Question 4667 Deck General

The correct answer is B) keel. The keel is the central longitudinal structural hull strength member of the lower hulls of semisubmersible mobile offshore drilling units (MODUs). The keel provides the primary structural support and strength for the lower hull, transferring loads from the deck and upper hull down into the lower hull structure. This is in accordance with the design requirements and regulations for semisubmersible MODU construction and stability. The other answer options are incorrect because: A) a rider plate is a secondary longitudinal structural member, C) a stress plate is a component of the deck or hull plating, and D) the main beam is a primary transverse structural member, not a longitudinal one.