ASCE 7-22 Load Combination Calculator (ASD & LRFD)
This professional-grade calculator helps structural engineers rapidly evaluate ASCE/SEI 7-22 Chapter 2 load combinations for both LRFD and ASD. Enter nominal load effects in any consistent units; the tool enumerates applicable combinations, evaluates wind and seismic in both directions, and reports the governing (maximum and minimum) results for documentation and design checks.
Results
All evaluated combinations
| Combination | Expression | Value |
|---|
Data Source and Methodology
Authoritative source: ASCE/SEI 7-22 — Minimum Design Loads and Associated Criteria for Buildings and Other Structures, Chapter 2: Combinations of Loads. Published by the American Society of Civil Engineers (2022). Official overview: ASCE/SEI 7-22.
Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.
Notes: This tool summarizes commonly applied LRFD and ASD combinations from ASCE/SEI 7-22 Chapter 2 at a high level. Project-specific modifiers (e.g., directionality, load reduction factors, ρ, Ω0, orthogonal effects, companion loads, importance factors, and serviceability checks) may apply. Always consult the full Standard and project requirements.
The Formulas Explained
LRFD (Strength Design), typical:
1) 1.4D
2) 1.2D + 1.6L + 0.5 X
3) 1.2D + 1.6X + 1.0L
4) 1.2D ± 1.0W + 1.0L + 0.5X
5) 1.2D ± 1.0E + 1.0L + 0.2S
6) 0.9D ± 1.0W
7) 0.9D ± 1.0E
Optional: H and F as applicable (e.g., 1.2D + 1.6H + 1.0L, 1.2D + 1.0F + 1.0L + 0.5S)
Where X ∈ {L_r, S, R}.
ASD (Allowable Stress Design), typical:
1) D
2) D + L
3) D + X
4) D + 0.75L + 0.75X
5) D + 0.6(±W) + 0.75L + 0.75X
6) D + 0.7(±E) + 0.75L + 0.2S
7) 0.6D ± 0.6W
8) 0.6D ± 0.7E
Optional: Include H and F as applicable (e.g., D + H + 0.75L, D + F + 0.75X)
Displayed using LaTeX:
LRFD example: $$U = 1.2D + 1.6L + 0.5X,\quad X \in \{L_r,S,R\}$$
ASD example: $$U_a = D + 0.75L + 0.75X,\quad X \in \{L_r,S,R\}$$
The calculator evaluates each applicable expression with both + and − for W and E, then reports the governing maximum and minimum values.
Glossary of Variables
- D: Dead load (permanent).
- L: Live load (floor live, excluding roof live).
- Lr: Roof live load.
- S: Snow load.
- R: Rain load (ponding where applicable).
- W: Wind effect (the tool evaluates both +W and −W).
- E: Seismic effect (the tool evaluates both +E and −E).
- H: Lateral soil/earth/hydrostatic load effects.
- F: Flood load effect.
- U: Resultant factored load effect (LRFD).
- Ua: Resultant combined effect under ASD.
How It Works: A Step-by-Step Example
Assume the following nominal effects (any consistent units): D=100, L=50, Lr=0, S=30, R=0, W=40, E=0, H=0, F=0.
- Choose LRFD. Evaluate key combinations:
- 1.4D = 1.4×100 = 140
- 1.2D + 1.6L + 0.5S = 1.2×100 + 1.6×50 + 0.5×30 = 120 + 80 + 15 = 215
- 1.2D + 1.0W + 1.0L + 0.5S = 120 + 40 + 50 + 15 = 225
- 0.9D − 1.0W = 90 − 40 = 50 (check both + and −)
- The maximum governing value in this example is 225 from 1.2D + 1.0W + 1.0L + 0.5S.
- Repeat with ASD if needed and compare serviceability combinations accordingly.
Frequently Asked Questions (FAQ)
Do I need to input negative values for uplift or direction?
No. Enter positive magnitudes for W and E. The calculator automatically evaluates both positive and negative directions and uses the controlling result.
Are companion load rules and reductions handled?
The tool captures common “X ∈ {Lr, S, R}” branches and typical companion placements. For advanced provisions (e.g., detailed live-load reductions, orthogonal effects, ρ and Ω0 factors), apply project-specific checks separately.
Can I treat outputs as forces, moments, or reactions?
Yes. The math is unit-agnostic. As long as all inputs represent the same type of effect in consistent units, the resulting U or Ua is meaningful for comparison and design.
What about uplift cases?
Uplift is captured by combinations such as 0.9D ± W (LRFD) and 0.6D ± 0.6W (ASD). If D is small relative to W, the minimum (most negative) result flags potential uplift concerns.
Does the calculator include flood load combinations?
Yes. Where F is provided, flood-inclusive combinations are evaluated in both LRFD and ASD sets as commonly applied in ASCE 7-22 practice.
Is this tool peer reviewed?
Content has been checked against the intent of ASCE/SEI 7-22 Chapter 2. Always verify with the Standard and your authority having jurisdiction.
How do I cite this in my calc package?
Use the “Copy results” button to paste the governing combinations and values. Include the reference “ASCE/SEI 7-22 Chapter 2, Combinations of Loads.”