In conventional car decks, for example of the kind indicated above, steel is used for the top plate as well as in the secondary reinforcement and the flange for the primary structure. For example, in accordance with US-4329935 A, where vertical uprights are attached to horizontal beams and decks by means of flanges and bolts. The material in the beams, flanges and decks is similar, i. e. a metal such as steel.

The dead weight of the panels is of the greatest significance in the construction of hoistable and liftable car decks. A low panel weight offers a number of advantages: The total weight of the Ro-Ro equipment on the vessel is reduced, which gives an increased load capacity or alternatively a lighter vessel, which in turn reduces the fuel consumption of the vessel and improves its stability. z Manoeuvring of the empty decks is facilitated, since a lighter deck requires smaller and lighter equipment for its manoeuvring. a The load of the cargo will be reduced for a given load level, which leads to lower stresses in the vessel.

These advantages provide a strong financial incentive to reduce the weight of the equipment.

The principal object of the present invention is thus, in the first instance, to solve the aforementioned problems with different materials in those places where they offer the greatest benefit.

The use of different materials, such as aluminium and steel, for such elements has not been attempted previously, but in order to be able to use these materials it is necessary to cause the plates and beams in question to be joined together via joints of an appropriate kind with the ability to absorb shear forces.

The principal object of the invention is achieved by means of an arrangement in accordance with the present invention, which is characterized essentially in that attached to the underside of the top plate are pairs of mutually opposing longitudinal primary steel beams, in that supplementary steel beams are attached to the underside of the top plate at an angle to the longitudinal primary steel beams, in that the aforementioned supplementary primary steel beams extend across the longitudinal primary steel beams, in that the top plate and the secondary reinforcement and flange intended for it consist of aluminium, and in that the load- carrying primary beams consist of steel, in conjunction with which the top plate is attached to the aforementioned beams via a number of joints with the ability to absorb shear forces.

The present invention is thus based on the idea of using aluminium where this material offers the greatest benefit, and using steel where this material has its advantages. In principle, this means: o Aluminium in elements that are large in terms of their volume, but are less stressed and have a lower requirement for deflection.

Li Steel where there is a requirement for strength and low deflection.

In the present case this leads to the use of aluminium as the top plate and secondary reinforcement, while steel is present in the long primary beams.

The invention is thus described below with reference to the accompanying drawings, in which:

Fig. 1 shows a sectioned view along the line I-I in Fig. 1A ; Fig. 1A shows a plan view of a car deck; Fig. 2 shows a sectioned view of the joining parts of two connected top plates and a load-carrying frame with flanges; and Figs. 3-6 show examples of different joints between the joining parts of the different materials.

An arrangement 1 for a hoistable and liftable car deck 2, which is intended for a ship and is so arranged as to comprise a load-carrying top plate 3 as a deck and reinforcing beams 4, 5, 6, 61, 6... 6n supporting same, has the top plate 3 and secondary reinforcement intended for it and a flange consisting of aluminium material, and the load- carrying primary beams 4-6n consist of steel material. In this case the top plate 3 is joined to the aforementioned beams 4-6n via a number of joints 7,71 with the ability to absorb shear forces.

The principal idea of invention is thus the means with which these two different materials are joined together.

It should be possible in principle simply to lay reinforced aluminium plate on a frame of steel. The problem then is that two important functions of the upper material are lost. In a conventional car deck the top plate in steel is also used as an upper flange for the primary structure.

In the present construction it is proposed to use aluminium material both for the top plate 3 itself and for the secondary reinforcement 8 and the flange 13 for the primary elements.

The joints 7,71 with the ability to absorb shear forces between the aluminium deck 3 and the steel beam 4-6n can consist of, for example, a screw 7, nail, adhesive 71, spring strip or welded joint, etc.

The examples illustrated in the drawings show embodiments of a construction that is envisaged for use in

conjunction with screwing, nailing or adhesive bonding of aluminium panels to steel beams.

The reinforcing construction of the top plate with beams can be appreciated from Figs. 1 and 1A. Pairs of mutually opposing longitudinal primary steel beams 4,5 extend along both longitudinal end edges 3A, 3B of the top plate on the under side 31 of the top plate. Extending at an angle x to these longitudinal primary steel beams 4,5 are supplementary primary steel beams 6-6n. The longitudinal steel beams 4,5 and the angled steel beams 6-6n extend preferably at right angles to one another.

Finally, it can be mentioned that the top plate 3, which can consist of an internal reinforcement 8 in the form of a lattice construction, is supported at the point of connection for mutually meeting aluminium panel sections 10, 11 of the frame 12 on a beam 4-6n. The aforementioned secondary reinforcement 8 also consists of aluminium.

The width B of a car deck 2 can be 11-12 metres, for example, and the length L can be 20 metres, for example.

The car deck 2 can thus be divided up into sections 9,91, 92-9n, for example seven in number, each of which can exhibit a width C of ca. 2.5-3 metres.

The invention is naturally not restricted to the embodiment described above and illustrated in the accompanying drawings. Modifications are possible, especially in respect of the nature of the different component parts, or by the use of equivalent technology, without departing from the extent of the protection conferred on the invention, as defined in the Patent Claims.