It is proposed to design an industrial building 12 m high for a 50-year life. The building size is in the range 20 m to 50 m, the topography of the site is practically plain and the terrain is in the city industrial area. If the risk coefficient k₁ = 1, terrain factor k₂ = 0·9, topography factor k₃ = 1 and wind speed Vb = 47 m/s, the design wind pressure at the site will be nearly
- A0·6 kN/m²
- B1·1 kN/m²Correct
- C2·1 kN/m²
- D2·6 kN/m²
Solution
Concept
Design wind speed and pressure
Formula
Vz = Vb k₁ k₂ k₃; pz = 0.6 Vz²
Step-by-step solution
1. Vz = 47 × 1 × 0.9 × 1 = 42.3 m/s. 2. pz = 0.6 × 42.3² = 1074 N/m² ≈ 1.1 kN/m².
Explanation
The design wind speed is the basic speed multiplied by the risk, terrain and topography factors. The pressure is 0.6 times its square.
Why the other options are wrong
0.6, 2.1 and 2.6 kN/m² do not match 0.6 × 42.3².
Shortcut
p = 0.6 Vz² (N/m², V in m/s).
Common mistake
Using Vb directly (would give 1.33 kN/m²).
Correct answer: B) 1·1 kN/m²