Abstract: In order to study the low cycle fatigue of steel frame beam-column connections under different amplitude regimes, the low-cycle fatigue test of six full-scale all-welded beam-column connections were designed and finished, and the fatigue crack initiation and expansion of welds was studied.The influence of cyclic amplitude and loading history on the fatigue performance of the connections was analyzed, and the cumulative degree of fatigue damage during normal amplitude, variable amplitude and random load was compared. The results show that under the three amplitude regimes, the welding toe of the flange welding hole isprone to fatigue cracking, and the final fracture path is the oblique development of the welding holes weld toe crack, which merges with the edge weld of the flange weld to cause full-section fracture. It is disadvantageous for the fatigue performance of connections to directly experience large deformation with equal amplitude. The loading process from small deformation to large deformation can give full play to the energy dissipation capacity. The larger the amplitude of loading, the faster the cumulative damage rate of connections, and the earlier the fatigue damage occurs.

Key words: beam-column connection, low cycle fatigue, experimental study