This collapse pattern occurs when the floor and/or roof assemblies on both sides of a center wall collapse into what might be seen as opposing lean-to collapses, offering habitable void spaces on both sides of the center wall.

• A. A-frame collapse
• B. Cantilever collapse
• C. Lean-to collapse
• D. Pancake collapse

Answer: (A)

This pattern tests your ability to recognize how loads fail around a central support to create two opposing, inward tilts. When the floors and roof on both sides of a center wall give way toward that wall, the structure forms two leaning sections that meet or hinge near the center, producing void spaces on both sides. The result resembles an A-frame shape, with each side collapsing inward and relatively stable coordination around the central wall. This is different from a single-side collapse (which would create a lean-to on one side), a pancake collapse (floors piling straight downward), or a cantilever pattern (one side failing while the other tips outward). Understanding this helps you anticipate where voids and potential collapse risks lie and how the center wall influences overall stability.