Fatigue of A514 Steel in Bolted Connections

Fatigue tests were conducted on bolted connections in high strength, quenched and tempered (A514) steel at the University of Illinois to provide data that can be used as a basis for the development of design specifications for high strength structural steels. Parameters related to joint proportioning were investigated; these included the bolt type, the relative proportions of tensile, shear, and bearing areas, and the ratio of the transverse fastener spacing to the fastener diameters. Several variations in joint assembly techniques which were also studied for their effect on fatigue performance, included additional tightening of bolts, bolt tensioning while joints were in bearing, and grit blasting of the joint faying surfaces. Constant amplitude fatigue tests were conducted at several ratios of minimum to maximum stress, with particular emphasis on zero-to-tension testing. An analysis of the fatigue data shows that extensions of present design specifications should permit higher allowable design stresses for bolted connections in quenched and tempered steels than for lower strength steels.