A guide to Load Combinations: AS/NZS 1170:2002
In Australia and New Zealand, the suitable standard for the combination of actions (load combinations) is AS/NZS 1170:2002. The focus of this standard is to provide structural designers with representations of the values for structural design actions. The code is split into 6 parts,
- Part 0: General Principals
- Part 1: Permanent, imposed, and other actions
- Part 2: Wind Actions
- Part 3: Snow and ice actions
- Part 4: Earthquake Loads
- Part 5: Earthquake actions – New Zealand
This article will focus on how SkyCiv’s auto-generated load combinations feature meets the load combination equations as specified in AS/NZS 1170:2002.
4.2.1 Stability
| Design Code Equation | Design Code Comment | SkyCiv Equation | SkyCiv Comment |
|---|---|---|---|
| Ed,stb = [0.9G] | Net Destabilizing: Permanent action only (does not apply to prestressing forces) | 1.35G | SPC: Permanent Destabilizing |
| Ed,stb = [1.35G] | Net Stabilizing: Permanent action only (does not apply to prestressing forces) | 0.9G | SPC: Permanent Stabilizing |
| Ed,stb = [1.2G,1.5Q] | Permanent and imposed action | 1.2G + 1.5QL | ULS: Permanent & Imposed. |
| Ed,stb = [1.2G, Wu, ψc,Q] | Permanent, wind and imposed action | 1.2G + ψ2,1QL + QW | ULS: Permanent, Wind & Imposed. The imposed action factor represented by the psi is determined by the type of QL that this equation acts against. |
| Ed,stb = [1.2G, Su,ψc,Q] | Permanent action, actions given in Clause 4.2.3 and imposed action. | 1.2G + ψ0,3QL + QS | ULS: Permanent, Other, & Imposed. The imposed action factor represented by the psi is determined by the type of QL that this equation acts against. |
4.2.2 Strength
| Design Code Equation | Design Code Comment | SkyCiv Equation | SkyCiv Comment |
|---|---|---|---|
| Ed = [1.35G] | Permanent action only (does not apply to prestressing forces) | 1.35G | Identical to Ed,stb |
| Ed = [1.2G,1.5Q] | Permanent and imposed action | 1.2G + 1.5QL | Identical to Ed,stb |
| Ed = [1.2G,1.5ψlQ] | Permanent and long term imposed action | 1.2G + 1.5ψ1QL | ULS: Permanent & Long-term Imposed. The imposed action factor represented by the psi is determined by the type of QL that this equation acts against. |
| Ed = [0.9G, Wu] | Permanent and wind action reversal | 0.9G + Qw | ULS: Permanent, Wind |
| Ed = [G, Eu, ψc,Q] | Permanent, earthquake and imposed action | G + ψ2,nQL + E | SPC: Permanent, Earthquake & Imposed |
| Ed = [1.2G, Su,ψc,Q] | Permanent action, actions are given in Clause 4.2.3, and imposed action. | 1.2G + ψ0,3QL + QS | Identical to Ed,stb |
4.2.3 Combinations for snow, liquid pressure, rainwater ponding, groundwater, and earth pressure
The actions 4.2.3 relate to snow, liquid pressure, water and earth pressure effects.
4.3 Combination of Actions for Serviceability Limit States
Appropriate combinations may include one or a number of the values for permanent, short-term imposed action, long-term imposed action, wind, earthquake, or other serviceability values of other actions as necessary.
| SkyCiv Equation | SkyCiv Comment |
|---|---|
| G + ψ0,1QL | SLS Permanent and Short-term Imposed |
| G + ψ1QL | SLS Permanent and Long-term Imposed |
Example: All Load Types Assigned
Whilst not practical, 12 load groups have been created and assigned to all 12 load types as seen below. This is done to check the equations that are formed from the load combinations
