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Fatigue of hybrid k-nodes for offshore structures made of vacuum-treated fine grained cast steel

Betriebsfestigkeit von Verbundrohrknoten für Offshore-Bauwerke aus vakuumbehandeltem feinkörnigem Stahlguß
: Christianus, D.; Umbach, R.; Sonsino, C.M.

Chung, J.S. ; International Society of Offshore and Polar Engineers -ISOPE-, Goldem/Colo.:
1st International Offshore and Polar Engineering Conference. Proceedings. Vol.IV
Golden/Colo., 1991
ISBN: 0-9626104-5-3
pp.464-474 : Abb.,Tab.,Lit.
International Offshore and Polar Engineering Conference <1, 1991, Edinburgh>
Conference Paper
Fraunhofer LBF ()
Betriebsfestigkeit; Meerwasserkorrosion; offshore construction; Offshore-Konstruktion; salt water corrosion; Schweißverbindung; Stahlguß; steel casting; structural fatigue strength; welded joint

The fatigue testing of welded tubular nodes and cast steel hybrid nodes under random loading and corrosion in artificial seawater shows clearly that the fatigue strength of the cast steel hybrid nodes is superior to that of the welded tubular nodes. This is related to the advantageous design of the cast steel inserts, as a result of which the high stress concentrations are substantially reduced and the welds transferred to areas of lower and, therefore, noncritical, stresses. The fact that the phase of crack propagation of the tubular nodes is many times longer than the fatigue life to crack initiation, provides a considerable reserve in fatigue design based on crack initiation. This makes it possible to detect damage at an early stage during routine inspections and thus to prevent serious failures. Concerning the design, however, emphasis should in any case be placed primarily on an increase of the fatigue life to crack initiation. In this respect, the use of cast steel inserts is an advantageous possibility.