The internal forces and capacities of a beam are calculated with respect to the cross-section center of gravity. This test problem studies the modeling of a rectangular and continuous beam which is solid along the left segment and hollow along the right. This void is located along the bottom of the element.

Default insertion-point settings locate each segment such that the center of gravity aligns with the element chord. As shown in the image at the top of Figures 1-4, this results in misalignment between each segment because the center of gravity is higher for the hollow section. This may be corrected through either of the following methods:

  1. Draw element chords to account for the difference in center-of-gravity location, as shown in the middle image of each figure.

  2. Use a bottom-center insertion point to draw the two segments along the same line as shown in the bottom image of each figure.




To demonstrate how each of these conditions affects response, a straight tendon is modeled below each beam. Tendon deflection and internal moment (relative to cross-section centroid) is presented. Results are correctly reported only for the second and third case, where the solid and hollow sections properly align.



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