HTS 7308.90.60Structures (excluding prefabricated buildings of heading 9406) and parts of structures (for example, bridges and bridge sections, lock gates, towers, lattice masts, roofs, roofing frameworks, doors and windows and their frames and thresholds for doors, shutters, balustrades, pillars and columns) of iron or steel; plates, rods, angles, shapes, sections, tubes and the like, prepared for use in structures, of iron or steel:Other: Columns, pillars, posts, beams, girders and similar structural units: Other

The steel, aluminum and copper tariff doesn't apply to “Articles provided for in subdivision (c) of U.S. note 16 to this subchapter that do not contain any aluminum, steel, or copper” (HTS 9903.82.01).

No forced-labor tariff here: products covered by the steel, aluminum and copper tariff (HTS 9903.82.02) are exempt from it.

The steel, aluminum and copper tariff instead adds 10% where this applies: “For derivative articles provided for in subdivisions (c)(ii), (vi), and (ix), at least 85 percent of the aluminum content of the article must be composed of aluminum that was smelted and cast in the United States. For derivative articles provided for in subdivisions (c)(iv), (vii), (x) and (xi), at least 85 percent of the steel content of the article must be composed of steel that was melted and poured in the United States. For articles provided for in subdivision (c)(viii), at least 85 percent of the copper content of the article must be composed of copper that was smelt and cast in the United States. These requirements are cumulative such that a derivative article in more than one subdivision must satisfy each requirement” (HTS 9903.82.06).