Selecting points for curves

There are several methods to select nodes and stress points that can be used for curve generation in the PLAXIS Output program.

Pre-calc vs. post-calc

When having nodes and stress points selected prior to the calculation (pre-calc), PLAXIS will store data for these pre-calc nodes and/or stress points for each calculation step. This data only involves the data for soil/rock elements, not for structural elements or interfaces. Pre-calc points will not store axial forces or bending moments, for instance.
From PLAXIS 3D 2017 and 2D 2018 and newer, there is no limit to the number of selected points: pre-calc nodes (labelled CN_#) and stress points (labelled CS_#).
For PLAXIS 2D 2017 and PLAXIS 3D 2016 and older, the number of selected points is limited: 10 pre-calc nodes (labelled A to J) and 10 stress points (labelled K to T).

For nodes and stress points selected after the calculation (post-calc), the data will be retrieved from the stored result files. By default, a phase will have the Max number of steps stored set to 1, so only the last step for this phase is remembered, hence only the result for this specific step will be shown for the selected post-calc node.

For more detailed curves, make sure to increase this Max number of steps stored to have more intermediate data points in a phase for the generated curve. If the Max number of steps stored is equal to the Max steps value, then all available data will be used for the curve.

Since the data for post-calc points is retrieved from the result step files after the calculation, you can also select as many post-calc nodes and stress points as desired. Note that the Output program will have to read all step data before creating the curve, so if a lot of steps/data is available, this may take some time.
Note that having a lot of results steps saved for each phase will also increase the disk space needed for the project.

The full list of selected curve points can be found in PLAXIS Output by clicking the button  Select points for curves or by running the command:

echo CurvePoints   # shows full list 

The details of each curve point can be found in the side panel or via the command line as shown below:

echo CurvePoints[0]   # zero-based list 
echo CurvePoints[0].Number   # shows the node or stress point number 

Figure 1. Information about curve points in PLAXIS Output

Nodes and stress points selection

To select these Pre-calc nodes/stress points, there are two options:

1. from the Input program, click the button for Select points for curves to start Output and:
   1. click on a node or stress point
   2. use the search closest option by filling in the coordinates

   Remember to click the Update button to store the information and close the Output program

2. use the command as described here: Select points for curves prior to calculation directly in Input

Figure 2. Selection of pre-calc nodes and stress points

Options to select Post-calc nodes and stress points (after calculation):

1. In the Output program, when viewing the results, click the button Select points for curves. Then, use the mouse to select a node (red sphere) or a stress point (purple diamond).
2. Click the button Select points for curves. On the side panel fill in coordinates to find the closest nodes and stress points. After clicking the button to search for the closest, select the appropriate node or stress point.
3. From the Model view, view at least two nodes or stress points in the Model tree (left) by activating the eye icon. Now right-click any node/stress point in the canvas, from the drop-down menu, choose Select for curves and then select the appropriate node.
4. In the curves manager window, choose the Select points tab. Then, fill in the coordinates to find the closest nodes and/or stress points. Now select the node and/or stress point from the results.

Figure 3: Selecting post-calc nodes and stress points, options 1-3

Figure 4: Selecting post-calc nodes and stress points, option 4

Interface and Structural nodes

Any pre-calc structural node will only display the displacements of the structure.

For post-calc structural nodes, there are several options, just as with the general selection of nodes and stress points. When viewing the normal model view (including the soil/rock) it works the same as above with these additions:

• For option 2, the search closest results will show the origin of the date, e.g. Data from Soil or Plate, Interface, etc.
• For option 3, the Select for curves menu items will also display the type of node being selected, e.g., of Soil, Interface, etc.

When viewing the structural plot (e.g. plate results), only the nodes for this structure will be displayed in the selection options.

Notes

• Note that some structural elements do not have a visual plot, e.g., fixed-end anchor and node-to-node anchor. To select these elements to be used for curves, in the general model view, right-click the (structural) node and choose the appropriate option from the Select points for curves option. For a more detailed explanation, see the related article about Creating axial force curve for Fixed End anchors
• When plotting the data vs. Steps, please be aware of the explanation mentioned in the related article about (non-consecutive) step numbers.