Define the Cross-Sectional Properties

First, we will define the cross-sectional area of both sets of beams.

1. Right-click the Element Type heading for Part 1 in the browser (tree view) and select Beam.
2. Double-click the Element Definition heading for Part 1 in the browser. There are two rows in the Sectional Properties table.  They correspond to the two layers in the model. The beams on Layer 1 are the 8x6 angles. The beams on Layer 2 are the 7x4 angles.
   1. Select the second row of the Sectional Properties table and click Cross-Section Libraries.  The Cross-Section Libraries dialog displays, and we can now edit the properties for Layer 1.
      1. Select aisc 14.1 (2013) in the Section database drop-down list.
      2. Select L in the Section type drop-down list.
      3. Select L8X6X1 in the Section name list.  
      4. Click OK.
   2. Select the second row of the Sectional Properties table and click Cross-Section Libraries. We can now edit the properties for Layer 2.
      1. Select aisc 14.1 (2013) in the Section database drop-down list.
      2. Select L in the Section type drop-down list.
      3. Select L7X4X3/4 in the Section name list. 
      4. Click OK.
   3. Click OK to exit the Element Definition dialog box.  

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