Deflection Summary
Limits
| Value | Description | TIA-222-H Limit |
|---|---|---|
| Max horizontal displacement | Tower top sway under service wind | H/200 (common carrier specification — not a TIA-222-H mandated limit) |
| Max twist | Differential displacement between legs | Per antenna manufacturer specs |
Example
A 54m tower: maximum allowable deflection = 54,000mm / 200 = 270mm under service wind.
Reading Deflection Results
- Deflection is reported for service load combinations (unfactored wind)
- Use the Deformed Shape visualization to see the deflection pattern
- Maximum displacement is typically at the tower top
- Check for excessive twist which can misalign antennas
When Deflection Governs
Deflection often governs over strength for:
- Tall, slender towers (high height-to-width ratio)
- Towers with microwave dishes (tight alignment tolerances)
- Towers with top-heavy loading (large antennas near the top)
If deflection exceeds limits but unity check ratios pass:
- Increase leg profile stiffness (higher moment of inertia)
- Consider wider base width
- Add bracing to reduce sway