Which collapse pattern is most susceptible to secondary collapse?

• A. Cantilever
• B. A-frame
• C. Pancake
• D. V-shaped

Answer: (A)

Secondary collapse risk rises when loads are redistributed after the first failure, causing more components to fail. A cantilever pattern leaves a long overhang that is supported by a relatively small portion of the structure. If that supporting element gives way, the overhang loses its support and drops, which dumps extra weight onto adjacent members and can trigger further failures. That chain reaction makes cantilever collapses especially prone to secondary collapse.

In contrast, other patterns distribute loads differently: an A-frame shares weight between two legs, so the failure of one leg doesn’t force the entire structure to lose support in the same way; pancake collapse involves floors dropping vertically onto each other, which often results in a more contained vertical failure with less outward load transfer; and V-shaped collapses involve leaning walls with different load paths, which may not propagate as readily as a cantilever’s outboard section.