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1616.5.1.2 Vertical Irregularity
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Buildings having one or more of the features listed in Table 1616.5.1.2 shall be designated as having vertical irregularity and shall comply with the requirements in the sections referenced in that table.
Exceptions:
- Structural irregularities of Type 1a, 1b or 2 in Table 1616.5.1.2 do not apply where no story drift ratio under design lateral load is greater than 130 percent of the story drift ratio of the next story above. Torsional effects need not be considered in the calculation of story drifts for the purpose of this determination. The story drift ratio relationship for the top two stories of the building is not required to be evaluated.
- Irregularities of Types 1a, 1b and 2 of Table 1616.5.1.2 are not required to be considered for one-story buildings in any seismic design category or for two-story buildings in Seismic Design Category B, C or D.
IRREGULARITY TYPE AND DESCRIPTION | REFERENCE SECTION |
SEISMIC DESIGN CATEGORYa APPLICATION |
|
---|---|---|---|
1a | Stiffness Irregularity—Soft Story |
9.5.2.5.1 of ASCE 7 | D |
1b | Stiffness Irregularity—Extreme Soft Story |
9.5.2.5.1 of ASCE 7 | D |
2 | Weight (Mass) Irregularity |
9.5.2.5.1 of ASCE 7 | D |
3 | Vertical Geometric Irregularity |
9.5.2.5.1 of ASCE 7 | D, E and F |
4 | In-plane Discontinuity in Vertical Lateral-Force-Resisting Elements |
1620.4.1 9.5.2.5.1 of ASCE 7 1620.2.9 |
D, D, B, C and D |
5 | Discontinuity in Capacity—Weak Story |
1620.2.3 9.5.2.5.1 of ASCE 7 |
B, C and D, D |
- Seismic design category is determined in accordance with Section 1616.
Related Code Sections
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NYC Building Code 2008 > 16 Structural Design > 1620 Earthquake Loads — Design, Detailing Requirements and Structural Component Load Effects > 1620.2 Structural Component Design and Detailing (For Use in the Simplified Analysis Procedure of Section 1617.5)