To calculate wind load on Pipe racks, open structures, cable trays and pipes as per ASCE 7-10, use the following approach, accounting for the cylindrical shape and exposure to wind.

1. Determine Basic Wind Speed (V)

• Obtain wind speed (V) in meters per second (m/s) from ASCE 7-10 maps, converting as needed.

2. Calculate Velocity Pressure (q)

• The velocity pressure q(z) at a height z in kPa (kiloPascal) can be calculated as: q(z)=0.613×Kz×Kzt×Kd×V²

where:

• 0.613   = conversion factor to metric (in kPa) for air density,
• V         = basic wind speed in m/s,
• Kz       = velocity pressure exposure coefficient (from ASCE 7-10 Table 27.3-1),
• Kzt      = topographic factor,
• Kd       = wind directionality factor.

3. Exposure Category

• Define Exposure Category (B, C, or D) based on the surrounding terrain, as this influences Kz​ values.

4. Calculate Projected Area (A)

• Use the projected area per unit length of the cable tray or pipe:

A=D×L

where:

• D = outer diameter of the pipe or effective width of the cable tray (m or ft),
• L = length of the pipe or cable tray (m or ft).

5. Calculate Wind Load (F)

• The wind force per unit length on the pipe or cable tray can be calculated as: F=q(z)×Cd×A

where:

• F          = wind load per unit length (kN/m or lb/ft),
• q(z)     = velocity pressure at height zzz,
• Cd​       = drag coefficient,
• A         = projected area per unit length.

6. Consider Combined Effects

• For long runs of cable trays or pipes, consider gust factors and structural sway, especially if elevated.

Design of wind load calculation as per ASCE 7-10.xls – download as Excel Spreadsheet (.xls), PDF File (.pdf), Text File (.txt) or read online for free on our blog spot.