Using the Autodesk AutoCAD Structural Detailing - Formwork Drawings module, you can define and modify prefabricated beams with a rectangular cross-section (tapered section):

You can also define positions of the cross-section at the beginning and end of a beam (how the cross-section defined at the beam beginning is positioned at the beam end):
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Some characteristic positions of cross-sections at the beginning / end of a beam |
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An arbitrary position of the cross-section determined by specifying values for parameters A and B. |
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