The full OEM Partial Part Replacement Search page for the 2020 Hyundai Sonata can be viewed on the I-CAR website. This will give you a good understanding of general areas for sectioning or partial replacement. I-CAR does not have permission to show exact locations for sectioning or the procedure itself. However, Hyundai has a paid subscription website with collision repair information.

The front lower and upper rails have partial part replacement procedures available; these are all at factory seams. The installation of the rails specifies adhesive, spot welding, and plug welding. The rear rails can also be partially replaced at factory seams. However, the body repair manual specifies removal of multiple related parts in order to access the rear rail. The trunk floor does not have any OEM procedures for sectioning or partial part replacement.

There are sectioning procedures available for the outer uniside, as well as a single sectioning location for the uniside reinforcement. Installation of the outer uniside specifies the use of adhesive, spot welding, and seam welding with an open butt joint. Full part replacements for the inner uniside components and the rear body panel are the only option.

For additional Hyundai information, check out the Hyundai OEM Information page.

Additional I-CAR Collision Repair News you may find helpful:
Collision Information Website Access: Hyundai
Step-By-Step: Accessing Hyundai Repair Information
What's A Hyundai Front Side Member