Wind load inputs appear in the Viento card on the main design form. They apply to all vessel types — vertical columns, horizontal vessels, and spherical vessels — though the effective projected area differs by geometry.
Wind Zones
The Wind Zone (auto) selector classifies the site into one of three hazard levels. If you do not enter a direct wind value, PSI uses the selected zone to look up a reference wind speed and compute design pressure internally.| Zone | Hazard Level | Typical Use Case |
|---|---|---|
| Zone 1 | Low wind exposure | Inland sites, sheltered areas, low-speed regions |
| Zone 2 | Moderate wind exposure | General onshore industrial sites |
| Zone 3 | High wind exposure | Coastal areas, elevated sites, high-speed wind corridors |
Parameters
Wind Zone (auto)Selects the nominal wind hazard zone for the site. Valid options are Zone 1, Zone 2, and Zone 3, corresponding to low, medium, and high wind exposure respectively. PSI uses this zone to derive a reference wind speed when no explicit wind value is provided.
Wind Value (optional)A direct wind speed or wind pressure override for the site. When provided, this value takes precedence over the zone-based lookup.
- SI units: enter in m/s (wind speed) or kPa (design wind pressure)
- US units: enter in mph (wind speed) or psf (design wind pressure)
Exposure CategoryDescribes the surface roughness of the terrain surrounding the site, which affects the wind velocity profile with height. Select B, C, or D per ASCE 7 Section 26.7.
Importance FactorA multiplier applied to the design wind pressure to account for the consequence of structural failure. Higher values increase the design load and result in more conservative support sizing. Typical values range from 0.87 to 1.15 depending on the risk category of the facility.
Exposure Categories
The exposure category governs how quickly wind speed increases with height above the ground. Select the category that best describes the upwind terrain for a distance of at least 1500 ft (457 m) in any direction.| Category | Terrain Description | Typical Examples |
|---|---|---|
| B | Urban and suburban areas, wooded terrain, or closely spaced obstructions | Residential neighborhoods, industrial parks with dense structures |
| C | Open terrain with scattered obstructions generally less than 30 ft (9 m) high | Flat open country, grasslands, some coastal areas |
| D | Flat, unobstructed areas and water surfaces | Coastlines, lakefronts, tidal flats, open water within 600 ft (183 m) |
Exposure Category D produces the highest wind pressures for a given speed because there is minimal terrain roughness to slow the wind near the ground. Coastal and offshore facilities typically use Category D.
Auto Zone vs. Manual Wind Value
PSI supports two workflows for wind load definition: Auto Zone workflow — Select a Wind Zone (1, 2, or 3) and let PSI derive the reference wind speed. This is appropriate when:- The project location maps cleanly to a hazard zone
- No project-specific wind study has been performed
- You are doing preliminary sizing or feasibility estimates
- A licensed meteorological study defines the site wind speed
- Local code or permit authority specifies a required design wind
- The site is in a complex topographic area (valley, ridge, escarpment) requiring a correction factor