Design of Pressure Vessel Supports 2

[Zach1]

I am going through the seismic design calculations for a vessel with unbraced legs. The formula for the horizontal force at the CG of vessel is Fh=Ch*W. Similarly the formula for the vertical force at the CG of vessel is Fv=(1+Cv)*W. I cannot find how to calculate the values for Ch and Cv. They are defined as horizontal and vertical seismic factors.

 

[marty007]

Ch and Cv will be functions of your local environment. You need to review local building codes to come up with these values.

In the US, you could reference ASCE 7, in Canada it would be the NBC, but I'm not sure what codes you would use in other countries.

 

[Zach1]

Thanks. I'm not seeing Ch or Cv in ASCE 7. Can I find them anywhere else? So these values aren't calculated they are just tabulated according to location? I'm not necessarily looking for an exact value, but if I knew the range of values in the US, it would be helpful.

 

[RVAmeche]

Equation 13.3-1 in 2005 version is for the Seismic Design Force. This form includes weight; if you divide out the weight you're left with an acceleration term that's called Ch (horizontal).

 

[marty007]

None of the codes I listed would use those exact terms (Ch, Cv). These are horizontal and vertical acceleration parameters.

The codes I listed have formulas for determining something similar, as pointed out by RVAmeche. They will not be tabulated where you can look up a single value.

Some of the factors that would need to be considered:
[ul]
[li]Elevation above grade[/li]
[li]Basic wind speed / reference wind pressure[/li]
[li]Wind exposure category[/li]
[li]Risk category / importance factor[/li]
[li]Site soil conditions (soft sand / bedrock / clay / etc...)[/li]
[li]Spectral response acceleration (various periods of vibration)[/li]
[li]etc...[/li]
[/ul]

 

[Zach1]

Thank you both for the clarification.