Inputs
Formula used
- Simplified dynamic pressure:
q = 0.5 · ρ · V² - Code-style pressure:
qz = 0.613 · V² · Kz · Kzt · Kd · (ρ/1.225) - Projected area: solid tower
A = H · B, lattice towerA = H · B · φ - Wind force:
F = q · G · Cd · A - Base moment:
M = F_tower · (H/2) + F_top · z
How to use this calculator
- Enter the site wind speed and pick the correct unit.
- Select a pressure method, then set terrain exposure if needed.
- Fill tower height, face width, and choose the tower type.
- Use typical Cd for quick checks, or enter a verified Cd.
- Add top equipment area if antennas or platforms are present.
- Click Calculate Wind Load to see results above.
- Use Download CSV or Download PDF for records.
Example data table
| Case | Wind speed | Method | Exposure | H (m) | B (m) | Type | Cd | φ | Top area (m²) | Base shear (kN) | Moment (kN·m) |
|---|---|---|---|---|---|---|---|---|---|---|---|
| A | 40 m/s | Code-style | C | 60 | 1.8 | Solid (cyl.) | 1.2 | — | 0 | Calculated by tool | Calculated by tool |
| B | 120 km/h | Simplified | — | 45 | 2.2 | Solid (square) | 2.0 | — | 1.5 | Calculated by tool | Calculated by tool |
| C | 90 mph | Code-style | D | 80 | 3.0 | Lattice | 2.2 | 0.20 | 3.0 | Calculated by tool | Calculated by tool |
Wind pressure behavior on slender towers
Wind action scales with the square of wind speed, so a 10% rise in speed increases pressure by about 21%. The calculator converts your input to m/s, evaluates velocity pressure, and then applies selected factors. At 40 m/s with 1.225 kg/m³ density, simplified dynamic pressure is roughly 980 N/m². Use one consistent wind basis across scenarios.
Terrain exposure and height amplification
Terrain roughness changes how wind speed increases with height. In the code-style option, an exposure factor Kz is estimated from tower height and exposure category, increasing pressure for taller structures. For short towers Kz shifts modestly; for tall towers, small exposure changes can materially affect base shear and overturning moment. Keep the height definition aligned to your standard.
Projected area and structural form
For solid shafts, projected area is approximated as A = H·B, where B is face width or diameter. For open-frame towers, the calculator uses a solidity ratio φ, so A = H·B·φ. A lattice tower with φ = 0.20 has about one-fifth of the solid projected area before Cd and gust effects are applied. Add antennas or platforms as top equipment area.
Drag, gust, and directionality factors
Drag coefficient Cd represents shape and member interaction; gust factor G represents turbulence and dynamic amplification. Directionality and topographic multipliers adjust pressure up or down. The “Use typical” toggle supports quick screening, but final Cd should come from code tables, testing, or supplier data. Use conservative values when uncertainty is high.
Interpreting outputs for design workflow
Base shear totals tower and top equipment forces. Overturning moment uses H/2 for the distributed tower load plus the specified height for appurtenance force. The uniform line load output helps apply a comparable distributed wind in structural models. Exported CSV/PDF outputs support traceable iterations during concept development, bids, and peer review. Choosing kN reports moments in kN·m, matching many analysis packages and simplifying checks during review and design updates.
FAQs
1) Which wind speed should I enter?
Enter the project wind speed required by your governing standard, using a consistent gust duration and return period. If you compare options, keep the same basis for all cases to avoid misleading trends.
2) When should I use the simplified method?
Use it for quick screening, early estimates, or sensitivity checks. For code compliance and terrain effects, select the code-style method and apply project-specific factors defined by your standard.
3) How do I select an appropriate drag coefficient?
Start with typical values for rapid checks, then verify Cd using code tables, wind tunnel data, or manufacturer information. Shape, surface roughness, and member shielding can shift Cd noticeably.
4) What does the solidity ratio mean for lattice towers?
Solidity ratio (φ) is the fraction of the tower face that is blocked by members. Lower φ reduces projected area and force. Use measured member areas or conservative values when details are unknown.
5) How do I include antennas, ladders, or platforms?
Add their combined projected area to “Top equipment projected area,” set a suitable Cd, and specify the height where the force acts. This separates appurtenance force from the main tower load.
6) Are the results ready for final structural design?
Use the outputs for preliminary sizing and documentation. Final design should apply the governing standard’s load combinations, importance factors, dynamic checks, and member-level modeling consistent with your tower system.