Investigation of the Alexander L. Kielland Failure—Metallurgical and Fracture Analysis

On March 27, 1980, the semi-submersible platform Alexander L. Kielland broke down in a storm in the North sea, resulting in a loss of 123 lives. The investigation subsequently performed by the inquiry commission showed that one of the lower tubular bracings had failed by fatigue. As a result, the vertical leg attached to it was torn off, and the platform capsized. The fatigue fracture had started from a double fillet weld joining a 0.325-m tubular attachment to the bracing. The fillet welds were partially cracked in the early history of the platform due to lammelar tearing. Cumulative damage calculations indicated that the design fatigue life of the bracing was inadequate.