Fatigue of bridge joints using welded tubes or cast steel node solutions

In the design of recently constructed steel-concrete composite bridges using hollow section trusses for the main load carrying structure, the fatigue verification of the tubular truss joints has been a main issue. Recent research on the fatigue behaviour of such joints has focussed on circular hollow section (CHS) K-joints with low diameter-to-thickness ratios - a geometric characteristic typical to tubular bridge trusses. Analytical and experimental research was carried out and joints with both directly welded tubes and cast steel nodes were studied. This paper presents the main results of these studies and shows comparisons between welded and cast steel solutions. The key issues for the design and fabrication of both types of nodes are reviewed and recommendations for the design and fabrication of tubular bridge structures are made.