structural: Weak story Vs. Soft story



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    Michael Ermann


    This building, damaged in the Loma Prieta earthquake, suffered the “soft-story problem” where the first floor lacks the stiffness of the floors above. When the building begins shaking, the spindly building legs fail. The problem is compounded because it is a corner building, with two storefront sides.

    In that earthquake, six of the seven collapsed buildings in San Francisco’s Marina district were just like this one: four-story tall, corner buildings, with first-floor parking garages.

    To your original question, what is the difference between a “soft story” and a “weak story?” Not much, as far as photo identification is concerned. Soft stories are less stiff than the story above; weak stories are weaker than the story above. Both are common in first-floor-parking or large-bay storefront conditions. I see a lot of chatter online from those worried about understanding the difference between these two. . . this is not worth worrying about as the exam is unlikely to ask you to differentiate them.



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    Tara Torabi

    Thank you so much, Michael!

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