rectangular tank design

[SJOT]

Hey guys, how's it going?

I have an issue that came up today at work. I have been doing a design of a cistern wall using a procedure in a document of the PCA. But later found out that I could also analyze that wall like a cantilever beam, since its behaviour tends to be like that.

The PCA method shows higher values of bending moment at the base than the cantilever beam approach. But i think its wrong because the second case is supposed to be the worst case scenario. What do you think I should do?

PS. I attached the pdf i used to base my structural analysis. (I Cant use a program because in my workplace at the moment dont have enough licenses for everybody).

 

[HTURKAK]

- Which procedure ?

- The assumption of cantilever beam is worst case scenario..









I cannot give you the formula for success, but I can give you the formula for failure..It is: Try to please everybody.

 

[SJOT]

The method works like this.

There has been numerous experiments of structural analysis on rectangular tanks done on the sap90. Then, it gives out a whole load of charts that have coefficients, in accordance to the height/width ratio and its supports, are used to calculate the bending moments. Now, if you calculate the moments based on this approach it tends to be higher than assuming it like a cantilever beam...

I also thought the same, how is it possible that this gives out even higher moments than the beam case.

 

[JLNJ]

Worse than a pure cantilever? Not possible given the same loading.

Usually there are many combinations of fixed/free/pinned on the four sides and uniform vs increasing pressures to consider. Sometime when looking at the tabular values from various sources it's tough to compare apples to apples.

 

[JLNJ]

Also, some tables were developed for steel plates and some for concrete. Poisson's ratio comes into play.