ASCE7 and ACI 318 load combinations 1

[rlmpellc]

ASCE7-10 list load combinations in section 2.4.1 as:
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 + (0.6W or 0.7E)
6a. D + 0.75L + 0.75(0.6W) = 0.75(Lr or S or R)
6b. D + 0.75L + 0.75(0.7E) + 0.75S
7. 0.6D + 0.6W
8. 0.6 D + 0.7E

ACI 318-11 requires entering service loads with factors as:

1.4D (9-1)
1.2D + 1.6L + 0.5(Lr or S or R) (9-2)
1.2D + 1.6(Lr or S or R) + (1.0L or 0.5W) (9-3)
1.2D + 1.0W + 1.0L + 0.5(Lr or S or R) (9-4)
1.2D + 1.0E 1.0L 0.2S (9-5)
0.9D + 1.0W (9-6)
0.9D + 1.0E (9-7)

So, would the service load for wind be 0.6W in (9-6) and then 0.75(0.6) in (9-4)?

The spreadsheet for this situation is getting cumbersome.

 

[Celt83]

The ASCE 7-10 and ACI 318-11 combinations expect that Wind and Seismic loads being used in the combination are ultimate level loads.

Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

 

[JAE]

rlmpellc,
I think you have it wrong on the ACI load combinations - those are from Chapter 9 of ACI 318-11 and are factored load combinations.
The wind load from ASCE 7, as Celt83 states, is an ultimate wind load.

Thus, ASCE 7 ASD load combinations reduce the wind to a service level using the 0.6 factor.
ASCE LRFD load combinations do not do so - i.e. 1.0W.

For ACI, note that the wind factor is 1.0 - i.e. the wind is already factored from ASCE 7.

ACI no longer directly adopts ASD design but for checking serviceability you would and should use 0.6W to drop the ultimate wind to a service level for deflection checks.

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