Sasha:
If you want to use objects, there is a
Wood I-Joist 15 object in the ArchiCAD Library. If you want to use a beam, then you can create your own TJI profile; if you are careful with the Stretch Lines placement, then one profile can be used for various sizes, see in the Help files: Virtual Building > Construction Elements > Place a Wall/Column/Beam with a Complex Profile >
Creating or Editing a Complex Profile Element.
You should add a Signature to your Profile (click the Profile button near the top of this page) with your ArchiCAD version and operating system (see mine for an example) for more accurate help in this forum.
David