Hi,
Assuming you are trying to spec heavy duty chain then this answer may not help you, but:-
Here in the UK there is a company called HPC Gears, they supply a booklet of there chain and gear sizes. in this booklet it gives you design parameters to allow you to choose the correct chain for any general application. It does make the distinction of having shock loading, etc and so is factored into the calculation process. i know this may not help you out if you live outside the UK, or are needing a quick answer.
Cheers
AndyR