"stressStrain" and "deformation" & Fatigue min/max

[IsmBaha]

Hello Frank,

I have a few simple questions:

1) What is the difference between section recorder options "stressStrain" and "deformation" in terms of strains?

recorder Element -file StressStrain.txt -time -ele 4 section 1 fiber 10.0 0.0 $matID stressStrain;
recorder Element -file AxialStrainCurvature.txt -time -ele 4 section 1 deformation;

Following above,

2) What is the min and max values in the fatigue material?
uniaxialMaterial Fatigue $matTag $tag <-E0 $E0> <-m $m> <-min $min> <-max $max>
It says global min/ max strain, is it corresponding to average axial strain or something? Or it is just the min/max strain for each fiber. The word "global" confuses me.

3) Which one is corresponding to fatigue min/max strain limits: "stressStrain" or "deformation"?

Regards,
Baha

[fmk]

1) section deformations (axial, curvature) are very different from the strain and stress at a fiber location in the section.
2)max and min values of strain allowed before material is determined to have failed, i.e. 0 tangent and stress no matter what the strain is strain EVER goes below min or above max.
3)strain.

[IsmBaha]

Thank you for explanation Frank.

Vesna used max strain = 0.04 in her CBF example for only braces, not for columns or beams. Do you know what 0.04 is based on?

Vesna's code: uniaxialMaterial Fatigue $matID_fatBrace $matID_Brace -E0 $E0 -m $m -min -1.0 -max 0.04

http://opensees.berkeley.edu/wiki/index ... n_elements

[IsmBaha]

Hello Frank,

Update on the fatigue material "max strain = +0.04" and the braced frame response:

* I created a simple HSS-Round (circular section) brace example with kink in the middle and used steel and fatigue materials mentioned earlier and I am cyclically pushing it. My observations are as follows.

1) as you said I observed fibers failing at max strain of +0.04, but some fibers failed at lower strains, such as the exterior fiber (@ D/2, 0.0) failed at +0.04, but the interior fiber (@ D/2-t, 0.0) failed at about strain of +0.019. Do you know why would such a behavior happen?

- and strain in the "stressstrain recorder" in the middle of the section e.g., at (0.0, D/2-t/2) is exactly equal to strain from the "deformation recorder"


* I also created created a 9 story braced frame and running an EQ analysis. Only Brace Elements are (fiber section) forcebeamcolumn elements. In this model:

2) Once the element "axial force" in "deformation recorder" goes to zero value (complete failure), does this cause EQ analysis to converge slower? I mean much slower b/c I am running this 9 story building example and it has been 3 days and it is still running. Hope it will finish... Or it is super slow b/c other non-failed elements go through significant deformations but not failed yet?

3) what are the ways of accelerating solution? Would removing brace elements that reached to zero axial force help for speeding up?

Thank you for your guidance Frank.

Sincerely,
Baha

[IsmBaha]

Hello Frank,

Any comments about speeding up the analysis?

Regards,
Baha

[fmk]

different solver, solution algorithm and removing braces that have failed.