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splice design in steel stack

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In the last couple of weeks I have asked a couple of questions on the design of a steel stack.  I would like to thank all those that replied.  The suggested references that were given were very helpful and I think I have the majority of the design for this stack figured out.  It is a very “beefy” stack being only 34 ft high and is 5 ft in diameter using ½” plate per the mfg’s request.


The mfg. also wants to use a splice in the stack.  One of the references that I obtained suggested in a table that for a 60 in. diameter stack to use a “companion flange” of 2.5”x.5”.  I am confident that this will work, but I would like to put some numbers to it in my calculations.  First I would ask if any of you have some design criteria for this situation and possibly an example.


Without that I am considering something that may be very simple, but for the low stresses and large number of bolts that the mfg wants to use will probably be an adequate method to check the companion flange connection.  Using the bolt line as a circle and conservatively using the bolt line diameter the same as the stack diameter calculating P/Circumference – M/Sw gives me a tension per inch.  Then multiplying that by the bolt spacing would give an approximate bolt tension.  I can check the plate thickness and bolt size with prying action at that point.  I have seen an older method for obtaining an anchor bolt size and base plate thickness based on compression on a concrete foundation, which I’m not sure I could use in this situation, and even at the base I don’t have a concrete pad as the stack is supported on a skid, which I will design last.


Any comments or suggestions are appreciated.


Joseph R. Grill, PE

Verde Valley Engineering, PLLC

email: VVEng(--nospam--at)