Fatigue of Bolted High Strength Structural Steel

Results of fatigue tests on bolted connections in high strength structural steel conducted at the University of Illinois are presented. The principal parameter varied was the bolt type; one additional variation was included also. Constant amplitude fatigue tests were conducted at various stress ratios, with particular emphasis on zero-to-tension testing. The results indicate improved fatigue strength for high strength structural steel (yield strength = 50.0 ksi) compared to A36 steel. Connections with A325 bolts exhibit approximately the same fatigue strength as those in which A490 bolts are used. A comparison of results of present study with those from other sources indicates that stress based on gross section area gives a better correlation with the number of load cycles to failure of steel in bolted connections than net section stress.