framework of a building; foundation
Literally the structural framework or skeleton of a building, especially the main supporting beams. Often used metaphorically.
古い家の屋台骨が腐ってしまった。
The framework of the old house has rotted.
地震で建物の屋台骨が大きく揺れた。
The building's framework shook violently in the earthquake.
mainstay; backbone; supporting pillar
Figurative use for the central supporting element of an organization, family, or system. Can refer to a person who is the main breadwinner or key figure.
彼は会社の屋台骨を支える存在だ。
He is the mainstay that supports the company.
父が亡くなって、家の屋台骨が傾いた。
After my father passed away, the family's foundation became shaky.