excel output 1

[akahama]

Hi everyone. Could anyone answer my simple question about excel output? What is the step type of "max" and "min" in the exported excel file for stress? I am applying uniform load on the plate, so how come do I obtain max and min at the grid? (I am not talking about the difference between "top" and "bot"). I will appreciate if anyone can help me! Thank you.

 

[JKStruct]

If I understand your question correctly, I believe the program is reporting an envelope of the max and min principle stresses of the elements. So, for example, if your loading conditions impose stress reversals on an element, it'll report the max positive stress and "max" negative stress under the "min" column. Be careful with your sign convention.

If you seek an envelope of max positive or negative stresses (Tension or Compression, for example), I suggest writing an external Excel script using the ABS() command with the exported data.

 

[akahama]

Thank you very much for your quick reply, JKStruct. What you wrote is exactly what I thought first time (the max positive stress and "max" negative stress under the "min" column). However, I am appliying just uniform, constant (spatiall and timely) loading. So the situation where stress reversals on an element should not be happen, I guess. Therefore, I got stuck.

For example, when applying loading from top to bottom, stress at the center of the plate at bottom side show only max value and min is zero. And the center stress at the top show both max and min values but the abs of min is 1 digit larger than the one of max. This makes sence since the bottom is in tension and the top is in compression.

Do you have any further suggestion? Thank you very much in advance.

 

[JKStruct]

Yeah, without knowing the exact application and the model, it'll be hard to speculate... but i'll try anyway:

In any finite element model, you have to be cognizant of your boundary conditions, restraints, and your element definitions (plate, shell, membrane... etc). If you're modeling a shell element, you could have axial forces imposing compression or tension that in places that you're not considering. Plus, if you're doing a time history analysis, to which you refer, the results will be dependent on the dynamic modal behavior of your modeled structure.

In short, paying special attention to your element definitions and boundary conditions will help you better understand the model.

I suspect you may have pinned joints that would behave differently than if they were rollers, for example.

Also, in SAP, you can specify which degrees of freedom to consider in design... which can offset some of the uncertainty in boundary restraint (try only analyzing Uz if you're only interested in vertical displacements, and don't want to include axial deformations which would influence the vertical displacements)

Sorry if it's not much help... but Good Luck!