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Description |
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1a. Stiffness–Soft Story Irregularity: The case exists where a story has a lateral stiffness is less than 70% of the above story or less than 80% of the average stiffness of the three floors above. |
1b. Stiffness–Extreme Soft Story Irregularity: The case exists where a story has a lateral stiffness is less than 60% of the above story or less than 70% of the average stiffness of the three floors above. |
The case where the effective story mass is more than 150% of the effective mass of the above or below the story. Light roof story need not be considered. |
The case where seismic force-resisting system dimension is more than 130% of that in the above or below story. |
The case where there is a discontinuity in a lateral force-resistance path, such as columns or structural walls are removed at some stories, or the structural walls of upper stories are supported by columns or beams underneath. |
5a. Discontinuity in Lateral Strength–Weak Story Irregularity: The case where in each of the orthogonal earthquake directions, the story lateral strength is less than 80% of that in the story above. |
5b. Discontinuity in Lateral Strength–Extreme Weak Story Irregularity: The case where in each of the orthogonal earthquake directions, the story lateral strength is less than 65% of that in the story above. |
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