THE EFFECT OF PRYING STRESS RANGES ON FATIGUE BEHAVIOR OF BOLTED CONNECTIONS - THE STATE-OF-THE-ART

When two or more bolts are assembled in a pattern to resist a tensile loading, deformations of the connected material may subject the bolts to a prying action as well as to a direct force. The effect on the pry ing action is to increase the total load that must be resisted by the bolts. Because the fatigue life of a bolt in tension is a function of the total force transmitted to the bolt and not simply the nominal app lied load, the effect of prying action, if it exists, must be determin ed so that the actual load in the bolt may be known. It is very eviden t that the prying effect has a large influence on the fatigue resistan ce of a bolt. Tests executed, mainly in Delf, on very typical connecti ons have clearly shown this problem. They also have the advantage to g ive general rules to design a connection keeping in mind the fatigue r esistance. These tests have been very useful to change the 'philosophy ' of the engineers concerning the conception of the connections.