The Ship Structure Committee has selected a few case studies which it hopes represent a wide range of structural failures, casualties and solutions. One of the studies addressing container ships describes recurring failure of side longitudinal passing through a web frame. Progressive failure occurred beginning with the fracture of a web frame flat bar stiffener attachment to the longitudinal, buckling of clips between the web frame and longitudinal, fracture of the longitudinal, fracture of the longitudinal weld to the shell and finally fracture of the shell leading to a fuel oil leak. In some instances a similar fracture occurred in the longitudinal bulkhead.

The ships in question (a class of three) were in regular transpacific service and operated at an essentially constant draft East and West bound. The fractures have been common on all three ships of the class. Because they occur in fuel oil tanks that are not subject to frequent interior inspection, the failures are first discovered when a sheen or oil is seen on the water around the forward end of the ship or when a fuel oil leak is visually detected in the cargo holds.The cause of these failures is poor detail design, incorporating the large open cutout for the longitudinals and the highly eccentric 8" x 6" angle longitudinals, in an area of the ship subject to repetitive impact loading from waves. The figure illustrates how the longitudinal is not adequately supported.