General Requirements¶

The General Requirements tab contains fundamental wind parameters that apply to all wind load calculations in the module. These parameters establish the baseline conditions for MWFRS and C&C analyses.

Key Features¶

• Support for ASCE 7-10 and ASCE 7-16 code years
• Basic wind speed input with risk category consideration
• Consolidated or direction-specific exposure categories
• Topographic factor calculation for hills, ridges, and escarpments
• Ground elevation factor for high-altitude sites (ASCE 7-16)
• Rigid and flexible building classification
• Enclosure classification with automatic GCpi calculation

Getting Started¶

1. Navigate to the Wind Load module in your structure
2. The General Requirements tab opens by default
3. Enter the basic wind speed for your project location
4. Select the exposure category (or configure by direction)
5. Enable topographic factor if site is on a hill, ridge, or escarpment
6. Configure building flexibility and enclosure classification
7. Proceed to MWFRS or C&C tabs for pressure calculations

Basic Wind Speed¶

The basic wind speed is the fundamental input for all wind load calculations per ASCE 7-16 Section 26.5.1.

1. Enter the basic wind speed value in mph
2. The value represents the 3-second gust wind speed at 33 ft above ground
3. Obtain values from ASCE 7 wind speed maps or local building codes
4. Risk Category determines which wind speed map to use

Exposure Category¶

Exposure category accounts for the ground surface roughness affecting wind flow. The module supports consolidated or separate exposure categories per direction.

Consolidated Exposure¶

By default, a single exposure category applies to all wind directions:

• Exposure B: Urban and suburban areas with numerous closely spaced obstructions
• Exposure C: Open terrain with scattered obstructions, flat open country
• Exposure D: Flat, unobstructed areas exposed to wind flowing over open water

Separate Exposure by Direction¶

Enable direction-specific exposure categories when site conditions vary by cardinal direction.

1. Check Separate exposure category for each direction
2. A confirmation dialog appears explaining the implications
3. Click Confirm to enable separate exposure
4. Configure Ground Surface Roughness and Exposure Category for each direction (N, S, E, W)

Topographic Factor¶

The topographic factor K_zt accounts for wind speed-up effects over hills, ridges, and escarpments per ASCE 7-16 Section 26.8.2.

1. Check Topographic factor, K_zt required to enable topographic calculations
2. Click Add new feature to add topographic features
3. Configure each feature with the parameters below

Topographic Feature Parameters¶

The module calculates K₁, K₂, K₃ multipliers and the resulting K_zt factor for both upwind and downwind conditions. When H/L_h exceeds allowable limits or conditions don't warrant speed-up, K_zt defaults to 1.00.

Ground Elevation Factor¶

The ground elevation factor K_e accounts for reduced air density at high elevations per ASCE 7-16 Section 26.9.

1. Check Include ground elevation factor, K_e to enable the calculation
2. Enter the ground elevation from sea level in feet
3. The K_e factor is calculated automatically

For sites at sea level, K_e = 1.000. Higher elevations result in lower K_e values, reducing wind pressures.

Building Flexibility¶

Building flexibility affects the gust effect factor used in wind pressure calculations.

• Rigid Buildings: Use gust effect factor G = 0.85 (default)
• Flexible Buildings: Require calculation of gust effect factor G_f based on building dynamic properties

1. Check Building classified as flexible if the building's fundamental natural frequency is less than 1 Hz
2. Enter the calculated G_f value per ASCE 7-16 Sections 26.11.3 and 26.11.4
3. G_f accounts for dynamic amplification from wind gusts

Enclosure Classification¶

Enclosure classification determines the internal pressure coefficient (GCpi) per ASCE 7-16 Section 26.13.

1. Select the enclosure classification from the dropdown
2. The Internal Pressure Coefficient (GCpi) updates automatically
3. This value applies to all MWFRS and C&C calculations

Best Practices¶

Wind Speed Selection¶

• Verify basic wind speed from ASCE 7 maps for your Risk Category
• Check with local building officials for higher requirements
• Use the more stringent value when local codes exceed ASCE 7

Exposure Category¶

• Use separate exposure categories when site conditions vary significantly by direction
• Document the basis for exposure category determination
• Consider future development that may change upwind conditions

Topographic Effects¶

• Include topographic factors for buildings on or near hills, ridges, or escarpments
• Verify H/L_h ratios meet requirements for speed-up effects
• Document site survey data supporting topographic inputs

Enclosure Classification¶

• Carefully evaluate glazing and opening sizes for enclosure determination
• Coordinate with architect on location and size of large openings
• Classify conservatively when opening status is uncertain during windstorm

Code Reference¶

General requirements per ASCE 7-16:

• Section 26.5.1: Basic Wind Speed
• Section 26.7: Exposure Categories
• Section 26.7.2: Ground Surface Roughness
• Section 26.8.2: Topographic Factor K_zt
• Section 26.9: Ground Elevation Factor K_e
• Section 26.10: Velocity Pressure
• Section 26.11: Gust Effect Factor
• Section 26.13: Internal Pressure Coefficient