TR.24 Element Plane Stress and Ignore Inplane Rotation Specification
These commands allow the user to model the following conditions on plate elements
General Format
ELEMENT { PLANE STRESS | RIG ID ( INPLANE ROTATION ) | IGNORE ( INPLANE ROTATION) }
element-list
The PLANE STRESS specification allows the user to model selected elements for PLANE STRESS action only [No bending or transverse shear stiffness].
The RIGID INPLANE ROTATION command causes the program to connect the corner Mz "in-plane rotation" action to the other corner Mz rotations rigidly. The STAAD plate element formulation normally produces a very soft Mz stiffness that improves the inplane shear deformation. However when the plate Mz is connected to a beam bending moment as the only load path for that moment, then the RIGID INPLANE option may be used to have that element carry the Mz moment to the other joints rigidly to avoid the instability at the beam end. Usually only the elements connected to beams in this manner would have this specification.
The IGNORE INPLANE ROTATION command causes the program to ignore "in-plane rotation" actions. The STAAD plate element formulation normally includes this important action automatically. However, it may be noted that some element formulations ignore this action by default. The user may utilize this option to compare STAAD results with solutions from these programs.
These options are exclusive of each other and also exclusive of element releases. No single element may have more than one of these options.