Hellow colleagues

I'm an equipment designer and i need to verify the stresses on the shell of an horizontal vessel over 3 saddles. I don't want to make a FEA analysis because is quite expensive to me.

I ask for your colaboration to find a method, other than Zick's one (only applicable for two saddles), to calculate the stresses on an horizontal vessel over multiple saddle supports.

I'll appreciate if  anyone can suggest me some reference articles or bibliography.

Thanks

Martin