Integration Sections

[zhwang]

Dear seismostruct support,

I have a two storey two bay steel frame, and I use 4 integration sections for the beams and columns. When I run the pushover analysis for this frame, in "Post-processor", I can check the Peak strains and stresses for section a, section b, section c, and section d.
From the manual, I understand that Labatto quadrature is used for 4 integration sections, and the approximate coordinates along the element's length of 4 integration sections are [-1 -0.447 0.447 1] x L/2.

Could you please suggest me whether section a to section d are in the sequence of the axial direction? and the length of section a is [-1-(-0.447)] x L/2, the length of section b is -0.447 x L/2, the length of section c is 0.447 x L/2, and the length of section d is [1-0.447] x L/2? I have drawn two pictures to describe the localisation of 4 integration sections in beam and column, if possible, could you please help me to check whether my understanding on these two pictures is correct? Or if I was wrong, could you please suggest the correct way for the localisation?

The two pictures are attached in dropbox:
https://www.dropbox.com/s/dzeez6i1z7e3z ... m.JPG?dl=0
https://www.dropbox.com/s/tgxddt5iqxm8j ... n.JPG?dl=0

Thank you very much for your kind help.

Best regards,
Summer

[huffte]

Hi Summer. Actually, I don't believe an integration section has a 'length'. It is an infnitely thin slice at a given location along the member. The sketches you made imply an additional section at the midspan of the members, which is not the case. There willonly be an integration section at midspan when the number of section sspecified is an odd number. I hope this helps. More information can be found in the Help System, an excellent tool, in the section 'Theoretical Background and Modeling Assumptions', subtopic 'Material Inelasticity', which you seem to have already found. Best of luck, Summer.

[zhwang]

Dear Huff,

Thank you very much for your kind reply. If when I check the "Peak strains and stresses" in "Post-processor", and found section a and section d occurred yielding of steel, and I would like to show the yielding on the following graph, could you please help me to check whether my understanding is correct?
https://www.dropbox.com/s/w04f6ac35hecu ... 5.JPG?dl=0

If I would like to show the crack of concrete in section b or section c, could you please also help me check?
https://www.dropbox.com/s/mraik8nmeb3cv ... 6.JPG?dl=0

Or no matter section a or section b or section c or section d in "Peak strains and stresses" in "Post-processor" occurred failure, I should mark the whole beam to describe the failure?
https://www.dropbox.com/s/a1h3fpo992oc4 ... 7.JPG?dl=0

If I was wrong, could you please suggest me how to mark the failure modes (yielding of steel, cracking of concrete and crushing of concrete) on beams and columns?

Thank you very much for your help.

Best regards,
Summer

[huffte]

Hi again Summer. I am not certain that I understand your question. But it seems that you are wanting to identify sections where crushing of concrete or yielding of steel occurs. This is easily done in the Performance Criteria specifications of the Pre-Processor. You can specify criteria for either core crushing or steel yielding (or others) for the members you wish to track. Your results file will then show which elements reached the criteria at which specific times and at which sections. I hope this helps. I didn't quite understand your sketches. Best of luck.