I'm working with big model, which has non-linear restraints. When I try to run the model, it does not converge for certain load cases.

I'm using default friction Stiffness value.
Friction value is mu=0.3 for all +y restraints.


I have checked that my load cases are ok, for the case that isn't converging,I used the [F2] key to see exactly which restraints aren't converging and why. The report shows which restraints aren't converged,

I am able to find few of the supports are sliding,not sliding & friction err.

so i have removed friction in few of the supports. after doing this i am able to converge.

whether i am getting the correct results by doing above.

am i doing correctly ?.

kindly suggest a solution.

Regards,
vkumar

Kumar,

The otherway/recommended way is,

Reduce your friction stifness. Caesar-II allows stifness upto 10,000 #/in.

Go to configuration setup--->Computational control----> friction stifness (Choose a number from the drop down box)


-Reub

If you find that the normal load on those now-frictionless supports is low, then your modified model is probably OK.

You may want to re-run the analyses that worked on the original job (under a different name) and compare results with the new model. If the common load cases yield similar results, then, again, you're probably OK.

I would caution against changing the default friction. Years ago we had a very low "Friction stiffness" and that did not generally agree with users' expectations. If you do reduce friction stiffness, you should check to see how much the "non-sliding" supports actually slide. These "non-sliding" supports will carry less than mu*N friction load but will moving anyway (due to that lower friction stiffness).

Another thing you might try to see what's going on is to simply reduce the friction multiplier in the Load Case Options. This will allow you to adjust the friction coeficient on a load case-by-load case basis.

You can also search this forum using this string "+friction +convergence" (without the quotes) to see other posts on this same subject.