Page Comparison

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.

1. Weight (Mass) Irregularity:

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.

1. Vertical Geometric Irregularity:

The case where seismic force-resisting system dimension is more than 130% of that in the above or below story.

1. In-Plane Discontinuity in Vertical Lateral Force-Resisting Element Irregularity:

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.