Investigation of Multiple Damage Mechanisms in Pin Rods of Short Suspenders on a Long-Span Suspension Bridge

Abstract

Pin joints are widely used connections for hanger assembly in suspension bridges. Significant rotary motions have been observed between pin rods and the connected members for long-span bridges subjected to traffic and environmental vibrations. Besides, the pin rods are under complex loading conditions and harsh environments, so they are prone to multitype damages. According to the investigations on the pin rods of suspenders at the midspan of the Jiangyin Yangtze Bridge, three main damaging mechanisms were found in the most damaged section covered by the lubricating bushing. It is observed that the half of the pin rod tightly contacted with the gusset plate was severely worn due to the galling seizure, while pitting corrosion was the predominant damage in the other half of the pin rod. Between the two zones, a small transition area was found damaged in the form of oxidational wear, indicating that it is affected by both friction and corrosion. It was found that the shear stress and bending stress are not threatening to the safety of the pin rods due to the appropriate material selection and sufficient load-bearing capability. However, stress concentration increased significantly due to the sharp step planes at the joint of the fork socket and the gusset plate, which is potentially risky to promote fracture of the pin rod.