Evaluation of remaining fatigue life for riveted truss bridges

Abstract

The remaining fatigue life of riveted structures is a topic of considerable importance, particularly for owners of bridges. Improved methods for the estimation of the actual fatigue life of such structures are required in order to make their continued safe use possible while at the same time avoiding the expense of unnecessary repairs. To evaluate the fatigue life expectancy of a structural detail, it is necessary to obtain an accurate estimate of the stress history. Two analytical models are assessed through comparison with measured strains taken from a bridge in service. The results illustrate that a simple model with pinned connections is adequate for the determination of stresses in truss members and that more advanced analysis methods give only marginal increases in accuracy. Stresses in the floor system are most accurately predicted by a model that has full bending moment continuity between connected members. Standard and advanced methods of fatigue life evaluation are discussed and are then implemented in the evaluation of the remaining fatigue life for components of the bridge. Comparison with the actual fatigue life of the components, which were obtained from laboratory experiments, shows that both prediction methods give reasonable estimates of the fatigue life.Key words: bridge, fatigue, rivets, steel, model, analysis.