JAPANESE classification society ClassNK has announced it will investigate risks of brittle fractures in the thicker steel used in bigger ships like the 20,000-TEUers now on order.
"Preventative measures for brittle fracture has become even more important with thicker steel in areas where higher stress occurs such as the upper deck and hatch side coaming of the cargo holds," said the ClassNK statement.
The project will be carried with the Japanese Welding Engineering Society (JWES), steel manufacturers, shipbuilders, and neutral research institutes, and is scheduled to be completed in mid-2016.
"With the introduction of 20,000-TEU containerships, the increased use of brittle crack arrest steel exceeding 80mm in thickness is expected," said the ClassNK statement.
"To ensure smooth adoption of thicker steel in the industry, ClassNK has embarked on a research project to develop technical standards to clarify the crack arrest parameter for steel plates exceeding 80mm in thickness.
"Through this, ClassNK aims to establish clearer evaluation methods to form the proposal for unified IACS [International Association of Classification Societies] requirements for brittle crack arrest steel exceeding 80mm for the benefit of the entire maritime industry," said the ClassNK statement.
Already there are IACS requirements in place outlining the necessary measures to be taken for the prevention of brittle crack propagation in the block-to-block butt joints of the hatch side coaming and upper deck to prevent large scale fracture of the hull girder.
"ClassNK will work towards establishing safer brittle crack arrest design for the construction of ultra-large containerships. By sharing results with the greater maritime community it aims to help develop improved unified IACS requirements," said the statement.