The kanji 架 primarily conveys the idea of something that is 架 or constructed, built, or supported. It often implies a structure that spans a space or provides a framework. It can refer to a literal structure like a bridge or a shelf, or a more abstract concept like setting up a plan.

・On-yomi (音読み): カ (ka) ・Kun-yomi (訓読み): か (ka) - to construct, to set up, to put up

⚫︎架空（かくう） Translation: fictitious; imaginary; unreal. ⚫︎架橋（かきょう） Translation: bridging; building a bridge. ⚫︎書架（しょか） Translation: bookshelf; book rack.

I am sorry, but I do not have enough information to explain the correspondence with Vietnamese.

The kanji 架 is a phono-semantic compound (形声文字 けいせいいもじ). The left side is 木 (ki, tree or wood) which serves as the semantic component, indicating that the kanji has to do with something made of wood or related to construction. The right side is 加 (ka, to add), which is the phonetic component, providing the sound. It originally represented a structure made of wood, such as a bridge or a shelf. Over time, the meaning expanded to include a wider range of constructions and supports.