| Application | PLAXIS 3D |
| Issue status | ✔ Solved |
| First Affected Version | PLAXIS 3D 2013.00 |
| Found in Version | PLAXIS 3D 2013.00 |
| Fixed and Released in Version | Solved in a recent version |
| Issue # | 21948 |
| Date created | 29 September 2014 |
| Date modified | 24 October 2016 |
Problem description
When performing a Safety analysis with a Target Factor of Safety (ΣMsf), the calculation will first pass the target value to ensure that this ΣMsf value is a “stable” value before returning to the specified target value, see also the related article for more background information.
However, in PLAXIS 3D 2013, when the calculation jumps back to the calculation step prior to reaching the target value, the force values in the beams and embedded piles are not (re)set to this calculation step (point C in the image below), but are still taken from the step with a higher ΣMsf (point B) before performing the final calculation step (point D). As a result the forces in the beams and embedded piles are not correct for this final step of the Safety analysis with a Target ΣMsf.
Solution
This issue is now solved for PLAXIS 3D AE.00.
For older versions, some work arounds are mentioned below:
Obtain correct force values (workaround for 3D 2013)
To find the correct forces in a beam or embedded pile, the step in which the value for ΣMsf is equal to the value for the Target ΣMsf should be manually determined and then inspected:
when necessary recalculate the phase and make sure to save all steps by setting the Max number of steps stored equal to the number of Additional steps.
- In the phase’s results, find the step in which the desired Target ΣMsf value is reached first. This can be seen in for example the menu option Project > Calculation per step, and then view the tab called Multipliers. ΣMsf can then be found in the last column.
- Open this step:
- In Output phase’s drop down, click on the button to select steps:
- Now, from the list, select the step with the ΣMsf value more or less equal to the target value.
- In Output phase’s drop down, click on the button to select steps:
Continue calculation (workaround for 3D 2013)
To continue phases from this situation with the correct value of ΣMsf:
- check how many steps are needed to get to this target ΣMsf value
- change the Calculation type to Safety analysis with Incremental multipliers (so not Target ΣMsf)
- recalculate the phase with this number of additional steps
- check the ΣMsf value for the last calculation step
- if correct, you can continue from this phase