WorksheetsEQ Irregularity
Total questions: 8
Worksheet time: 4mins
A mid‑level storey has stiffness 0.65 times that of the storey above and 0.78 times the average stiffness of the three storeys above. How should it be classified?
Indeterminate without dynamic analysis results
Not soft story because both checks are satisfied
Soft story because it violates only the 70% rule
Not soft story because one check is satisfied
Soft story because it violates both code checks
During a retrofit assessment, you estimate stiffness ratios for a target storey relative to the one above as 0.74, and relative to the average of the three above as 0.85. Which action best aligns with soft‑story mitigation priorities suggested by observed failure patterns?
Ignore this storey because upper drifts are larger
Prioritize strengthening because it fails the stricter 70% check
Monitor only because it passes the 80% average check
Defer action because collapse patterns are uncommon
Reduce mass only because stiffness criteria are marginal
A 12‑story building has typical story mass of 500 tons. The 7th story includes a heavy transfer slab raising that story’s effective mass to 780 tons. All other stories remain at 500 tons. Does this meet a vertical mass irregularity criterion, and why?
No, because mass irregularity requires 200% mass increase
No, because penthouse exclusion eliminates mid‑story checks
Yes, because 780 exceeds 130% geometric offset limit
Yes, because 780 exceeds 150% of adjacent story mass
A tower steps back at the 10th floor, reducing one horizontal plan dimension from 30 m to 22 m while the other remains 30 m. Evaluate if a vertical geometric irregularity exists using a horizontal dimension ratio rule and note any common exclusion.
Yes, ratio 22/30 violates a 0.7 geometric limit and penthouses are excluded
No, ratio 22/30 exceeds a 0.5 limit and penthouses are excluded
Yes, ratio 22/30 violates a 0.5 geometric limit and roofs are excluded
No, ratio 22/30 exceeds a 0.7 limit and basements are excluded
A mid-rise building has a shear wall that steps in-plane by 1.5 m at the second story, forcing diaphragm shear to transfer through a collector into a shorter wall line. Which design action best reduces the risk associated with this in-plane discontinuity during seismic loading?
Reduce base shear by assuming higher ductility class
Increase floor mass to damp out torsional demand
Remove collectors so shear redistributes to frames
Provide continuous wall with reduced offset length
An eight-story moment frame has the first story columns designed for only 70% of the total story shear that upper stories can resist because of large openings at ground level. During a design review, you must judge if this is a capacity discontinuity. Which reasoning is most appropriate?
Yes, discontinuity occurs when diaphragm stiffness decreases
No, capacity is governed by mass, not lateral strength
Yes, weak story exists when story strength is significantly lower
No, upper stories stronger offsets lower story yielding
A building’s plan shows maximum transverse storey drift at one edge is 1.2 times the average storey drift across the diaphragm when accidental torsion is included. Using the 1.2 drift ratio limit for torsional irregularity, what conclusion should you draw about plan Type 1 irregularity and why?
It is indeterminate because accidental torsion is excluded from checks
It is torsionally regular because average drift controls diaphragm design
It is not torsionally irregular because drifts are exactly balanced
It is torsionally irregular because edge drift exceeds average by 20 percent
You are checking torsional effects for a diaphragm with unbalanced resistance between two sides. Accidental torsion is applied, and measured edge drifts along the transverse axis are 25 mm and 18 mm. The average storey drift is 20 mm. Based on the 1.2 limit, which action best addresses plan irregularity risk?
Remove accidental torsion because it is a conservative load
Reconfigure lateral elements to reduce edge drift to ≤ 24 mm
Increase gravity framing stiffness along longitudinal axis
Ignore unbalanced resistance because average drift is acceptable
