Fatigue Response of Bridge Fingerplate Expansion Joints

Fingerplate expansion joints are often used in bridges to account for large movements in bridge decks due to thermal expansion or contraction. These joints, meant to last the bridge’s lifetime, have shown premature degradation under heavy vehicular loads. Thus, fatigue tests simulating cyclic vehicular loading were conducted to identify failure modes and effective design practices. Fingerplate joint specimens followed MoDOT designs, varying fingerplate thickness, flange stiffeners, and concrete embedment. Two optimized designs were also tested. Two failure types occurred: fatigue failure in specimens with flange stiffeners, marked by crack propagation through the fingerplate’s back weld, and serviceability failure in specimens without stiffeners, which buckled under load. The optimized designs showed no fatigue degradation and higher strengths. Generally, thicker fingerplates improved stiffness and fatigue performance, while bolted connections eliminated fatigue-related crack propagation.