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Serviceability load combinations used by Sizer for deflection design are taken from CSA O86-14 Section 5.2.4.2 inc.Table 5.2.4.2. Section 5.5 on deflection design was also consulted. The NBC does not address this issue, however the following NBC Structural Commentaries have been consulted:
The following table gives the serviceability load combinations used for design for total elastic deflection (CSA O86-14 5.5.2) with the original Sizer Load types D, L, S and W. The comments below the table explain how to extend this to the new load types Ds, Lf/s, H and E.
For the modifications to these combinations to deal with live deflection and permanent deflection (5.5.3) refer to Deflection Design.
Load Type |
Combination |
Case |
D |
1.0D |
1 |
D,L |
1.0D + 1.0L plus D only |
2 |
D,S |
1.0D + 1.0S plus D only |
3 |
D,W |
1.0D + 1.0W plus D only |
4 |
D,L,W |
1.0D + 1.0L + 0.4W 1.0D + 1.0W + 0.5L plus D,L; D,W, and D |
2 4 |
D,L,S2 |
1.0D + 1.0L + 0.5S2 1.0D + 1.0S + 0.5L2 plus D; D,L and D,S |
2 3 |
D,S,W |
1.0D + 1.0S + 0.4W 1.0D + 1.0W + 0.5S plus D; D,S and D,W |
3 4 |
D,L,W,S |
D,L,S; D,L,W; and D,W, S; (no combinations with all of L, S, W) |
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1Note that this creates two extra load cases by splitting up D + S and D + L compared to what is required by the design code.
2These combinations will only be created if not on an exterior surface -refer to the setting for this feature.
Dead Loads Due to Soil
The load combinations for Dead (soil) load types are arrived at by replacing D with D + Ds in this table, without repeating the load combinations for D only. The main Load Combinations page gives a list of serviceability combinations that contain Ds.
Hydrostatic Loads
The load combinations for hydrostatic loads H can be arrived at by adding H to each of these combinations, while also retaining the combinations without H. Refer to Hydrostatic Load Combinations for a list of these combinations and explanation.
Sustained Live Loads Ls and Lf
Sustained live loads are not included in this table. In general, Replace L by L + Ls if such loads occur, with the appropriate factors, without also repeating all of the load combinations that have L only, or creating combinations with Ls only. An exception to the above is that the load combinations D (+ Ds + H) + L and D ( + Ds + H) + Ls will be created.
In other words, for D, L, Ls, S, the following are created:
And the following are not created:
Refer to Sustained Load Combinations for a complete list of sustained load combinations for ultimate limit states design and explanation. These correspond to the serviceability states, with the appropriate change in principal factors, with the following exception:
For the permanent deflection check the program will only check those combinations for which the sustained live load for controlled fluids Lf is the principal load. This will govern over the cases that it is the companion load, as D, Ds, and Lf are generally in the same direction and not oriented as H is. This assumes that controlled fluids on one side of a wall will never be used to resist the lateral pressure of earth and groundwater on the other side.
Earthquake Loads
Serviceability load combinations are not created for Earthquake load types, and deflection design is not done for earthquake load combinations.
Pattern Loads
Serviceability combinations are patterned whenever the corresponding ultimate limit state combination is patterned.
The load types referred to here are D=dead W=wind S=snow H=earth,groundwater E=earthquake L=live(use,occupancy) Ls=live(storage,equipment) Lf =live(controlled fluids) ) Ds=dead load due to soil.