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Compressive strength of double-bottom under alternate hold loading condition
Published in C. Guedes Soares, Y. Garbatov, Progress in the Analysis and Design of Marine Structures, 2017
Bulk carriers are designed to carry bulk cargo that can often have a higher density than water. This means that these ships frequently sail with maximum draft despite the cargo spaces were not completely full. As a rule, the option is not to use partially filled holds to avoid the bulk cargo run to a board causing large angles of heel. Since the holds cannot go all full or half-empty is normal in these ships carry cargo in alternate loading condition, i.e. alternate full hold empty hold. This type of loading induces bending moments and high shear forces in the structures of the ship, since the structure of the double bottom is subjected to pressure caused by the load weight at the bottom of the holds and pressure caused by the sea water at the bottom plating. In Figure 1 one can see the usual loading scheme of bulk carriers and the lateral pressures that act on the double-bottom structures on the central holds.
Emergency ship manoeuvres
Published in D.J. House, Ship Handling, 2007
The total loss of underkeel clearance for the vessel tends to occur with resulting contact with whatever surface is under the ship at the time. The benefits of ships built with double bottom (DB) structures can be clearly seen as a positive asset; bearing in mind that, if the outer ship's shell plate is broached, then the tank tops of the DB construction could prevent the flooding of the vessel. A ship can also float on her tank tops, provided these are not damaged.
Finite element-based structural optimization of assemblies found in ship hulls
Published in C. Guedes Soares, T.A. Santos, Trends in Maritime Technology and Engineering Volume 1, 2022
G. Giannopoulos, K.N. Anyfantis
The geometry of a bulk carrier’s double bottom has been selected together with a specific load case, that is Alternate Holding Loading (AHL), as shown in Figure 1a. This type of loading induces bending moments and high shear forces in the hull of the ship, since the structure of the double bottom is subjected to pressure caused by the load weight at the bottom of the holds and pressure caused by the sea water at the external plating.
Analysis of hull girder ultimate strength for cruise ship with multi-layer superstructures
Published in Ships and Offshore Structures, 2019
Generally, double bottom structures are arranged in a cruise ship, and the cabin above the inner bottom is set as light dry cargo space or void space. During navigation period, the double bottom structures are subjected to outboard pressure. Especially for a cruise ship with the long distance between two adjacent transverse bulkheads, the double bottom presents vertical deformation between transverse bulkheads, and transverse stresses will be acted along ship breadth, which will reduce buckling strength of outer bottom and inner bottom with longitudinal framing structures. Another point should be noted that the deformation direction induced by bottom lateral loads is the same as that induced by hogging bending moment. Therefore, the bottom lateral loads will have an important reduction effect on hogging ultimate strength for a cruise ship.
Reduction in ultimate strength capacity of corroded ships involved in collision accidents
Published in Ships and Offshore Structures, 2018
Jonas W. Ringsberg, Zhiyuan Li, Erland Johnson, Artjoms Kuznecovs, Roozbeh Shafieisabet
Figure 2 presents the mid-ship section scantlings of the struck ships which are collided amidships by the striking tanker; see Table 2 for the gross scantlings. The RoPax ship is a coastal RoRo cargo vessel with a typical side-shell structure with small distance between the inner and the outer side-shells, which makes the ship sensitive to collision damage (Karlsson 2009). It has three RoRo decks, one on the tank top, one on the main deck and one outdoors on the upper deck. The ship is longitudinally stiffened above the main deck and in the double bottom, and it has a transversely stiffened double side-shell. The spacing between deck beams is 2.4 m. The double side-shell and double bottom structures also act as water ballast tanks. The coastal oil tanker has longitudinally stiffened double bottom and weather deck, while the double side-shell structure is transversely stiffened. It has a corrugated longitudinal bulkhead in the centre plane of the cross-section. The corrugation is vertical; hence, the bulkhead may be omitted in the ultimate strength calculations since it does not contribute effectively to the hull girder longitudinal strength (IACS 2017).