Australian Code Load Combinations

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March 13, 2026

Civil and Structural Design Calculations, Engineering Concepts – Civil & Structural

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(For Steel Structures & RCC Buildings)

1. Relevant Australian Standards

AS/NZS 1170.0
AS/NZS 1170.1
AS/NZS 1170.2
AS/NZS 1170.4
AS 4100
AS 3600

These standards define Ultimate Limit State (ULS) and Serviceability Limit State (SLS) load combinations.

1. Ultimate Limit State (ULS) Load Combinations

Used for strength design (collapse prevention).

1. Dead + Live Load

$1.2G + 1.5Q$ 1.2G+1.5Q

Where

G = Dead Load (self weight, finishes, walls)
Q = Live Load (occupancy load)

2. Dead + Live + Wind

$1.2G + 1.5Q + W$ 1.2G+1.5Q+W

or $0.9G + W$ 0.9G+W

Used when wind causes uplift or overturning.

Where

W = Wind load

3. Dead + Earthquake

$1.2G + E + \psi Q$ 1.2G+E+ψQ

or $0.9G + E$ 0.9G+E

Where

E = Earthquake load
ψQ = reduced live load factor

4. Dead + Wind Only

$1.2G + W$ 1.2G+W

For structures where live load is negligible.

2. Serviceability Limit State (SLS) Load Combinations

Used for deflection, cracking, vibration checks.

Basic Combination

$G + Q$ G+Q

With Wind

$G + \psi Q + W$ G+ψQ+W

Where

ψ = combination factor (usually 0.4–0.7 depending on occupancy)

3. Typical Combination Table (Australian Practice)

Combination	Equation
ULS 1	1.2G + 1.5Q
ULS 2	1.2G + W + ψQ
ULS 3	0.9G + W
ULS 4	1.2G + E + ψQ
ULS 5	0.9G + E
SLS 1	G + Q
SLS 2	G + ψQ + W

4. Load Symbols Used in Australian Codes

Symbol	Meaning
G	Permanent load (dead load)
Q	Live load
W	Wind load
E	Earthquake load
ψ	Load combination factor

5. Steel vs RCC – Difference in Australia

The load combinations remain the same, but design standards differ:

Steel Structures

Design using AS 4100

Checks include:

Member capacity
Buckling
Lateral torsional buckling
Connection design

Reinforced Concrete Structures

Design using AS 3600

Checks include:

Flexure
Shear
Crack control
Deflection

Below is a practical structural engineering reference used in real projects based on AS/NZS 1170.0, along with wind from AS/NZS 1170.2 and earthquake from AS/NZS 1170.4. These standards define load factors and combinations used in structural design for buildings.

I will give you two things engineers actually use:

1️⃣ Complete load combination table (20+ combinations)
2️⃣ STAAD.Pro load combination template

1. Load Symbols (Australian Code)

Symbol	Meaning
G	Dead Load
Q	Live Load
W	Wind Load
E	Earthquake Load
ψQ	Reduced live load factor
ULS	Ultimate Limit State
SLS	Serviceability Limit State

Typical ψ factor = 0.4 – 0.7 depending occupancy.

2. Ultimate Limit State (ULS) Load Combinations

(Strength design – collapse prevention)

Comb No	Load Combination
1	1.2G + 1.5Q
2	1.2G + 1.5Q + 0.9W
3	1.2G + 1.5W
4	1.2G + 1.5W + 0.4Q
5	0.9G + 1.5W
6	0.9G + 1.5W + 0.4Q
7	1.2G + 1.3E
8	1.2G + 1.3E + 0.4Q
9	0.9G + 1.3E
10	0.9G + 1.3E + 0.4Q
11	1.2G + 1.5Q + 1.5W
12	1.2G + 1.5Q + 1.3E

3. Wind Direction Combinations

Because wind acts in ±X and ±Z directions, engineers normally include additional combinations.

Comb No	Load Combination
13	1.2G + 1.5Q + 1.5WX
14	1.2G + 1.5Q + 1.5W-X
15	1.2G + 1.5Q + 1.5WZ
16	1.2G + 1.5Q + 1.5W-Z
17	0.9G + 1.5WX
18	0.9G + 1.5W-X

4. Earthquake Direction Combinations

Comb No	Load Combination
19	1.2G + 1.3EX
20	1.2G + 1.3E-X
21	1.2G + 1.3EZ
22	1.2G + 1.3E-Z

5. Serviceability Limit State (SLS)

Used for deflection and cracking checks.

Comb No	Load Combination
S1	G
S2	G + Q
S3	G + 0.7Q
S4	G + W
S5	G + 0.4Q + W
S6	G + E

6. Typical Load Case Definition in STAAD

Example:

LOAD 1 DEAD LOAD
SELFWEIGHT Y -1
FLOOR LOADLOAD 2 LIVE LOAD
FLOOR LOADLOAD 3 WIND +XLOAD 4 WIND -XLOAD 5 WIND +ZLOAD 6 WIND -ZLOAD 7 EQ +XLOAD 8 EQ -XLOAD 9 EQ +ZLOAD 10 EQ -Z

7. STAAD.Pro Load Combination Template

LOAD COMB 101 ULS 1
1.2 1 1.5 2LOAD COMB 102 ULS 2
1.2 1 1.5 3 0.4 2LOAD COMB 103 ULS 3
1.2 1 1.5 4 0.4 2LOAD COMB 104 ULS 4
1.2 1 1.5 5 0.4 2LOAD COMB 105 ULS 5
1.2 1 1.5 6 0.4 2LOAD COMB 106 ULS 6
0.9 1 1.5 3LOAD COMB 107 ULS 7
0.9 1 1.5 4LOAD COMB 108 ULS 8
1.2 1 1.3 7 0.4 2LOAD COMB 109 ULS 9
1.2 1 1.3 8 0.4 2LOAD COMB 110 ULS 10
1.2 1 1.3 9 0.4 2LOAD COMB 111 ULS 11
1.2 1 1.3 10 0.4 2