# Calculation of the foundation mat on undermined territory, why non-linear calculation takes too much time using FE 262?

The foundation mat is calculated on undermined territory. Account of the difference surface settlement is modeled by elements FE 262 with a gap. Number of stiffness FE 262 ~380, number of elements ~5500. Gaps are ranged from 0.0 to 2.5 cm, rounded to 0.01 cm. Time of one step calculation is 5 hours. There are automatically set 20000 iterations (for one step). Is it possible to reduce number of iterations for rough estimation? What generally affects the choice of this step? Another problem has only 2000...

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Calculation of the foundation mat on undermined territory, why non-linear calculation takes too much time using FE 262?
 ak1m Visitor Posts: 52 Points: 51 Joined: May 23, 2014 #1 People who like this:/ Dec 10, 2014 11:32:55 The foundation mat is calculated on undermined territory. Account of the difference surface settlement is modeled by elements FE 262 with a gap. Number of stiffness FE 262 ~380, number of elements ~5500. Gaps are ranged from 0.0 to 2.5 cm, rounded to 0.01 cm. Time of one step calculation is 5 hours. There are automatically set 20000 iterations (for one step). Is it possible to reduce number of iterations for rough estimation? What generally affects the choice of this step? Another problem has only 2000 iterations. Is it possible to reduce them to 200?)))LIRA-SAPR 2011 R6
 рекс Expert Posts: 592 Points: 580 Joined: Sep 10, 2007 #2 People who like this:/ Dec 10, 2014 12:49:19 It depends on the stiffness ration. Try to change stiffness of FE262 on test case. Also, very with other stiffness. For instance, according to the plan, FE 262 is almost unyielding and you set an excessive axial stiffness for practical necessity.
 ak1m Visitor Posts: 52 Points: 51 Joined: May 23, 2014 #3 People who like this:/ Dec 10, 2014 14:17:44 I have set stiffness 20000 t/m (will try with less one), and below the lower end there is low stiffness plate with applied subgrade reaction coefficients to take into account stiffness of the soil. Initially I had a variable C. When I have changed it on permanent and rounded up to 0.1 cm, the number of iterations become 1600 in one step (instead of 20000). Already less)) Instead of 5 days, it was calculated for 5 hours. But still it is somehow long. Was the process accelerated in new versions of PC LIRA?
 рекс Expert Posts: 592 Points: 580 Joined: Sep 10, 2007 #4 People who like this:/ Dec 10, 2014 16:17:58 I have not solved such problems. But, apparently, under the established structure occurs a failure. And, there occurs settlement of what stands on it. The only thing comes to mind is to make an array of soil solids. To model lens using system "assemblage" by stages and demolish it by parts. For the first make it in linear formulation. Then try non-linear FE of the soil (they are also iterative). If you will build this problem in linear formulation, try to make this lens using at list 10 different sets of FE instead of one. Divide the stiffness (Edef) between them and make each stiffness exclusive that it was convenient to access them. Demolishing them gradually would reduce the stiffness of the structure. The building on the top will react the changes. There is also another way. You may use set of springs and type of processor. In addition, there are possible not only machinery iterations, but also their modelling. In linear formulation, all will be calculated faster. There will be enough 100 of iterations, may be even less.
 ak1m Visitor Posts: 52 Points: 51 Joined: May 23, 2014 #5 People who like this:/ Dec 11, 2014 11:52:22 We don’t have assemble module and unfortunately I am not familiar with it. But for the overall development is worth reading)))
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