topic Re: Foundation elasticity in Robot Structural Analysis Forum

Foundation elasticity

mgaafar — Tue, 13 Mar 2012 23:49:23 GMT

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

Re: Foundation elasticity

Artur.Kosakowski — Wed, 14 Mar 2012 07:48:21 GMT

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.

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Re: Foundation elasticity

mgaafar — Thu, 15 Mar 2012 23:37:13 GMT

Thanks very much for the clarification

Re: Foundation elasticity

dimogrec — Mon, 19 Mar 2012 12:54:26 GMT

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?

Re: Foundation elasticity

Artur.Kosakowski — Mon, 19 Mar 2012 13:37:23 GMT

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.

Re: Foundation elasticity

athurD — Fri, 25 May 2012 16:15:18 GMT

Hi. I is prolem. Please help me. Thanks

Thanks

Re: Foundation elasticity

Anonymous — Sat, 26 May 2012 03:45:22 GMT

Hello,

The right solution is 1'st point.

Re: Foundation elasticity

athurD — Sat, 26 May 2012 04:07:32 GMT

Hi. thanks

please see picture.

So 1 or 2 is true or right.

Re: Foundation elasticity

kamlinmoodley — Wed, 13 Jul 2016 13:27:00 GMT

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

Re: Foundation elasticity

Artur.Kosakowski — Fri, 22 Jul 2016 07:08:00 GMT

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

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Re: Foundation elasticity

kamlinmoodley — Mon, 25 Jul 2016 09:00:24 GMT

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

Re: Foundation elasticity

Artur.Kosakowski — Mon, 25 Jul 2016 09:19:04 GMT

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.