CAESAR II sets load variation as (K*delta)/(balancing load); where K is the proposed spring stiffness, delta is the "free vertical growth" (from hanger load case 2), and balancing load is the "restrained weight" load (from hanger load case 1). After a spring is collected from the hanger table, that K is used in the load variation check to confirm that the load variation is not exceeded.
A general definition of load variation, as you say, is the change in load divided by the operating load for the spring. For typical hot (operating) load design, the CAESAR II balancing load will be this hot load and everything is in order.
But when the user selects "cold load design", the calculated balancing load is considered the cold load. Since this "cold load" is now the independent variable,the program's calculated load variation will not reference the hot load; it will be (K*delta)/(cold load) instead.
Since:
Cold Load = Hot Load + K*delta
I think we can adjust our load variation for cold load design to this:
Load Variation = (K*delta)/[balance load-(K*delta)]
Comments are welcome.
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Dave Diehl