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ACI 350.3 and ASCE 7-05

ACI 350.3 and ASCE 7-05

ACI 350.3 and ASCE 7-05

(OP)
Hi,

I am currently designing a concrete tank. Per 4.1 in ACI 350.3, "The walls of liquid-containing structures shall be designed for... dynamic forces in addition to the static pressures." I have already computed the convective, impulsive, and wall lateral forces due to seismic activity. According to the excerpt in ACI 350.3, I am to consider these lateral forces in addition to the static water pressure case. I understand that this static water pressure be considered as a fluid load F. In ASCE 7-05, there are no LRFD load combinations with both F and E, although there is an ASD combination with the two. Why is this? Should I consider this static fluid load as a live load instead?

Thanks

RE: ACI 350.3 and ASCE 7-05

There is a major disconnect between the concrete tank designing industry and ACI (not the 350 committee) and ASCE. Even though it seems that fluid loads meet the criteria of dead loads (easily predictable, not subject to variance), we don't use the 1.4 (or 1.2) load factor. We use 1.7 factor like a live load and then multiply by 1.3 for a load factor of 2.21. ACI 350 has section 9.2.6 that sort of simulates this.
Do not get caught short in tank designs. The forces are immense and relentless. And to add insult to injury, when they fail, they leak.

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