A roof in Hawaii's 150 mph wind zone requires uplift resistance. If the roof area is 2,000 sq ft and design uplift pressure is 45 psf, what total uplift force must the connection system resist?
Correct Answer
C) 90,000 lbs
Total uplift force = Area × Pressure = 2,000 sq ft × 45 psf = 90,000 lbs total uplift force.
Why This Is the Correct Answer
Total uplift force = Area × Pressure = 2,000 sq ft × 45 psf = 90,000 lbs. This is a direct application of the pressure-force relationship: Force (lbs) = Pressure (lbs/sq ft) × Area (sq ft).
Why the Other Options Are Wrong
Option A: 112,500 lbs
112,500 lbs would result from multiplying 2,500 sq ft × 45 psf, or using an incorrect area. No basis in the given numbers for this result.
Option B: 135,000 lbs
135,000 lbs would result from multiplying 3,000 sq ft × 45 psf, or using 67.5 psf × 2,000 sq ft — neither matches the given values.
Option D: 67,500 lbs
67,500 lbs would result from using half the area (1,500 sq ft × 45 psf) or halving the pressure (2,000 × 33.75). Some candidates mistakenly think only half the roof resists uplift or apply a 0.75 reduction factor incorrectly.
Memory Technique
Force = Area × Pressure. Think of it like weight on a scale: if 45 lbs pushes on every square foot, and there are 2,000 square feet, that's 45 × 2,000 = 90,000 lbs total. Hawaii's high wind zones make this a critical life-safety calculation.
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