The Sliding Hinge Joint is a low damage beam-column connection used in steel moment resisting frames. It dissipates energy through sliding in Asymmetric Friction Connections (AFCs) in the bottom web and bottom flange bolt groups. The AFC confines earthquake induced damage to bolts that can be retightened or replaced following a major earthquake. The other joint components sustain negligible damage and would be kept in service and may thus be subjected to further earthquake shaking during the lifetime of the building. The bottom and top flange plates are also subject to inelastic action about their minor axis under joint rotation. This study evaluates the behaviour of the bottom and top flange plates to determine the weld and plate susceptibility to low-cycle fatigue failure. The basic flange plate deformation was approximated by an arc, with the effects of shear slip considered to obtain estimates of likely strain demands. It was shown that even in the most critical case the fatigue life is more than six times the demand expected in a design level earthquake. As a result, it is concluded that properly designed, detailed and connected flange plates are not prone to low-cycle fatigue failure.