This paper is a summary of a study "on the tubular joints in the steel gates of the Eastern ScheIdt storm surge barrier in the Netherlands". This study was commissioned by the Directorate-General for Public Works and Water Management (Rijkswaterstaat) and carried out in the period 1985–1992. At a late stage during the fabrication of the Eastern ScheIdt storm surge barrier it was found that, due to improper control during rolling, many tubes were made of steel with a relatively coarse grain. It was therefore decided to use probabilistic methods to determine the failure probability and optimum inspection strategy. The optimum strategy was determined on economic grounds, based on a consideration of the investments, costs of inspection, costs of repair and failure costs. Safety was included as a boundary condition. The study indicated that it was necessary for financial reasons to differentiate inspection schedules, depending on the load and type of material.
When fabricating the steel gates for the Eastern ScheIdt storm surge barrier in the Netherlands it was discovered that the tubes of the main structure contained coarse-grained steel. This was due to insufficient control during hot rolling of the plates to produce these tubes. Coarse-grain material may lead to brittleness. This was confirmed by further tests (Charpy V and CTOD). When the barrier is closed and exposed to a large difference in water levels and high wave loads, unstable cracks may grow from weld defects (undercuts, or slag inclusion) or fatigue cracks in the tubular joints. Experiments on coarse-grain Y-joints removed from the structure showed that a chord could fail completely due to such cracks. At the time the presence of coarse grain structures was discovered a number of gates had already been installed, while others were ready for installation.
