Fatigue Assessment of Critical Connections in a Historic Eyebar Suspension Bridge

Abstract

The Hercílio Luz Bridge is an eyebar suspension bridge with a riveted girder built in 1926 in Brazil, in which severe fatigue damage was found after years of service. To provide guidance for rehabilitation of the bridge, a fatigue assessment is conducted under Eurocode fatigue load models to obtain stress ranges for the riveted and welded connections, as well as equivalent stress range and cumulative damage for the fatigue safety verification defined by Eurocode standards. Because the original design and construction of the bridge was completed per 1926 AASHTO requirements, for comparison, a fatigue assessment of the proposed rehabilitation is performed according to the more recent AASHTO recommended procedures. The floor-beam-to-truss and stringer-to-floor-beam connections, especially near the eyebar chain transition, are identified to be most prone to fatigue due to the occurrence of significant stress concentration. The predicted fatigue lives indicate that those connections may be weak and need to be strengthened. Analysis results reveal that the stresses under the Eurocode truck load are larger than those under the AASHTO truck load, due to larger gross weight and shorter total axle spacing of the Eurocode truck. In addition, the recommended number of cycles in both codes caused by a single passing truck is insufficient for connections under or near the loading position.