A revolution in ship building?
Steel and light weight concrete sandwich construction may
The strategic research department of DNV and Aker Yards are exploring
the potential for building ships using a novel cellular construction method.
Stiffeners and secondary structural elements are to a large extent eliminated
by way of using a sandwich of thin, double steel plates with
light weight concrete as a core material in between. New concretes lighter
than water have been developed and tested. A prototype Panamax bulk ship
has been studied; a particularly interesting result was that the overall
weight came out to be equal to or less than that of a conventional steel
ship. The proposed construction method has potentially many interesting
safety features, such as improved integrity of the ship in collision and
grounding, increased fatigue life, less corrosion, improved fire resistance,
enhanced environmental performance etc. These aspects will be studied
further in the future.
Several barges were built in this period. The first patent for design
of concrete ship capable of deep-sea trading came from Fougner (Norway)
in 1912. Unable to find a ship owner willing to place a firm order, the
ship was built on own risk and launched in 1917. With the success of the
ship, several small ships were built and some are still afloat. The casting
of the first ships, when the frame is completed, took only two days. A
1,000-ton ship was completed in six weeks.
In the following years (19171921), 12 large concrete ships were
built. A typical cost for a 5,000 ton concrete freighter was USD 750,000.
During WWII, several large concrete ships were built due to steel supply
shortage. Innovations in cement mixing and composition made these ships
stronger than the previous fleet. In 1942, the United States Maritime
Commission built a new fleet of 24 concrete ships. The ships were built
at an incredible rate, with one being launched every month. Concrete hulls
were particularly well suited for carrying dry cargo as the condensation
problems that plagued steel ships did not occur. These vessels worked
well but were only capable of a maximum of ten knots due to the high light
weight. Of all the American concrete ships built during WW I and II, only
ten are known to today be afloat. These ships form a massive floating
breakwater on the Malaspina Strait in the City of Powell River in British
About the Steel-Concrete Cellular Sandwich Concept
The concept of using steel and light-weight concrete sandwich construction
aims at developing a new generation of merchant ships with enhanced properties
with regard to safety, economy, environmental performance and overall
operational efficiency. In particular, the proposed cellular design implies
that the concept will be scalable and applied to ships of any size and
still maintain its intended properties of weight and price competitiveness.
The innovative concept may represent new opportunities for the ship builders
and the ship owners as well as being a step forward for everyone concerned
with safety at sea.
It is necessary to make ships safer
Making ships safer is necessary and is demanded by the society at large.
The Erika and Prestige catastrophes have in a dramatic way illustrated
the risks of pollution linked to maritime transportation, particularly
the risks of old ships and single skin design. Also the recent Rocknes
catastrophe definitely leads to increased attention to grounding accidents
and integrity performance of the ship hulls. The steel-concrete sandwich
concept may introduce an important step forward in terms of hull performance
and ship safety.
Lower material and maintenance cost
Risk based design (Quantitative Risk Assessment) complying with the principles for Formal Safety Assessment according to IMO circulars will be applied to demonstrate that the design is as safe as or safer than existing designs and that the risk level is As Low As Reasonably Practicable.
Risk based design offers freedom to the designer to choose optimal solutions
to meet safety targets and opens the door for innovation, as radically
novel and inventive design solutions may become feasible.
Generally it is foreseen that the concept may first of all be of interest
for chemical carriers and gas carriers because different steel qualities
may be applied in the sandwich concept with no/reduced thermal bridge
between the steel plates.
Stainless steel or other materials for low or high temperature applications
may be used on the surface towards the load and normal structural steel
can be used on the other surface. The low density concrete core has very
good insulation and fire properties, and the properties of the concrete
can be varied for different application areas and purposes throughout
the ship. The specific weight of the concrete which will be applied will
typically vary between 350 and 1,200 kg/cbm.
An initial feasibility study of a new and alternative way to design dry
bulk carriers by using the ideas of the steelconcrete sandwich concept
has been performed.
Further work will thus concentrate on other ship types that may have
stronger safety and cost saving potential than the somewhat simple
bulk carriers. Two UK patent applications and a PCT application have been
submitted in connection with the first phase of the project.
When considering the main benefits of the Cellular Sandwich Concept several application areas seem very promising. The technology may also open new possibilities within maritime transport giving feasibility to new conceptual ideas.
The main benefits of the concept are believed to be:
A technical qualification program has been started involving Aker Ostsee
Werft, DNV Research, Universität der Bundeswehr München and
Liapor Gmbh & Co. Laboratory testing, technological investigations
and manufacturing studies will be the main activities of this phase.
Sources: ConcreteShips. Org and Maritime Research of Uddevalla
Latest update 18-10-2006 8:49