EPA Tables
The EPA tab in the bottom panel shows Effective Projected Area per section and wind direction.
Columns
| Column | Description | Unit |
|---|---|---|
| Section | Section number (1 = bottom) | — |
| Height | Section elevation range | m |
| Gross Area | Total face area of the panel | m² |
| Af (flat) | Projected area of angular/flat members | m² |
| Ar (round) | Projected area of round members | m² |
| Solidity Ratio | (Af + Ar) / Gross Area | — |
| Cf | Force coefficient per TIA-222-H Table 2-8 | — |
| Rr | Round member reduction factor | — |
| Df, Dr | Direction factors for flat and round members per Table 2-7 | — |
| EPA | Effective Projected Area | m² |
| qz | Velocity pressure at section midpoint | N/m² |
| FST | Design wind force = qz × Gh × EPA | kN |
Per Wind Direction
EPA is reported separately for each wind direction:
- Triangular: 9 total directions (3 faces × 3 approach patterns)
- Square: 8 total directions (4 faces × 2 approach patterns)
The governing direction varies by section — bottom sections may be governed by 0° while upper sections (with antennas) may be governed by the direction facing the antennas.
What to Look For
- High solidity ratio (> 0.3) — section has a lot of steel, consider lighter bracing
- EPA spikes at specific sections — usually where antennas are mounted
- FST distribution — forces should generally decrease from bottom to top (wider base = more area, but also higher qz at top)