Download Prefem - DNV GL

SESAM
Prefem
Program version 7.1
01-JUN-2003
3-49
3.49
Figure 3.49 Automatically calculated eccentricity for L- and I-sections
3.5.4
Thickness
All surfaces for which 2-D elements (membrane, plate and shell elements) are created must be assigned a
thickness. (Surfaces with axi-symmetric elements, however, need no thickness.) The PROPERTY THICKNESS command is used for this purpose. Observe that rather than giving a single value for the thickness, i.e.
a constant value over the surface, a varying thickness can be defined by varying value input; see Section 3.7.
3.5.5
Local Coordinate System for Surface Elements
For most 2-D elements (membrane, plate and shell elements) the local coordinate system is not defined
within Prefem. The local z-axis (surface normal) is implicitly defined by the way the surface was defined:
the right-hand-rule combined with the sequence in which the lines where referred to when defining the surface determines the general direction of the local z-axis. The exact direction of the local z-axis and also the
orientation of the local x-axis and y-axis are determined by the analysis program, e.g. Sestra, depending on
the type of element.
The direction of the z-axis may, however, be reversed by the CHANGE ROTATION-OF-SURFACE and
CHANGE NORMAL-OF-SURFACE commands. Also see Section 3.12.3.
The layered element type, however, require the local coordinate system to be defined, i.e. the orientation of
the local x- and y-axes. This is done by the PROPERTY LOCAL-COORDINATE-SURFACE command.
Note that this command will have no effect for other than layered elements.
3.5.6
Material
The PROPERTY MATERIAL command is used for defining the material types:
• Elastic − for all element types except for sandwich elements