How to Use Offsets to Combine Beam and Plate Elements

When modeling an assembly that has beam elements attached to plate elements, the nodes of the different element types must match in order to transfer forces during a structural analysis. Therefore, the neutral axis of the beam must be drawn in the same plane as the midplane of the plate. However, the thickness of the plate and the shape of the beam (I-beam, L-beam, tapered beam, etc.) should be taken into consideration. For example, if you want to attach the beam to the top or bottom of the plate, the beam must be offset by half the plate's thickness plus the distance from the beam's neutral axis to the plate's top or bottom surface (see Figure 1).

Figure 1: A beam element is attached to the midplane of a plate element (left). To draw the beam on top of the plate, the beam must be offset by half the plate's thickness plus the distance from the beam's neutral axis to the top of the plate (right).

Within FEMPRO, you can specify an offset for beam elements to accurately model a beam-plate assembly as follows:

• Select one or more beam elements using the "Selection:Select:Lines" command.
• Right click in the display area to access a pop-up menu of options for the selected elements.
• Choose "Add:Beam Offsets..." to access the "Creating nn Beam Offset Objects" dialog.
• Enter values to specify the magnitude of the offset at the I-node and the J-node (see Figure 2).

Note: You can use the "Editor Tools:Show Element Orientation Marks" command sequence to display orientation marks for beam elements, which will let you visualize the I-node and the J-node.

Figure 2: An offset for selected beam elements was specified by using the "Creating 32 Beam Offset Objects" dialog.

The added offsets will then be displayed in the model tree and in the display area as shown in Figure 3. The offsets will also be displayed in the Superview IV Results environment.

Figure 3: The added offsets were displayed graphically. Information about an offset can be obtained by placing the cursor over it.

Thus, the capability to add offsets for beam elements within FEMPRO provides a convenient means for accurately modeling beam-plate assemblies.

For more information about using offsets, see the ALGOR User's Guide.