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Model I-Beam

Model Overview

You can model an extrusion using the SimMechanics™ shape General Extrusion. Examples of extrusions include the I-beam and box-beam shapes. In this example, you model a simple solid with I-beam shape using the General Extrusion shape. For an example that shows you how to model a box beam, see Model Box Beam.

Modeling Approach

To represent the I-beam geometry, first identify its cross-section. This is the 2-D area that SimMechanics extrudes to obtain the 3-D I-beam. You can then specify the cross-section coordinates in the Solid block dialog box. The figure shows the I-beam cross-section that you specify in this example.

The [0 0] coordinate identifies the solid reference frame origin. To place the reference frame at the center of the I-beam, specify the coordinates so that the [0 0] coordinate is at the cross-section center. Because the I-beam cross-section is symmetric about the horizontal and vertical axes, you need only define the coordinates for one cross-section half—e.g, the right half. You can then define the left half coordinates in terms of the right half coordinates.

By parameterizing the cross-section coordinates in terms of relevant I-beam dimensions, you can quickly change the I-beam dimensions without having to reenter the cross-section coordinates. The figure shows the cross-section dimensions and coordinates that you must specify to represent the I-beam.

Using the cross-section points that the figure shows, you define the coordinate matrix as:

HalfCS = [A; B; C; D; E; F];
CS = [HalfCS; -HalfCS];

Build Model

Add and connect the blocks to represent the I-beam. Include a Solver Configuration block so that you can visualize the solid in Mechanics Explorer during the modeling process.

  1. Drag these blocks into a new model.

    LibraryBlockQuantity
    Body ElementsSolid1
    Simscape™ UtilitiesSolver Configuration1

  2. Connect the blocks as shown.

  3. In the Solid block dialog box, specify these parameters.

    ParameterValue
    Geometry > ShapeSelect General Extrusion
    Geometry > Cross-SectionEnter CS. Select units of cm.
    Geometry > LengthEnter L. Select units of cm
    Graphic > Visual Properties > ColorEnter RGB

  4. Select the Solid block and generate a new subsystem, e.g., by pressing Ctrl+G.

Specify Parameter Values

In the subsystem mask, initialize the solid parameters. Then, in the subsystem dialog box, specify their values.

  1. Select the Subsystem block and create a subsystem mask, e.g., by pressing Ctrl+M.

  2. In the Parameters & Dialog tab of the Mask Editor, drag five edit boxes into the Parameters group and specify these parameters.

    PromptName
    Length (in)L
    Height (in)H
    Width (in)W
    Thickness (in)T
    Color [R G B]RGB

  3. In the Initialization tab of the Mask Editor, enter the initialization code for the xsection variable and click OK:

    D = H/2-T;
    HalfCS = [W/2, -H/2; W/2, -D; T/2, -D;
    T/2, D; W/2, D; W/2, H/2];
    CS = [HalfCS; -HalfCS];
  4. In the Subsystem block dialog box, specify these parameters.

    ParameterValue
    Length10
    Height4
    Width2
    Thickness0.2
    Color[0.85 0.45 0]

Visualize I-Beam in Mechanics Explorer

You can now visualize the I-beam that you modeled. To do this, on the Simulink® menu bar, select Simulation > Update Diagram. Mechanics Explorer opens with a 3-D display of your model. Rotate, pan, and zoom to explore.

Try modifying the I-beam geometry. To do this, in the subsystem dialog box, change the dimension parameter values. Then, update the model. The figure shows some examples.

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