0.9 OW + 0.6 Superimposed deadload + 0.6W+ 1H

[Alin shair]

I have a question regarding the service combination 7a on 2.4.1 which is 0.6D + 0.6W with having uplift pressure forces on the raft due to water table I will add H which will end the load combination in 0.6D + 0.6W + 1 Uplift .My question is should I change the load combination to be 0.9 OW + 0.6 Superimposed deadload +0.6W + 1H as the own weight is already existed or I can't change it ?

 

[Lomarandil]

The 0.6 factor on dead loads includes both an allowance for the self weight being lower than estimated (10% tolerance -> 0.9) and a 50% "factor of safety" which has traditionally been applied and considered appropriate for global stability checks like sliding, overturning and uplift.

In short, 0.6D is appropriate.

However, when using 0.6D, you do not need an additional "safety factor" for those stability checks.