70 - creating and using beam sections

7/28/2019 70 - Creating and Using Beam Sections

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Idealizations Creating and Using Beam Sections – Lecture

CreatingandUsingBeamSections.mp3 Creating and Using Beam Sections

Beam Sections define the area properties of a Beam Idealization.

Beam Section types

Standard

Sketched

General

General Section parameters



Square Rectangle Hollow Rectangle Channel I-Beam L-Section

Diamond Solid Circle Hollow Circle Solid Ellipse Hollow Ellipse

Lecture Notes

Beam Sections

Beam Sections define the area properties of a Beam Idealization. You can specify thecross-section shape from a Mechanica library of common beam cross-section types oryou can create the cross-section in sketcher mode. In either of these cases,Mechanica calculates the 2-D properties of the sections based on geometry. As a thirdoption you can specify the 2-D properties of the area directly using the General

section type.

Beam sections can be created on the fly as needed, or stored and retrieved from alibrary of cross-sections. For more information on managing beam section libraries,see the Mechanica help files.

Standard Beam Section

To use a Standard Beam Section, you select the cross-sectional shape and specify itsdimensions. Standard shapes include: Square, Rectangle, Hollow Rectangle, Channel,I-Beam, L-Section, Diamond, Solid Circle, Hollow Circle, Solid Ellipse, and HollowEllipse.

Sketched Beam Sections

You can sketch the shape of a beam cross-section if necessary for your analysis. Afteryou create the geometry, Mechanica calculates the area's parameters based on the

geometry you sketched. You can sketch two different types of cross-sections:

Solid: With the solid sketched beam section, you use sketch mode to sketch anddimension the cross-sectional shape of the beam. In cases in which thegeometry is not symmetric about the Sketcher coordinate system, there are



provisions for you to be able to specify how far away the shear center is fromthe Sketcher coordinate system (DY and DZ) after the sketch is complete.

Thin: With the thin sketched beam section, you sketch the centerline of thingeometry in sketch mode. You then must use the Sketch > Feature Tools >Thickness command to specify the thickness of the cross-section around eachentity you created in the sketch. This thickness specification can be applied to

any of the entities individually, entities in a chain, or a global definition of thickness can be made for all of the entities in the sketch. The thickness isapplied symmetrically about each entity.

General Beam Sections

For general Beam Sections, instead of selecting or sketching the cross-sectional shapeand having Mechanica calculate its geometric properties, you provide themathematical properties of the cross-section directly. These properties include Area,2D Moment's of Inertia (Iyy, Iyz, Izz), torsional stiffness (J), shear form factors, shearcenter displacements from the parameters, and stress grids.

Stress Grids

In order to retrieve meaningful results, the specific locations inside of a beam cross-section where you wish to recover stress measurements must be specified. Thesepoints are known as beam stress recovery points. Standard sections have thelocations of these points already specified in their definitions. For sketched beamsections, you must manually create a sketcher point in each location where you wishto recover stress measurements for the analysis results. For General beam sections,there are provisions to specify where these points lie in relation to the Beam ShapeCoordinate System.

Best Practices

When using Sketched Thin Beam Sections, the overall characteristic dimension of the

sketch should be 20:1 or greater as compared to the thickness of the entities.

Creating and Using Beam Sections – Demonstration CreatingandUsingBeamSections_demo.mp4

Creating and Using Beam Sections – Procedure Procedure: Creating and Using Beam Sections

ScenarioCreate Beam Idealizations for a welded frame analysis model.

BeamSections frame_beam.prt



Task 1. Enter the Mechanica Application and create Beam Idealizations.

1. Click Applications > Mechanica.

2. Click Beam from the Mechanica toolbar.

3. Press CTRL and select the nine curves references shown.

The yellow direction arrows are not shown in this figure for clarity.

Additionally, they do not matter for this example due to the symmetric

nature of the beam sections you will be using.

4. Click More... next to the Material field. Select steel.mtl from the list of materialsand click Add Material > OK to add steel.mtl to the part and assign it to thebeam.

Task 2. Create two Beam Sections.

1. Click More... next to the Beam Section field to open the Beam Sections dialog box.

2. Click New... to open the Beam Section Definition dialog box.

3. Type OD50_ID46 in the Name field.

4. Select Hollow Circle from the Type drop-down menu.

5. Type 25 in the R field and type 23 in the Ri field. The dialog box should now appear

as shown in the figure.



6. Click OK to close the Beam Section Definition dialog box.

7. Click New... to open the Beam Section Definition dialog box.

8. Type OD25_ID21 in the Name field.

9. Select Hollow Circle from the Type drop-down menu.

10. Type 12.5 in the R field and type 10.5 in the Ri field.

11. Click OK to close the Beam Section Definition dialog box. Click OK to close the

Beam Sections dialog box.

12. Select OD50_ID46 from the Beam Section drop-down list and click OK to

complete the beam definition.

Note the addition of a depiction of the beam section to each of the curves

you selected.

Task 3. Create another Beam Idealization, save the model, and erase it frommemory.



1. Click Beam from the Mechanica toolbar.

2. Select STEEL from the Material drop-down menu

3. Verify OD25_ID21 is selected in the Beam Section field.

4. Select the five remaining curve references from the left side of the model as shown

in the figure.

5. Click OK to complete the beam definition.

6. Return to the Standard Pro/ENGINEER mode by clicking Applications > Standard.

7. Click Save from the main toolbar and click OK to save the model.

8. Click File > Erase > Current > Yes to erase the model from memory.

This completes the procedure.

70 - creating and using beam sections

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