A contractor is constructing a new 5-story hotel (Group R-1) in an area prone to seismic activity. The building is designed as a Type II-A construction. According to IBC, what is the minimum required wind design speed (3-second gust) for a building in a region with a basic wind speed of 115 mph (185 km/h) and Exposure Category C?
- A130 mph (209 km/h)
- B140 mph (225 km/h)
- C115 mph (185 km/h)
- D120 mph (193 km/h)
Show answer & explanationAnswer & explanation
Correct answer: C. 115 mph (185 km/h)
The question asks for the 'minimum required wind design speed (3-second gust)' based on a 'basic wind speed'. According to IBC Section 1609.3, the basic wind speed, V, for the determination of the wind loads shall be determined from Figure 1609.3(1), (2), or (3). The basic wind speed is the 3-second gust speed. Therefore, if the basic wind speed is given as 115 mph, that is the design speed to be used, before application of other factors (importance factor, exposure, etc.) to calculate wind pressure. The question is specifically asking for the design speed, which is the basic wind speed itself in this context.
Why the other options are wrong
- A. This value would be a result of applying various factors to the basic wind speed, which is not what the question is asking for directly.
- B. This value would be a result of applying various factors to the basic wind speed, which is not what the question is asking for directly.
- D. This value would be a result of applying various factors to the basic wind speed, which is not what the question is asking for directly.
Basic Wind Speed (IBC)
The basic wind speed (V) is the 3-second gust wind speed at 33 feet (10 m) above ground in Exposure Category C, used as the starting point for wind load calculations.
- Determined from IBC Figure 1609.3 maps.
- Represents the 3-second gust speed.
- Used with importance factor, exposure category, and other coefficients to calculate design wind pressures.
Memory trick: Wind speed: Map it out, that's your starting point.