KanjiJLPT N1
Frame

erect, frame, mount, support, shelf, construct

Mnemonic

You add a tree trunk stretched across two posts to frame a bridge. The long tree spans the gap perfectly, and you keep adding more timber on top, building a sturdy frame that holds everything steady above the crossing.
Additional thoughts
Add (加) sits on top of Tree (木) in the kanji. Picture adding planks onto a tree base to erect a spanning frame. The tree is raw material; the act of adding transforms it into a purposeful structure.
Quick recall
Add a tree across the gap to frame a bridge.

Details

The keyword for 架 is frame. This kanji conveys the idea of building a structure or frame that spans across a space, such as a bridge, shelf, or rack. It carries the sense of constructing something that supports or holds objects up, often by stretching across two points. By extension, it can also refer to setting something up or erecting a structure, emphasizing the act of bridging or mounting.
On'yomi
Kun'yomi
か.ける、か.かる