Load Combinations

TowerPlot generates load combinations automatically per TIA-222-H Chapter 2.

Standard Combinations

Load factors per ANSI/TIA-222-H, Table 2-1. Refer to the published standard for authoritative values.

#	Combination	Limit State	Purpose
1	1.2D + 1.0W	Ultimate	Strength check — primary wind
2	0.9D + 1.0W	Ultimate	Uplift check — minimum dead load
3	1.0D + 1.0W	Service	Deflection check — serviceability

Ice Combinations (when ice > 0)

#	Combination	Limit State	Purpose
4	1.2D + 1.0Di + 1.0Wi	Ultimate	Strength under ice + wind
5	0.9D + 1.0Di + 1.0Wi	Ultimate	Uplift check under ice + wind

Seismic Combinations (when seismic is enabled)

#	Combination	Limit State	Purpose
6	(1.2 + 0.2SDS)D + 1.0Eh	Ultimate	Strength under seismic + amplified dead load
7	(0.9 − 0.2SDS)D + 1.0Eh	Ultimate	Uplift check under seismic + reduced dead load

Definitions

Symbol	Meaning
D	Dead load — self-weight of structure + all appurtenances
W	Design wind — full wind speed, no ice
Wi	Wind-on-ice — reduced wind speed per TIA-222-H for iced conditions
Di	Ice dead load — weight of radial ice on all members
Eh	Horizontal seismic force
SDS	Design spectral response acceleration at short periods

Multi-Directional Analysis

Each combination is analyzed for every wind direction:

• Triangular towers: 9 total directions (3 faces × 3 approach patterns)
• Square towers: 8 total directions (4 faces × 2 approach patterns)

This means a triangular tower with ice produces 5 combinations × 9 directions = 45 analysis cases.

Standard Differences

• TIA-222-F (ASD): Unfactored combinations — D + W (wind), D + 0.75Wi + I (ice + wind). No load factors applied.
• TIA-222-G (LRFD): 1.2D + 1.6W and 0.9D + 1.6W. Higher wind load factor than 222-H.
• TIA-222-H (LRFD): 1.2D + 1.0W and 0.9D + 1.0W. Uses 3-second gust speeds with Ke and Ks factors.

The governing case (producing the highest member forces) is automatically identified and reported.