Offset a cross section

Video: Offset a beam cross section

This topic describes how to offset a cross section from a 1D mesh.

Note:

When Abaqus is the selected solver, you can offset an I-beam or trapezoidal section using the d or l properties in the section definition. For more information, see Beam Section dialog box.

In this example, suppose the goal is to define an offset to align the cross section with the beam mesh. The beam mesh is aligned with the back wall of the solid geometry.

Solid geometry (1); beam mesh (2); cross section (3)

Select a reference point

You offset the cross section from the beam mesh according to a reference point on the cross section. By default, this point is the section centroid (for ANSYS and LS-DYNA) or the shear center (for Nastran), but you can select a different reference point on the section.

Note:

If ANSYS is the selected solver, the default offset reference point is the section centroid. However, when you solve the model, the software adjusts the offset to be a distance from the section origin, which is how the ANSYS solver expects the offset.

1. In the Simulation Navigator, right-click the 1D mesh and choose Edit Mesh Associated Data.The beam mesh is shown along with a reference line indicating the placement of the section. In the example, there is an existing offset in the Z-axis.

2. In the Mesh Associated Data dialog box, under the Section Offsets group, click Pick point on section .

3. In the Cross Section Preview window, note the default offset reference point represented by a small sphere . To change the offset reference point, select the new point in the Cross Section Preview window.The default offset reference point is (the example shown is for Nastran, which offsets the section to the shear center by default). In this example, it will be easier to align the cross section with the beam mesh if you change the offset reference point to the back wall of the cross section (indicated by ).

4. Click Done .In the graphics window, the new offset reference point is indicated by a small sphere ().

Next, you must specify the target position of the cross section. You can do this graphically by selecting curves, points, or other geometry, or by entering offset values manually.

Specify the offset target point graphically

1. In the Mesh Associated Data dialog box, from the Section Placement Method list, select Graphical.

2. Next to Specify Section Location, choose the appropriate point constructor tool to help you select the point to which the cross section should be offset. For example, click Inferred Point to infer the point by selecting geometry.

3. In the graphics window, select the point to which the cross section should be offset.For example, if you use the Inferred Point tool, on the solid geometry, select the arc circle of the hole ().This selection aligns the offset reference point on the cross section to the center of the hole.

4. (Optional) To apply a different offset to the two ends of the cross section, clear the Offset End B = Offset End A check box. Then, in the End B group, repeat the previous steps to define a separate offset for end B of the section.

5. Click OK to dismiss the Mesh Associated Data dialog box.

Specify an offset by entering values

Instead of using the graphical method described previously, you can enter values to offset the section as a distance in the X, Y, and Z directions of the element coordinate system from the specified point on the section.

1. In the Mesh Associated Data dialog box, follow the steps in Select a reference point.

2. In the Offset to Point on Section group, enter values in model units to offset the section in the X, Y, and/or Z directions of the element coordinate system. Offset Along Element refers to the 1D element X-axis.Note: ANSYS does not support offsets along the element X-axis.

Offset to shear center (Nastran)

If you are using Nastran, you can offset the beam mesh to the cross section shear center in terms of the nodal displacement coordinate system (which is, by default, the absolute coordinate system).

1. In the Mesh Associated Data dialog box, from the Section Placement Method list, choose Language-Specific.

2. Next to Specify Section Location, select the appropriate point constructor tool to help you select the point to which the cross section should be offset, as described in step 2 in the previous section.

3. (Optional) In the Offset in Nodal Displacement CSYS group, enter displacement values in model units to further offset the section in the X, Y, and Z directions of the nodal displacement coordinate system.

4. Click OK to dismiss the Mesh Associated Data dialog box.

How do I

Create a 1D mesh

Beam cross section workflow

Create a standard cross section

Create a cross section from the face of a solid

Create a cross section from a sketch

Create a cross section by entering properties

Assign a cross section to a beam mesh

Define cross section orientation

Improving performance for narrow beam cross sections

Learn more

1D meshing

1D element coating meshes

Ensuring consistent 1D element orientation during mesh creation

Creating beam cross sections

End releases for 1D elements

Displaying beam cross sections

Reusable beam cross sections

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