Shear center

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Are loads applied through the section centroid?

Extended Question: When a member is modeled with an insertion point which offsets the section centroid from the chord between end nodes, are loads still applied to the centroid, or are loads applied to the chord from which the member is offset?

Answer: With or without object offset, loads which are applied directly to frame objects are always located in the plane of the section centroid. This alignment with section centroid, in conjunction with insertion-point assignment, enables the modeling of eccentric loading on asymmetrical sections, in which shear center differs from centroid location.

When eccentricity between shear center and object centroid should induce torsion, how is this effect modeled?

Answer: When loading is applied to asymmetrical objects, where the object centroid differs from the shear center, loading still projects through the object centroid. To capture the torsional effect of eccentricity between centroid and shear center, an insertion point should be specified to offset the centroid from the chord between end nodes. The value of this offset should be equal to the eccentricity, and the object should be offset toward the shear center. While loading will still project through the offset centroid, loading will now align with the shear center, and the object will respond relative to the support conditions located at the chord between end nodes, which represents the previous centroid location.