Wind Velocity Pressure Calculation

Mediumwindvelocity pressure

Wind velocity pressure is given by qz = 0.00256 Kz Kzt Kd V² (qz in psf, V in mph). For this case Kz = 0.90, Kzt = 1.0, Kd = 0.85 and V = 120 mph. No other factors apply. Find qz.

A0.235 psf
B28.20 psf
C5.64 psf
D33.18 psf

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Answer: B. 28.20 psf

Equation: qz = 0.00256 Kz Kzt Kd V². Inputs: factor product = 0.90(1.0)(0.85) = 0.765; V² = 120² = 14,400. Substitution: qz = 0.00256(0.765)(14,400) = 28.20 psf. Wrong: 0.235 psf forgets to square V (0.00256·0.765·120); 5.64 psf inserts V in m/s (53.6) although the constant is tied to mph; 33.18 psf drops Kd (0.00256·0.90·14,400). This is velocity pressure before pressure coefficients.

q_{z}

= 0.00256 (0.90) (1.0) (0.85) (120)^{2}

= 0.00256 (0.765) (14400)

= 28.20

psf

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Wind Velocity Pressure Calculation

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