Saddle Analysis on Horizontal Flat head tank using Zick's method 1

[kos1]

This might be turned out to be a silly question, but I could not find any reference anywhere.

Im trying to calculate the Bending Moment at the saddle of flat head horizontal tank using Zick's analysis. In his bending moment equation, he has value called 'H', he defined it as the depth of the head for hemispherical, elliptical, or torispherical. Since my tank has a flat head, would the 'H' value be equal to zero (H=0)?

 

[HTURKAK]

The answer is YES !!

This is the bending moment formula at the saddle ..If you look to the formula , the first term (2Q/(L+4H/3) is the average uniform load . And this formula gives the support moment at the centerline of the vessel.

Alternatively, you may calculate the support moment using statics.

Is the figure in your post snap from ( PV handbook of Henry BEDNAR )?

 

[JStephen]

I would suggest to calculate (or confirm) via statics, as some of that is just confusing as presented.
One thing to note: If you cut a cross section of the tank and sum moments about one side of that cross section to find the moments in the tank shell- there is also a moment due to the hydrostatic pressure variation of liquid across the height of the tank. If you do not include that moment in your calculation, it will throw your calculated moment off. IE, you can't just treat the tank as a beam and find the moments due to vertical loads.

 

[kos1]

@HTURKAK, Thanks for the confirmation. This snap is directly from the Zick's papaer

@JStephen, if the tank has two saddles only, one of the assumption Zick makes on his paper is to treat the tank as beam. His numbers are bit on the conservative side, his method of analysis has become industry best practice.

 

[JStephen]

I was thinking Zick had that figured in, but that's why I say to confirm. He makes a statement about "it can be shown hemispherical ends don't impart a moment to the shell" and I think that's the effect behind that statement.