Patent Publication Number: US-6212839-B1

Title: Design element for building structures

Description:
TECHNICAL FIELD 
     The invention relates to a structural element for building structures comprising a frame structure and an outer plane. The outer plane is constituted by a plurality of plate-formed sandwich elements. The structural element of the present type can be used for example as a movable or fixed vehicle deck on ships. 
     BACKGROUND TO THE INVENTION 
     Structural elements such as ships&#39; decks, loading hatches and the like are traditionally made up of steel beams and arrays of plates. The steel beams are part of a more or less complete frame structure comprising, amongst other things, reinforcements for preventing buckling in said plate arrays. Such constructions are used nowadays for instance as movable vehicle decks in Ro-Ro ships. Since these movable vehicle decks are intended to be lowered down from an elevated, stowed position below an overlying deck, attempts are made to make the deck as light as possible. The desired load capacity for modern Ro-Ro ships is ever increasing, which often means more fixed and movable vehicle decks on board new ships. This increases the requirement for weight savings in the ship. Today&#39;s traditionally constructed vehicle decks are however already almost as light as possible when taking account of their structural limitations. 
     PRIOR ART 
     EP-A-0 074 732 discloses a structural element for building structures, having panels which merely are cover panels which have merely a two-dimensional connection to the beams of the framework. Their contribution to the overall strength of the structural element is very poor. 
     OBJECT OF THE INVENTION 
     The object of the present invention is to solve the aforementioned problems by providing a structural element for use, for example, as a movable vehicle deck, which offers an appreciable weight saving with respect to known devices and at the same time leaves the strength of the structural element unaffected. 
     SOLUTION 
     The above-mentioned object is achieved in the present invention by providing a structural element for building structures which is characterized in that said sandwich element comprises a core positioned between two cover plates, that said core consisting of a framework structure, that said sandwich elements serve as flanges for beams with conventional webs which are included in the structural element and that the sandwich elements are directly connected with the webs of the beams, whereby the sandwich elements are connected with said frame structure in such a way that they integrally contribute to the overall strength of the structural element. 
     Said sandwich elements preferably comprise a core positioned between two cover plates, said core consisting of a pyramidal framework structure. It should be mentioned however that the sandwich element can also be constructed in many other different ways. The core can also present for example a corrugated board structure or a honeycomb pattern. 
     As a result of the invention, a weight saving of up to 30% can be achieved when compared to traditionally built structural elements. This allows, for example, new Ro-Ro ships to be able to be built with notably increased load capacity without a resultant reduction in the ship&#39;s stability. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described in more detail with reference to the accompanying drawings, in which: 
     FIG. 1 shows a cross-sectional view through a structural element according to the invention, 
     FIG. 2 shows a plan view of the structural element depicted in FIG. 1, 
     FIG. 3 shows a cross-sectional view taken along line II—II in FIG. 2, 
     FIG. 4 shows a partial cross-sectional view of an end-beam structure which is included in the structural element according to the invention, 
     FIG. 5 shows a partial cross-sectional view of a typical intermediate-beam structure according to the invention, 
     FIG. 6 shows a partial cross-sectional view of another embodiment of an end-beam structure according to the invention, 
     FIG. 7 shows a partial cross-sectional view of a further embodiment of an intermediate-beam structure according to the invention, 
     FIG. 8 shows an enlarged, partial cross-sectional view of a sandwich element according to the invention, 
     FIG. 9 shows a partial perspective view of the construction of a sandwich element according to the invention, 
     FIG. 10 shows an enlarged perspective view of a bar-pyramid of the type which is included in the core of the sandwich element shown in FIG. 9, and 
     FIG. 11 finally shows a perspective view of an alternative sandwich element according to the invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Reference numeral  1  in FIG. 1 generally denotes a structural element in accordance with the invention. In the depicted embodiment, the structural element  1  is used as a movable vehicle deck in a Ro-Ro ship. It should be remembered however that the structural element  1  is also suitable for use as a floor, other types of ships&#39; decks, ships&#39; bulkheads, loading ramps, loading hatches or similar applications where high strength and low weight are sought. 
     The structural element  1  comprises a frame structure  2  and a support plane  3 . The support plane  3  is constituted in accordance with the invention by a plurality of plate-like sandwich elements  4  which are connected with said frame structure  2  in such a way that they integrally contribute to the overall strength of the structural element  1 . 
     FIG. 2 shows the structural element  1  from above. From here it is clear that the structural element  1  in the shown embodiment comprises twenty-four sandwich element pieces. The shown structural element  1  constitutes a part of a movable vehicle deck in a Ro-Ro ship. The cross-section which is shown in FIG. 1 is, more precisely, a cross-sectional view along line I—I in FIG.  2 . The size of the included sandwich elements  4  is advantageously adapted for transport in standardised load units such as load containers for land and sea transport. This allows efficient transport of prefabricated sandwich elements from sub-suppliers to the building docks. This is of importance, none the least since the transport distance is often appreciable. 
     FIG. 3 shows the appearance of the structural element  1  in a cross-sectional view along line II—II in FIG.  2 . From here it can be seen that the frame structure  2  comprises end-beam structures  6  and intermediate beam structures  7  respectively. These are also clearly shown in FIG.  1 . 
     FIG. 4 shows an enlarged, partial representation of the end-beam structure  6  which is shown in FIG.  1 . The sandwich element  4  serves here as a flange in a beam (in this case the end-beam structure  6 ) which presents a conventional web  10 , an upper end flange  11  as well as a lower flange  12 . The web  10  and the flanges  11  and  12  respectively are constructed in a conventional manner, i.e. by simple plates welded together. The end-beam structure  6  is hereby joined with the aid of the welds  14 ,  15  and  16 . 
     In a corresponding manner, FIG. 5 shows a typical intermediate-beam structure  7  included in the structural element  1 . As is clear form the figure, the intermediate-beam structure  7  comprises two sandwich elements  4  which serve as the upper flange for the beam constituted by the intermediate-beam structure  7 . Similarly to the end-beam structure  6 , the intermediate-beam structure  7  presents a conventional web  10  as well as a conventional lower flange  12 . The intermediate-beam structure  7  is joined by means of welds  14 ,  15  and  16  respectively. In the FIGS. 4 and 5 it is also clear that the sandwich elements  4  present edge portions  18  which are constituted by U-shaped beams. The open sides of the U-shaped beams face inwardly towards the rest of the sandwich element  4 . The web  10  advantageously extends inbetween the two U-shaped beams, up to the weld  15  which joins the web and the U-shaped beams together, i.e. to the support plane  3 . The construction of the sandwich element  4  will be described in more detail with reference to FIG. 8 onwards. 
     Alternative embodiments of the end-beam structure  6  and the intermediate-beam structure are shown in FIGS. 6 and 7. FIG. 6 differs from the embodiment in FIG. 4 in that a horizontal support plate  20  is placed beneath the sandwich element  4 . The other components are identical to the components in FIG.  4 . Similarly, in FIG. 7, horizontal support plates  20  are placed beneath the sandwich elements  4 . In this embodiment, the intermediate-beam structure is additionally provided with a vertical flange  21  for increased strength. In other respects the components in FIG. 7 correspond to those in FIG.  5 . 
     The thickness of the sandwich element  4  constitutes a maximum of 30% of the total thickness of the structural element  1 . In the most preferred embodiment, the thickness of the sandwich element  4  constitutes about 15% of said total thickness. 
     FIG. 8 shows an enlarged partial cross-section of a preferred sandwich element  4  according to the invention. Parts of this sandwich element  4  are also shown in FIGS. 9 and 10. As is clear from the figures, the sandwich element comprises a core  25  positioned between two cover plates  23 ,  24 , said core  25  consisting of a pyramidal framework structure. The separate pyramid structure can be clearly seen in FIGS. 9 and 10, the pyramid structure here being denoted by reference numeral  27 . The pyramid structure  27  is in turn constructed from two V-shaped bent bars  28  and  29  respectively as depicted in FIG.  10 . The above-described sandwich element  4  is suitably a so-called “PTC”-panel (Pyramidal Truss Core panel), which is manufactured and marketed by the Jonathan Corporation in the USA. The high durability characteristics of the PTC panel make it particularly suitable for use as the sandwich element  4  in the structural element  1  according to the invention. It should however be noted that the invention is not limited to a sandwich element  4  comprising a pyramidal framework structure. The core  25  can instead present a so-called corrugated-board structure for example, as shown in FIG. 11. A further alternative is that the core  25  presents a so-called honeycomb pattern with a plurality of connected polygons (not shown). 
     A structural element  1  according to the invention is appreciably lighter than a corresponding element constructed in a conventional manner with simple steel beams and plate arrays. This is demonstrated well by the fact that a corresponding conventionally constructed structural element  1  has a surface weight of about 110 kg/m2 which should be compared with a substantially lower surface weight of between 72-73 kg/m2 for a structural element  1  according to the invention. This large weight saving is clearly advantageous for the building of new Ro-Ro ships with a requirement for increased load capacity. By using a structural element in accordance with the invention, an additional vehicle deck can be added without the stability of the ship being affected appreciably. 
     The present invention is not limited to the embodiments described above and depicted in the drawings, but can be varied freely within the scope of the appended claims. Thus, the structural element  1  according to the invention is equally suitable for use in floors, other types of ships&#39; decks, ships&#39; bulkheads, loading ramps, loading hatches or similar structures. Additionally, other building structures may be envisaged such as chimneys, house buildings etc.