Experimental study on fatigue performance of Q460 and Q690 steel bolted connections

In this paper, we present an experimental study of the fatigue performance of high-strength steels base materials, perforated plate, and bolted connection. The corresponding fatigue life was predicted. According to the stress concentration degree, the location of the initial crack was discussed, and the reduction degree in fatigue strength was quantitatively analyzed by the fatigue notch factor. Finally, the fatigue damage development process was analyzed on the basis of fatigue damage theory. Results indicated that the base materials and perforated plate showed good fatigue performance in the finite fatigue range. Their fatigue limit was clearly higher than the code value. The fatigue strengths of the Q690 base material and the perforated plate under the 95% survival probability were 1.3 and 1.2 times that of Q460, respectively. The fatigue performance of bolted connection Q690 was significantly higher than of Q460. Under the 95% survival probability, the fatigue strength of bolted connection Q690 was 1.5 times that of Q460. The stress concentration led to enhanced local stress and stress gradient. It also restricted crack initiation at maximum stress and reduced the fatigue strength of specimens. Damage value could better reflect the internal state changes of the components well in the process of fatigue failure. With the fatigue cycles times increased, the damage value gradually increased, whereas the effective bearing area and bearing capacity decreased, and the instantaneous fracture occurred.