Types of construction
Transverse framing is used primarily for ships less than 120 metres in length. The floors, frames and beams form rings spaced closely together. Longitudinal strength is provided by the keel, centre girder, side girders, deck girders, the entire bottom, deck and side shell plating, and the tank top. Transverse framing ensures good cross sectional strength to handle overall stresses, vertical loads, rolling and dry docking. However, on very long ships, sheer stresses can cause deformations between the rings.
Longitudinal framing is mandatory for very large ships, oil tankers and bulk-ore carriers. The rings are formed of floors, deck beams and web frames that replace the frames. These rings are farther apart than in transverse framing. The longitudinal reinforcement members are deck girders, girders, the keel and a large number of deck, bottom and side longitudinals. The longitudinals are slender but there are very many of them.
Mixed framing combines longitudinal and transverse framing. One type of framing is used in one part of the ship and the other type is used in another part. The most common combination is longitudinal framing for the bottoms and the deck, and transverse framing for the sides.