When having multiple surfaces on the same location in PLAXIS 3D’s structure mode, the program will merge these surfaces when going to one of these modes: mesh mode, water mode and staged construction mode. When conflicting items are defined, PLAXIS 3D takes the settings from the first defined surface: this can include different surface load values on these overlapping surfaces, or when both surfaces have been defined as a plate and the assigned plate material is not the same.Usually this is not a big issue since it can be changed easily in the phases: e.g. change a material assignment to a plate, or change the load values in the appropriate phase.
However, one item that cannot be changed in the staged construction mode, is the definition of the local axis direction. For any local axis dependent parameter, this can become a problem then. Some examples when this can go wrong:
Users are advised to check the direction of the local axis after the intersection and in the staged construction when defining the phases.
This has been fixed since PLAXIS 3D AE.00: when surfaces overlap with a conflicting local axis definition, the program will give a warning to the user when going from one of the blue modes (Soil/Structures) to one of the green modes (Mesh/Flow conditions/Staged construction). Now it is easy to inspect these differences and judge if the local axis definition is still correct.
To avoid this in PLAXIS 3D 2013 or earlier: