Constraints for shells can be either applied to points or lines. In this example, the constraints are applied to 3 lines of the boundary of the shell.
The contour line AB has a membrane constraint with prescriptions in the directions X and Z for the displacements and theta Y for the rotations (rigid wall).
![]() |
|
Lines CD and DA have symmetry constraints. Their prescriptions are:
|
|
|
In this condition, the local axes have no relationship with the shell local axes defined in the properties section. The GLOBAL option means to prescribe related to the global axes of the problem. This is used in this case. Local axes are used to prescribe the displacement or rotation in a direction not coincident with any of the global axes. The values part of the condition is used to prescribe a fixed amount of displacement or rotation. Default units are meters for the X, Y and Z displacements and radians for the prescribed rotations. In this case, the prescribed displacements and rotations are all zero.
X Constraint, Y Constraint and Z Constraint mean the displacements along the axes. Theta x Constraint, theta y constraints and theta z constraints mean the rotations around the axes. Signs are as follows (right hand rule):
![]() |
|
This condition must be assigned to the lines described in the picture. In all cases, the prescribed displacements and rotations are zero.