ABSTRACT
Recently, steel-concrete composite bridges have been built using circular hollow section (CHS) members for the main load carrying structure, with cast steel nodes to join the braces and the chord. An experimental study of a planar tubular truss with cast steel nodes is being conducted in order to clarify their fatigue behaviour. Preliminary test results show that the fatigue failure of the girth butt welds presents a significant problem, since cracks initiate and propagate at weld root defects. No fatigue cracks have been observed in the cast nodes so far. Numerical investigations of the stress flow in the cast steel nodes show good agreement between measured and calculated stresses. With a validated FE model, the influence of possible defects in the cast nodes on the fatigue behaviour will be investigated.
