AN INVESTIGATION OF THE ESTIMATED FATIGUE DAMAGE IN MEMBERS OF THE 380-FT MAIN SPAN, FRASER RIVER BRIDGE

This paper uses the load spectrum defined by checks of past traffic and for future traffic based on marketing projections to evaluate the fatigue life of a bridge already over 70 years old. The Canadian National bridge near Vancouver, B.C., was built in 1904 of a weak design initially, and is today subjected to heavy unit train loads. Fatigue cracks can grow from riveted connections or other structural details such as pin plates and weldments. Strain gauge tests of certain bridge members were used to define the fatigue life of the hangers and stringers. Care in interpreting results and cautions about using field measurements are indicated.