Section for Resultant Forces can be defined using any of the three modes described in detail below:
Mode: Select the procedure to define the section-cut planes for resultant forces.
If Structure Group is selected
If Polygon Select is selected
If Elements Select is selected
Note1
Virtual section’s local axis can be displayed from property Tab available under View > Display > Property tab > Virtual Section Local Axis.
Note2 If any change in elements' nodes assigned to virtual section is needed, the user can manually select or deselect the elements or nodes in the model view and click Modify. This will modify the centroid coordinates as per the new virtual section defined. Modify can be used to select or deselect the elements/nodes which is adjacent from the previous virtual section so that the program can automatically detect the new cutting plane.
Note3
The local axis of virtual beam is always oriented along ‘I’ end to ‘J’ end of the virtual sections enclosing the virtual beam. The orientation of local axis of virtual beam must be identical to the local x-axis of virtual section which can be modified using Direction Vector.

Note4 Specifically for curved bridges, users are recommended to use Polygon select mode due to following limitations.
1) Structure group mode may fail to generate the virtual sections when sections lie in a different plane longitudinally due to varying direction vector requirement.
2) Element select option may fail to generate a desired virtual section in case when the selected elements are not in a plane.
Note5 In one virtual section position excepting for the girder start and end, two virtual sections will be automatically generated for i-end and j-end.

 
Section ID 2 for j-end of virtual beam ID 1 Section ID 3 for i-end of virtual beam ID 2
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