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Soft first story

The Northridge Meadows apartment building suffered collapse in the Northridge earthquake of 1994. The first floor of the building was mostly open for auto parking under the apartments. The wood frame structure collapsed and the open parking story disappeared.

Which typical soft first story condition existed?
A. flexible first floor
B. discontinuity: indirect load path
C. heavy superstructure

AnswerA. flexible first floor. The first floor was more flexible than the upper floors with a large discrepancy in stiffness.
ARE 4.0 exam prep: SS

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