Which collapse pattern occurs when the outer walls remain intact and the upper and/or roof structure fail in the middle, offering a good chance of habitable spaces along the outer walls?

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

Answer: (A)

Understanding collapse patterns helps predict where safe, habitable spaces might still exist after a collapse. When the outer walls stay upright while the roof or upper floors fail in the middle, the debris tends to drop straight down toward the center, creating a V-shaped collapse. The intact exterior walls act as stable boundaries, so you often find habitable spaces along those outer lines because the damage concentrates toward the middle rather than along the walls.

This pattern contrasts with a pancake collapse, where floors fail in a stacked, flat manner and walls don’t preserve that outer boundary; a lean-to collapse involves the structure tipping on one side rather than dropping evenly in the middle; and a cantilever collapse features an overhanging portion failing outward, not a symmetrical middle failure with intact exterior walls.