Liquid storage tank "sloshing" weight

[CTW]

In ASCE 7-05 section 15.7.6, it lists a Wc variable which is defined as the portion of the liquid weight sloshing. Can anyone offer any guidance on how this is calculated?

 

[JStephen]

See AWWA D100-05.

Per Eq. 13-26, Wc = 0.230(D/H) tanh(3.67H/D) WT, where WT is the total liquid weight.

Don't expect AWWA D100-05 (Or API-650 Add. 4) and ASCE 7 to be consistent with each other- they're not exactly in sync with each other.

 

[swearingen]

Also, the API 650 standard gives criteria and calculation methods for earthquake sloshing in tanks.

 

[CTW]

The AWWA equation makes sense, but what's got me puzzled with ASCE 7-05 is that they say the "portion of the liquid", whereas AWWA uses the total liquid. If the total liquid weight is used with ASCE, then the total liquid weight is being used twice to determine the base shear since the impulsive force, Wi, also includes the liquid weight.

By the way, this is not being used to design the tank. Only as a check of the vendors loads supplied for foundation design.

 

[JStephen]

That equation above gives you the convective portion of the liquid. Wt is the total liquid weight, Wc is not.

Wi is the impulsive portion of the liquid, given by a different formula, and is not the total liquid weight, either.