Comprehensive comparison of load combinations across ASCE 7-10, ASCE 7-16, and ASCE 7-22, covering strength and serviceability combinations, load factors, and detailed worked examples for each code version with practical applications.
1. Introduction
Load combinations are fundamental to structural design, ensuring that structures can safely resist the most critical combination of loads that may occur simultaneously. ASCE 7 has evolved through multiple editions, with significant changes in load combination philosophy and factors. This comprehensive guide compares load combinations across ASCE 7-10, ASCE 7-16, and ASCE 7-22, providing detailed examples and practical applications.
2. Overview of ASCE 7 Evolution
2.1 Key Changes Timeline
- ASCE 7-10: Introduced strength design load combinations with load factors
- ASCE 7-16: Refined load factors and added new combinations
- ASCE 7-22: Latest edition with updated factors and combinations
2.2 Load Types and Notation
Standard Load Notation:
• D = Dead load
• L = Live load
• Lr = Roof live load
• S = Snow load
• W = Wind load
• E = Seismic load
• H = Lateral earth pressure
• F = Fluid load
• T = Self-straining force
• D = Dead load
• L = Live load
• Lr = Roof live load
• S = Snow load
• W = Wind load
• E = Seismic load
• H = Lateral earth pressure
• F = Fluid load
• T = Self-straining force
3. ASCE 7-10 Load Combinations
3.1 Strength Design Load Combinations
ASCE 7-10 Section 2.3.2 - Strength Design Load Combinations:
1. 1.4D
2. 1.2D + 1.6L + 0.5(Lr or S or R)
3. 1.2D + 1.6(Lr or S or R) + (0.5L or 0.8W)
4. 1.2D + 1.3W + 0.5L + 0.5(Lr or S or R)
5. 1.2D + 1.0E + 0.5L + 0.2S
6. 0.9D + 1.3W
7. 0.9D + 1.0E
1. 1.4D
2. 1.2D + 1.6L + 0.5(Lr or S or R)
3. 1.2D + 1.6(Lr or S or R) + (0.5L or 0.8W)
4. 1.2D + 1.3W + 0.5L + 0.5(Lr or S or R)
5. 1.2D + 1.0E + 0.5L + 0.2S
6. 0.9D + 1.3W
7. 0.9D + 1.0E
3.2 Serviceability Load Combinations
ASCE 7-10 Section 2.4 - Serviceability Load Combinations:
1. D
2. D + L
3. D + (Lr or S or R)
4. D + 0.75L + 0.75(Lr or S or R)
5. D + 0.75W
6. D + 0.75E
7. D + 0.75L + 0.75(Lr or S or R) + 0.75W
8. D + 0.75L + 0.75(Lr or S or R) + 0.75E
1. D
2. D + L
3. D + (Lr or S or R)
4. D + 0.75L + 0.75(Lr or S or R)
5. D + 0.75W
6. D + 0.75E
7. D + 0.75L + 0.75(Lr or S or R) + 0.75W
8. D + 0.75L + 0.75(Lr or S or R) + 0.75E
4. ASCE 7-16 Load Combinations
4.1 Strength Design Load Combinations
ASCE 7-16 Section 2.3.2 - Strength Design Load Combinations:
1. 1.4D
2. 1.2D + 1.6L + 0.5(Lr or S or R)
3. 1.2D + 1.6(Lr or S or R) + (0.5L or 0.8W)
4. 1.2D + 1.0W + 0.5L + 0.5(Lr or S or R)
5. 1.2D + 1.0E + 0.5L + 0.2S
6. 0.9D + 1.0W
7. 0.9D + 1.0E
1. 1.4D
2. 1.2D + 1.6L + 0.5(Lr or S or R)
3. 1.2D + 1.6(Lr or S or R) + (0.5L or 0.8W)
4. 1.2D + 1.0W + 0.5L + 0.5(Lr or S or R)
5. 1.2D + 1.0E + 0.5L + 0.2S
6. 0.9D + 1.0W
7. 0.9D + 1.0E
4.2 Key Changes from ASCE 7-10
Major Changes in ASCE 7-16:
• Wind load factor reduced from 1.3 to 1.0
• Simplified load combination format
• Updated seismic load combinations
• Enhanced serviceability requirements
• Wind load factor reduced from 1.3 to 1.0
• Simplified load combination format
• Updated seismic load combinations
• Enhanced serviceability requirements
5. ASCE 7-22 Load Combinations
5.1 Strength Design Load Combinations
ASCE 7-22 Section 2.3.2 - Strength Design Load Combinations:
1. 1.4D
2. 1.2D + 1.6L + 0.5(Lr or S or R)
3. 1.2D + 1.6(Lr or S or R) + (0.5L or 0.8W)
4. 1.2D + 1.0W + 0.5L + 0.5(Lr or S or R)
5. 1.2D + 1.0E + 0.5L + 0.2S
6. 0.9D + 1.0W
7. 0.9D + 1.0E
1. 1.4D
2. 1.2D + 1.6L + 0.5(Lr or S or R)
3. 1.2D + 1.6(Lr or S or R) + (0.5L or 0.8W)
4. 1.2D + 1.0W + 0.5L + 0.5(Lr or S or R)
5. 1.2D + 1.0E + 0.5L + 0.2S
6. 0.9D + 1.0W
7. 0.9D + 1.0E
5.2 New Features in ASCE 7-22
ASCE 7-22 Enhancements:
• Updated load factors based on latest research
• Enhanced wind load provisions
• Improved seismic load combinations
• New serviceability criteria
• Updated material-specific load factors
• Updated load factors based on latest research
• Enhanced wind load provisions
• Improved seismic load combinations
• New serviceability criteria
• Updated material-specific load factors
6. Detailed Comparison Table
| Load Combination | ASCE 7-10 | ASCE 7-16 | ASCE 7-22 | Key Changes |
|---|---|---|---|---|
| Dead Load Factor | 1.2 (tension), 0.9 (compression) | 1.2 (tension), 0.9 (compression) | 1.2 (tension), 0.9 (compression) | No change |
| Live Load Factor | 1.6 | 1.6 | 1.6 | No change |
| Wind Load Factor | 1.3 | 1.0 | 1.0 | Reduced in 7-16 |
| Seismic Load Factor | 1.0 | 1.0 | 1.0 | No change |
| Snow Load Factor | 1.6 | 1.6 | 1.6 | No change |
7. Worked Examples
7.1 Example 1: Steel Beam Design (ASCE 7-10)
Problem: Design a steel beam for the following loads:
• Dead load: 2.5 kN/m
• Live load: 4.0 kN/m
• Wind load: 1.8 kN/m
• Beam span: 8.0 m
Solution using ASCE 7-10:
• Dead load: 2.5 kN/m
• Live load: 4.0 kN/m
• Wind load: 1.8 kN/m
• Beam span: 8.0 m
Solution using ASCE 7-10:
7.1.1 Load Combination Analysis
Combination 1: 1.4D = 1.4 × 2.5 = 3.5 kN/m
Combination 2: 1.2D + 1.6L = 1.2 × 2.5 + 1.6 × 4.0 = 3.0 + 6.4 = 9.4 kN/m
Combination 4: 1.2D + 1.3W + 0.5L = 1.2 × 2.5 + 1.3 × 1.8 + 0.5 × 4.0 = 3.0 + 2.34 + 2.0 = 7.34 kN/m
Combination 6: 0.9D + 1.3W = 0.9 × 2.5 + 1.3 × 1.8 = 2.25 + 2.34 = 4.59 kN/m
Critical combination: 9.4 kN/m (Combination 2)
Combination 2: 1.2D + 1.6L = 1.2 × 2.5 + 1.6 × 4.0 = 3.0 + 6.4 = 9.4 kN/m
Combination 4: 1.2D + 1.3W + 0.5L = 1.2 × 2.5 + 1.3 × 1.8 + 0.5 × 4.0 = 3.0 + 2.34 + 2.0 = 7.34 kN/m
Combination 6: 0.9D + 1.3W = 0.9 × 2.5 + 1.3 × 1.8 = 2.25 + 2.34 = 4.59 kN/m
Critical combination: 9.4 kN/m (Combination 2)
7.1.2 Moment Calculation
Maximum moment: M = wL²/8 = 9.4 × 8²/8 = 75.2 kN·m
Required section modulus: Sreq = M/Fy = 75.2 × 10⁶/250 = 300,800 mm³
Select: W310×39 (S = 547,000 mm³) ✓
Required section modulus: Sreq = M/Fy = 75.2 × 10⁶/250 = 300,800 mm³
Select: W310×39 (S = 547,000 mm³) ✓
7.2 Example 2: Concrete Column Design (ASCE 7-16)
Problem: Design a concrete column for:
• Dead load: 800 kN
• Live load: 600 kN
• Wind load: 200 kN
• Seismic load: 300 kN
Solution using ASCE 7-16:
• Dead load: 800 kN
• Live load: 600 kN
• Wind load: 200 kN
• Seismic load: 300 kN
Solution using ASCE 7-16:
7.2.1 Load Combination Analysis
Combination 1: 1.4D = 1.4 × 800 = 1,120 kN
Combination 2: 1.2D + 1.6L = 1.2 × 800 + 1.6 × 600 = 960 + 960 = 1,920 kN
Combination 4: 1.2D + 1.0W + 0.5L = 1.2 × 800 + 1.0 × 200 + 0.5 × 600 = 960 + 200 + 300 = 1,460 kN
Combination 5: 1.2D + 1.0E + 0.5L = 1.2 × 800 + 1.0 × 300 + 0.5 × 600 = 960 + 300 + 300 = 1,560 kN
Combination 6: 0.9D + 1.0W = 0.9 × 800 + 1.0 × 200 = 720 + 200 = 920 kN
Combination 7: 0.9D + 1.0E = 0.9 × 800 + 1.0 × 300 = 720 + 300 = 1,020 kN
Critical combination: 1,920 kN (Combination 2)
Combination 2: 1.2D + 1.6L = 1.2 × 800 + 1.6 × 600 = 960 + 960 = 1,920 kN
Combination 4: 1.2D + 1.0W + 0.5L = 1.2 × 800 + 1.0 × 200 + 0.5 × 600 = 960 + 200 + 300 = 1,460 kN
Combination 5: 1.2D + 1.0E + 0.5L = 1.2 × 800 + 1.0 × 300 + 0.5 × 600 = 960 + 300 + 300 = 1,560 kN
Combination 6: 0.9D + 1.0W = 0.9 × 800 + 1.0 × 200 = 720 + 200 = 920 kN
Combination 7: 0.9D + 1.0E = 0.9 × 800 + 1.0 × 300 = 720 + 300 = 1,020 kN
Critical combination: 1,920 kN (Combination 2)
7.3 Example 3: Foundation Design (ASCE 7-22)
Problem: Design a spread footing for:
• Dead load: 500 kN
• Live load: 300 kN
• Wind load: 150 kN
• Snow load: 100 kN
Solution using ASCE 7-22:
• Dead load: 500 kN
• Live load: 300 kN
• Wind load: 150 kN
• Snow load: 100 kN
Solution using ASCE 7-22:
7.3.1 Load Combination Analysis
Combination 1: 1.4D = 1.4 × 500 = 700 kN
Combination 2: 1.2D + 1.6L + 0.5S = 1.2 × 500 + 1.6 × 300 + 0.5 × 100 = 600 + 480 + 50 = 1,130 kN
Combination 3: 1.2D + 1.6S + 0.5L = 1.2 × 500 + 1.6 × 100 + 0.5 × 300 = 600 + 160 + 150 = 910 kN
Combination 4: 1.2D + 1.0W + 0.5L + 0.5S = 1.2 × 500 + 1.0 × 150 + 0.5 × 300 + 0.5 × 100 = 600 + 150 + 150 + 50 = 950 kN
Combination 6: 0.9D + 1.0W = 0.9 × 500 + 1.0 × 150 = 450 + 150 = 600 kN
Critical combination: 1,130 kN (Combination 2)
Combination 2: 1.2D + 1.6L + 0.5S = 1.2 × 500 + 1.6 × 300 + 0.5 × 100 = 600 + 480 + 50 = 1,130 kN
Combination 3: 1.2D + 1.6S + 0.5L = 1.2 × 500 + 1.6 × 100 + 0.5 × 300 = 600 + 160 + 150 = 910 kN
Combination 4: 1.2D + 1.0W + 0.5L + 0.5S = 1.2 × 500 + 1.0 × 150 + 0.5 × 300 + 0.5 × 100 = 600 + 150 + 150 + 50 = 950 kN
Combination 6: 0.9D + 1.0W = 0.9 × 500 + 1.0 × 150 = 450 + 150 = 600 kN
Critical combination: 1,130 kN (Combination 2)
8. Serviceability Considerations
8.1 Deflection Limits
Typical Deflection Limits:
• Beams: L/360 (live load), L/240 (total load)
• Cantilevers: L/180 (live load), L/120 (total load)
• Floors: L/360 (live load)
• Roofs: L/240 (live load)
• Beams: L/360 (live load), L/240 (total load)
• Cantilevers: L/180 (live load), L/120 (total load)
• Floors: L/360 (live load)
• Roofs: L/240 (live load)
8.2 Serviceability Load Combinations
Serviceability Combinations (All ASCE 7 versions):
1. D
2. D + L
3. D + (Lr or S or R)
4. D + 0.75L + 0.75(Lr or S or R)
5. D + 0.75W
6. D + 0.75E
1. D
2. D + L
3. D + (Lr or S or R)
4. D + 0.75L + 0.75(Lr or S or R)
5. D + 0.75W
6. D + 0.75E
9. Practical Design Recommendations
9.1 Load Combination Selection
- Always check all applicable load combinations
- Consider the most critical combination for each design element
- Use appropriate load factors for the specific material code
- Verify serviceability requirements separately
9.2 Common Design Mistakes
Avoid These Common Errors:
• Using outdated load factors
• Ignoring uplift conditions (0.9D combinations)
• Not considering all applicable load types
• Mixing load factors from different code versions
• Neglecting serviceability requirements
• Using outdated load factors
• Ignoring uplift conditions (0.9D combinations)
• Not considering all applicable load types
• Mixing load factors from different code versions
• Neglecting serviceability requirements
10. Code Transition Guidelines
10.1 Upgrading from ASCE 7-10 to ASCE 7-16/22
Key Considerations:
• Wind load factors reduced from 1.3 to 1.0
• Review existing designs for wind-governed cases
• Update design software and spreadsheets
• Train design team on new requirements
• Verify local building code adoption
• Wind load factors reduced from 1.3 to 1.0
• Review existing designs for wind-governed cases
• Update design software and spreadsheets
• Train design team on new requirements
• Verify local building code adoption
10.2 Implementation Checklist
- Review current design procedures
- Update load combination templates
- Modify design software settings
- Train engineering staff
- Update quality control procedures
- Verify compliance with local codes
⚠️ Important: Always Verify with Manual Calculations
Remember: The engineer is always responsible for the accuracy of calculations, regardless of the tools used.
11. Summary and Conclusions
Key Takeaways:
• ASCE 7-16 and 7-22 reduced wind load factors from 1.3 to 1.0
• Dead and live load factors remain consistent across versions
• Seismic load factors unchanged at 1.0
• Serviceability combinations remain similar
• Always use the most current code version for new designs
• Consider all applicable load combinations for each design element
• ASCE 7-16 and 7-22 reduced wind load factors from 1.3 to 1.0
• Dead and live load factors remain consistent across versions
• Seismic load factors unchanged at 1.0
• Serviceability combinations remain similar
• Always use the most current code version for new designs
• Consider all applicable load combinations for each design element
12. Code Reference Section
12.1 ASCE 7-10 Load Combinations (Section 2.3.2)
Strength Design Load Combinations:
1. 1.4D
2. 1.2D + 1.6L + 0.5(Lr or S or R)
3. 1.2D + 1.6(Lr or S or R) + (0.5L or 0.8W)
4. 1.2D + 1.3W + 0.5L + 0.5(Lr or S or R)
5. 1.2D + 1.0E + 0.5L + 0.2S
6. 0.9D + 1.3W
7. 0.9D + 1.0E
1. 1.4D
2. 1.2D + 1.6L + 0.5(Lr or S or R)
3. 1.2D + 1.6(Lr or S or R) + (0.5L or 0.8W)
4. 1.2D + 1.3W + 0.5L + 0.5(Lr or S or R)
5. 1.2D + 1.0E + 0.5L + 0.2S
6. 0.9D + 1.3W
7. 0.9D + 1.0E
12.2 ASCE 7-16 Load Combinations (Section 2.3.2)
Strength Design Load Combinations:
1. 1.4D
2. 1.2D + 1.6L + 0.5(Lr or S or R)
3. 1.2D + 1.6(Lr or S or R) + (0.5L or 0.8W)
4. 1.2D + 1.0W + 0.5L + 0.5(Lr or S or R)
5. 1.2D + 1.0E + 0.5L + 0.2S
6. 0.9D + 1.0W
7. 0.9D + 1.0E
1. 1.4D
2. 1.2D + 1.6L + 0.5(Lr or S or R)
3. 1.2D + 1.6(Lr or S or R) + (0.5L or 0.8W)
4. 1.2D + 1.0W + 0.5L + 0.5(Lr or S or R)
5. 1.2D + 1.0E + 0.5L + 0.2S
6. 0.9D + 1.0W
7. 0.9D + 1.0E
12.3 ASCE 7-22 Load Combinations (Section 2.3.2)
Strength Design Load Combinations:
1. 1.4D
2. 1.2D + 1.6L + 0.5(Lr or S or R)
3. 1.2D + 1.6(Lr or S or R) + (0.5L or 0.8W)
4. 1.2D + 1.0W + 0.5L + 0.5(Lr or S or R)
5. 1.2D + 1.0E + 0.5L + 0.2S
6. 0.9D + 1.0W
7. 0.9D + 1.0E
1. 1.4D
2. 1.2D + 1.6L + 0.5(Lr or S or R)
3. 1.2D + 1.6(Lr or S or R) + (0.5L or 0.8W)
4. 1.2D + 1.0W + 0.5L + 0.5(Lr or S or R)
5. 1.2D + 1.0E + 0.5L + 0.2S
6. 0.9D + 1.0W
7. 0.9D + 1.0E
12.4 Serviceability Load Combinations (All Versions)
Serviceability Load Combinations (ASCE 7-10, 7-16, 7-22):
1. D
2. D + L
3. D + (Lr or S or R)
4. D + 0.75L + 0.75(Lr or S or R)
5. D + 0.75W
6. D + 0.75E
1. D
2. D + L
3. D + (Lr or S or R)
4. D + 0.75L + 0.75(Lr or S or R)
5. D + 0.75W
6. D + 0.75E
12.5 Load Factor Comparison Table
| Load Type | ASCE 7-10 | ASCE 7-16 | ASCE 7-22 | Notes |
|---|---|---|---|---|
| Dead Load (D) | 1.2 / 0.9 | 1.2 / 0.9 | 1.2 / 0.9 | No change |
| Live Load (L) | 1.6 | 1.6 | 1.6 | No change |
| Wind Load (W) | 1.3 | 1.0 | 1.0 | Reduced in 7-16 |
| Seismic Load (E) | 1.0 | 1.0 | 1.0 | No change |
| Snow Load (S) | 1.6 | 1.6 | 1.6 | No change |
| Roof Live Load (Lr) | 1.6 | 1.6 | 1.6 | No change |
12.6 Key Code Sections
Important Code References:
• ASCE 7-10 Section 2.3.2: Strength Design Load Combinations
• ASCE 7-10 Section 2.4: Serviceability Load Combinations
• ASCE 7-16 Section 2.3.2: Strength Design Load Combinations
• ASCE 7-16 Section 2.4: Serviceability Load Combinations
• ASCE 7-22 Section 2.3.2: Strength Design Load Combinations
• ASCE 7-22 Section 2.4: Serviceability Load Combinations
• IBC 2021 Section 1605: Load Combinations
• ACI 318-19 Section 5.3: Load Combinations for Concrete
• AISC 360-16 Section B2: Load Combinations for Steel
• ASCE 7-10 Section 2.3.2: Strength Design Load Combinations
• ASCE 7-10 Section 2.4: Serviceability Load Combinations
• ASCE 7-16 Section 2.3.2: Strength Design Load Combinations
• ASCE 7-16 Section 2.4: Serviceability Load Combinations
• ASCE 7-22 Section 2.3.2: Strength Design Load Combinations
• ASCE 7-22 Section 2.4: Serviceability Load Combinations
• IBC 2021 Section 1605: Load Combinations
• ACI 318-19 Section 5.3: Load Combinations for Concrete
• AISC 360-16 Section B2: Load Combinations for Steel
12.7 Load Combination Notes
Important Considerations:
• Load combinations shall be investigated to determine the most critical effect
• Where effects of differential settlement, creep, shrinkage, or temperature change are significant, they shall be included with the most critical combination
• For load combinations including wind load, the direction of the wind shall be considered
• For load combinations including seismic load, the direction of the seismic force shall be considered
• Where structural effects of differential settlement, creep, shrinkage, or temperature change are significant, they shall be included with the most critical combination
• Load combinations shall be investigated to determine the most critical effect
• Where effects of differential settlement, creep, shrinkage, or temperature change are significant, they shall be included with the most critical combination
• For load combinations including wind load, the direction of the wind shall be considered
• For load combinations including seismic load, the direction of the seismic force shall be considered
• Where structural effects of differential settlement, creep, shrinkage, or temperature change are significant, they shall be included with the most critical combination
13. References
- ASCE/SEI 7-10, Minimum Design Loads for Buildings and Other Structures.
- ASCE/SEI 7-16, Minimum Design Loads and Associated Criteria for Buildings and Other Structures.
- ASCE/SEI 7-22, Minimum Design Loads and Associated Criteria for Buildings and Other Structures.
- IBC 2021, International Building Code.
- ACI 318-19, Building Code Requirements for Structural Concrete.
- AISC 360-16, Specification for Structural Steel Buildings.