Service Load Combinations for ACI 350-06

[tngolfer]

Q1: What load combinations do you all use when checking foundations for structures at a water treatment plant or waste water treatment plant? ACI 350 only lists ultimate load combinations in 9.2.1 and 2006/2009 IBC does not list F loads in Eq. 16-14 or 16-15 where the dead load is reduced. For an unbalanced wall this load case would basically control overturning.

Q2: Which building code references ACI 350? It is not listed in IBC, Ch. 35 - Referenced Standards.

 

[JedClampett]

A2. ACI 350 should be technically referenced in IBC. Alternatively, it could be included by local code. I'm guessing that if every specialty structure had its code referenced in IBC, it would just get too unwieldy. Even though it's not referenced, it's the best available information and guidance, so you need to use it.
A1. For foundations and overturning, plain working stress level loads are used. A 1.5 factor of safety is traditionally used for overturning and more importantly, sliding. Working stress loads are used since the soil capacities are usually given at allowable levels, not factored.

 

[tngolfer]

JedClampett, thanks for the answer to Q2. I agree it's the State of the Art literature on designing environmental structures and why not use it. I was just curious if anyone references it to make it legally adopted. Reason I was asking is that I read an article in one of my engineering magazines where the structural engineer got in trouble for using load combinations that were not listed in the adopted building code. I was wondering if this is a similar case since IBC does not reference ACI 350.

I'm not sure if your response to my Q1 is relevant. I agree 100% that I need to use working stress loads. My question is in regards to which Load Combinations to use. ACI 350 does not give working stress load combinations and IBC does not include Fluid Loads in theirs.

 

[JedClampett]

Working stress is one times everything. If you have a fluid load, you calculate the shears, moments and reactions based on a factor of one.