When one or more wall of a multistory building collapses, leaving the floors attached to and supported by the remaining walls, the pattern is most vulnerable to secondary collapse. Which collapse is described?

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

Answer: (A)

When walls fail but the floors stay attached to and supported by the remaining walls, the structure is effectively using a wall as a cantilever. The floors project outward from that intact wall, creating a cantilevered section that is highly vulnerable to progressive failure. If the cantilever loses its support or the wall begins to fail, the floors can drop, triggering additional collapse in the surrounding structure. This pattern of collapse—where a portion of the building is supported by a single wall and fails in a progressive, beam-like way—is called a cantilever collapse.

Pancake collapse would involve floors dropping onto each other in a stacked fashion, without the single-wall cantilever effect. Lean-to and V-shape collapses describe tilting or inward/outward leaning patterns, not the scenario where floors are anchored to a remaining wall and fail progressively as a cantilever.