is *Boundary, Fixed option at second steps supported in PrePoMax? i do simple test but the results shown not as expected. It seems some extra definition generates, these lead to discarding the fixed definition.
after remove by commenting few of extra definition in Text editor and rerunning, then shown as expected by combined results of both analysis step.
or, maybe i miss something behind the concept of multi steps analysis in CalculiX?
*BOUNDARY, FIXED is supported in PrePoMax (as it’s added to the input file) but it may interfere with OP=NEW which is always enabled in PrePoMax.
Another thing is that *BOUNDARY, FIXED only makes sense in steps other than first and with non-zero prescribed displacements.
Ooooh. 
You both make my day. That must be the answer why my pretension bolt loses the pretension in the second Step.
At least in Abaqus, it should work also for force-type pre-tension. In the second step you need *CLOAD, OP=NEW and *BOUNDARY, OP=NEW, FIXED. I had a support case where a customer omitted that and the second step resulted in the meme cat effect from the CalculiX forum 
This may also be relevant:
When a pre-tension node is not controlled by a boundary condition, make sure that the components of the structure are kinematically constrained; otherwise, the structure could fall apart due to the presence of rigid body modes.
P.S. I modified my initial reply slightly to avoid the confusion.
indeed, it was available in menus, but some extra keywords generate and lead to discarding.
also, CalculiX does not overwrite as in element type e.g shell S8 to S8R with composite options.
Maybe a simple feature to remove by commenting in ‘Edit Keywords’ is needed for such condition?
Ultimately, it should be possivble to use OP=MOD in PrePoMax but it has already been requested in the past.
Do you mean both toghether, one after the other?
This seems what is happening with my first test where the bolt falls appart.
It’s not always necessary but:
The OP=NEW parameter must be used with the FIXED parameter if there are any other *BOUNDARY options in the same step that have the OP=NEW parameter.
It’s from Abaqus documentation but I assume that it should be the same in CalculiX. However, sometimes such assumptions turn out to be invalid.
i have the same expereinces also, tried different approach in modeling of pretension bolt and further to compare to another methods. However, result of second step seems not combined with previous.
hopefully, there is a workaround to eliminate this problem inside PrePoMax.
Thank you.
Unfortunately, currently the only way is to export the input file and edit it manually.
the step input generate is not hiding and allowed to select, thanks. I do copying the second steps, deactivated in menus and paste in Keyword Editor for minor editing. Currently, only by these methods seems to be possible and done inside PrePoMax.
Is that behavior exclusive of pretension or is any previous Stress State erased on a multi-step analysis?
OP=NEW only affects a given type of feature (*BOUNDARY, *CLOAD and so on). Stress/deformation state may not be preserved in subsequent steps just because the deformation wasn’t permanent (plastic).
I read the whole conversation to figure out what the actual problem is. If the goal is to have a two-step analysis, as was the original question, this is doable. You only have to remember that in the second step, you should have all the forces and boundary conditions from the first step active. If you have only a single load and you add it to the first step and then remove it from the second step, the structure will be unloaded. Any step’s loads and boundary conditions represent that step’s active loads and boundary conditions. All of them.
What about the homogeneous BC defined outside the step. Could they be removed.?
OP=NEW removes them too so you have to respecify them to keep them active.
Where?.
Homogeneous BC go outside the Step. Should them be inbetween the END STEP and second STEP.?
With OP=NEW they are redefined within the step as if they were inhomogenous BCs (just without a non-zero magnitude).
This input deck was generated by Abaqus when I deactivated BC-2 in the second step. BC-1 was automatically respecified in that step. Then I just added CalculiX output requests.
Wouldn’t that second
*Boundary , op=New Override the previous Boundary definitions leaving Set-1 Unconstrained?.
