In a connection using 5/8"  (UNF-18, SAE Grade 8) bolts, each bolt is subjected to a varying external load between 10.Kips to 20.Kips. Bolts can be preloaded between 0% (no preload) to 100% (at 10% intervals) of their proof strength. You are to decide what range of preload is prudent so the fatigue life of this joint is infinite without gross yielding and joint separation. (Notes: Joint stiffness is triple the bolt stiffness; Use Modified Goodman’s Criteria for fatigue; Also, at min. show full calculations for the cases of no preload and at 50% preload level. The rest can be done by software.) (Hint: To decide, calculate/tabulate/plot maximum stresses & factors of safety for infinite life vs. preload as a % of proof strength as well as check for gross yielding and joint separation of these bolts & then establish workable range and optimum value for preload.)