use either of these options:

Also, Where would you suggest I block rotations , Rx, Ry, Rz? The position of these boundary conditions have an effect on the moment at the slab at that position and hence the steel reinforcement. 

When translational d.o.fs are blocked in each node of the panel then rotations are restrained as well.

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

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