removing elements

[mtsonicc]

Dear everyone,

I'm trying to remove elements during static (or dynamic) analysis.

I have two questions.

1) Would somebody please tell me which of the following is right for the 'MinMax' material?
one, 'MinMax' material actually removes element.
two, 'MinMax' material modifies stiffness of the material to zero.

2) When using 'remove element' command, can sudden change of internal forces induced by removing elements cause convergence error? (sometimes OpenSees freezes without responding)

[m12s12sa]

Hi,
I can answer to your first question.
MinMax material does NOT remove the element when the minimum or maximum strain are achieved during the analysis. Simply, after that point, the material will show zero stress and tangent stiffness. The actual element will be left in the model (e.g. you will be still able to record its displacements, forces, etc. and it will be there if you PRINT the model.)
Regards,
F.L.

[fmk]

and the answer to 2 is yes .. if the element being removed has element end forces, those forces must be redistributed for structural equilibrium at next step .. if structure cannot redristribute te forces then convergence errors will pop up.