The subject of this paper is the behavior of MarkIII corrugated primary membrane under breaking wave impacts. The study is based on the database of the large scale impact tests from the Sloshel project. Unidirectional breaking waves were generated in a flume tank in order to break onto an instrumented wall covered by a corrugated surface reproducing the MarkIII membrane at scale 1:6. Pressure sensors were positioned in between the corrugations. A special sensor was designed to measure the net force in the upward and downward direction on a horizontal corrugation. Special care was taken to observe the interaction between the wave impact and the corrugations by high speed cameras synchronized with the data acquisition system. Four sources of impact loads on the corrugations were observed: the wave trough, the wave crest, the jet formed after wave impact or the entrapped air. This observation gave evidence that more mechanisms are involved during sloshing-corrugation interaction than those indentified previously with wet drop tests. Moreover, the pressure measured upstream and downstream of a horizontal corrugation is correlated to the global vertical force, but this relation depends highly on the sensor position with regards to the corrugation, and the source of loading. The paper describes the different kinds of corrugation loadings during breaking wave impacts. It emphasizes the need to take into account the sloshing corrugation interaction into a sloshing assessment methodology but shows that applying scaled corrugations in small scale tests (scale around 1:40 – 1:35) is not adequate.
MarkIII is one of the membrane Cargo Containment Systems (CCS) designed by GTT for LNG carriers. It is mainly composed of 3 m x 1 m panels of polyurethane foam covered by a stainless steel corrugated membrane in contact with the LNG at -162°C (see Figure 1).