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wjrfd
Posts: 8
Registered: ‎08-21-2012

-ve soil reactions

167 Views, 3 Replies
01-16-2013 06:28 AM

Good Afternoon!

 

I have assigned a steel bridge with pad foundations with a vertical soil stiffness assigned (Kz).  When I run the model however, the results map of the pad foundations show a -ve soil reaction, implying the soil is acting in tension. 

pic1.PNG

 

Is there a way to make sure any reactions are zero if in uplift?  I have tried ticking allowing selecting Uz+ when defining the Foundation elasticity, however seemingly to no avail!

pic2.PNG

Hope you can help!

 

 

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Artur.Kosakowski
Posts: 5,105
Registered: ‎12-17-2010

Re: -ve soil reactions

01-16-2013 06:45 AM in reply to: wjrfd

Have you ignored any instability warning and have you checked if the analysis converged?

 

uplift.PNG

 

 



Artur Kosakowski
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Active Member
wjrfd
Posts: 8
Registered: ‎08-21-2012

Re: -ve soil reactions

01-16-2013 06:56 AM in reply to: Artur.Kosakowski

Hello Artur,

 

Thank you for the speedy reply.

 

There are indeed instability warnings. I get an instability in one of the mesh nodes in the pad foundation, however it is a type 3.  I was under the impression that this sort of instability usually occurs around rigid links due to stiffness differences?

 

I have applied line supports to ensure lateral stability (which you have applied i your model)

 

The analysis does not fully converge no, this seems to be associated with selecting the uplift as Uz+.

 

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Artur.Kosakowski
Posts: 5,105
Registered: ‎12-17-2010

Re: -ve soil reactions

01-16-2013 07:07 AM in reply to: wjrfd

 

The analysis does not fully converge


 

In such case the results cannot be correct.

You may try to change the method to Full Newton Raphson and check if this help. Otherwise you have to examine the model and find out why this happens.

 



Artur Kosakowski
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