A ___ collapse occurs when floor supports fail in a structure causing large sections to drop while one side remains supported.

A ___ collapse occurs when floor supports fail in a structure causing large sections to drop while one side remains supported.

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

Answer: (C)

The pattern being tested is a lean-to collapse, which happens when floor supports fail on one side while the opposite side remains supported. When one edge loses its support, the section of the floor or roof tilts and drops toward the failed side, using the still-supported edge as a pivot. You can picture a floor spanning between supports: if supports on one edge give way, that edge sinks and the whole section leans down on that side, rather than dropping straight down as a whole or collapsing symmetrically. This differs from a pancake collapse, where everything gives way evenly and the floor falls straight down in its plane, and from patterns like a V-shaped or A-frame collapse, which involve different, more symmetrical or inward-towing failure shapes rather than a single-sided drop. Understanding this helps firefighters assess hazards and plan approaches that avoid working under the unsupported, leaning portion.

The pattern being tested is a lean-to collapse, which happens when floor supports fail on one side while the opposite side remains supported. When one edge loses its support, the section of the floor or roof tilts and drops toward the failed side, using the still-supported edge as a pivot. You can picture a floor spanning between supports: if supports on one edge give way, that edge sinks and the whole section leans down on that side, rather than dropping straight down as a whole or collapsing symmetrically.

This differs from a pancake collapse, where everything gives way evenly and the floor falls straight down in its plane, and from patterns like a V-shaped or A-frame collapse, which involve different, more symmetrical or inward-towing failure shapes rather than a single-sided drop. Understanding this helps firefighters assess hazards and plan approaches that avoid working under the unsupported, leaning portion.