A "collapsed building" refers to a structure that has fallen down or caved in, usually due to some sort of structural failure or disaster. Full definition
Culled from an unspecified collection, the two Morris Louis paintings, Beth Samach (1958) and Gamma (1960), play multiple roles: They are asked to represent the ideals and aspirations of a historical moment of great confidence and aspiration, and to model the falling motion of collapsing buildings in their blooming color drags. (dailyserving.com)
A local building official in Utah commented about how disturbed she was to see the twisted strands of rebar (concrete reinforcing steel) in photos of collapsed buildings in this quake and how concerned that made her for «un» reinforced structures. (dotearth.blogs.nytimes.com)
So lots of people were inside the night of April 5, and many were crushed by collapsing buildings. (sciencenews.org)