In light frame buildings that are more than three stories, __________ collapses are more likely than in one- or two-story light frame buildings.

• A. Primary
• B. Secondary
• C. Tertiary
• D. Progressive

Answer: (B)

When a light-frame structure loses a key element, the loads it was carrying must be taken by surrounding members. In taller buildings—more than three stories—the amount of weight above and the number of floors that can be affected by that redistribution are greater, and the connections in wood-frame construction offer limited redundancy. This means the initial failure can push stresses onto adjacent joists, walls, and floor assemblies, causing those elements to fail as well. That sequence, where additional parts fail after the first break, is what we call a secondary collapse. In shorter buildings, there are fewer floors to influence and less potential for those subsequent failures, so the cascade is less likely to involve multiple nearby elements.